WDIFF

draft-ietf-dhc-dhcpv6-22.txt --> draft-ietf-dhc-dhcpv6-23.txt

Internet Engineering Task Force J. Bound
INTERNET DRAFT Compaq
DHC Working Group M. Carney
Obsoletes: draft-ietf-dhc-dhcpv6-21.txt draft-ietf-dhc-dhcpv6-22.txt Sun Microsystems, Inc
C. Perkins
Nokia Research Center
Ted Lemon
Nominum
Bernie Volz
Ericsson
R. Droms(ed.)
Cisco Systems
21 Dec 2001
1 Feb 2002

Dynamic Host Configuration Protocol for IPv6 (DHCPv6)
draft-ietf-dhc-dhcpv6-22.txt
draft-ietf-dhc-dhcpv6-23.txt

Status of This Memo

This document is a submission by the Dynamic Host Configuration
Working Group of the Internet Engineering Task Force (IETF). Comments
should be submitted to the dhcwg@ietf.org mailing list.

Distribution of this memo is unlimited.

This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026. Internet-Drafts are working
documents of the Internet Engineering Task Force (IETF), its areas,
and its working groups. Note that other groups may also distribute
working documents as Internet-Drafts.

Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at
any time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."

The list of current Internet-Drafts can be accessed at:
http://www.ietf.org/ietf/1id-abstracts.txt
The list of Internet-Draft Shadow Directories can be accessed at:
http://www.ietf.org/shadow.html.

Abstract

The Dynamic Host Configuration Protocol for IPv6 (DHCP) enables
DHCP servers to pass configuration parameters such as IPv6 network
addresses to IPv6 nodes. It offers the capability of automatic
allocation of reusable network addresses and additional configuration
flexibility. This protocol is a stateful counterpart to "IPv6

Droms (ed.), et al. Expires 1 Aug 2002 [Page i]

Internet Draft DHCP for IPv6 (-23) 1 Feb 2002

Stateless Address Autoconfiguration" [23], [21], and can be used separately
or concurrently with the latter to obtain configuration parameters.

Bound, Carney, Perkins, Droms (ed.) Expires 30 May 2002 [Page i]

Internet Draft DHCP for IPv6 (-22) 21 Dec 2001

Contents

Status of This Memo i

Abstract i

1. Introduction 1

2. Requirements 2

3. Background 2

4. Design Goals 3

5. Non-Goals 4

6. Terminology 4
6.1. IPv6 Terminology . . . . . . . . . . . . . . . . . . . . 4
6.2. DHCP Terminology . . . . . . . . . . . . . . . . . . . . 5

7. DHCP Constants 7
7.1. Multicast Addresses . . . . . . . . . . . . . . . . . . . 7
7.2. UDP ports . . . . . . . . . . . . . . . . . . . . . . . . 7
7.3. DHCP message types . . . . . . . . . . . . . . . . . . . 8
7.4. Status Codes . . . . . . . . . . . . . . . . . . . . . . 9
7.4.1. Generic Status Codes . . . . . . . . . . . . . . 9
7.4.2. Server-specific Status Codes . . . . . . . . . . 11 10
7.5. Configuration Variables . . . . . . . . . . . . . . . . . 11

8. Message Formats 12 11
8.1. DHCP Solicit Message Format . . . . . . . . . . . . . . . 12
8.2. DHCP Advertise Message Format . . . . . . . . . . . . . . 12
8.3. DHCP Request Message Format . . . . . . . . . . . . . . . 13 12
8.4. DHCP Confirm Message Format . . . . . . . . . . . . . . . 13
8.5. DHCP Renew Message Format . . . . . . . . . . . . . . . . 13
8.6. DHCP Rebind Message Format . . . . . . . . . . . . . . . 14 13
8.7. DHCP Reply Message Format . . . . . . . . . . . . . . . . 14 13
8.8. DHCP Release Message Format . . . . . . . . . . . . . . . 14 13
8.9. DHCP Decline Message Format . . . . . . . . . . . . . . . 14
8.10. DHCP Reconfigure Message Format . . . . . . . . . . . . . 15 14
8.11. Information-Request Message Format . . . . . . . . . . . 15 14

9. Relay messages 16 14
9.1. Relay-forward message . . . . . . . . . . . . . . . . . . 16 15
9.2. Relay-reply message . . . . . . . . . . . . . . . . . . . 17 16

10. Representation and use of domain names 17 16

11. DHCP unique identifier (DUID) 17 16

Droms (ed.), et al. Expires 1 Aug 2002 [Page ii]

Internet Draft DHCP for IPv6 (-23) 1 Feb 2002

11.1. DUID contents . . . . . . . . . . . . . . . . . . . . . . 18 17
11.2. DUID based on link-layer address plus time . . . . . . . 18 17
11.3. Vendor-assigned unique ID (VUID) . . . . . . . . . . . . . . . . 19

Bound, Carney, Perkins, Droms (ed.) Expires 30 May 2002 [Page ii]

Internet Draft DHCP for IPv6 (-22) 21 Dec 2001 18
11.4. Link-layer address . . . . . . . . . . . . . . . . . . . 20 19

12. Identity association 20

13. Selecting addresses for assignment to an IA 21

14. Management of temporary addresses 22

15. Reliability of Client Initiated Message Exchanges 23

16. Message validation 24
16.1. Use of Transaction-ID field . . . . . . . . . . . . . . . 25 24
16.2. Solicit message . . . . . . . . . . . . . . . . . . . . . 25
16.3. Advertise message . . . . . . . . . . . . . . . . . . . . 25
16.4. Request message . . . . . . . . . . . . . . . . . . . . . 25
16.5. Confirm message . . . . . . . . . . . . . . . . . . . . . 25
16.6. Renew message . . . . . . . . . . . . . . . . . . . . . . 26
16.7. Rebind message . . . . . . . . . . . . . . . . . . . . . 26
16.8. Decline messages . . . . . . . . . . . . . . . . . . . . 26
16.9. Release message . . . . . . . . . . . . . . . . . . . . . 26 27
16.10. Reply message . . . . . . . . . . . . . . . . . . . . . . 26 27
16.11. Reconfigure message . . . . . . . . . . . . . . . . . . . 27
16.12. Inform Information-request message . . . . . . . . . . . . . . . . . . . . . 27
16.13. Relay-forward message . . . . . . . . . . . . . . . . . . 27 28
16.14. Relay-reply message . . . . . . . . . . . . . . . . . . . 27 28

17. Client Source Address and Interface Selection 28

18. DHCP Server Solicitation 27
17.1. 28
18.1. Client Behavior . . . . . . . . . . . . . . . . . . . . . 27
17.1.1. 29
18.1.1. Creation of Solicit messages . . . . . . . . . . 28
17.1.2. 29
18.1.2. Transmission of Solicit Messages . . . . . . . . 28
17.1.3. 29
18.1.3. Receipt of Advertise messages . . . . . . . . . . 29
17.2. 30
18.2. Server Behavior . . . . . . . . . . . . . . . . . . . . . 30
17.2.1. 31
18.2.1. Receipt of Solicit messages . . . . . . . . . . . 30
17.2.2. 31
18.2.2. Creation and transmission of Advertise messages . 30

18. 31

19. DHCP Client-Initiated Configuration Exchange 31
18.1. 32
19.1. Client Behavior . . . . . . . . . . . . . . . . . . . . . 31
18.1.1. 33
19.1.1. Creation and transmission of Request messages . . 31
18.1.2. 33
19.1.2. Creation and transmission of Confirm messages . . 33
18.1.3. 34
19.1.3. Creation and transmission of Renew messages . . . 34
18.1.4. 35
19.1.4. Creation and transmission of Rebind messages . . 35
18.1.5. 37
19.1.5. Creation and Transmission of Inform Information-request
messages . . 36
18.1.6. . . . . . . . . . . . . . . . 38
19.1.6. Receipt of Reply message in response to a Request,
Confirm, Renew, Rebind or Inform Information-request
message . 37
18.1.7. . . . . . . . . . . . . . . . . 38
19.1.7. Creation and transmission of Release messages . . 39
18.1.8. 40

Droms (ed.), et al. Expires 1 Aug 2002 [Page iii]

Internet Draft DHCP for IPv6 (-23) 1 Feb 2002

19.1.8. Receipt of Reply message in response to a Release
message . . . . . . . . . . . . . . . . . 40
18.1.9. 41
19.1.9. Creation and transmission of Decline messages . . 40
18.1.10. 41
19.1.10. Receipt of Reply message in response to a Decline
message . . . . . . . . . . . . . . . . . 41
18.2. 42
19.2. Server Behavior . . . . . . . . . . . . . . . . . . . . . 41
18.2.1. 42
19.2.1. Receipt of Request messages . . . . . . . . . . . 41
18.2.2. 42
19.2.2. Receipt of Confirm messages . . . . . . . . . . . 42

Bound, Carney, Perkins, Droms (ed.) Expires 30 May 2002 [Page iii]

Internet Draft DHCP for IPv6 (-22) 21 Dec 2001

18.2.3. 43
19.2.3. Receipt of Renew messages . . . . . . . . . . . . 43
18.2.4. 44
19.2.4. Receipt of Rebind messages . . . . . . . . . . . 44
18.2.5. 45
19.2.5. Receipt of Inform Information-request messages . . . . . . . . . . . 45
18.2.6. 46
19.2.6. Receipt of Release messages . . . . . . . . . . . 45
18.2.7. 47
19.2.7. Receipt of Decline messages . . . . . . . . . . . 46
18.2.8. Receipt of Information-Request messages . . . . . 46
18.2.9. Sending 47
19.2.8. Transmission of Reply messages . . . . . . . . . . . . 46

19. 47

20. DHCP Server-Initiated Configuration Exchange 47
19.1. 48
20.1. Server Behavior . . . . . . . . . . . . . . . . . . . . . 47
19.1.1. 48
20.1.1. Creation and transmission of Reconfigure messages 47
19.1.2. 48
20.1.2. Time out and retransmission of Reconfigure
messages . . . . . . . . . . . . . . . . . 48
19.1.3. 49
20.1.3. Receipt of Renew messages . . . . . . . . . . . . 48
19.2. 49
20.2. Receipt of Information-request messages . . . . . . . . . 48
19.3. 49
20.3. Client Behavior . . . . . . . . . . . . . . . . . . . . . 49
19.3.1. 50
20.3.1. Receipt of Reconfigure messages . . . . . . . . . 49
19.3.2. 50
20.3.2. Creation and sending transmission of Renew messages . . . . . 50
19.3.3. 51
20.3.3. Creation and sending transmission of Renew Information-request
messages . . . . . 50
19.3.4. . . . . . . . . . . . . 51
20.3.4. Time out and retransmission of Renew or
Information-request messages . . . . . . . 50
19.3.5. 51
20.3.5. Receipt of Reply messages . . . . . . . . . . . . 50

20. 51

21. Relay Behavior 50
20.1. 52
21.1. Relaying of client messages . . . . . . . . . . . . . . . 50
20.2. 52
21.2. Relaying of server messages . . . . . . . . . . . . . . . 51

21. 52

22. Authentication of DHCP messages 51
21.1. 53
22.1. DHCP threat model . . . . . . . . . . . . . . . . . . . . 52
21.2. 53
22.2. Security of messages sent between servers and relay agents 52
21.3. 54
22.3. Summary of DHCP authentication . . . . . . . . . . . . . 52
21.4. 54
22.4. Replay detection . . . . . . . . . . . . . . . . . . . . 53
21.5. 54
22.5. Configuration token protocol . . . . . . . . . . . . . . 53
21.6. 54
22.6. Delayed authentication protocol . . . . . . . . . . . . . 54
21.6.1. 55
22.6.1. Management issues in the delayed authentication
protocol . . . . . . . . . . . . . . . . . 54
21.6.2. 55
22.6.2. Use of the Authentication option in the delayed
authentication protocol . . . . . . . . . 54
21.6.3. 55
22.6.3. Message validation . . . . . . . . . . . . . . . 55
21.6.4. 56
22.6.4. Key utilization . . . . . . . . . . . . . . . . . 55
21.6.5. 57
22.6.5. Client considerations for delayed authentication
protocol . . . . . . . . . . . . . . . . . 56
21.6.6. 57
22.6.6. Server considerations for delayed authentication
protocol . . . . . . . . . . . . . . . . . 58

22. 59

Droms (ed.), et al. Expires 1 Aug 2002 [Page iv]

Internet Draft DHCP for IPv6 (-23) 1 Feb 2002

23. DHCP options 58
22.1. 60
23.1. Format of DHCP options . . . . . . . . . . . . . . . . . 59
22.2. DHCP unique identifier 60
23.2. Client Identifier option . . . . . . . . . . . . . . 59
22.3. . . 60
23.3. Server Identifier option . . . . . . . . . . . . . . . . 61
23.4. Identity association option . . . . . . . . . . . . . . . 60
22.4. 61
23.5. IA Address option . . . . . . . . . . . . . . . . . . . . 62
22.5. 63
23.6. Requested Temporary Addresses (RTA) Option . . . . . . . 63
22.6. 65
23.7. Option request Request option . . . . . . . . . . . . . . . . . . 64
22.7. 65
23.8. Preference option . . . . . . . . . . . . . . . . . . . . 64

Bound, Carney, Perkins, Droms (ed.) Expires 30 May 2002 [Page iv]

Internet Draft DHCP for IPv6 (-22) 21 Dec 2001

22.8. 66
23.9. Elapsed Time . . . . . . . . . . . . . . . . . . . . . . 65
22.9. 67
23.10. Client message option . . . . . . . . . . . . . . . . . . 65
22.10. 67
23.11. Server message option . . . . . . . . . . . . . . . . . . 66
22.11. DSTM Global IPv4 Address Option . . . 68
23.12. Authentication option . . . . . . . . . . 66
22.12. DSTM Tunnel EndPoint Option . . . . . . . . 68
23.13. Server unicast option . . . . . . 67
22.13. Authentication option . . . . . . . . . . . . 69
23.14. Status Code Option . . . . . . 67
22.14. Server unicast option . . . . . . . . . . . . . 70
23.15. User Class Option . . . . . 68
22.15. Domain Search Option . . . . . . . . . . . . . . . 70
23.16. Vendor Class Option . . . 69
22.16. Domain Name Server Option . . . . . . . . . . . . . . . . 70
22.17. Status Code 71
23.17. Interface-Id Option . . . . . . . . . . . . . . . . . . . 70
22.18. Circuit-ID Option 72

24. Security Considerations 73

25. Year 2000 considerations 73

26. IANA Considerations 74
26.1. Multicast addresses . . . . . . . . . . . . . . . . . . . . 71
22.19. User Class Option . . . . . . . . . . . . . . . . . . . . 72
22.20. Vendor Class Option . . . . . . . . . . . . . . . . . . . 72
22.21. SIP Servers Domain Name List . . . . . . . . . . . . . . 74
22.22. SIP Servers IPv6 Address List . . . . . . . . . . . . . . 74

23. Security Considerations 75

24. Year 2000 considerations 75

25. IANA Considerations 75
25.1. Multicast addresses . . . . . . . . . . . . . . . . . . . 75
25.2.
26.2. DHCPv6 message types . . . . . . . . . . . . . . . . . . 75
25.3. 74
26.3. DUID . . . . . . . . . . . . . . . . . . . . . . . . . . 76
25.4. 74
26.4. DHCPv6 options . . . . . . . . . . . . . . . . . . . . . 76
25.5. 74
26.5. Status codes . . . . . . . . . . . . . . . . . . . . . . 76
25.6. 74
26.6. Authentication option . . . . . . . . . . . . . . . . . . 76

26. 75

27. Acknowledgments 76

A. Full Copyright Statement 75

References 75

Chair's Address 77

Authors' Addresses 77

A. Appearance of Options in Message Types 78

C. 79

B. Appearance of Options in the Options Field of DHCP Messages 79

References 79

Chair's Address 81

Authors' Addresses 82

C. Full Copyright Statement 80

1. Introduction

This document describes DHCP for IPv6 (DHCP), a UDP [20] [19]
client/server protocol designed to reduce the cost of management
of IPv6 nodes in environments where network managers require more
control over the allocation of IPv6 addresses and configuration
of network stack parameters than that offered by "IPv6 Stateless

Droms (ed.), et al. Expires 1 Aug 2002 [Page 1]

Internet Draft DHCP for IPv6 (-23) 1 Feb 2002

Address Autoconfiguration" [23]. [21]. DHCP is a stateful counterpart to
stateless autoconfiguration. Note that both stateful and stateless
autoconfiguration can be used concurrently in the same environment,

Bound, Carney, Perkins, Droms (ed.) Expires 30 May 2002 [Page 1]

Internet Draft DHCP for IPv6 (-22) 21 Dec 2001
leveraging the strengths of both mechanisms in order to reduce the
cost of ownership and management of network nodes.

DHCP reduces the cost of ownership by centralizing the management
of network resources such as IP addresses, routing information, OS
installation information, directory service information, and other
such information on a few DHCP servers, rather than distributing such
information in local configuration files among all network node.
DHCP is designed to be easily extended to carry new configuration
parameters through the addition of new DHCP "options" defined to
carry this information.

Those readers familiar with DHCP for IPv4 [8] [7] will find DHCP for
IPv6 provides a superset of the features of DHCP and benefits from
the additional features of IPv6 and freedom from the constraints of
backward compatibility with BOOTP [6]. [4].

2. Requirements

The keywords MUST, MUST NOT, REQUIRED, SHALL, SHALL NOT, SHOULD,
SHOULD NOT, RECOMMENDED, MAY, and OPTIONAL, when they appear in this
document, are to be interpreted as described in [4]. [2].

This document also makes use of internal conceptual variables
to describe protocol behavior and external variables that an
implementation must allow system administrators to change. The
specific variable names, how their values change, and how their
settings influence protocol behavior are provided to demonstrate
protocol behavior. An implementation is not required to have them in
the exact form described here, so long as its external behavior is
consistent with that described in this document.

3. Background

The IPv6 Specification provides the base architecture and design of
IPv6. Related work in IPv6 that would best serve an implementor
to study includes the IPv6 Specification [7], [5], the IPv6 Addressing
Architecture [10], [9], IPv6 Stateless Address Autoconfiguration [23], [21], IPv6
Neighbor Discovery Processing [18], [17], and Dynamic Updates to DNS [24]. [22].
These specifications enable DHCP to build upon the IPv6 work to
provide both robust stateful autoconfiguration and autoregistration
of DNS Host Names.

The IPv6 Addressing Architecture specification [10] [9] defines the
address scope that can be used in an IPv6 implementation, and the
various configuration architecture guidelines for network designers
of the IPv6 address space. Two advantages of IPv6 are that support
for multicast is required, and nodes can create link-local addresses

Droms (ed.), et al. Expires 1 Aug 2002 [Page 2]

Internet Draft DHCP for IPv6 (-23) 1 Feb 2002

during initialization. This means that a client can immediately use
its link-local address and a well-known multicast address to begin

Bound, Carney, Perkins, Droms (ed.) Expires 30 May 2002 [Page 2]

Internet Draft DHCP for IPv6 (-22) 21 Dec 2001
communications to discover neighbors on the link. For instance, a
client can send a Solicit message and locate a server or relay.

IPv6 Stateless Address Autoconfiguration [23] [21] specifies procedures
by which a node may autoconfigure addresses based on router
advertisements [18], [17], and the use of a valid lifetime to support
renumbering of addresses on the Internet. In addition the
protocol interaction by which a node begins stateless or stateful
autoconfiguration is specified. DHCP is one vehicle to perform
stateful autoconfiguration. Compatibility with stateless address
autoconfiguration is a design requirement of DHCP (see Section 4).

IPv6 Neighbor Discovery [18] [17] is the node discovery protocol in IPv6
which replaces and enhances functions of ARP [19]. [18]. To understand
IPv6 and stateless address autoconfiguration it is strongly
recommended that implementors understand IPv6 Neighbor Discovery.

Dynamic Updates to DNS [24] [22] is a specification that supports the
dynamic update of DNS records for both IPv4 and IPv6. DHCP can use
the dynamic updates to DNS to integrate addresses and name space to
not only support autoconfiguration, but also autoregistration in
IPv6.

4. Design Goals

- DHCP is a mechanism rather than a policy. Network administrators
set their administrative policies through the configuration
parameters they place upon the DHCP servers in the DHCP domain
they're managing. DHCP is simply used to deliver parameters
according to that policy to each of the DHCP clients within the
domain.

- DHCP is compatible with IPv6 stateless address
autoconfiguration [23], [21], statically configured, non-participating
nodes and with existing network protocol implementations.

- DHCP does not require manual configuration of network parameters
on DHCP clients, except in cases where such configuration is
needed for security reasons. A node configuring itself using
DHCP should require no user intervention.

- DHCP does not require a server on each link. To allow for scale
and economy, DHCP must work across DHCP relays.

- DHCP clients can operate on a link without IPv6 routers present.

- DHCP will provide the ability to renumber network(s) when
required by network administrators [5]. [3].

Droms (ed.), et al. Expires 1 Aug 2002 [Page 3]

Internet Draft DHCP for IPv6 (-23) 1 Feb 2002

- A DHCP client can make multiple, different requests for
configuration parameters when necessary from one or more DHCP
servers at any time.

Bound, Carney, Perkins, Droms (ed.) Expires 30 May 2002 [Page 3]

Internet Draft DHCP for IPv6 (-22) 21 Dec 2001

- DHCP will contain the appropriate time out and retransmission
mechanisms to efficiently operate in environments with high
latency and low bandwidth characteristics.

5. Non-Goals

This specification explicitly does not cover the following:

- Specification of a DHCP server to server protocol.

- How a DHCP server stores its DHCP data.

- How to manage a DHCP domain or DHCP server.

- How a DHCP relay is configured or what sort of information it may
log.

6. Terminology

This sections defines terminology specific to IPv6 and DHCP used in
this document.

6.1. IPv6 Terminology

IPv6 terminology relevant to this specification from the IPv6
Protocol [7], [5], IPv6 Addressing Architecture [10], [9], and IPv6 Stateless
Address Autoconfiguration [23] [21] is included below.

address An IP layer identifier for an interface
or a set of interfaces.

unicast address An identifier for a single interface.
A packet sent to a unicast address is
delivered to the interface identified by
that address.

multicast address An identifier for a set of interfaces
(typically belonging to different
nodes). A packet sent to a multicast
address is delivered to all interfaces
identified by that address.

host Any node that is not a router.

IP Internet Protocol Version 6 (IPv6). The
terms IPv4 and IPv6 are used only in

Droms (ed.), et al. Expires 1 Aug 2002 [Page 4]

Internet Draft DHCP for IPv6 (-23) 1 Feb 2002

contexts where it is necessary to avoid
ambiguity.

interface A node's attachment to a link.

Bound, Carney, Perkins, Droms (ed.) Expires 30 May 2002 [Page 4]

Internet Draft DHCP for IPv6 (-22) 21 Dec 2001

link A communication facility or medium over
which nodes can communicate at the link
layer, i.e., the layer immediately below
IP. Examples are Ethernet (simple or
bridged); Token Ring; PPP links, X.25,

Frame Relay, or ATM networks; and
Internet (or higher) layer "tunnels",
such as tunnels over IPv4 or IPv6
itself.

link-layer identifier A link-layer identifier for an
interface. Examples include IEEE 802
addresses for Ethernet or Token Ring
network interfaces, and E.164 addresses
for ISDN links.

link-local address An IPv6 address having link-only
scope, indicated by having the prefix
(FE80::0000/64), that can be used to
reach neighboring nodes attached to
the same link. Every interface has a
link-local address.

neighbor A node attached to the same link.

node A device that implements IP.

packet An IP header plus payload.

prefix The initial bits of an address, or a
set of IP address that share the same
initial bits.

prefix length The number of bits in a prefix.

router A node that forwards IP packets not
explicitly addressed to itself.

6.2. DHCP Terminology

Terminology specific to DHCP can be found below.

agent address The address of a neighboring DHCP Agent
on the same link as the DHCP client.

Droms (ed.), et al. Expires 1 Aug 2002 [Page 5]

Internet Draft DHCP for IPv6 (-23) 1 Feb 2002

binding A binding (or, client binding) is a
group of server data records containing
the information the server has about
the addresses in an IA and any other
configuration information assigned to

Bound, Carney, Perkins, Droms (ed.) Expires 30 May 2002 [Page 5]

Internet Draft DHCP for IPv6 (-22) 21 Dec 2001
the client. A binding is indexed by the
tuple <DUID, IAID>.

DHCP Dynamic Host Configuration Protocol
for IPv6. The terms DHCPv4 and DHCPv6
are used only in contexts where it is
necessary to avoid ambiguity.

configuration parameter An element of the configuration
information set on the server and
delivered to the client using DHCP.
Such parameters may be used to carry
information to be used by a node to
configure its network subsystem and
enable communication on a link or
internetwork, for example.

DHCP client (or client) A node that initiates requests on a link
to obtain configuration parameters from
one or more DHCP servers.

DHCP domain A set of links managed by DHCP and
operated by a single administrative
entity.

DHCP server (or server) A server is a node that responds to
requests from clients, and may or
may not be on the same link as the
client(s).

DHCP relay (or relay) A node that acts as an intermediary to
deliver DHCP messages between clients
and servers, and is on the same link as
a client.

DHCP agent (or agent) Either a DHCP server on the same link as
a client, or a DHCP relay.

DUID A DHCP Unique IDentifier for a client; DHCP
participant; each DHCP client and server
has exactly one DUID DUID.

Identity association (IA) A collection of addresses assigned to
a client. Each IA has an associated
IAID. An IA may have 0 or more addresses
associated with it.

Droms (ed.), et al. Expires 1 Aug 2002 [Page 6]

Internet Draft DHCP for IPv6 (-23) 1 Feb 2002

Identity association identifier (IAID) An identifier for an IA,
chosen by the client. Each IA has an
IAID, which is chosen to be unique among
all IAIDs for IAs belonging to that
client.

Bound, Carney, Perkins, Droms (ed.) Expires 30 May 2002 [Page 6]

Internet Draft DHCP for IPv6 (-22) 21 Dec 2001

message A unit of data carried in a packet,
exchanged between DHCP agents and
clients.

transaction-ID An unsigned integer to match responses
with replies initiated either by a
client or server.

7. DHCP Constants

This section describes various program and networking constants used
by DHCP.

7.1. Multicast Addresses

DHCP makes use of the following multicast addresses:

All_DHCP_Agents address: FF02::1:2 (FF02::1:2) This link-scoped multicast address
is used by clients to communicate with the
on-link agent(s) when they do not know the
link-local address(es) for those agents. All
agents (servers and relays) are members of this
multicast group.

All_DHCP_Servers address: FF05::1:3 (FF05::1:3) This site-scoped multicast address is
used by clients or relays to communicate with
server(s), either because they want to send
messages to all servers or because they do not
know the server(s) unicast address(es). Note
that in order for a client to use this address,
it must have an address of sufficient scope to
be reachable by the server(s). All servers
within the site are members of this multicast
group.

7.2. UDP ports

DHCP uses the following destination UDP [20] [19] port numbers. While
source ports MAY be arbitrary, client implementations SHOULD permit
their specification through a local configuration parameter to
facilitate the use of DHCP through firewalls.

546 Client port. Used by servers as the destination port
for messages sent to clients and relays. Used by relay

Droms (ed.), et al. Expires 1 Aug 2002 [Page 7]

Internet Draft DHCP for IPv6 (-23) 1 Feb 2002

agents as the destination port for messages sent to
clients.

547 Agent port. Used as the destination port by clients
for messages sent to agents. Used as the destination
port by relays for messages sent to servers.

Bound, Carney, Perkins, Droms (ed.) Expires 30 May 2002 [Page 7]

Internet Draft DHCP for IPv6 (-22) 21 Dec 2001

7.3. DHCP message types

DHCP defines the following message types. More detail on these
message types can be found in Section 8. Message types not listed
here are reserved for future use. The message code for each message
type is shown with the message name.

SOLICIT (1) The Solicit message is used by clients to
locate servers.

ADVERTISE (2) The Advertise message is used by servers
responding to Solicits.

REQUEST (3) The Request message is used by clients to
request configuration parameters from servers.

CONFIRM (4) The Confirm message is used by clients to
confirm that the addresses assigned to an IA
and the lifetimes for those addresses, as
well as the current configuration parameters
assigned by the server to the client are still
valid.

RENEW (5) The Renew message is used by clients to
update the addresses assigned to an IA and the
lifetimes for those addresses, as well as the
current configuration parameters assigned by
the server to the client. A client sends a
Renew message to the server that originally
populated the IA at time T1.

REBIND (6) The Rebind message is used by clients to extend
the lifetimes of addresses assigned to an IA,
as well as the current configuration parameters
assigned by the server to the client. A
client sends a Rebind message to all available
DHCP servers at time T2 only after the client
has been unable to contact the server that
originally populated the IA with a Renew
message.

REPLY (7) The Reply message is used by servers
responding to Request, Confirm, Renew, Rebind,
Information-request, Release and Decline
messages. In the case of responding to

Droms (ed.), et al. Expires 1 Aug 2002 [Page 8]

Internet Draft DHCP for IPv6 (-23) 1 Feb 2002

a Request, Confirm, Information-request,
Renew or Rebind message, the Reply contains
configuration parameters destined for the
client.

RELEASE (8) The Release message is used by clients to
indicate to a server that the client will no
longer use one or more addresses in an IA.

Bound, Carney, Perkins, Droms (ed.) Expires 30 May 2002 [Page 8]

Internet Draft DHCP for IPv6 (-22) 21 Dec 2001

DECLINE (9) The Decline message is used by clients to
indicate that the client has determined that
one or more addresses in an IA are already
in use on the link to which the client is
connected.

RECONFIGURE (10) The Reconfigure message is sent by server(s) a server
to inform client(s) a client that the server(s) server has new or
updated configuration parameters, and that
the client(s) are client is to initiate a Request/Reply Renew/Reply or
Information-request/Reply transaction with
the server(s) server in order to receive the updated
information.

INFORMATION-REQUEST (11) The Information-request message is sent
by clients to request configuration parameters
without the assignment of any IP addresses to
the client.

RELAY-FORW (12) The Relay-forward message is used by relays to
forward client messages to servers. The client
message is encapsulated in an option in the
Relay-forward message.

RELAY-REPL (13) The Relay-reply message is used by servers to
send messages to clients through a relay. The
server encapsulates the client message as an
option in the Relay-reply message, which the
relay extracts and forwards to the client.

7.4. Status Codes

This section describes status codes exchanged between DHCP
implementations. These status codes may appear in the Status Code
option or in the status field of an IA.

7.4.1. Generic Status Codes

The status codes in this section are used between clients and servers
to convey status conditions. The following table contains the status
codes, the name for each code (as used in this document) and a brief

Droms (ed.), et al. Expires 1 Aug 2002 [Page 9]

Internet Draft DHCP for IPv6 (-23) 1 Feb 2002

description. Note that the numeric values do not start at 1, nor are
they consecutive. The status codes are organized in logical groups.

Name Code Description
---------- ---- -----------
Success 0 Success
UnspecFail 16 Failure, reason unspecified
AuthFailed 17 Authentication failed or nonexistent
PoorlyFormed 18 Poorly formed message
AddrUnavail 19 Addresses unavailable
OptionUnavail 20 Requested options unavailable

Bound, Carney, Perkins, Droms (ed.) Expires 30 May 2002 [Page 9]

Internet Draft DHCP for IPv6 (-22) 21 Dec 2001

Bound, Carney, Perkins, Droms (ed.) Expires 30 May 2002 [Page 10]

Internet Draft DHCP for IPv6 (-22) 21 Dec 2001

7.4.2. Server-specific Status Codes

The status codes in this section are used by servers to convey status
conditions to clients. The following table contains the status
codes, the name for each code (as used in this document) and a brief
description. Note that the numeric values do not start at 1, nor are
they consecutive. The status codes are organized in logical groups.

Name Code Description
---- ---- -----------
NoBinding 32 Client record (binding) unavailable
ConfNoMatch 33 Client record Confirm doesn't match IA
RenwNoMatch 34 Client record Renew doesn't match IA
RebdNoMatch 35 Client record Rebind doesn't match IA
InvalidSource 36 Invalid Client IP address
NoPrefixMatch 37 One or more prefixes of the addresses
in the IA is not valid for the link
from which the client message was received

Droms (ed.), et al. Expires 1 Aug 2002 [Page 10]

Internet Draft DHCP for IPv6 (-23) 1 Feb 2002

7.5. Configuration Variables

This section presents a table of client and server configuration
variables and the default or initial values for these variables.

Parameter Default Description
-------------------------------------
MIN_SOL_DELAY 1 sec Min delay of first Solicit
MAX_SOL_DELAY 5 secs Max delay of first Solicit
SOL_TIMEOUT 500 msecs Initial Solicit timeout
SOL_MAX_RT 30 secs Max Solicit timeout value
REQ_TIMEOUT 250 msecs Initial Request timeout
REQ_MAX_RT 30 secs Max Request timeout value
REQ_MAX_RC 10 Max Request retry attempts
CNF_TIMEOUT 250 msecs Initial Confirm timeout
CNF_MAX_RT 1 sec Max Confirm timeout
CNF_MAX_RD 10 secs Max Confirm duration
REN_TIMEOUT 10 sec Initial Renew timeout
REN_MAX_RT 600 secs Max Renew timeout value
REB_TIMEOUT 10 secs Initial Rebind timeout
REB_MAX_RT 600 secs Max Rebind timeout value
INF_TIMEOUT 500 ms Initial Inform Information-request timeout
INF_MAX_RT 30 secs Max Inform Information-request timeout value
REL_TIMEOUT 250 msecs Initial Release timeout
REL_MAX_RT 1 sec Max Release timeout
REL_MAX_RC 5 MAX Release/Decline Release attempts
DEC_TIMEOUT 250 msecs Initial Release Decline timeout
DEC_MAX_RT 1 sec Max Release Decline timeout
DEC_MAX_RC 5 MAX Release/Decline Max Decline attempts

Bound, Carney, Perkins, Droms (ed.) Expires 30 May 2002 [Page 11]

Internet Draft DHCP for IPv6 (-22) 21 Dec 2001

8. Message Formats

All DHCP messages sent between clients and servers share an identical
fixed format header and a variable format area for options. Not all
fields in the header are used in every message.

All values in the message header and in options are in network order.

Droms (ed.), et al. Expires 1 Aug 2002 [Page 11]

Internet Draft DHCP for IPv6 (-23) 1 Feb 2002

The following diagram illustrates the format of DHCP messages sent
between clients and servers:

0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| msg-type | transaction-ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| server-address |
| (16 octets) |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
. options .
. (variable) .
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

The following sections describe the use of the fields in the DHCP
message header in each of the DHCP messages. In these descriptions,
fields that are not used in a message are marked as "unused". All
unused fields in a message MUST be transmitted as zeroes and ignored
by the receiver of the message.

8.1. DHCP Solicit Message Format

msg-type SOLICIT

transaction-ID An unsigned integer generated by the client used
to identify this Solicit message.

server-address (Unused) MUST be zero

options See section 22. 23.

8.2. DHCP Advertise Message Format

msg-type ADVERTISE

Bound, Carney, Perkins, Droms (ed.) Expires 30 May 2002 [Page 12]

Internet Draft DHCP for IPv6 (-22) 21 Dec 2001

transaction-ID An unsigned integer used to identify this
Advertise message. Copied from the Solicit
message received from the client.

server-address The IP address of the server that generated this
message. The address must have sufficient scope
to be reachable from the client.

options See section 22. 23.

8.3. DHCP Request Message Format

msg-type REQUEST

transaction-ID An unsigned integer generated by the client used
to identify this Request message.

server-address The IP address of the server to which this
message is directed, copied from an Advertise
message.

options See section 22. 23.

Droms (ed.), et al. Expires 1 Aug 2002 [Page 12]

Internet Draft DHCP for IPv6 (-23) 1 Feb 2002

8.4. DHCP Confirm Message Format

msg-type CONFIRM

transaction-ID An unsigned integer generated by the client used
to identify this Confirm message.

server-address MUST be zero.

options See section 22. 23.

8.5. DHCP Renew Message Format

msg-type RENEW

transaction-ID An unsigned integer generated by the client used
to identify this Renew message.

server-address The IP address of the server to which this Renew
message is directed, which MUST be the address
of the server from which the IAs in this message
were originally assigned.

options See section 22.

Bound, Carney, Perkins, Droms (ed.) Expires 30 May 2002 [Page 13]

Internet Draft DHCP for IPv6 (-22) 21 Dec 2001 23.

8.6. DHCP Rebind Message Format

msg-type REBIND

transaction-ID An unsigned integer generated by the client used
to identify this Rebind message.

server-address MUST be zero.

options See section 22. 23.

8.7. DHCP Reply Message Format

msg-type REPLY

transaction-ID An unsigned integer used to identify this
Reply message. Copied from the client Request,
Confirm, Renew or Rebind message received from
the client.

server-address The IP address of the server.

options See section 22. 23.

8.8. DHCP Release Message Format

msg-type RELEASE

transaction-ID An unsigned integer generated by the client used
to identify this Release message.

server-address The IP address of the server that assigned the
addresses.

options See section 22. 23.

Droms (ed.), et al. Expires 1 Aug 2002 [Page 13]

Internet Draft DHCP for IPv6 (-23) 1 Feb 2002

8.9. DHCP Decline Message Format

msg-type DECLINE

transaction-ID An unsigned integer generated by the client used
to identify this Decline message.

server-address The IP address of the server that assigned the
addresses.

options See section 22.

Bound, Carney, Perkins, Droms (ed.) Expires 30 May 2002 [Page 14]

Internet Draft DHCP for IPv6 (-22) 21 Dec 2001 23.

8.10. DHCP Reconfigure Message Format

msg-type RECONFIG

transaction-ID An unsigned integer generated by the server used
to identify this Reconfigure message.

server-address The IP address of the DHCP server issuing the
Reconfigure message. The address must have
sufficient scope to be reachable from the client.

options See section 22. 23.

8.11. Information-Request Message Format

msg-type INFORM INFORMATION-REQUEST

transaction-ID An unsigned integer generated by the client used
to identify this Inform Information-request message.

server-address Contains IP address of server to which this
message is directed, or 0 if any server may
respond.

options See section 22.

Bound, Carney, Perkins, Droms (ed.) Expires 30 May 2002 [Page 15]

Internet Draft DHCP for IPv6 (-22) 21 Dec 2001 23.

9. Relay messages

Relay agents exchange messages with servers to forward messages
between clients and servers that are not connected to the same link.

Droms (ed.), et al. Expires 1 Aug 2002 [Page 14]

Internet Draft DHCP for IPv6 (-23) 1 Feb 2002

There are two relay messages, which share the following format:

0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| msg-type | |
+-+-+-+-+-+-+-+-+ |
| link-address |
| |
| |
| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-|
| | |
+-+-+-+-+-+-+-+-+ |
| client-return-address |
| |
| |
| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-|
| | |
+-+-+-+-+-+-+-+-+ |
. .
. options (variable number and length) .... .
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

The following sections describe the use of the Relay message header.

9.1. Relay-forward message

The following table defines the use of message fields in a
Relay-forward message.

msg-type RELAY-FORW

link-address An address with a prefix that is assigned
to the link from which the client should
be assigned an address.

client-return-address The IPv6 source address in which the
message from the client was received by
the relay agent

options MUST include a "Client message option";
see section 22.9; 23.10; MAY include other
options added by the relay agent

Bound, Carney, Perkins,

Droms (ed.) (ed.), et al. Expires 30 May 1 Aug 2002 [Page 16] 15]

Internet Draft DHCP for IPv6 (-22) 21 Dec 2001 (-23) 1 Feb 2002

9.2. Relay-reply message

The following table defines the use of message fields in a
Relay-reply message.

msg-type RELAY-REPL

link-address The link-address copied from the
Relay-forward message; used by the relay
agent to select the link on which the
message is returned to the client

client-return-address The source address from the IP datagram
in which the message from the client was
received by the relay agent

options MUST include a "Server message option";
see section 22.10; 23.11; MAY include other
options

10. Representation and use of domain names

So that domain names may be encoded uniformly and compactly, a
domain name or a list of domain names is encoded using the technique
described in sections 3.1 and 4.1.4 of RFC1035 [15]. [14]. Section 4.1.4
of RFC1035 describes how more than one domain name can be represented
in a list of domain names. For use in this specification, in a
list of domain names, the compression pointer (see section 4.1.4 of
RFC1035) refers to the offset within the list.

If a single domain name is being used by a vendor as a vendor
identifier, then the vendor MUST ensure that the domain name has not
previously been used by a different vendor.

11. DHCP unique identifier (DUID)

Each DHCP client and server has a DUID. DHCP servers use DUIDs to
identify clients for the selection of configuration parameters and
in the association of IAs with clients. See section 22.2 for the
representation DHCP clients use DUIDs to
identify a server in messages where a server needs to be identified.
See sections 23.3 and 23.2 for the representation of a DUID in a DHCP
message.

Servers

Clients and servers MUST treat DUIDs as opaque values and MUST only
compare DUIDs for equality. Servers Clients and servers MUST NOT in any
other way interpret DUIDs.
Servers Clients and servers MUST NOT restrict
DUIDs to the types defined in this document as additional DUID types
may be defined in the future.

Droms (ed.), et al. Expires 1 Aug 2002 [Page 16]

Internet Draft DHCP for IPv6 (-23) 1 Feb 2002

The DUID is carried in an option because it may be variable length
and because it is not required in all DHCP options (e.g., messages
sent by servers need not include a DUID). options. The DUID is
designed to be unique across all DHCP clients, clients and servers, and
consistent for any specific

Bound, Carney, Perkins, Droms (ed.) Expires 30 May 2002 [Page 17]

Internet Draft DHCP for IPv6 (-22) 21 Dec 2001 client or server - that is, the DUID used
by a client or server SHOULD NOT change over time, for example, as a
result of network hardware reconfiguration.

The motivation for having more than one type of DUID is that the DUID
must be globally unique, and must also be easy to generate. The sort
of globally-unique identifier that is easy to generate for any given
device can differ quite widely. Also, some devices may not contain
any persistent storage. Retaining a generated DUID in such a device
is not possible, so the DUID scheme must accommodate such devices.

11.1. DUID contents

A DUID consists of a sixteen-bit type code represented in network
order, followed by a variable number of octets that make up the
actual identifier. A DUID can be no more than 256 octets long. The
following types are currently defined:

1 Link-layer address plus time
2 Vendor-assigned unique ID
3 Link-layer address

Formats for the variable field of the DUID for each of the above
types are shown below.

11.2. DUID based on link-layer address plus time

This type of DUID consists of four octets containing a time value,
followed by two octet type field containing the
value 1, a two octet network hardware type code, four octets containing
a time value, followed by link-layer address of any one network
interface that is connected to the DHCP client device at the time that the
DUID is generated. The time value is the time that the DUID is
generated represented in seconds since midnight (UTC), January 1,
2000, modulo 2^32. The hardware type MUST be a valid hardware type
assigned by the IANA as described in the section on ARP in RFC 826.
Both the time and the hardware type are stored in network order.

Droms (ed.), et al. Expires 1 Aug 2002 [Page 17]

Internet Draft DHCP for IPv6 (-23) 1 Feb 2002

The following diagram illustrates the format of a DUID based on
link-layer address plus time:

0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Time (32 bits) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1 | Hardware type (16 bits) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Time (32 bits) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. .
. link-layer address (variable length) .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Bound, Carney, Perkins, Droms (ed.) Expires 30 May 2002 [Page 18]

Internet Draft DHCP for IPv6 (-22) 21 Dec 2001

The choice of network interface can be completely arbitrary, as long
as that interface provides a unique link-layer address, and the same
DUID should be used in configuring all network interfaces connected
to the device, regardless of which interface's link-layer address was
used to generate the DUID.

DHCP clients

Clients and servers using this type of DUID MUST store the DUID
in stable storage, and MUST continue to use this DUID even if the
network interface used to generate the DUID is removed. DHCP clients Clients and
servers that do not have any stable storage MUST NOT use this type of
DUID.

DHCP clients

Clients and servers that use this DUID SHOULD attempt to configure
the time prior to generating the DUID, if that is possible, and MUST
use some sort of time source (e.g., a real-time clock) in generating
the DUID, even if that time source could not be configured prior to
generating the DUID. The use of a time source makes it unlikely that
two identical DUIDs will be generated if the network interface is
removed from the client and another client then uses the same network
interface to generate a DUID. A DUID collision is very unlikely even
if the clocks haven't been configured prior to generating the DUID.

This method of DUID generation is recommended for all general purpose
computing devices such as desktop computers and laptop computers, and
also for devices such as printers, routers, and so on, that contain
some form of writable non-volatile storage.

11.3. Vendor-assigned unique ID (VUID)

The vendor-assigned unique ID consists of an eight-octet
vendor-unique a two-octet value giving
the length of the identifier, followed by the value of the idnetifier and the
vendor's registered domain name.

Droms (ed.), et al. Expires 1 Aug 2002 [Page 18]

Internet Draft DHCP for IPv6 (-23) 1 Feb 2002

The following diagram summarizes the structure of a VUID:

0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| VUID (64 bits) | 2 | identifier length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. .
. identifier .
. (variable length) .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. .
. domain name (variable length) .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

The structure source of the VUID identifier is left up to the vendor defining it,
but each device containing such a identifier part of each VUID MUST be unique to each the device
that is using it, and MUST be assigned to the device at the time of
manufacture and stored in some form of non-volatile storage. The
VUID SHOULD be recorded in non-erasable storage. The domain name
is simply any domain name that has been legally registered by the
vendor in the domain name system [14], [13], stored in the form described
in section 10.

Bound, Carney, Perkins, Droms (ed.) Expires 30 May 2002 [Page 19]

Internet Draft DHCP for IPv6 (-22) 21 Dec 2001

An example DUID of this type might look like this:

+--+---+---+---+-+-+-+--+---+---+--+---+---+---+---+--+--+---+---+
|12|192|132|221|3|0|9|18|101|120|97|109|112|108|101|46|99|111|109|
+--+---+---+---+-+-+-+--+---+---+--+---+---+---+---+--+--+---+---+

This is eight octets of VUID data, followed by

+---+---+---+---+---+---+---+---+
| 0 | 2 | 0 | 8 | 12|192|132|221|
+---+---+---+---+---+---+---+---+
| 3 | 0 | 9 | 18|101|120| 97|109|
+---+---+---+---+---+---+---+---+
|112|108|101| 46| 99|111|109|
+---+---+---+---+---+---+---+

This example includes the two-octet type of 2, the two-octet length
of 8, eight octets of identifier data, followed by "example.com"
represented in ASCII.

11.4. Link-layer address

This type of DUID consists of two octets containing the DUID type 3,
a two octet network hardware type code, followed by the link-layer
address of any one network interface that is permanently connected
to the DHCP client or server device and cannot be removed. The hardware
type MUST be a valid hardware type assigned by the IANA as described
in the section on ARP in RFC 826. The hardware type is stored in
network order.

Droms (ed.), et al. Expires 1 Aug 2002 [Page 19]

Internet Draft DHCP for IPv6 (-23) 1 Feb 2002

The following diagram illustrates the format of a DUID based on
link-layer address:

0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 3 | Hardware type (16 bits) | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. .
. link-layer address (variable length) .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

The choice of network interface can be completely arbitrary, as
long as that interface provides a unique link-layer address and
is permanently attached to the device on which the DUID is being
generated. The same DUID should be used in configuring all network
interfaces connected to the device, regardless of which interface's
link-layer address was used to generate the DUID.

This type of DUID is recommended for devices that have a
permanently-connected network interface with a link-layer address and
do not have nonvolatile, writable stable storage. This type of DUID
MUST NOT be used by DHCP clients or servers that cannot tell whether
or not a network interface is permanently attached to the device on
which the DHCP client is running.

12. Identity association

An "identity-association" (IA) is a construct through which a server
and a client can identify, group and manage IPv6 addresses. Each IA
consists of an IAID and associated configuration information.

Bound, Carney, Perkins, Droms (ed.) Expires 30 May 2002 [Page 20]

Internet Draft DHCP for IPv6 (-22) 21 Dec 2001

A client must associate at least one distinct IA with each of
its network interfaces and uses that IA to obtain configuration
information from a server for that interface. Other distinct IAs may
be associated with applications. Each IA must be associated with
exactly one interface.

The IAID uniquely identifies the IA and must be chosen to be unique
among the IAIDs on the client. The IAID is chosen by the client.
For any given use of an IA by the client, the IAID for that IA MUST
be consistent across restarts of the DHCP client. The client may
maintain consistency either by storing the IAID in non-volatile
storage or by using an algorithm that will consistently produce the
same IAID as long as the configuration of the client has not changed.
There may be no way for a client to maintain consistency of the IAIDs
if it does not have non-volatile storage and the client's hardware
configuration changes.

Droms (ed.), et al. Expires 1 Aug 2002 [Page 20]

Internet Draft DHCP for IPv6 (-23) 1 Feb 2002

The configuration information in an IA consists of one or more IPv6
addresses and other parameters. The parameters are specified as DHCP
options within the IA, and are associated with the addresses in the
IA and the interface to which the IA belongs. Other parameters that
are not associated with a particular interface may be specified in
the options section of a DHCP message, outside the scope of any IA.

Each address in an IA has a preferred lifetime and a valid lifetime,
as defined in RFC2462 [23]. [21]. The lifetimes are transmitted from the
DHCP server to the client in the IA option. The lifetimes apply to
the use of IPv6 addresses as described in section 5.5.4 of RFC2462.
An address whose valid lifetime has expired MAY be discarded from the
IA.

See section 22.3 23.4 for the representation of an IA in a DHCP message.

13. Selecting addresses for assignment to an IA

A server selects addresses to be assigned to an IA according to the
address assignment policies determined by the server administrator
and the specific information the server determines about the client
from the following sources:

- The link to which the client is attached: attached. The server determines
the link as follows:

* If the server receives the message directly from the client
and the source address in the IP datagram in which the
message was received is a link-local address, then the client
is on the same link to which the interface over which the
message was received is attached

* If the server receives the message directly from the client
and the source address in the IP datagram in which the
message was received is not a link-local address, then the

Bound, Carney, Perkins, Droms (ed.) Expires 30 May 2002 [Page 21]

Internet Draft DHCP for IPv6 (-22) 21 Dec 2001

client is on the link identified by the source address in the
IP datagram

* If the server receives the message from a forwarding relay
agent, then the client is on the same link as the one to
which the interface identified by the link-address field in
the message from the relay is attached

- The DUID supplied by the client

- Other information in options supplied by the client

- Other information in options supplied by the relay agent

The addresses that

- If the server selects for receives the message directly from the client MUST be valid on and
the link to source address in the IP datagram in which the interface message was
received is attached, regardless of not a link-local address, then the way client is on the
link identified by the source address in
which the IP datagram (note
that this situation can occur only if the server selects has enabled the addresses.

14. Management
use of temporary addresses

A unicast message delivery by the client may be assigned temporary addresses [17]. Clients and
servers simply label addresses as "temporary". DHCPv6 handling
of the client has
sent a message for which unicast delivery is allowed)

Droms (ed.), et al. Expires 1 Aug 2002 [Page 21]

Internet Draft DHCP for IPv6 (-23) 1 Feb 2002

The addresses that the server selects for the client MUST be valid on
the link to which the interface is attached, regardless of the way in
which the server selects the addresses.

14. Management of temporary addresses

A client may be assigned temporary addresses [16]. Clients and
servers simply label addresses as "temporary". DHCPv6 handling
of address lifetimes and lifetime extensions is no different for
temporary addresses. DHCPv6 says nothing about details of temporary
addresses like lifetimes, lifetime extensions, how clients use
temporary addresses, rules for generating successive temporary
addresses, etc.

In DHCP, temporary addresses are identified with T-bit set in the IA
Address Option(see section 22.4). 23.5). A client may have zero or more
temporary addresses. Addresses with the T-bit set MUST be intended
for the client to use for the general purposes described in RFC3041.
Addresses that otherwise have short lifetimes or are not intended to
be renewed by the server MUST NOT have the T-bit set.

Clients ask for temporary addresses and servers assign them. When
a client sends an IA to a server, the client lists all of the
temporary addresses it knows about and optionally indicates how many
additional temporary addresses it wants in the Requested Temporary
Addresses
Option 22.5. Option(see section 23.6). The server compares the number
of requested additional temporary addresses against any previously
allocated temporary addresses for the IA that were not reported
by the client in the IA but still have some reasonable preferred
lifetime left. If the number of temporary addresses is less than the
requested number, the server adds additional temporary addresses to
the IA to satisfy the requested number (subject to server policy).

DISCUSSION:

It is important that the server include any allocated
temporary addresses that were not reported by the client as
it is possible the client never received an earlier Reply

Bound, Carney, Perkins, Droms (ed.) Expires 30 May 2002 [Page 22]

Internet Draft DHCP for IPv6 (-22) 21 Dec 2001
that contained these additional temporary addresses. If
the server did not consider these, a client that fails to
receive a server's reply might cause the server to allocate
many temporary addresses.

When the valid lifetime on a temporary address expires, both the
client and server silently discard the address from the IA. The
discarded address no longer counts against the client's allotment of
temporary addresses.

A server SHOULD NOT assign a client temporary addresses without the
client having specifically asked for it. The client is not obligated
to install address(es) that it receives and did not request and can
release any addresses it does not want.

Droms (ed.), et al. Expires 1 Aug 2002 [Page 22]

Internet Draft DHCP for IPv6 (-23) 1 Feb 2002

The server MAY update the DNS for a temporary address as described in
section 4 of RFC3041, and MUST NOT update the DNS in any other way
for a temporary address.

15. Reliability of Client Initiated Message Exchanges

DHCP clients are responsible for reliable delivery of messages in the
client-initiated message exchanges described in sections 17 18 and 18. 19.
If a DHCP client fails to receive an expected response from a server,
the client must retransmit its message. This section describes the
retransmission strategy to be used by clients in client-initiated
message exchanges.

Note that the procedure described in this section is slightly
modified for use with the Solicit message (section 17.1.2). 18.1.2).

The client begins the message exchange by transmitting a message to
the server. The message exchange terminates when either the client
successfully receives the appropriate response or responses from a
server or servers, or when the message exchange is considered to have
failed according to the retransmission mechanism described below.

The client retransmission behavior is controlled and described by the
following variables:

RT Retransmission timeout

IRT Initial retransmission time

MRC Maximum retransmission count

MRT Maximum retransmission time

MRD Maximum retransmission duration

RAND Randomization factor

Bound, Carney, Perkins, Droms (ed.) Expires 30 May 2002 [Page 23]

Internet Draft DHCP for IPv6 (-22) 21 Dec 2001

With each message transmission or retransmission, the client sets RT
according to the rules given below. If RT expires before the message
exchange terminates, the client recomputes RT and retransmits the
message.

Each of the computations of a new RT include a randomization factor
(RAND), which is a random number chosen with a uniform distribution
between -0.1 and +0.1. The randomization factor is included to
minimize synchronization of messages transmitted by DHCP clients.
The algorithm for choosing a random number does not need to be
cryptographically sound. The algorithm SHOULD produce a different
sequence of numbers from each invocation of the DHCP client.

RT for the first message transmission is based on IRT:

Droms (ed.), et al. Expires 1 Aug 2002 [Page 23]

Internet Draft DHCP for IPv6 (-23) 1 Feb 2002

RT = 2*IRT + RAND*IRT

RT for each subsequent message transmission is based on the previous
value of RT:

RT = 2*RTprev + RAND*RTprev

MRT specifies an upper bound on the value of RT. If MRT has a value
of 0, there is no upper limit on the value of RT. Otherwise:

if (RT > MRT)
RT = MRT + RAND*MRT

MRC specifies an upper bound on the number of times a client may
retransmit a message. If MRC has a value of 0, the client MUST
continue to retransmit the original message until a response is
received. Otherwise, the message exchange fails once the client has
transmitted the message MRC times.

MRD specifies an upper bound on the length of time a client may
retransmit a message. If MRD has a value of 0, the client MUST
continue to retransmit the original message until a response is
received. Otherwise, the message exchange fails once the client has
transmitted the message MRD seconds.

If both MRC and MRD are non-zero, the message exchange fails whenever
either of the conditions specified in the previous two paragraphs are
met.

16. Message validation

Servers MUST discard any received messages that include
authentication information and fail the authentication check by the
server.

Bound, Carney, Perkins, Droms (ed.) Expires 30 May 2002 [Page 24]

Internet Draft DHCP for IPv6 (-22) 21 Dec 2001

Clients MUST discard any received messages that include
authentication information and fail the authentication check by the
client, except as noted in section 21.6.5.2. 22.6.5.2.

16.1. Use of Transaction-ID field

The "transaction-ID" field holds a value used by clients and servers
to synchronize server responses to client messages. A client SHOULD
choose a different transaction-ID for each new message it sends. A
client MUST leave the transaction-ID unchanged in retransmissions of
a message.

Droms (ed.), et al. Expires 1 Aug 2002 [Page 24]

Internet Draft DHCP for IPv6 (-23) 1 Feb 2002

16.2. Solicit message

Clients MUST discard any received Solicit messages.

Relay agents MUST discard any Solicit messages received through port
546.

Servers MUST discard any Solicit messages that do not include a
Client Identifier option.

16.3. Advertise message

Clients MUST discard any received Advertise messages in which that meet any of
the following conditions:

- the message does not include a Server Identifier option

- the message does not include a Client Identifier option

- the contents of the Client Identifier option does not match the
client's DUID

- the "Transaction-ID" field value does not match the value the
client used in its Solicit message. message

Servers and relay agents MUST discard any received Advertise
messages.

16.4. Request message

Clients MUST discard any received Request messages.

Relay agents MUST discard any Request messages received through port
546.

Servers MUST discard any received Request message in which that meet any of
the value
in following conditions:

- the "server-address" field message does not match any include a Server Identifier option

- the contents of the addresses
used by Server Identifier option do not match the
server's identifier

- the server.

16.5. Confirm message

Clients MUST discard any received does not include a Client Identifier option

16.5. Confirm messages.

Relay agents message

Clients MUST discard any Confirm messages received through port
546.

Bound, Carney, Perkins, Confirm messages.

Droms (ed.) (ed.), et al. Expires 30 May 1 Aug 2002 [Page 25]

Internet Draft DHCP for IPv6 (-22) 21 Dec 2001 (-23) 1 Feb 2002

Relay agents MUST discard any Confirm messages received through port
546.

Servers MUST discard any Confirm messages received that do not
include a Client Identifier option.

16.6. Renew message

Clients MUST discard any received Renew messages.

Relay agents MUST discard any Renew messages received through port
546.

Servers MUST discard any received Renew message in which that meets any of the value in
following conditions:

- the "server-address" field message does not match any include a Server Identifier option

- the contents of the addresses used
by Server Identifier option do not match the server.
server's identifier

- the message does not include a Client Identifier option

16.7. Rebind message

Clients MUST discard any received Rebind messages.

Relay agents MUST discard any Rebind messages received through port
546.

Servers MUST discard any received Rebind message that does not
include a Client Identifier option.

16.8. Decline messages

Clients MUST discard any received Decline messages.

Relay agents MUST discard any Decline messages received through port
546.

Servers MUST discard any received Decline message in which that meets any of
the value
in following conditions:

- the "server-address" field message does not match any include a Server Identifier option

- the contents of the addresses
used by Server Identifier option do not match the server.
server's identifier

- the message does not include a Client Identifier option

Droms (ed.), et al. Expires 1 Aug 2002 [Page 26]

Internet Draft DHCP for IPv6 (-23) 1 Feb 2002

16.9. Release message

Clients MUST discard any received Release messages.

Relay agents MUST discard any Release messages received through port
546.

Servers MUST discard any received Release

- the message in which does not include a Server Identifier option

- the value
in contents of the "server-address" field does Server Identifier option do not match any of the addresses
used by
server's identifier

- the server. message does not include a Client Identifier option

16.10. Reply message

Clients MUST discard any received Reply messages in which that meet any of the
following conditions:

- the message does not include a Server Identifier option

- the "transaction-ID" field in the message does not match the
value used in the original message. message

- the message does not include a Client Identifier option

- the contents of the Client Identifier option does not match the
DUID of the client

Servers and relay agents MUST discard any received Reply messages.

Bound, Carney, Perkins, Droms (ed.) Expires 30 May 2002 [Page 26]

Internet Draft DHCP for IPv6 (-22) 21 Dec 2001

16.11. Reconfigure message

Servers and relay agents MUST discard any received Reconfigure
messages.

Clients MUST discard any Reconfigure messages that do not meet any of the
following conditions:

- the message does not include a Server Identifier option

- the message does not contain an authentication option or that fail

- the message fails the authentication validation performed by the client.
client

16.12. Inform Information-request message

Clients MUST discard any received Inform Information-request messages.

Droms (ed.), et al. Expires 1 Aug 2002 [Page 27]

Internet Draft DHCP for IPv6 (-23) 1 Feb 2002

Relay agents MUST discard any Inform Information-request messages received
through port 546.

Servers MAY choose to discard any received Information-request
messages that do not include a Client Identifier option.

Servers MUST discard any received Information-request message that
includes a Server Identifier option and the DUID in the option does
not match the server's DUID.

16.13. Relay-forward message

Clients MUST discard any received Relay-forward messages.

16.14. Relay-reply message

Clients and servers MUST discard any received Relay-reply messages.

17. Client Source Address and Interface Selection

When a client sends a DHCP message to the All_DHCP_Agents multicast
address, it MUST use the IPv6 link-local address assigned to
the interface for which the client is interested in obtaining
configuration as the source address in the header of the IP datagram.

When a client sends a DHCP message directly to a server using unicast
(after receiving the Server Unicast option from that server), it
MUST use an address assigned to the interafce for which the client
is interested in obtaining configuration, which is suitable for use
by the server in responding to the client, as the source address in
the header of the IP datagram. See "Default Address Selection for
IPv6" [6] for more details.

The client MUST transmit the message on the link that the interface
for which configuration information is being obtained is attached
to. The client SHOULD send the message through that interface. The
client MAY send the message through another interface attached to the
same link if and only if the client is certain the two interface are
attached to the same link.

18. DHCP Server Solicitation

This section describes how a client locates servers that will assign
addresses to IAs belonging to the client.

The client is responsible for creating IAs and requesting that a
server assign configuration information, including IPv6 addresses,
to the IA. The client first creates an IA and assigns it an IAID.
The client then transmits a Solicit message containing an IA option

Droms (ed.), et al. Expires 1 Aug 2002 [Page 28]

Internet Draft DHCP for IPv6 (-23) 1 Feb 2002

describing the IA. Servers that can assign configuration information
to the IA respond to the client with an Advertise message. The
client then initiates a configuration exchange as described in
section 18.

17.1. 19.

18.1. Client Behavior

A client uses the Solicit message to discover DHCP servers configured
to serve addresses on the link to which the client is attached.

Bound, Carney, Perkins, Droms (ed.) Expires 30 May 2002 [Page 27]

Internet Draft DHCP for IPv6 (-22) 21 Dec 2001

17.1.1.

18.1.1. Creation of Solicit messages

The client sets the "msg-type" field to SOLICIT. The client generates
a transaction ID and inserts this value in the "transaction-ID"
field.

The client MUST include a DUID Client Identifier option to identify itself
to the server. The client MUST include one or more IA options for
any IAs to which it wants the server to assign addresses. The client
MAY include addresses in the IAs as a hint to the server about
addresses for which the client has a preference. The client MAY
include an Option Request Option in the Solicit message. The client
MUST NOT include any other options except those specifically allowed
as defined by specific options.

17.1.2. Transmission of Solicit Messages

The client sends the Solicit message to

If the All_DHCP_Agents
multicast address. The client MUST use an IPv6 address assigned chooses to request specific options from the interface for server,
it does so by including an Option Request option (see section 23.7,
which the client is interested in obtaining
configuration information as the source address in the IP header of
the datagram carrying the Solicit message.

The Solicit message MUST be transmitted on include all of the link that options the
interface for which configuration information is being obtained
is attached to. The client SHOULD send the message through that
interface. is requesting. The
client MAY send the message through another interface
attached include options with data values as hints to the same link if and only if server
about parameter values the client is certain would like to have returned.

18.1.2. Transmission of Solicit Messages

The client sends the
two interface are attached Solicit message to the same link. All_DHCP_Agents multicast
address.

The first Solicit message from the client on the interface MUST
be delayed by a random amount of time between MIN_SOL_DELAY and
MAX_SOL_DELAY. This random delay desynchronizes clients which start
at the same time (e.g., after a power outage).

Droms (ed.), et al. Expires 1 Aug 2002 [Page 29]

Internet Draft DHCP for IPv6 (-23) 1 Feb 2002

The client transmits the message according to section 15, using the
following parameters:

IRT SOL_TIMEOUT

MRT SOL_MAX_RT

MRC 0

MRD 0

The mechanism in section 15 is modified as follows for use in the
transmission of Solicit messages. The message exchange is not
terminated by the receipt of an Advertise before SOL_TIMEOUT IRT has elapsed.
Rather, the client collects Advertise messages until
SOL_TIMEOUT IRT has elapsed.
Also, the first RT MUST be selected to be

Bound, Carney, Perkins, Droms (ed.) Expires 30 May 2002 [Page 28]

Internet Draft DHCP for IPv6 (-22) 21 Dec 2001 strictly greater than SOL_TIMEOUT IRT
by choosing RAND to be strictly greater than 0.

A client MUST collect Advertise messages for SOL_TIMEOUT IRT seconds, unless
it receives an Advertise message with a preference value of 255.
The preference value is carried in the Preference option (section 22.7).
23.8). Any Solicit that does not include a Preference option is
considered to have a preference value of 0. If the client receives
an Advertise message with a preference value of 255, then the client
MAY act immediately on that Advertise message without waiting for any
additional Advertise messages.

A DHCP client SHOULD choose MRC and MRD to be 0.

If the DHCP client
is configured with either MRC or MRD set to a value other than
0, does not receive any Advertise messages before IRT
has elapsed, it MUST stop trying to configure the interface if begins the message
exchange fails. retransmission mechanism described in
section 15. The client terminates the retransmission process as
soon as it recieves any Advertise message, and the client acts on
the received Advertise message without waiting for any additional
Advertise messages.

A DHCP client SHOULD choose MRC and MRD to be 0. If the DHCP client
is configured with either MRC or MRD set to a value other than
0, it MUST stop trying to configure the interface if the message
exchange fails. After the DHCP client stops trying to configure the
interface, it SHOULD choose to restart the reconfiguration process
after some external event, such as user input, system restart, or
when the client is attached to a new link.

17.1.3.

18.1.3. Receipt of Advertise messages

The client MUST ignore any Advertise message that includes a Status
Code option containing the value AddrUnavail, with the exception that
the client MAY display the associated status message to the user.

Droms (ed.), et al. Expires 1 Aug 2002 [Page 30]

Internet Draft DHCP for IPv6 (-23) 1 Feb 2002

Upon receipt of one or more valid Advertise messages, the client
selects one or more Advertise messages based upon the following
criteria.

- Those Advertise messages with the highest server preference value
are preferred over all other Advertise messages.

- Within a group of Advertise messages with the same server
preference value, a client MAY select those servers whose
Advertise messages advertise information of interest to the
client. For example, the client may choose a server that
returned an advertisement with configuration options of interest
to the client.

- The client MAY choose a less-preferred server if that server has
a better set of advertised parameters, such as the available
addresses advertised in IAs.

Once a client has selected Advertise message(s), the client will
typically store information about each server, such as server
preference value, addresses advertised, when the advertisement was
received, and so on. Depending on the requirements of the user that
invoked the DHCP client, the client MAY initiate a configuration
exchange with the server(s) immediately, or MAY defer this exchange
until later.

Bound, Carney, Perkins, Droms (ed.) Expires 30 May 2002 [Page 29]

Internet Draft DHCP for IPv6 (-22) 21 Dec 2001

If the client needs to select an alternate server in the case that a
chosen server does not respond, the client chooses the next server
according to the criteria given above.

17.2.

18.2. Server Behavior

A server sends an Advertise message in response to Solicit messages
it receives to announce the availability of the server to the client.

17.2.1.

18.2.1. Receipt of Solicit messages

The server determines the information about the client and its
location as described in section 13. If administrative policy
permits the server to respond to the client, the server will generate
and send an Advertise message to the client.

17.2.2.

18.2.2. Creation and transmission of Advertise messages

The server sets the "msg-type" field to ADVERTISE and copies the
contents of the transaction-ID field from the Solicit message
received from the client to the Advertise message. The server
places one of
includes its IP addresses in the "server-address" field of the
Advertise message. The administrator must be able to configure the
address used server identifier in the "server-address" field. a Server Identifier option.

Droms (ed.), et al. Expires 1 Aug 2002 [Page 31]

Internet Draft DHCP for IPv6 (-23) 1 Feb 2002

The server MAY add a Preference option to carry the preference value
for the Advertise message. The server implementation SHOULD allow
the setting of a server preference value by the administrator.
The server preference value MUST default to zero unless otherwise
configured by the server administrator.

The server MUST include IA options in the Advertise message
containing any addresses that would be assigned to IAs contained in
the Solicit message from the client. The server MAY include some or
all of the IA options from the client in the Advertise message.

If the server will not assign any addresses to IAs in a subsequent
Request from the client, the server SHOULD either send an Advertise
message to the client that includes only a status code option with
the status code set to AddrUnavail and a status message for the user
or not respond to the Solicit message.

The server may choose to assign fewer temporary addresses than
the client requested with an RTA option (see section 23.6) and
includes a status code of Success in the IA. If the server will
assign no temporary addresses, the server includes a status code of
AddrUnavail.

The server MAY include other options the server will return to the
client in a subsequent Reply message. The information in these
options will be used by the client in the selection of a server if
the client receives more than one Advertise message. The server
SHOULD include options specifying values for options requested by the
client in an Option Request Option included in the Solicit message.

Bound, Carney, Perkins, Droms (ed.) Expires 30 May 2002 [Page 30]

Internet Draft DHCP for IPv6 (-22) 21 Dec 2001

If the Solicit message was received directly by the server, the
server unicasts the Advertise message directly to the client using
the address in the source address field from the IP datagram in
which the Solicit message was received. The Advertise message MUST
be unicast through the interface on which the Solicit message was
received.

If the Solicit message was received in a Relay-forward message,
the server constructs a Relay-reply message with the Advertise
message in the payload of a "server-message" option. The server
unicasts the Relay-reply message directly to the relay agent using
the address in the source address field from the IP datagram in which
the Relay-forward message was received.

18.

19. DHCP Client-Initiated Configuration Exchange

A client initiates a message exchange with a server or servers to
acquire or update configuration information of interest. The client
may initiate the configuration exchange as part of the operating
system configuration process or when requested to do so by the
application layer.

18.1.

Droms (ed.), et al. Expires 1 Aug 2002 [Page 32]

Internet Draft DHCP for IPv6 (-23) 1 Feb 2002

19.1. Client Behavior

A client will use Request, Confirm, Renew, Rebind and Inform
Information-request messages to acquire and confirm the
validity of configuration information. The client uses the server address
identifier information and information about IAs from previous
Advertise messages for use in constructing Request messages. Note
that a client may request configuration information from one or more
servers at any time.

18.1.1.

19.1.1. Creation and transmission of Request messages

The client uses a Request message to populate IAs with addresses
and obtain other configuration information. The client includes
one or more IA options in the Request message, with addresses and
information about the IAs that were obtained from the server in a
previous Advertise message. The server then returns addresses and
other information about the IAs to the client in IA options in a
Reply message.

The client generates a transaction ID and inserts this value in the
"transaction-ID" field.

The client places the address identifier of the destination server in the
"server-address" field. a
Server Identifier option.

The client MUST include a DUID Client Identifier option to identify itself
to the server. The client adds any other appropriate options,
including one or more IA options (if the client is requesting that
the server

Bound, Carney, Perkins, Droms (ed.) Expires 30 May 2002 [Page 31]

Internet Draft DHCP for IPv6 (-22) 21 Dec 2001 assign it some network addresses). The list of addresses
in each included IA MUST include the addresses received by the client
in a previous Advertise message.

If the client has a source address of sufficient scope that chooses to request specific options from the server,
it does so by including an Option Request option (see section 23.7,
which MUST include all of the options the client is requesting. The
client MAY include options with data values as hints to the server
about parameter values the client would like to have returned.

If the client has a source address of sufficient scope that can be
used by the server as a return address and the client has received
a Server Unicast option (section 22.14) 23.13) from the server, the client
SHOULD unicast the Request message to the server. Otherwise, the
client MUST send the Request message to the All_DHCP_Agents multicast
address. The client MUST use an address assigned to the interface
for which the client is interested in obtaining configuration
information as the source address in the IP header of the datagram
carrying the Request message.

DISCUSSION:

Use of multicast and relay agents enables the inclusion of
relay agent options in all messages sent by the client. The
server should enable the use of unicast only when relay
agent options will not be used.

If the client multicasts the Request message, the message MUST be
transmitted on the link that the interface

Droms (ed.), et al. Expires 1 Aug 2002 [Page 33]

Internet Draft DHCP for which configuration
information is being obtained is attached to. The client SHOULD send
the message through that interface. The client MAY send the message
through another interface attached to the same link if and only if
the client is certain the the two interface are attached to the same
link. IPv6 (-23) 1 Feb 2002

The client transmits the message according to section 15, using the
following parameters:

IRT REQ_TIMEOUT

MRT REQ_MAX_RT

MRC REQ_MAX_RC

MRD 0

If the message exchange fails, the client MAY choose one of the
following actions:

- Select another server from a list of servers known to the client;
e. g., servers that responded with an Advertise message

- Initiate the server discovery process described in section 17 18

- Terminate the configuration process and report failure

Bound, Carney, Perkins, Droms (ed.) Expires 30 May 2002 [Page 32]

Internet Draft DHCP for IPv6 (-22) 21 Dec 2001

18.1.2.

19.1.2. Creation and transmission of Confirm messages

Whenever a client may have moved to a new link, its IPv6 addresses
and other configuration information may no longer be valid. Examples
of times when a client may have moved to a new link include:

o The client reboots

o The client is physically disconnected from a wired connection

o The client returns from sleep mode

o The client using a wireless technology changes access points

In any situation when a client may have moved to a new link, the
client MUST initiate a Confirm/Reply message exchange. The client
includes any IAs, along with the addresses associated with those IAs,
in its Confirm message. Any responding servers will indicate the
acceptability of the addresses with the status in the Reply message
it returns to the client.

The client sets the "msg-type" field to CONFIRM. The client generates
a transaction ID and inserts this value in the "transaction-ID"
field.

The client sets the "server-address" field to 0.

The client MUST include a DUID Client Identifier option to identify itself
to the server. The client adds any appropriate options, including
one or more IA options. The client MUST include the addresses the
client currently has associated with those IAs.

The client sends the Confirm message to the All_DHCP_Agents multicast
address. The client MUST use an

Droms (ed.), et al. Expires 1 Aug 2002 [Page 34]

Internet Draft DHCP for IPv6 address that (-23) 1 Feb 2002

If the client has
confirmed chooses to be valid on request specific options from the link to which server,
it is currently attached
and that is assigned to the interface for does so by including an Option Request option (see section 23.7,
which MUST include all of the options the client is
interested in obtaining configuration information requesting. The
client MAY include options with data values as hints to the source
address in the IP header of the datagram carrying server
about parameter values the Confirm
message. client would like to have returned.

The client sends the Confirm message to the All_DHCP_Agents multicast
address. The client MUST use an IPv6 address that the client has
confirmed to be transmitted valid on the link that the
interface for to which configuration information is being obtained it is currently attached to. The client SHOULD send the message through
and that
interface. The client MAY send the message through another interface
attached is assigned to the same link if and only if interface for which the client is certain
interested in obtaining configuration information as the source
address in the IP header of the two interface are attached to datagram carrying the same link. Confirm
message.

The client transmits the message according to section 15, using the
following parameters:

IRT CNF_TIMEOUT

MRT CNF_MAX_RT

Bound, Carney, Perkins, Droms (ed.) Expires 30 May 2002 [Page 33]

Internet Draft DHCP for IPv6 (-22) 21 Dec 2001

MRC 0

MRD CNF_MAX_RD

If the client receives no responses before the message transmission
process as described in section 15 terminates, the client SHOULD
continue to use any IP addresses, using the last known lifetimes for
those addresses, and SHOULD continue to use any other previously
obtained configuration parameters.

18.1.3.

19.1.3. Creation and transmission of Renew messages

To extend the valid and preferred lifetimes associated with
addresses, the client sends a Renew message to the server containing
an "IA option" for the IA and its associated addresses. The server
determines new lifetimes for the addresses in the IA according to the
administrative configuration of the server. The server may also add
new addresses to the IA. The server may remove addresses from the IA
by setting the preferred and valid lifetimes of those addresses to
zero.

The server controls the time at which the client contacts the server
to extend the lifetimes on assigned addresses through the T1 and T2
parameters assigned to an IA.

At time T1 for an IA, the client initiates a Renew/Reply message
exchange to extend the lifetimes on any addresses in the IA. The
client includes an IA option with all addresses currently assigned to
the IA in its Renew message.

Droms (ed.), et al. Expires 1 Aug 2002 [Page 35]

Internet Draft DHCP for IPv6 (-23) 1 Feb 2002

The client sets the "msg-type" field to RENEW. The client generates a
transaction ID and inserts this value in the "transaction-ID" field.

The client places the address identifier of the destination server in the
"server-address" field. a
Server Identifier option.

The client MUST include a DUID Client Identifier option to identify
itself to the server. The client adds any appropriate options,
including one or more IA options (if the client is requesting that
the server extend the lifetimes of the addresses assigned to those
IAs; note that the client may check the status of other configuration
parameters without asking for lifetime extensions). The client MUST
include the list of addresses the client currently has associated
with the IAs in the Renew message.

If the client chooses to request specific options from the server,
it does so by including an Option Request option (see section 23.7,
which MUST include all of the options the client is requesting. The
client MAY include options with data values as hints to the server
about parameter values the client would like to have returned.

DISCUSSION:

Use of multicast and relay agents enables the inclusion of
relay agent options in all messages sent by the client. The client
server MUST use an address assigned to the interface
for which the client is interested in obtaining configuration

Bound, Carney, Perkins, Droms (ed.) Expires 30 May 2002 [Page 34]

Internet Draft DHCP for IPv6 (-22) 21 Dec 2001

information as the source address in NOT enable the IP header use of the datagram
carrying the Renew message.

If the Renew message is multicast, it MUST be transmitted on the
link that the interface unicast for which configuration information is being
obtained is attached to. The client SHOULD send the message through
that interface. The client MAY send the message through another
interface attached to the same link if and only if the a client is
certain the the two interface when
relay agent options are attached to the same link. required for that client.

The client transmits the message according to section 15, using the
following parameters:

IRT REN_TIMEOUT

MRT REP_MAX_RT

MRC 0

MRD 0

The mechanism in section 15 is modified as follows for use in the
transmission of Renew messages. The message exchange is terminated
when time T2 is reached (see section 18.1.4), 19.1.4), at which time the
client begins a Rebind message exchange.

18.1.4.

Droms (ed.), et al. Expires 1 Aug 2002 [Page 36]

Internet Draft DHCP for IPv6 (-23) 1 Feb 2002

19.1.4. Creation and transmission of Rebind messages

At time T2 for an IA (which will only be reached if the server to
which the Renew message was sent at time T1 has not responded),
the client initiates a Rebind/Reply message exchange. The client
includes an IA option with all addresses currently assigned to the
IA in its Rebind message. The client sends this message to the
All_DHCP_Agents multicast address.

The client sets the "msg-type" field to REBIND. The client generates
a transaction ID and inserts this value in the "transaction-ID"
field.

The client sets the "server-address" field to 0.

The client MUST include a DUID Client Identifier option to identify
itself to the server. The client adds any appropriate options,
including one or more IA options. The client MUST include the list
of addresses the client currently has associated with the IAs in the
Rebind message.

The client sends the Rebind message to the All_DHCP_Agents multicast
address.

The client MUST use an IPv6 address assigned
to transmits the interface for which message according to section 15, using the client is interested
following parameters:

IRT REB_TIMEOUT

MRT REB_MAX_RT

MRC 0

MRD 0

The mechanism in obtaining
configuration information section 15 is modified as the source address follows for use in the IP header
transmission of Rebind messages. The message exchange is terminated
when the datagram carrying the Rebind message.

Bound, Carney, Perkins, Droms (ed.) Expires 30 May 2002 [Page 35]

Internet Draft DHCP for IPv6 (-22) 21 Dec 2001

The Rebind message MUST be transmitted on the link that the interface
for which configuration information is being obtained is attached
to. The client SHOULD send the message through that interface. The
client MAY send the message through another interface attached to the
same link if and only if the client is certain the the two interface
are attached to the same link.

The client transmits the message according to section 15, using the
following parameters:

IRT REB_TIMEOUT

MRT REB_MAX_RT

MRC 0

MRD 0

The mechanism in section 15 is modified as follows for use in the
transmission of Rebind messages. The message exchange is terminated
when the lifetimes of all of lifetimes of all of the addresses assigned to the IA expire
(see section 12), at which time the client has several alternative
actions to choose from:

- The client may choose to use a Solicit message to locate a new
DHCP server and send a Request for the expired IA to the new
server

- The client may have other addresses in other IAs, so the client
may choose to discard the expired IA and use the addresses in the
other IAs

18.1.5.

Droms (ed.), et al. Expires 1 Aug 2002 [Page 37]

Internet Draft DHCP for IPv6 (-23) 1 Feb 2002

19.1.5. Creation and Transmission of Inform Information-request messages

The client uses an Inform Information-request message to obtain
configuration information without having addresses assigned to it.
The client sets the "msg-type" field to INFORM. INFORMATION-REQUEST. The
client generates a transaction ID and inserts this value in the
"transaction-ID" field.

The client sets the "server-address" field to 0.

The client MUST SHOULD include a DUID Client Identifier option to identify
itself to the server. The If the client adds does not include a Client
Identifier option, the server will not be able to return any appropriate
client-specific options such as an ORO to
indicate the client.

If the client chooses to request specific options from the server what configuration information server,
it does so by including an Option Request option (see section 23.7,
which MUST include all of the options the client is
interested in obtaining. requesting. The
client MAY include options with data values as hints to the server
about parameter values the client would like to have returned. The
client MUST NOT include any IA options.

The

If the client MUST use has an IPv6 address assigned of sufficient scope, the
client MAY choose to send the interface for
which the client is interested in obtaining configuration information
as the source address in the IP header of the datagram carrying the
Rebind message.

Bound, Carney, Perkins, Droms (ed.) Expires 30 May 2002 [Page 36]

Internet Draft DHCP for IPv6 (-22) 21 Dec 2001

If the client has an IPv6 address of sufficient scope, the client MAY
choose to send the Inform message to Information-request message to the
All_DHCP_Servers multicast address. Otherwise, the client MUST send
the Inform Information-request message to the All_DHCP_Agents multicast
address.

The Inform message MUST be transmitted on the link that the interface
for which configuration information is being obtained is attached
to. The client SHOULD send the message through that interface. The
client MAY send the message through another interface attached to the
same link if and only if the client is certain the the two interface
are attached to the same link.

The client transmits the message according to section 15, using the
following parameters:

IRT INF_TIMEOUT

MRT INF_MAX_RT

MRC 0

MRD 0

18.1.6.

19.1.6. Receipt of Reply message in response to a Request, Confirm,
Renew, Rebind or Inform Information-request message

Upon the receipt of a valid Reply message in response to a Request,
Confirm, Renew, Rebind or Inform Information-request message, the client
extracts the configuration information contained in the Reply. The
client MAY choose to report any status code or message from the
status code option in the Reply message.

The client SHOULD perform duplicate address detection [23] [21] on each
of the addresses in any IAs it receives in the Reply message after
a Request message. If any of the addresses are found to be in use
on the link, the client sends a Decline message to the server as
described in section 18.1.9. 19.1.9.

Droms (ed.), et al. Expires 1 Aug 2002 [Page 38]

Internet Draft DHCP for IPv6 (-23) 1 Feb 2002

The client records the T1 and T2 times for each IA in the Reply
message. The client records any addresses included with IAs in
the Reply message. The client updates the preferred and valid
lifetimes for the addresses in the IA from the lifetime information
in the IA option. The client leaves any addresses that the client
has associated with the IA that are not included in the IA option
unchanged.

The client SHOULD respond to the server with a Release message for
any addresses in the Reply message that have a valid lifetime of 0.
The client constructs and transmits this message as described in
section 18.1.7.

Bound, Carney, Perkins, Droms (ed.) Expires 30 May 2002 [Page 37]

Internet Draft DHCP for IPv6 (-22) 21 Dec 2001 19.1.7.

If the Reply was received in response to a Renew or Rebind message,
the client must update the information in any IA option contained in
the Reply message. The client adds any new addresses from the IA
option to the IA, updates lifetimes for existing addresses in the IA
from the IA option and discards any addresses with a lifetime of zero
in the IA option.

Management of the specific configuration information is detailed in
the definition of each option, in section 22. 23.

When the client receives a NoPrefixMatch status in an IA from the
server the client can assume it needs to send a Request to the server
to obtain appropriate addresses for the IA. If the client receives
any Reply messages that do not indicate a NoPrefixMatch status, the
client can use the addresses in the IA and ignore any messages that
do indicate a NoPrefixMatch status.

When the client receives an AddrUnavail status in an IA from the
server for a Request message the client will have to find a new
server to create an IA.

When the client receives a NoBinding status in an IA from the server
for a Confirm message the client can assume it needs to send a
Request to reestablish an IA with the server.

When the client receives a ConfNoMatch status in an IA from the
server for a Confirm message the client can send a Renew message to
the server to extend the lifetimes of the addresses.

When the client receives a NoBinding status in an IA from the server
for a Renew message the client can assume it needs to send a Request
to reestablish an IA with the server.

When the client receives a RenwNoMatch status in an IA from the
server for a Renew message the client can assume it needs to send a
Request to reestablish an IA with the server.

When the client receives an AddrUnavail status in an IA from the
server for a Renew message the client can assume it needs to send a
Request to reestablish an IA with the server.

Droms (ed.), et al. Expires 1 Aug 2002 [Page 39]

Internet Draft DHCP for IPv6 (-23) 1 Feb 2002

When the client receives a NoBinding status in an IA from the server
for a Rebind message the client can assume it needs to send a Request
to reestablish an IA with the server or try another server.

When the client receives a RebdNoMatch status in an IA from the
server for a Rebind message the client can assume it needs to send a
Request to reestablish an IA with the server or try another server.

When the client receives an AddrUnavail status in an IA from the
server for a Rebind message the client can assume it needs to send a
Request to reestablish an IA with the server or try another server.

Bound, Carney, Perkins, Droms (ed.) Expires 30 May 2002 [Page 38]

Internet Draft DHCP for IPv6 (-22) 21 Dec 2001

18.1.7.

19.1.7. Creation and transmission of Release messages

The client sets the "msg-type" field to RELEASE. The client generates
a transaction ID and places this value in the "transaction-ID" field.

The client places the IP address identifier of the server that allocated the
address(es) in the "server-address" field. a Server Identifier option.

The client MUST include a DUID Client Identifier option to identify itself
to the server. The client includes options containing the IAs it
is releasing in the "options" field. The addresses to be released
MUST be included in the IAs. The client continues to use any other
addresses in the IAs. The appropriate "status" field in the options
MUST be set to indicate the reason for the release.

The client MUST NOT use any of the addresses in the IAs in the
message as the source address in the Release message or in any
subsequently transmitted message.

If the client has a source address of sufficient scope that can be
used by the server as a return address and the client has received
a Server Unicast option (section 22.14) 23.13) from the server, the client
SHOULD unicast the Release message to the server. Otherwise, the
client MUST send the Release message to the All_DHCP_Agents multicast
address. The client MUST use an address for the interface to which
the IAs in the Release message are assigned as the source address for
the Release message.

DISCUSSION:

Use of multicast and relay agents enables the inclusion of
relay agent options in all messages sent by the client. The
server MUST NOT enable the use of unicast for a client when
relay agent options are required for that client.

If the Release

A client MAY choose to wait for a Reply message is multicast, it MUST be transmitted on from the
link that server in
response to the interface Release message. If the client does wait for which configuration information is being
obtained is attached to. The client SHOULD send the message through
that interface. The client MAY send the message through another
interface attached to the same link if and only if the client is
certain the the two interface are attached to the same link.

A client MAY choose to wait for a Reply message from the server in
response to the Release message. If the client does wait for a
Reply, the a
Reply, the client MAY choose to retransmit the Release message.

Droms (ed.), et al. Expires 1 Aug 2002 [Page 40]

Internet Draft DHCP for IPv6 (-23) 1 Feb 2002

The client transmits the message according to section 15, using the
following parameters:

IRT REL_TIMEOUT

MRT 0

Bound, Carney, Perkins, Droms (ed.) Expires 30 May 2002 [Page 39]

Internet Draft DHCP for IPv6 (-22) 21 Dec 2001

MRC REL_MAX_MRC

MRD 0

The client MUST abandon the attempt to release addresses if the
Release message exchange fails.

The client MUST stop using all of the addresses in the IA(s) being
released as soon as the client begins the Release message exchange
process. If an IA is released but the Reply from a DHCP server
is lost, the client will retransmit the Release message, and the
server may respond with a Reply indicating a status of "Nobinding".
Therefore, the client does not treat a Reply message with a status
of "Nobinding" in a Release message exchange as if it indicates an
error.

Note that if the client fails to release the IA, the addresses
assigned to the IA will be reclaimed by the server when the lifetime
of the address expires.

18.1.8.

19.1.8. Receipt of Reply message in response to a Release message

Upon receipt of a valid Reply message, the client can consider the
Release event successful.

18.1.9.

19.1.9. Creation and transmission of Decline messages

The client sets the "msg-type" field to DECLINE. The client generates
a transaction ID and places this value in the "transaction-ID" field.

The client places the IP address identifier of the server that allocated the
address(es) in the "server-address" field. a Server Identifier option.

The client MUST include a DUID Client Identifier option to identify itself
to the server. The client includes options containing the IAs it is
declining in the "options" field. The addresses to be declined MUST
be included in the IAs. The client continues to use other addresses
in the IAs. The appropriate "status" field in the options MUST be
set to indicate the reason for declining the address.

The client MUST NOT use any of the addresses in the IAs in the
message as the source address in the Decline message or in any
subsequently transmitted message.

Droms (ed.), et al. Expires 1 Aug 2002 [Page 41]

Internet Draft DHCP for IPv6 (-23) 1 Feb 2002

If the client has a source address of sufficient scope that can be
used by the server as a return address and the client has received
a Server Unicast option (section 22.14) 23.13) from the server, the client
SHOULD unicast the Decline message to the server. Otherwise, the
client MUST send the Decline message to the All_DHCP_Agents multicast
address. The client MUST use an IPv6 address for the interface to

Bound, Carney, Perkins, Droms (ed.) Expires 30 May 2002 [Page 40]

Internet Draft DHCP for IPv6 (-22) 21 Dec 2001

which the IAs in the Decline message are assigned as the source
address for the Decline message.

DISCUSSION:

If the Decline message is multicast, it MUST be transmitted on the
link that the interface for which configuration information is being
obtained is attached to. The client SHOULD send the message through
that interface. The client MAY send the message through another
interface attached to the same link if and only if the client is
certain the the two interface are attached to the same link.

The client transmits the message according to section 15, using the
following parameters:

IRT DEC_TIMEOUT

MRT DEC_MAX_RT

MRC DEC_MAX_RC

MRD 0

The client MUST abandon the attempt to decline addresses if the
Decline message exchange fails.

18.1.10.

19.1.10. Receipt of Reply message in response to a Decline message

Upon receipt of a valid Reply message, the client can consider the
Decline event successful.

18.2.

19.2. Server Behavior

For this discussion, the Server is assumed to have been configured in
an implementation specific manner with configuration of interest to
clients.

18.2.1.

19.2.1. Receipt of Request messages

The server MAY choose to discard Request messages received via
unicast from a client to which the server has not sent a unicast
option.

When the server receives a Request the client is requesting the
configuration of a new IA by the server. The server MUST take the

Bound, Carney, Perkins, Droms (ed.) Expires 30 May 2002 [Page 41]

Internet Draft DHCP for IPv6 (-22) 21 Dec 2001
IA from the client and associate a binding for that client in an
implementation-specific manner within the configuration parameter
database for DHCP clients managed by the server.

Droms (ed.), et al. Expires 1 Aug 2002 [Page 42]

Internet Draft DHCP for IPv6 (-23) 1 Feb 2002

Upon the receipt of a valid Request message from a client the server
can respond to, (implementation-specific administrative policy
satisfied) the server scans the options field.

The server then constructs a Reply message and sends it to the
client.

The server SHOULD process each option for the client in an
implementation-specific manner. The server MUST construct a Reply
message containing the following values:

msg-type REPLY

transaction-ID The transaction-ID from the Request message.

The server address One of the IP addresses assigned to the interface
through which the server received MUST include a Server Identifier option containing the message
from
server's DUID in the client. Reply message.

If the server finds that the prefix on one or more IP addresses in
any IA in the message from the client is not a valid prefix for the
link to which the client is connected, the server MUST return the IA
to the client with the status field set to NoPrefixMatch.

If the server cannot assign any addresses to any of the IAs in
the message from the client, the server SHOULD include the IAs in
the Reply message with the status field set to AddrUnavail and no
addresses in the IA.

For any IAs to which the server can assign addresses, server includes
the IA with addresses and other configuration parameters a status of
Success, and add the IA as a new client binding.

The server may choose to assign fewer temporary addresses than
the client requested with an RTA option (see section 23.6) and
includes a status code of Success in the IA. If the server chooses to
assign no temporary addresses, the server includes a status code of
AddrUnavail.

The server adds options to the Reply message for any other
configuration information to be assigned to the client.

18.2.2.

19.2.2. Receipt of Confirm messages

When the server receives a Confirm message, the client is requesting
confirmation that the configuration information it will use is valid.
The server SHOULD locate the binding for that client and compare the
information in the Confirm message from the client to the information
associated with that client.

Upon the receipt of a valid Confirm message from a client the server
can respond to, (implementation-specific administrative policy
satisfied) the server scans the options field.

Bound, Carney, Perkins,

Droms (ed.) (ed.), et al. Expires 30 May 1 Aug 2002 [Page 42] 43]

Internet Draft DHCP for IPv6 (-22) 21 Dec 2001 (-23) 1 Feb 2002

If the server cannot determine if the information in the Confirm
message is valid or invalid, the server MUST NOT send a reply to the
client. For example, if the server does not have a binding for the
client, but the configuration information in the Confirm message
appears valid, the server does not reply.

If the server finds that the information for the client does not
match what is in the binding for that client or the configuration
information is not valid, the server sends a Reply message containing
a Status Code option with the value ConfNoMatch.

If the server finds that the information for the client does match
the information in the binding for that client, and the configuration
information is still valid, the server sends a Reply message
containing a Status Code option with the value Success.

The server SHOULD process each option for the client in an
implementation-specific manner. The server MUST construct a Reply
message containing the following values:

msg-type REPLY

transaction-ID The transaction-ID from the Confirm message.

The Reply message from the server MUST contain a Status Code option
and MUST NOT include any other options.

18.2.3.

19.2.3. Receipt of Renew messages

The server MAY choose to discard Renew messages received via unicast
from a client to which the server has not sent a unicast option.

Upon the receipt of a valid Renew message from a client the server
can respond to, (implementation-specific administrative policy
satisfied) the server scans the options field.

When the server receives a Renew and IA option from a client it
SHOULD locate the clients binding and verify the information in the
IA from the client matches the information stored for that client.

If the server cannot find a client entry for this IA the server
SHOULD return an IA containing no addresses with status set to
NoBinding.

If the server finds that the addresses in the IA for the client
do not match the client binding the server should return an IA
containing no addresses with status set to RenwNoMatch.

Bound, Carney, Perkins,

Droms (ed.) (ed.), et al. Expires 30 May 1 Aug 2002 [Page 43] 44]

Internet Draft DHCP for IPv6 (-22) 21 Dec 2001 (-23) 1 Feb 2002

If the server cannot Renew addresses for the client it SHOULD send
back an IA containing no addresses to the client with the status
field set to AddrUnavail.

If the server finds the addresses in the IA for the client then the
server SHOULD send back the IA to the client with new lifetimes and
T1/T2 times if the default is not being used, and set status to
Success. The server may choose to change the list of addresses and
the lifetimes of addresses in IAs that are returned to the client.

The server may choose to assign fewer temporary addresses than
the client requested with an RTA option (see section 23.6) and
includes a status code of Success in the IA. If the server chooses to
assign no temporary addresses, the server includes a status code of
AddrUnavail.

The server SHOULD process each option for the client in an
implementation-specific manner. The server MUST construct a Reply
message containing the following values:

msg-type REPLY

transaction-ID The transaction-ID from the Confirm message.

The server address One of the IP addresses assigned to the interface
through which the server received MUST include a Server Identifier option containing the message
from
server's DUID in the client.

18.2.4. Reply message.

19.2.4. Receipt of Rebind messages

Upon the receipt of a valid Rebind message from a client the server
can respond to, (implementation-specific administrative policy
satisfied) the server scans the options field.

When the server receives a Rebind and IA option from a client it
SHOULD locate the clients binding and verify the information in the
IA from the client matches the information stored for that client.

If the server cannot find a client entry for this IA the server
SHOULD return an IA containing no addresses with status set to
NoBinding.

If the server finds that the addresses in the IA for the client
do not match the client binding the server should return an IA
containing no addresses with status set to RebdNoMatch.

If the server cannot Rebind addresses for the client it SHOULD send
back an IA containing no addresses to the client with the status
field set to AddrUnavail.

If the server finds the addresses in the IA for the client then the
server SHOULD send back the IA to the client with new lifetimes and

Droms (ed.), et al. Expires 1 Aug 2002 [Page 45]

Internet Draft DHCP for IPv6 (-23) 1 Feb 2002

T1/T2 times if the default is not being used, and set status to
Success.

The server SHOULD process each option for the client in an
implementation-specific manner. The server MUST construct a Reply
message containing the following values:

Bound, Carney, Perkins, Droms (ed.) Expires 30 May 2002 [Page 44]

Internet Draft DHCP for IPv6 (-22) 21 Dec 2001

msg-type REPLY

transaction-ID The transaction-ID from the Confirm message.

The server address One of the IP addresses assigned to the interface
through which the server received MUST include a Server Identifier option containing the message
from
server's DUID in the client.

18.2.5. Reply message.

19.2.5. Receipt of Inform Information-request messages

When the server receives an Inform Information-request message, the client
is requesting configuration information that does not include
the assignment of any addresses. The server SHOULD determine all
configuration parameters appropriate to the client, based on the
server configuration policies known to the server.

Upon the receipt of a valid Inform Information-request message from a client
the server can respond to, (implementation-specific administrative
policy satisfied) the server scans the options field. The server
then constructs a Reply message and sends it to the client.

The server SHOULD process each option for the client in an
implementation-specific manner. The server MUST construct a Reply
message containing the following values:

msg-type REPLY

transaction-ID The transaction-ID from the Confirm message.

The server adds options to the Reply message for all of the
configuration parameters to be returned to the client.

18.2.6.

Droms (ed.), et al. Expires 1 Aug 2002 [Page 46]

Internet Draft DHCP for IPv6 (-23) 1 Feb 2002

19.2.6. Receipt of Release messages

The server MAY choose to discard Release messages received via
unicast from a client to which the server has not sent a unicast
option.

Upon the receipt of a valid Release message, the server examines the
IAs and the addresses in the IAs for validity. If the IAs in the
message are in a binding for the client and the addresses in the IAs
have been assigned by the server to those IAs, the server deletes
the addresses from the IAs and makes the addresses available for
assignment to other clients. The server ignores invalid addresses
(though it may choose to log an error if it finds an invalid
address).

Bound, Carney, Perkins, Droms (ed.) Expires 30 May 2002 [Page 45]

Internet Draft DHCP for IPv6 (-22) 21 Dec 2001

After all the addresses have been processed, the server generates a
Reply message and includes a Status Code option with value Success. Success
and a Server Identifier option with the server's DUID. The server
MUST NOT include any other options in the Reply message.

A server is not required to (but may choose to as an implementation
strategy) retain any record of an IA from which all of the addresses
have been released.

18.2.7.

19.2.7. Receipt of Decline messages

The server MAY choose to discard Decline messages received via
unicast from a client to which the server has not sent a unicast
option.

Upon the receipt of a valid Decline message, the server examines the
IAs and the addresses in the IAs for validity. If the IAs in the
message are in a binding for the client and the addresses in the IAs
have been assigned by the server to those IA, the server deletes
the addresses from the IAs. The server SHOULD mark the addresses
declined by the client so that those addresses are not assigned to
other clients, and MAY choose to make a notification that addresses
were declined. The server ignores invalid addresses (though it may
choose to log an error if it finds an invalid address).

After all the address have been processed, the server generates a
Reply message and includes a Status Code option with value Success.
The server MUST NOT include any other options in the Reply message.

18.2.8. Receipt of Information-Request messages

Upon the receipt of a valid Inform message, the server determines the
appropriate configuration parameters Success
and returns those parameters to
the client in a Reply message. Server Identifier option with the server' DUID. The server MUST
NOT include any IA other options in the Reply message.

18.2.9. Sending

19.2.8. Transmission of Reply messages

If the Request, Confirm, Renew, Rebind, Release, Decline or Inform
Information-request message from the client was originally received
in a Relay-forward message from a relay, the server places the
Reply message in the options field of a Relay-response message and

Droms (ed.), et al. Expires 1 Aug 2002 [Page 47]

Internet Draft DHCP for IPv6 (-23) 1 Feb 2002

copies the link-address and client-return-address fields from the
Relay-forward message into the Relay-response message.

The server then unicasts the Reply or Relay-reply to the source
address from the IP datagram in which the original message was
received.

Bound, Carney, Perkins, Droms (ed.) Expires 30 May 2002 [Page 46]

Internet Draft DHCP for IPv6 (-22) 21 Dec 2001

19.

20. DHCP Server-Initiated Configuration Exchange

A server initiates a configuration exchange to cause DHCP clients
to obtain new addresses and other configuration information. For
example, an administrator may use a server-initiated configuration
exchange when links in the DHCP domain are to be renumbered. Other
examples include changes in the location of directory servers,
addition of new services such as printing, and availability of new
software (system or application).

19.1.

20.1. Server Behavior

A server sends a Reconfigure message to cause a client to initiate
immediately a Renew/Reply or Information-request/Reply message
exchange with the server.

19.1.1.

20.1.1. Creation and transmission of Reconfigure messages

The server sets the "msg-type" field to RECONFIGURE. The server
generates a transaction-ID and inserts it in the "transaction-ID"
field. The server places its address (of appropriate scope) identifier in the
"server-address" field. a Server Identifier
option.

The server MAY include an ORO Option Request option to inform the client
of what information has been changed or new information that has been
added. In particular, the server specifies the IA option in the ORO
Option Request option if the server wants the client to obtain new
address information.

The server MUST include an authentication option with the appropriate
settings and add that option as the last option in the "options"
field of the Reconfigure message.

The server MUST NOT include any other options in the Reconfigure
except as specifically allowed in the definition of individual
options.

A server sends each Reconfigure message to a single DHCP client,
using an IPv6 unicast address of sufficient scope belonging to the
DHCP client. The server may obtain the address of the client through
the information that the server has about clients that have been in
contact with the server, or the server may be configured with the
address of the client through some external agent.

Droms (ed.), et al. Expires 1 Aug 2002 [Page 48]

Internet Draft DHCP for IPv6 (-23) 1 Feb 2002

To reconfigure more than one client, the server unicasts a separate
message to each client. The server may initiate the reconfiguration
of multiple clients concurrently; for example, a server may
send a Reconfigure message to additional clients while previous
reconfiguration message exchanges are still in progress.

The Reconfigure message causes the client to initiate a Renew/Reply
or Information-request/Reply message exchange with the server. The

Bound, Carney, Perkins, Droms (ed.) Expires 30 May 2002 [Page 47]

Internet Draft DHCP for IPv6 (-22) 21 Dec 2001
server interprets the receipt of a Renew or Information-request
message from the client as satisfying the Reconfigure message
request.

19.1.2.

20.1.2. Time out and retransmission of Reconfigure messages

If the server does not receive a Renew or Information-request message
from the client in RECREP_MSG_TIMEOUT milliseconds, the server
retransmits the Reconfigure message, doubles the RECREP_MSG_TIMEOUT
value and waits again. The server continues this process until
REC_MSG_ATTEMPTS unsuccessful attempts have been made, at which point
the server SHOULD abort the reconfigure process for that client.

Default and initial values for RECREP_MSG_TIMEOUT and
REC_MSG_ATTEMPTS are documented in section 7.5.

19.1.3.

20.1.3. Receipt of Renew messages

The server generates and sends Reply message(s) to the client as
described in section 18.2.9, 19.2.8, including in the "options" field new
values for configuration parameters.

It is possible that the client may send a Renew message after the
server has sent a Reconfigure but before the Reconfigure is received
by the client. In this case, the Renew message from the client
may not include all of the IAs and requests for parameters to be
reconfigured by the server. To accommodate this scenario, the server
MAY choose to send a Reply with the IAs and other parameters to be
reconfigured, even if those IAs and parameters were not in the Renew
message from the client.

19.2.

20.2. Receipt of Information-request messages

If the server has assigned addresses to one or more IAs that belong
to the responding client, the server MUST silently discard the
Information-request message.

The server generates and sends Reply message(s) to

If the client as
described in section 18.2.9, including has requested options in the "options" field new
values for configuration parameters.

It is possible an Option Request option that
the server is unable to provide to the client, the server MAY send
a Reply message with only those options it can provide. If the
server sends a Reply message that does not include all of the options

Droms (ed.), et al. Expires 1 Aug 2002 [Page 49]

Internet Draft DHCP for IPv6 (-23) 1 Feb 2002

requested by the client, it MUST include a Status Code option with
code OptionUnavail.

The server generates and sends Reply message(s) to the client as
described in section 19.2.8, including in the "options" field new
values for configuration parameters.

It is possible that the client may send an Information-request
message after the server has sent a Reconfigure but before
the Reconfigure is received by the client. In this case, the
Information-request message from the client may not include request all of
the IAs and requests for parameters to be reconfigured by the server. To accommodate
this scenario, the server MAY choose to send a Reply with the IAs and other
parameters to be reconfigured, even if those
IAs and parameters were not
specified in the Information-request message from the client.

Bound, Carney, Perkins, Droms (ed.) Expires 30 May 2002 [Page 48]

Internet Draft DHCP for IPv6 (-22) 21 Dec 2001

19.3.

20.3. Client Behavior

A client MUST always monitor UDP port 546 for Reconfigure messages
on interfaces for which it has acquired DHCP parameters. Since the
results of a reconfiguration event may affect application layer
programs, the client SHOULD log these events, and MAY notify these
programs of the change through an implementation-specific interface.

19.3.1.

20.3.1. Receipt of Reconfigure messages

Upon receipt of a valid Reconfigure message, the client initiates a
transaction with the server. While the transaction is in progress,
the client silently discards any Reconfigure messages it receives.

If the client has IAs with addresses that have been assigned by the
server from which the Reconfigure message was received, the client
MUST respond with a Renew message. Otherwise, the client responds
with an Information-request message.

DISCUSSION:

The Reconfigure message acts as a trigger that signals the
client to complete a successful message exchange. Once
the client has received a Reconfigure, the client proceeds
with the message exchange (retransmitting the Renew or
Information-request message if necessary); the client
ignores any additional Reconfigure messages (regardless
of the transaction ID in the Reconfigure message) until
the exchange is complete. Subsequent Reconfigure messages
(again independent of the transaction ID) cause the client
to initiate a new exchange.

How does this mechanism work in the face of duplicated or
retransmitted Reconfigure messages? Duplicate messages
will be ignored because the client will begin the exchange

Droms (ed.), et al. Expires 1 Aug 2002 [Page 50]

Internet Draft DHCP for IPv6 (-23) 1 Feb 2002

after the receipt of the first Reconfigure. Retransmitted
messages will either trigger the exchange (if the first
Reconfigure was not received by the client) or will be
ignored. The server can discontinue retransmission of
Reconfigure messages to the client once the server receives
the Renew or Information-request message from the client.

It might be possible for a duplicate or retransmitted
Reconfigure to be sufficiently delayed (and delivered out of
order) to arrive at the client after the exchange (initiated
by the original Reconfigure) has been completed. In this
case, the client would initiate a redundant exchange. The
likelihood of delayed and out of order delivery is small
enough to be ignored. The consequence of the redundant
exchange is inefficiency rather than incorrect operation.

Bound, Carney, Perkins, Droms (ed.) Expires 30 May 2002 [Page 49]

Internet Draft DHCP for IPv6 (-22) 21 Dec 2001

19.3.2.

20.3.2. Creation and sending transmission of Renew messages

When responding to a Reconfigure, the client creates and sends
the Renew message in exactly the same manner as outlined in
section 18.1.3, 19.1.3, with the exception: if the server included on ORO Option
Request option specifying the IA option, the client MUST include IA
options containing the addresses the client currently has assigned to
ALL IAs for the interface through which the Reconfigure message was
received.

19.3.3.

20.3.3. Creation and sending transmission of Renew Information-request messages

When responding to a Reconfigure, the client creates and sends the
Information-request message in exactly the same manner as outlined in
section 18.1.5.

19.3.4. 19.1.5, with the exception that the client includes a Server
Identifier option with the identifier from the Reconfigure message to
which the client is responding.

20.3.4. Time out and retransmission of Renew or Information-request
messages

The client uses the same variables and retransmission algorithm as
it does with Rebind Renew or Information-request messages generated as part
of a client-initiated configuration exchange. See section 18.1.3 sections 19.1.3
and 18.1.5 19.1.5 for details.

19.3.5.

20.3.5. Receipt of Reply messages

Upon the receipt of a valid Reply message, the client extracts the
contents of the "options" field, and sets (or resets) configuration
parameters appropriately. The client records and updates the
lifetimes for any addresses specified in IAs in the Reply message.
If the configuration parameters changed were requested by the

Droms (ed.), et al. Expires 1 Aug 2002 [Page 51]

Internet Draft DHCP for IPv6 (-23) 1 Feb 2002

application layer, the client notifies the application layer of the
changes using an implementation-specific interface.

20.

21. Relay Behavior

For this discussion, the Relay MAY be configured to use a list of
server destination addresses, which MAY include unicast addresses,
the All_DHCP_Servers multicast address, or other multicast addresses
selected by the network administrator. If the Relay has not been
explicitly configured, it MUST use the All_DHCP_Servers multicast
address as the default.

20.1.

21.1. Relaying of client messages

When a Relay receives a valid client message, it constructs a
Relay-forward message. The relay places an address with a prefix
assigned to the link on which the client should be assigned an
address in the link-address field. This address will be used by the

Bound, Carney, Perkins, Droms (ed.) Expires 30 May 2002 [Page 50]

Internet Draft DHCP for IPv6 (-22) 21 Dec 2001
server to determine the link from which the client should be assigned
an address and other configuration information.

If the relay cannot use the address in the link-address field to
identify the interface through which the response to the client will
be forwarded, the relay MUST include a circuit-id an Interface-id option (see
section 22.18)in 23.17) in the Relay-forward message. The server will include
the circuit-id Interface-id option in its Relay-reply message.

The relay copies the source address from the IP datagram in which the
message was received from the client into the client-return-address
field in the Relay-forward message.

The relay constructs a "client-message" option 22.9 23.10 that contains
the entire message from the client in the data field of the
option. The relay places the "relay-message" option along with any
"relay-specific" options in the options field of the Relay-forward
message. The Relay MUST send the Relay-forward message to the list
of server destination addresses that with which it has been configured with and
MUST NOT send the message just to the server (if present) identified
in the server-address field in the client message.

20.2. configured.

21.2. Relaying of server messages

When the relay receives a Relay-reply message, it extracts the server
message from the "server-message" option. If the Relay-reply message
includes a circuit-id Interface-id option, the relay forwards the message from
the server to the client on the link identified by the circuit-id Interface-id
option. Otherwise, the relay forwards the message on the link
identified by the link-address field. In either case, the relay
forwards the message to the address in the client-return-address
field in the Relay-reply message.

21.

Droms (ed.), et al. Expires 1 Aug 2002 [Page 52]

Internet Draft DHCP for IPv6 (-23) 1 Feb 2002

22. Authentication of DHCP messages

Some network administrators may wish to provide authentication of
the source and contents of DHCP messages. For example, clients may
be subject to denial of service attacks through the use of bogus
DHCP servers, or may simply be misconfigured due to unintentionally
instantiated DHCP servers. Network administrators may wish to
constrain the allocation of addresses to authorized hosts to avoid
denial of service attacks in "hostile" environments where the network
medium is not physically secured, such as wireless networks or
college residence halls.

Because of the risk of denial of service attacks against DHCP
clients, the use of authentication is mandated in Reconfigure
messages. A DHCP server MUST include an authentication option in
Reconfigure messages sent to clients.

Bound, Carney, Perkins, Droms (ed.) Expires 30 May 2002 [Page 51]

Internet Draft DHCP for IPv6 (-22) 21 Dec 2001

The DHCP authentication mechanism is based on the design of
authentication for DHCP for IPv4 [9].

21.1. [8].

22.1. DHCP threat model

The threat to DHCP is inherently an insider threat (assuming a
properly configured network where DHCPv6 ports are blocked on the
perimeter gateways of the enterprise). Regardless of the gateway
configuration, however, the potential attacks by insiders and
outsiders are the same.

The attack specific to a DHCP client is the possibility of the
establishment of a "rogue" server with the intent of providing
incorrect configuration information to the client. The motivation
for doing so may be to establish a "man in the middle" attack or it
may be for a "denial of service" attack.

There is another threat to DHCP clients from mistakenly or
accidentally configured DHCP servers that answer DHCP client requests
with unintentionally incorrect configuration parameters.

The threat specific to a DHCP server is an invalid client
masquerading as a valid client. The motivation for this may be for
"theft of service", or to circumvent auditing for any number of
nefarious purposes.

The threat common to both the client and the server is the resource
"denial of service" (DoS) attack. These attacks typically involve
the exhaustion of valid addresses, or the exhaustion of CPU or
network bandwidth, and are present anytime there is a shared
resource. In current practice, redundancy mitigates DoS attacks the
best.

21.2.

Droms (ed.), et al. Expires 1 Aug 2002 [Page 53]

Internet Draft DHCP for IPv6 (-23) 1 Feb 2002

22.2. Security of messages sent between servers and relay agents

Relay agents and servers that choose to exchange messages securely
use the IPsec mechanisms for IPv6 [11]. [10]. The way in which IPsec
is employed by relay agents and servers is not specified in this
document.

21.3.

22.3. Summary of DHCP authentication

Authentication of DHCP messages is accomplished through the use of
the Authentication option. The authentication information carried
in the Authentication option can be used to reliably identify the
source of a DHCP message and to confirm that the contents of the DHCP
message have not been tampered with.

The Authentication option provides a framework for multiple
authentication protocols. Two such protocols are defined here.

Bound, Carney, Perkins, Droms (ed.) Expires 30 May 2002 [Page 52]

Internet Draft DHCP for IPv6 (-22) 21 Dec 2001
Other protocols defined in the future will be specified in separate
documents.

The protocol field in the Authentication option identifies the
specific protocol used to generate the authentication information
carried in the option. The algorithm field identifies a specific
algorithm within the authentication protocol; for example, the
algorithm field specifies the hash algorithm used to generate the
message authentication code (MAC) in the authentication option. The
replay detection method (RDM) field specifies the type of replay
detection used in the replay detection field.

21.4.

22.4. Replay detection

The Replay Detection Method (RDM) field determines the type of replay
detection used in the Replay Detection field.

If the RDM field contains 0x00, the replay detection field MUST be
set to the value of a monotonically increasing counter. Using a
counter value such as the current time of day (e.g., an NTP-format
timestamp [13]) [12]) can reduce the danger of replay attacks. This method
MUST be supported by all protocols.

21.5.

22.5. Configuration token protocol

If the protocol field is 0, the authentication information field
holds a simple configuration token. The configuration token is an
opaque, unencoded value known to both the sender and receiver. The
sender inserts the configuration token in the DHCP message and the
receiver matches the token from the message to the shared token. If
the configuration option is present and the token from the message
does not match the shared token, the receiver MUST discard the
message.

Droms (ed.), et al. Expires 1 Aug 2002 [Page 54]

Internet Draft DHCP for IPv6 (-23) 1 Feb 2002

Configuration token may be used to pass a plain-text configuration
token and provides only weak entity authentication and no message
authentication. This protocol is only useful for rudimentary
protection against inadvertently instantiated DHCP servers.

DISCUSSION:

The intent here is to pass a constant, non-computed token
such as a plain-text password. Other types of entity
authentication using computed tokens such as Kerberos
tickets or one-time passwords will be defined as separate
protocols.

Bound, Carney, Perkins, Droms (ed.) Expires 30 May 2002 [Page 53]

Internet Draft DHCP for IPv6 (-22) 21 Dec 2001

21.6.

22.6. Delayed authentication protocol

If the protocol field is 1, the message is using the "delayed
authentication" mechanism. In delayed authentication, the client
requests authentication in its Solicit message and the server replies
with an Advertise message that includes authentication information.
This authentication information contains a nonce value generated by
the source as a message authentication code (MAC) to provide message
authentication and entity authentication.

The use of a particular technique based on the HMAC protocol [12] [11]
using the MD5 hash [21] [20] is defined here.

21.6.1.

22.6.1. Management issues in the delayed authentication protocol

The "delayed authentication" protocol does not attempt to address
situations where a client may roam from one administrative domain
to another, i.e. interdomain roaming. This protocol is focused on
solving the intradomain problem where the out-of-band exchange of a
shared secret is feasible.

21.6.2.

22.6.2. Use of the Authentication option in the delayed authentication
protocol

In a Solicit message, the Authentication option carries the Protocol,
Algorithm, RDM and Replay detection fields, but no Authentication
information.

In an Advertise, Request, Renew, Rebind, Confirm, Decline, Release
or Information-request message, the Authentication option carries
the Protocol, Algorithm, RDM and Replay detection fields and
Authentication information.

Droms (ed.), et al. Expires 1 Aug 2002 [Page 55]

Internet Draft DHCP for IPv6 (-23) 1 Feb 2002

The format of the Authentication information is:

0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Secret ID (32 bits) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| HMAC-MD5 (128 bits) |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Bound, Carney, Perkins, Droms (ed.) Expires 30 May 2002 [Page 54]

Internet Draft DHCP for IPv6 (-22) 21 Dec 2001

The following definitions will be used in the description of the
authentication information for delayed authentication, algorithm 1:

Replay Detection - as defined by the RDM field
K - a secret value shared between the source and
destination of the message; each secret has a
unique identifier (secret ID)
secret ID - the unique identifier for the secret value
used to generate the MAC for this message
HMAC-MD5 - the MAC generating function.

The sender computes the MAC using the HMAC generation algorithm [12] [11]
and the MD5 hash function [21]. [20]. The entire DHCP message (except
the MAC field of the authentication option itself), including the
DHCP message header and the options field, is used as input to the
HMAC-MD5 computation function. The 'secret ID' field MUST be set to
the identifier of the secret used to generate the MAC.

DISCUSSION:

Algorithm 1 specifies the use of HMAC-MD5. Use of a
different technique, such as HMAC-SHA, will be specified as
a separate protocol.

Delayed authentication requires a shared secret key for each
client on each DHCP server with which that client may wish
to use the DHCP protocol. Each secret key has a unique
identifier that can be used by a receiver to determine which
secret was used to generate the MAC in the DHCP message.
Therefore, delayed authentication may not scale well in an
architecture in which a DHCP client connects to multiple
administrative domains.

21.6.3.

22.6.3. Message validation

To validate an incoming message, the receiver first checks that
the value in the replay detection field is acceptable according

Droms (ed.), et al. Expires 1 Aug 2002 [Page 56]

Internet Draft DHCP for IPv6 (-23) 1 Feb 2002

to the replay detection method specified by the RDM field. Next,
the receiver computes the MAC as described in [12]. [11]. The receiver
MUST set the 'MAC' field of the authentication option to all 0s for
computation of the MAC. If the MAC computed by the receiver does not
match the MAC contained in the authentication option, the receiver
MUST discard the DHCP message.

21.6.4.

22.6.4. Key utilization

Each DHCP client has a key, K. The client uses its key to encode
any messages it sends to the server and to authenticate and verify
any messages it receives from the server. The client's key SHOULD
be initially distributed to the client through some out-of-band

Bound, Carney, Perkins, Droms (ed.) Expires 30 May 2002 [Page 55]

Internet Draft DHCP for IPv6 (-22) 21 Dec 2001
mechanism, and SHOULD be stored locally on the client for use in all
authenticated DHCP messages. Once the client has been given its key,
it SHOULD use that key for all transactions even if the client's
configuration changes; e.g., if the client is assigned a new network
address.

Each DHCP server MUST know, or be able to obtain in a secure manner,
the keys for all authorized clients. If all clients use the same
key, clients can perform both entity and message authentication for
all messages received from servers. However, the sharing of keys
is strongly discouraged as it allows for unauthorized clients to
masquerade as authorized clients by obtaining a copy of the shared
key. To authenticate the identity of individual clients, each client
MUST be configured with a unique key.

21.6.5.

22.6.5. Client considerations for delayed authentication protocol

21.6.5.1.

22.6.5.1. Sending Solicit messages

When the client sends a Solicit message and wishes to use
authentication, it includes an Authentication option with the desired
protocol, algorithm, RDM and replay detection field as described
in section 21.6. 22.6. The client does not include any authentication
information in the Authentication option.

21.6.5.2.

22.6.5.2. Receiving Advertise messages

The client validates any Advertise messages containing an
Authentication option specifying the delayed authentication protocol
using the validation test described in section 21.6.3. 22.6.3.

Client behavior if no Advertise messages include authentication
information or pass the validation test is controlled by local policy
on the client. According to client policy, the client MAY choose to
respond to a Advertise message that has not been authenticated.

Droms (ed.), et al. Expires 1 Aug 2002 [Page 57]

Internet Draft DHCP for IPv6 (-23) 1 Feb 2002

The decision to set local policy to accept unauthenticated messages
should be made with care. Accepting an unauthenticated Advertise
message can make the client vulnerable to spoofing and other
attacks. If local users are not explicitly informed that the client
has accepted an unauthenticated Advertise message, the users may
incorrectly assume that the client has received an authenticated
address and is not subject to DHCP attacks through unauthenticated
messages.

A client MUST be configurable to discard unauthenticated messages,
and SHOULD be configured by default to discard unauthenticated
messages. A client MAY choose to differentiate between Advertise
messages with no authentication information and Advertise messages
that do not pass the validation test; for example, a client might
accept the former and discard the latter. If a client does accept an

Bound, Carney, Perkins, Droms (ed.) Expires 30 May 2002 [Page 56]

Internet Draft DHCP for IPv6 (-22) 21 Dec 2001
unauthenticated message, the client SHOULD inform any local users and
SHOULD log the event.

21.6.5.3.

22.6.5.3. Sending Request, Confirm, Renew, Rebind, Decline or Release
messages

If the client authenticated the Advertise message through which the
client selected the server, the client MUST generate authentication
information for subsequent Request, Confirm, Renew, Rebind or Release
messages sent to the server as described in section 21.6. 22.6. When the
client sends a subsequent message, it MUST use the same secret used
by the server to generate the authentication information.

21.6.5.4.

22.6.5.4. Sending Information-request messages

If the client has negotiated a secret with the server through a
previous message exchange, the client MUST use the same secret used
by the server to generate the authentication information. If the
client has not negotiated a secret with the server, the client MUST
use a secret that has been selected for the client through some
external mechanism.

21.6.5.5.

22.6.5.5. Receiving Reply messages

If the client authenticated the Advertise it accepted, the client
MUST validate the associated Reply message from the server. The
client MUST discard the Reply if the message fails to pass validation
and MAY log the validation failure. If the Reply fails to pass
validation, the client MUST restart the DHCP configuration process by
sending a Solicit message. The client MAY choose to remember which
server replied with a Reply message that failed to pass validation
and discard subsequent messages from that server.

Droms (ed.), et al. Expires 1 Aug 2002 [Page 58]

Internet Draft DHCP for IPv6 (-23) 1 Feb 2002

If the client accepted an Advertise message that did not include
authentication information or did not pass the validation test, the
client MAY accept an unauthenticated Reply message from the server.

21.6.5.6.

22.6.5.6. Receiving Reconfigure messages

The client MUST validate the Reconfigure message from the server.
The client MUST discard the Reconfigure if the message fails to pass
validation and MAY log the validation failure.

Bound, Carney, Perkins, Droms (ed.) Expires 30 May 2002 [Page 57]

Internet Draft DHCP for IPv6 (-22) 21 Dec 2001

21.6.6.

22.6.6. Server considerations for delayed authentication protocol

21.6.6.1.

22.6.6.1. Receiving Solicit messages and Sending Advertise messages

The server selects a secret for the client and includes
authentication information in the Advertise message returned to the
client as specified in section 21.6. 22.6. The server MUST record the
identifier of the secret selected for the client and use that same
secret for validating subsequent messages with the client.

21.6.6.2.

22.6.6.2. Receiving Request, Confirm, Renew, Rebind or Release messages
and Sending Reply messages

The server uses the secret identified in the message and validates
the message as specified in section 21.6.3. 22.6.3. If the message fails to
pass validation or the server does not know the secret identified by
the 'secret ID' field, the server MUST discard the message and MAY
choose to log the validation failure.

If the message passes the validation procedure, the server responds
to the specific message as described in section 18.2. 19.2. The server
MUST include authentication information generated using the secret
identified in the received message as specified in section 21.6.

21.6.6.3. 22.6.

22.6.6.3. Sending Reconfigure messages

The server MUST include authentication information in a Reconfigure
message, generated as specified in section 21.6 22.6 using the secret the
server initially negotiated with the client to which the Reconfigure
message is to be sent.

If the server has not previously negotiated a secret with the client,
the server MUST use a secret that has been selected for the client
through some external mechanism.

22.

Droms (ed.), et al. Expires 1 Aug 2002 [Page 59]

Internet Draft DHCP for IPv6 (-23) 1 Feb 2002

23. DHCP options

Options are used to carry additional information and parameters
in DHCP messages. Every option shares a common base format, as
described in section 22.1. 23.1. All values in options is represented in
network order.

This document describes the DHCP options defined as part of the base
DHCP specification. Other options may be defined in the future in a
separate document.

Bound, Carney, Perkins, Droms (ed.) Expires 30 May 2002 [Page 58]

Internet Draft DHCP for IPv6 (-22) 21 Dec 2001

22.1.

23.1. Format of DHCP options

0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| option-code | option-len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| option-data |
| (option-len octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

option-code An unsigned integer identifying the specific option
type carried in this option.

option-len An unsigned integer giving the length of the
option-data field in this option in octets.

option-data The data for the option; the format of this data
depends on the definition of the option.

DHCPv6 options are scoped by using encapsulation. Some options apply
generally to the client, some are specific to an IA, and some are
specific to the addresses within an IA. These latter two cases are
discussed in sections 22.3 23.4 and 22.4.

22.2. DHCP unique identifier 23.5.

23.2. Client Identifier option

The DHCP unique identifier Client Identifier option is used to carry a DUID. The format
for the DUID is keyed to mark the type of identifier identifying a
client between a client and is of
variable length. a server. The Client Identifier option
MUST appear before any IA options in the DHCP message. The format of
the DUID option is:

Droms (ed.), et al. Expires 1 2 Aug 2002 [Page 60]

Internet Draft DHCP for IPv6 (-23) 1 Feb 2002

0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| OPTION DUID OPTION_CLIENTID | option-len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|
. .
. DUID type | .
. (variable length) .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

option-code OPTION_CLIENTID (TBD)

option-len Length of DUID in octets

option-data The DUID for the client

23.3. Server Identifier option

The Server Identifier option is used to carry a DUID identifying
a server between a client and a server. The format of the Server
Identifier option is:

0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | OPTION_SERVERID | option-len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. .
. DUID (cont.) .
. (variable length) .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Bound, Carney, Perkins, Droms (ed.) Expires 30 May 2002 [Page 59]

Internet Draft DHCP

option-code OPTION_SERVERID (TBD)

option-len Length of DUID in octets

option-data The DUID for IPv6 (-22) 21 Dec 2001

22.3. the server

23.4. Identity association option

The identity association option is used to carry an identity
association, the parameters associated with the IA and the addresses
assigned to the IA.

Droms (ed.), et al. Expires 1 Aug 2002 [Page 61]

Internet Draft DHCP for IPv6 (-23) 1 Feb 2002

The format of the IA option is:

0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| OPTION IA | option-len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IAID (4 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| T1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| T2 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IA Status | |
+-+-+-+-+-+-+-+-+ |
. Options .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

option-code OPTION_IA (TBD)

option-len See section 22. 23.

IAID The unique identifier for this IA.

T1 The time at which the client contacts the
server from which the addresses in the IA
were obtained to extend the lifetimes of the
addresses assigned to the IA.

T2 The time at which the client contacts any
available server to extend the lifetimes of
the addresses assigned to the IA.

IA status Status of the IA in this option.

options Options associated with this IA.

The Options field encapsulates those options that are specific
to this IA. For example, all of the Address Options carrying the
addresses associated with this IA are in the Options field.

Note that an IA has no explicit "lifetime" or "lease length" of
its own. When the lifetimes of all of the addresses in an IA have
expired, the IA can be considered as having expired. T1 and T2

Bound, Carney, Perkins, Droms (ed.) Expires 30 May 2002 [Page 60]

Internet Draft DHCP for IPv6 (-22) 21 Dec 2001
are included to give servers explicit control over when a client
recontacts the server about a specific IA.

In a message sent by a client to a server, values in the T1 and
T2 fields indicate the client's preference for those parameters.
The client may send 0 if it has no preference for T1 and T2. In a

Droms (ed.), et al. Expires 1 Aug 2002 [Page 62]

Internet Draft DHCP for IPv6 (-23) 1 Feb 2002

message sent by a server to a client, the client MUST use the values
in the T1 and T2 fields for the T1 and T2 parameters. The values in
the T1 and T2 fields are the number of seconds until T1 and T2.

The server MUST set the T1 and T2 times to values that will allow
the client to extend as appropriate the lifetimes of any addresses
in the IA. If the server does not intend for a client to extend the
lifetimes of a particular address in an IA, the server MAY set the
renewal time values to occur after the lifetimes on that address
expire.

T1 is the time at which the client SHOULD begin the lifetime
extension process by sending a Renew message to the server that
originally assigned the addresses to the IA. T2 is the time at which
the client SHOULD start sending a Rebind message to any server. A
client MAY begin the lifetime extension process prior to T1 if it
needs additional addresses for some reason.

T1 and T2 are specified as unsigned integers that specify the time
in seconds relative to the time at which the messages containing the
option is received.

Bound, Carney, Perkins, Droms (ed.) Expires 30 May 2002 [Page 61]

Internet Draft DHCP for IPv6 (-22) 21 Dec 2001

22.4.

23.5. IA Address option

The IA Address option is used to specify IPv6 addresses associated
with an IA. The IA Address option must be encapsulated in the
Options field of an Identity Association option. The Options field
encapsulates those options that are specific to this address.

Droms (ed.), et al. Expires 1 Aug 2002 [Page 63]

Internet Draft DHCP for IPv6 (-23) 1 Feb 2002

The format of the IA Address option is:

0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| OPTION_IAADDR | option-len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|T| addr status | prefix length | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
| IPv6 address |
| (16 octets) |
| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | preferred lifetime |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| pref. lifetime (cont.) | valid lifetime |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| valid lifetime (cont.) | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
. .
. Options .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

option-code OPTION_IADDR (TBD)

option-len See section 22. 23.

T When set to 1, indicates that this address is a
"temporary address" [17]; [16]; when set to 0, the address
is not a temporary address.

addr status Status of this address in this IA.

prefix length Prefix length for this address.

IPv6 address An IPv6 address

preferred lifetime The preferred lifetime for the IPv6 address in
the option.

valid lifetime The valid lifetime for the IPv6 address in the
option

Bound, Carney, Perkins, Droms (ed.) Expires 30 May 2002 [Page 62]

Internet Draft DHCP for IPv6 (-22) 21 Dec 2001

options Options associated with this address

In a message sent by a client to a server, values in the preferred
and valid lifetime fields indicate the client's preference for those
parameters. The client may send 0 if it has no preference for the
preferred and valid lifetimes. In a message sent by a server to a
client, the client MUST use the values in the preferred and valid

Droms (ed.), et al. Expires 1 Aug 2002 [Page 64]

Internet Draft DHCP for IPv6 (-23) 1 Feb 2002

lifetime fields for the preferred and valid lifetimes. The values in
the preferred and valid lifetimes are the number of seconds remaining
in each lifetime.

One or more IA Address Options can appear anywhere in an IA option.

22.5.

23.6. Requested Temporary Addresses (RTA) Option

The Requested Temporary Addresses (RTA) option is used by a client to
request a server to assign additional temporary addresses to an IA.

0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| OPTION_RTA | option-len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| num-requested |
+-+-+-+-+-+-+-+-+

option-code OPTION_RTA (TBD)

option-len See section 22. 23.

num-requested The number of additional temporary addresses the
client is requesting. This is an unsigned value.

This option MUST only be sent by a client and only in a Solicit,
Request, Renew, or Rebind message. It MUST only appear encapsulated
within an Identity association option. A client that does not need
any additional temporary addresses does not need to MUST only include
this
option.

Bound, Carney, Perkins, Droms (ed.) Expires 30 May 2002 [Page 63]

Internet option when it wants to have additional temporary address
allocated; a client SHOULD NOT send this option if 'num-requested' is
0.

23.7. Option Request option

The Option Request option is used to identify a list of options in a
message between a client and a server.

Droms (ed.), et al. Expires 1 Aug 2002 [Page 65]

Internet Draft DHCP for IPv6 (-22) 21 Dec 2001

22.6. (-23) 1 Feb 2002

The format of the Option request Request option is:

0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| OPTION_ORO | option-len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| requested-option-code-1 | requested-option-code-2 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

option-code OPTION_ORO (TBD)

option-len See section 22. 23.

requested-option-code-n The option code for an option requested by
the client.

A client MAY include an Option Request option in a Solicit, Request,
Renew, Rebind or Rebind, Confirm or Information-request message to inform the
server about options the client wants the server to send to the
client.

22.7.

23.8. Preference option

0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| OPTION_PREFERENCE | option-len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| pref value |
+-+-+-+-+-+-+-+-+

option-code OPTION_PREFERENCE (TBD)

option-len See section 22. 23.

pref value The preference value for the server in this message.

A server MAY include a Preference option in an Advertise message to
control the selection of a server by the client. See section 17.1.3 18.1.3
for the use of the Preference option by the client and the
interpretation of Preference option data value.

Bound, Carney, Perkins,

Droms (ed.) (ed.), et al. Expires 30 May 1 Aug 2002 [Page 64] 66]

Internet Draft DHCP for IPv6 (-22) 21 Dec 2001

22.8. (-23) 1 Feb 2002

23.9. Elapsed Time

0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| OPTION_ELAPSED_TIME | option-len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| elapsed time |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

option-code OPTION_ELAPSED_TIME (TBD)

option-len See section 22. 23.

elapsed time The amount of time since the client began its
current DHCP transaction. This time is expressed in
hundredths of a second (10^-2 seconds).

A client MAY include an Elapsed Time option in messages to indicate
how long the client has been trying to complete a DHCP transaction.
Servers and Relay Agents MAY use the data value in this option
as input to policy controlling how a server responds to a client
message.

22.9.

23.10. Client message option

0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| OPTION_CLIENT_MSG | option-len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
. DHCP client message .
. .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

option-code OPTION_CLIENT_MSG (TBD)

option-len See section 22. 23.

DHCP client message The message received from the client;
forwarded verbatim to the server.

A relay agent forwards a message from a client to a server as the
contents of a Client Message option in a Relay-forward message.

Bound, Carney, Perkins,

Droms (ed.) (ed.), et al. Expires 30 May 1 Aug 2002 [Page 65] 67]

Internet Draft DHCP for IPv6 (-22) 21 Dec 2001

22.10. (-23) 1 Feb 2002

23.11. Server message option

0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| OPTION_SERVER_MSG | option-len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
. DHCP server message .
. .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

option-code OPTION_SERVER_MSG (TBD)

option-len See section 22. 23.

DHCP server message The message received from the server;
forwarded verbatim to the client.

A server sends a DHCP message to be forwarded to a client by a relay
agent as the contents of a Server Message option in a Relay-reply
message.

22.11. DSTM Global IPv4 Address Option

23.12. Authentication option

The DSTM Global IPv4 Address Option informs a client or server that Authentication option carries authentication information to
authenticate the Identity Association Option (IA) encapsulated identity and contents of DHCP messages. The use of
the Authentication option is described in this section 22. If present,
the Authentication option
contains or requests an IPv4-Mapped IPv6 Address [10], MUST appear as used the first option in the
``Dual Stack Transition Mechanism'' (DSTM) [3]. DHCP
message.

Droms (ed.), et al. Expires 1 Aug 2002 [Page 68]

Internet Draft DHCP for IPv6 (-23) 1 Feb 2002

The format of the Authentication option is:

option-code OPTION_DSTM OPTION_AUTH (TBD)

option-len See section 22.

options Options associated with DSTM.

Bound, Carney, Perkins, Droms (ed.) Expires 30 May 2002 [Page 66]

Internet Draft DHCP for IPv6 (-22) 21 Dec 2001

One Identity Association Option MUST always be encapsulated within 23.

protocol The authentication protocol used in
this authentication option

algorithm The algorithm used in the DSTM Global IPv4 Address Option options field and that Identity
Association MUST only be
authentication protocol

RDM The replay detection method used in
this authentication option

Replay detection The replay detection information for IPv4-Mapped IPv6 Addresses.

A DSTM Tunnel End Point Option MAY be encapsulated within
the DSTM
Global IPv4 Address Option RDM

Authentication information The authentication information,
as specified by the protocol and
algorithm used in this authentication
option

23.13. Server unicast option

The server MAY send this option to a client to indicate to specify one or more tunnel endpoints.

DISCUSSION:

By encapsulation the Identity Association Option within client
that is allowed to unicast messages to the DSTM Global IPv4 Address Option, a server. The server that does
not support
specifies the IPv6 address type will simply ignore to which the entire
option and therefore not improperly allocate any addresses client is to send unicast
messages in the Identity Association. This technique of using an
address typing server-address field. When a client receives this
option, SHOULD be used for other where permissible, the client MAY send messages directly to
the server using the IPv6 address
types that may be needed specified in the future.

22.12. DSTM Tunnel EndPoint Option

A DSTM Tunnel EndPoint Option can be used to provide a set server-address
field of IPv6
addresses to be used as the Tunnel Endpoint (TEP) option.

Details about when the client may send messages to encapsulate an the server using
unicast are in section 19.

Droms (ed.), et al. Expires 1 Aug 2002 [Page 69]

Internet Draft DHCP for IPv6 packet within IPv6. (-23) 1 Feb 2002

0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| OPTION_DSTM_TEP OPTION_UNICAST | option-length option-len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Tunnel End Point (TEP) |
| (16 octets) server-address |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

option-code OPTION_DSTM_TEP OPTION_UNICAST (TBD)

option-len See section 22.

tunnel end point IPv6 23.

server-address The IP address or addresses.

A DSTM Tunnel EndPoint to which the client should send
messages delivered using unicast

23.14. Status Code Option MUST NOT be used except when
encapsulated in a DSTM Global IPv4 Address option.

22.13. Authentication option

The Authentication

This option carries authentication information returns a status indication related to
authenticate the identity and contents of DHCP messages. The use of
the Authentication option is described message
in section 21.

Bound, Carney, Perkins, Droms (ed.) Expires 30 May 2002 [Page 67]

Internet Draft DHCP for IPv6 (-22) 21 Dec 2001

The format of the Authentication option is: which it appears.

0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| OPTION_AUTH OPTION_STATUS_CODE | option-len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Protocol | Algorithm | RDM | Replay detect.|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Replay Detection (64 bits) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Replay cont. | Auth. Info |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| status-code | status-message | Authentication Information
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
| ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

option-code OPTION_AUTH OPTION_STATUS_CODE (TBD)

option-len See section 22.

protocol The authentication protocol used in
this authentication option

algorithm The algorithm used in the
authentication protocol

RDM The replay detection method used in
this authentication option

Replay detection 23.

status-code The replay detection information numeric code for the RDM

Authentication information The authentication information,
as specified by the protocol and
algorithm used status encoded in
this authentication
option

22.14. Server unicast option option. The server MAY send this status codes are defined in
section 7.4.

status-message A UTF-8 encoded text string, which MUST NOT
be null-terminated.

23.15. User Class Option

This option to a client to indicate to the client
that is allowed to unicast messages to the server. When used by a client
receives this option, where permissible, the client MAY send messages to identify the server using the IPv6 address that the server specifies type or category of
user or applications it represents. The information contained in the
server address field in this option.

Bound, Carney, Perkins,

Droms (ed.) (ed.), et al. Expires 30 May 1 Aug 2002 [Page 68] 70]

Internet Draft DHCP for IPv6 (-22) 21 Dec 2001

Details about when the client may send messages to the server using
unicast are in section 18.

0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 (-23) 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| OPTION_UNICAST | option-len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

option-code OPTION_UNICAST (TBD)

option-len See section 22.

22.15. Domain Search Option

This Feb 2002

data area of this option provides a list is contained in one or more opaque fields
that represent the user class or classes of domain names a which the client can use to
resolve DNS names.

0 1 2 3 is a
member. The user class information carried in this option MUST be
configurable on the client.

0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| OPTION_DOMAIN_SEARCH_LIST OPTION_USER_CLASS | option-len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Domain Search List user class data |
| ... . . . |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

option-code OPTION_DOMAIN_SEARCH_LIST (TBD) TBD

option-len See section 22.

Domain Search List 23.

user class data The DNS domain search list user classes carried by the client
should use to resolve names. client.

The domain search list is stored in data area of the user class option according to
section 10.

Bound, Carney, Perkins, Droms (ed.) Expires 30 May 2002 [Page 69]

Internet Draft DHCP for IPv6 (-22) 21 Dec 2001

22.16. Domain Name Server Option

This option provides a list of MUST contain one or more IP addresses
instances of DNS
servers to which a client's DNS resolver MAY send DNS [14] queries. user class data. Each instance of the user class data
is formatted as follows:

+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-...-+-+-+-+-+-+-+
| user class len | user class data |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-...-+-+-+-+-+-+-+

The DNS servers are listed in user class len is two octets long and specifies the order length of preference for use by the
client resolver.

0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| OPTION_DNS_SERVERS | option-len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| DNS server (IP address) |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| DNS server (IP address) |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

option-code OPTION_DNS_SERVERS (11)

option-len See section 22.

DNS server IPv6 address
opaque user class data in network order.

Servers can interpret the meanings of multiple class specifications
in an implementation dependent or configuration dependent manner,
and so the use of multiple classes by a DNS name DHCP client should be based
on the specific server for implementation and configuration which will
be used to process that User class option. Servers not equipped to
interpret the user class information sent by a client to use.

22.17. Status Code MUST ignore it
(although it may be reported).

23.16. Vendor Class Option

This option returns a status indication related is used by clients and servers to the DHCP message exchange
vendor-specific information. The definition of this information
is vendor specific. The vendor is indicated in which the vendor
class identifier option. Servers not equipped to interpret
the vendor-specific information sent by a client MUST ignore it appears.

0
(although it may be reported). Clients which do not receive desired
vendor-specific information SHOULD make an attempt to operate without
it, although they may do so (and announce they are doing so) in a
degraded mode.

Droms (ed.), et al. Expires 1 2 3 Aug 2002 [Page 71]

Internet Draft DHCP for IPv6 (-23) 1 Feb 2002

0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| OPTION_STATUS_CODE OPTION_VENDOR_CLASS | option-len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| status-code | status-message vendor-id |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| option-data | ... |
. .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

option-code OPTION_STATUS_CODE (TBD)

Bound, Carney, Perkins, Droms (ed.) Expires 30 May 2002 [Page 70]

Internet Draft DHCP for IPv6 (-22) 21 Dec 2001 TBD

option-len See section 22.

status-code The numeric code for 23.

vendor-id A domain name belonging to the status encoded in vendor used to
identify the vendor that defined this vendor
class option.

option-data An opaque object of option-len octets,
presumably interpreted by vendor-specific
code on the clients and servers

The status codes are defined vendor-id must adhere to the rules in section 7.4.

status-message A UTF-8 encoded text string, which 10.

The Encapsulated vendor-specific options field MUST NOT be null-terminated.

22.18. Circuit-ID encoded as
a sequence of code/length/value fields of identical format to the
DHCP options field. Each of the encapsulated options is formatted as
follows.

0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| opt-code | option-len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| option-data |
| . . . |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

opt-code The code for the encapsulated option

option-len See section 23.

option-data The data area for the encapsulated option

23.17. Interface-Id Option

The relay agent MAY send the Circuit-ID Interface-id option to identify the
circuit-id
interface on which the client message was received. If a relay

Droms (ed.), et al. Expires 1 Aug 2002 [Page 72]

Internet Draft DHCP for IPv6 (-23) 1 Feb 2002

receives a Relay-reply message with an Interface-id option, the relay
forwards the message to the client through the interface identified
by the option

0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| OPTION_CIRCUIT_ID OPTION_INTERFACE_ID | option-len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| Circuit-ID Interface-Id |
. .
. .
. .
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

option-code OPTION_CIRCUIT_ID OPTION_INTERFACE_ID (TBD)

option-len See section 22.

Circuit-ID 23.

Interface-Id An opaque value of arbitrary length generated
by the relay agent. agent to identify one of the
relay agent's interfaces

The server MUST copy the Circuit-ID Interface-Id option from the Relay-Forward
message into the Relay-Reply message the server sends to the relay
agent in response to the Relay-Forward message. This option MUST NOT
appear in any message except a Relay-Forward or Relay-Reply message.

Bound, Carney, Perkins, Droms (ed.) Expires 30 May 2002 [Page 71]

Internet Draft DHCP

Servers MAY use the Interface-ID for IPv6 (-22) 21 Dec 2001

22.19. User Class Option

This option is used by a client to identify the type or category of
user or applications it represents. parameter assignment policies.
The information contained in
this option is Interface-ID SHOULD be considered an opaque field value, with policies
based on exact string match only; that represents the user class of
which is, the client is a member. The user class information carried in
this option MUST Interface-ID SHOULD
NOT be configurable on the client.

0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| OPTION_USER_CLASS | option-len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| user class data |
| . . . |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

option-code TBD

option-len See section 22.

user class data The user classes carried internally parsed by the client.

The user class option MUST contain one or more instances of user
class data. Each instance of the user class data is formatted as
follows:

+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-...-+-+-+-+-+-+-+
| user class len | user class data |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-...-+-+-+-+-+-+-+

The user class len is two octets long server.

24. Security Considerations

Section 22 describes a threat model and specifies an option that provides an
authentication framework to defend against that threat model.

25. Year 2000 considerations

Since all times are relative to the length current time of the
opaque user class data in network order.

Servers can interpret transaction,
there is no problem within the meanings of multiple class specifications
in an implementation dependent DHCPv6 protocol related to any
hardcoded dates or configuration dependent manner,
and so the use two-digit representation of multiple classes by a DHCP client should be based
on the specific server implementation and configuration which will
be used to process that User class option. Servers not equipped to
interpret the user class information sent by a client MUST ignore it
(although it may be reported).

22.20. Vendor Class Option

This option is used by clients and servers to exchange
vendor-specific information. The definition of this information
is vendor specific. The vendor is indicated in the vendor
class identifier option. Servers not equipped to interpret
the vendor-specific information sent by a client MUST ignore it
(although it may be reported). Clients which do not receive desired
vendor-specific information SHOULD make an attempt to operate without

Bound, Carney, Perkins, current year.

Droms (ed.) (ed.), et al. Expires 30 May 1 Aug 2002 [Page 72] 73]

Internet Draft DHCP for IPv6 (-22) 21 Dec 2001

it, although they may do so (and announce they are doing so) in a
degraded mode.

0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 (-23) 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| OPTION_VENDOR_CLASS | option-len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| vendor-id |
. .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| option-data |
. .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

option-code TBD

option-len See section 22.

vendor-id A domain Feb 2002

26. IANA Considerations

This document defines several new name belonging spaces associated with DHCPv6
and DHCPv6 options. IANA is requested to manage the vendor used allocation of
values from these name spaces, which are described in the remainder
of this section. These name spaces are all to
identify be managed separately
from the vendor that name spaces defined this vendor
class option.

option-data An opaque object for DHCPv4 [7, 1].

New values in each of option-len octets,
presumably interpreted these name spaces should be approved by vendor-specific
code on the clients and servers

The vendor-id must adhere
process of IETF consensus [15].

26.1. Multicast addresses

Section 7.1 defines the following multicast addresses, which have
been assigned by IANA for use by DHCPv6:

All_DHCP_Agents address: FF02::1:2

All_DHCP_Servers address: FF05::1:3

IANA is requested to manage definition of additional multicast
addresses in the rules future.

26.2. DHCPv6 message types

IANA is requested to record the message types defined in section 10.

The Encapsulated vendor-specific options field MUST be encoded as
a sequence 7.3.
IANA is requested to manage definition of code/length/value fields additional message types in
the future.

26.3. DUID

IANA is requested to record the DUID types defined in section 11.1.
IANA is requested to manage definition of identical format additional DUID types in
the future.

26.4. DHCPv6 options

IANA is requested to assign option-codes to the
DHCP options field. Each defined in
section 23. IANA is requested to manage the definition of additional
DHCPv6 option-codes in the encapsulated options future.

26.5. Status codes

IANA is formatted as
follows.

opt-code The code for requested to record the encapsulated option

option-len See status codes defined in section 22.

option-data The data area for 7.4.
IANA is requested to manage the encapsulated option

Bound, Carney, Perkins, definition of additional status codes
in the future.

Droms (ed.) (ed.), et al. Expires 30 May 1 Aug 2002 [Page 73] 74]

Internet Draft DHCP for IPv6 (-22) 21 Dec 2001

22.21. SIP Servers Domain Name List

This (-23) 1 Feb 2002

26.6. Authentication option specifies a list of fully-qualified domain names

Section 22 defines three new name spaces associated with the
Authentication Option (section 23.12), which are to be used created and
maintained by IANA: Protocol, Algorithm and RDM.

Initial values assigned from the SIP client to locate a SIP server (see
<draft-ietf-sip-srv-02.txt> [22] for more details.

The option MAY contain multiple domain names, but these SHOULD refer
to different SRV records, rather than different A records. Domain
names SHOULD be listed in order of preference.

0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 Protocol name space are 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| OPTION_SIP_SERVER_D | option-len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SIP Server Domain Name List |
| ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

option-code OPTION_SIP_SERVER_D (TBD)

option-len See (for the
configuration token Protocol in section 22.

SIP Server Domain List The list of SIP servers 22.5) and 1 (for the client
should use (see delayed
authentication Protocol in section 10 22.6). Additional protocols may
be defined in the future.

The Algorithm name space is specific to individual Protocols. That
is, each Protocol has its own Algorithm name space. The guidelines
for assigning Algorithm name space values for
encoding details).

22.22. SIP Servers IPv6 Address List

This option specifies a list particular protocol
should be specified along with the definition of IPv6 addresses indicating
SIP outbound proxy servers available to a new Protocol.

For the client (see
<draft-ietf-sip-srv-02.txt> [22] for more details. Servers SHOULD configuration token Protocol, the Algorithm field MUST be
listed
0, as described in order of preference.

0 1 2 3 4 5 6 7 8 9 0 section 22.5. For the delayed authentication
Protocol, the Algorithm value 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| OPTION_SIP_SERVER_A | option-len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| SIP Server (IP address) |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| SIP Server (IP address) |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Bound, Carney, Perkins, Droms (ed.) Expires 30 May 2002 [Page 74]

Internet Draft DHCP for IPv6 (-22) 21 Dec 2001

option-code OPTION_SIP_SERVER_A (TBD)

option-len See section 22.

SIP Server IPv6 address of a SIP server for the client is assigned to use.
The servers are listed in the order of preference HMAC-MD5
generating function as defined in section 22.6. Additional
algorithms for
use by the client.

23. Security Considerations

Section 21 describes a threat model and an option that provides an delayed authentication framework to defend against that threat model.

24. Year 2000 considerations

Since all times are relative to the current time of the transaction,
there is no problem within the DHCPv6 protocol related to any
hardcoded dates or two-digit representation may be defined in
the future.

The initial value of 0 from the current year.

25. IANA Considerations

This document defines several new RDM name spaces associated with DHCPv6
and DHCPv6 options. IANA space is requested assigned to manage the allocation
use of
values from these name spaces, which are described a monotonically increasing value as defined in the remainder
of this section. These name spaces are all to section 22.4.
Additional replay detection methods may be managed separately
from the name spaces defined for DHCPv4 [8, 2].

New values in each of these name spaces should be approved by the
process of IETF consensus [16].

25.1. Multicast addresses

Section 7.1 defines future.

27. Acknowledgments

Thanks to the following multicast addresses, which have
been assigned by IANA DHC Working Group for use their time and input into the
specification. In particular, thanks also for the consistent input,
ideas, and review by DHCPv6:

All_DHCP_Agents address: FF02::1:2

All_DHCP_Servers address: FF05::1:3

IANA is requested (in alphabetical order) Thirumalesh Bhat,
Vijayabhaskar, Brian Carpenter, Matt Crawford, Francis Dupont,
Josh Littlefield, Gerald Maguire, Jack McCann, Thomas Narten, Erik
Nordmark, Yakov Rekhter, Mark Stapp, Matt Thomas, Sue Thomson, and
Phil Wells.

Thanks to manage definition of additional multicast
addresses in Steve Deering and Bob Hinden, who have consistently
taken the future.

25.2. DHCPv6 message types

IANA is requested time to record discuss the message types defined more complex parts of the IPv6
specifications.

Bill Arbaugh reviewed the authentication mechanism described in
section 7.3.
IANA is requested 22.

And, thanks to manage definition of additional message types Steve Deering for pointing out at IETF 51 in London
that the future.

Bound, Carney, Perkins, DHCPv6 specification has the highest revision number of any
Internet Draft.

Droms (ed.) (ed.), et al. Expires 30 May 1 Aug 2002 [Page 75]

Internet Draft DHCP for IPv6 (-22) 21 Dec 2001

25.3. DUID

IANA is requested to record the DUID types defined in section 11.1.
IANA is requested to manage definition of additional DUID types in
the future.

25.4. DHCPv6 options

IANA is requested to assign option-codes to the options defined
in section 22.1. IANA is requested to manage the definition of
additional DHCPv6 option-codes (-23) 1 Feb 2002

References

[1] S. Alexander and R. Droms. DHCP Options and BOOTP Vendor
Extensions, March 1997. RFC 2132.

[2] S. Bradner. Key words for use in the future.

25.5. Status codes

IANA is requested RFCs to record Indicate Requirement
Levels, March 1997. RFC 2119.

[3] S. Bradner and A. Mankin. The Recommendation for the status codes defined in section 7.4.
IANA is requested to manage the definition of additional status codes
in the future.

25.6. Authentication option

Section 21 defines three new name spaces associated with the
Authentication Option (section 22.13), which are to be created IP Next
Generation Protocol, January 1995. RFC 1752.

[4] W.J. Croft and
maintained by IANA: J. Gilmore. Bootstrap Protocol, Algorithm September 1985.
RFC 951.

[5] S. Deering and RDM.

Initial values assigned from the Protocol name space are 0 (for the
configuration token Protocol R. Hinden. Internet Protocol, Version 6 (IPv6)
Specification, December 1998. RFC 2460.

[6] R. Draves. Default Address Selection for IPv6, September 2001.
work in section 21.5) progress.

[7] R. Droms. Dynamic Host Configuration Protocol, March 1997. RFC
2131.

[8] R. Droms, Editor, W. Arbaugh, and 1 (for the delayed
authentication Protocol in section 21.6). Additional protocols may
be defined in the future.

The Algorithm name space is specific to individual Protocols. That
is, each Protocol has its own Algorithm name space. The guidelines Editor. Authentication for assigning Algorithm name space values
DHCP Messages, June 2001. RFC 3118.

[9] R. Hinden and S. Deering. IP Version 6 Addressing Architecture,
July 1998. RFC 2373.

[10] S. Kent and R. Atkinson. Security Architecture for a particular protocol
should be specified along with the definition of a new Protocol.

For the configuration token Protocol, the Algorithm field MUST be
0, as described in section 21.5. For the delayed authentication Internet
Protocol, the Algorithm value 1 is assigned to the HMAC-MD5
generating function as defined in section 21.6. Additional
algorithms for the delayed authentication protocol may be defined in
the future.

The initial value of 0 from the RDM name space is assigned to the
use of a monotonically increasing value as defined in section 21.4.
Additional replay detection methods may be defined November 1998. RFC 2401.

[11] H. Krawczyk, M. Bellare, and R. Canetti. HMAC: Keyed-Hashing
for Message Authentication, February 1997. RFC 2104.

[12] David L. Mills. Network Time Protocol (Version 3)
Specification, Implementation, March 1992. RFC 1305.

[13] P.V. Mockapetris. Domain names - concepts and facilities,
November 1987. RFC 1034.

[14] P.V. Mockapetris. Domain names - implementation and
specification, November 1987. RFC 1035.

[15] T. Narten and H. Alvestrand. Guidelines for Writing an IANA
Considerations Section in the future.

26. Acknowledgments

Thanks to the DHC Working Group RFCs, October 1998. RFC 2434.

[16] T. Narten and R. Draves. Privacy Extensions for their time Stateless
Address Autoconfiguration in IPv6, January 2001. RFC 3041.

[17] T. Narten, E. Nordmark, and input into
the specification. In particular, thanks also W. Simpson. Neighbor Discovery for the consistent

Bound, Carney, Perkins,
IP Version 6 (IPv6), December 1998. RFC 2461.

Droms (ed.) (ed.), et al. Expires 30 May 1 Aug 2002 [Page 76]

Internet Draft DHCP for IPv6 (-22) 21 Dec 2001

input, ideas, and review by (in alphabetical order) Brian Carpenter,
Matt Crawford, Francis Dupont, Ted Lemon, Josh Littlefield, Gerald
Maguire, Jack McCann, Thomas Narten, Erik Nordmark, Yakov Rekhter,
Mark Stapp, Matt Thomas, Sue Thomson, Bernie Volz and Phil Wells.

Thanks to Steve Deering and Bob Hinden, who have consistently
taken the time (-23) 1 Feb 2002

[18] D.C. Plummer. Ethernet Address Resolution Protocol: Or
converting network protocol addresses to discuss the more complex parts of the IPv6
specifications.

Bill Arbaugh reviewed the authentication mechanism described in
section 21.

The Domain Search option described in section 22.15 is based on the
DHCPv4 domain search option, [1], and was reviewed by Bernard Aboba.

And, thanks to Steve Deering 48.bit Ethernet address
for pointing out at IETF 51 in London
that the DHCPv6 specification has (at least currently) the highest
revision number of any Internet Draft.

A. Full Copyright Statement

[19] J. Postel. User Datagram Protocol, August 1980. RFC 768.

This document and translations of it may be copied MD5 Message-Digest Algorithm, April 1992. RFC
1321.

[21] S. Thomson and furnished to
others, T. Narten. IPv6 Stateless Address
Autoconfiguration, December 1998. RFC 2462.

[22] P. Vixie, Ed., S. Thomson, Y. Rekhter, and derivative works that comment on or otherwise explain it
or assist J. Bound. Dynamic
Updates in its implementation may the Domain Name System (DNS UPDATE), April 1997. RFC
2136.

Chair's Address

The working group can be prepared, copied, published
and distributed, in whole or in part, without restriction of any
kind, provided that contacted via the above copyright notice and this paragraph
are included on all such copies and derivative works. However, current chair:

Ralph Droms
Cisco Systems
300 Apollo Drive
Chelmsford, MA 01824

Phone: (978) 244-4733
E-mail: rdroms@cisco.com

Authors' Addresses

Questions about this document itself may not memo can be modified in any way, such as by
removing the copyright notice or references to the Internet Society
or other directed to:

Droms (ed.), et al. Expires 1 Aug 2002 [Page 77]

Internet organizations, except as needed Draft DHCP for the purpose
of developing Internet standards in which case the procedures
for copyrights defined in the Internet Standards process must be
followed, or as required to translate it into languages other than
English.

The limited permissions granted above are perpetual and will not be
revoked by the Internet Society or its successors or assigns.

This document and the information contained herein is provided on an
"AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.

Bound, Carney, Perkins, IPv6 (-23) 1 Feb 2002

Jim Bound
Compaq Computer Corporation
ZK3-3/W20
110 Spit Brook Road
Nashua, NH 03062-2698
USA
Voice: +1 603 884 0062
E-mail: Jim.Bound@compaq.com

Mike Carney
Sun Microsystems, Inc
Mail Stop: UMPK17-202
901 San Antonio Road
Palo Alto, CA 94303-4900
USA
Voice: +1-650-786-4171
E-mail: mwc@eng.sun.com

Charles E. Perkins
Communications Systems Lab
Nokia Research Center
313 Fairchild Drive
Mountain View, California 94043
USA
Voice: +1-650 625-2986
E-mail: charliep@iprg.nokia.com
Fax: +1 650 625-2502

Ted Lemon
Nominum, Inc.
950 Charter Street
Redwood City, CA 94043
E-mail: Ted.Lemon@nominum.com

Bernie Volz
Ericsson
959 Concord St
Framingham, MA 01701
Voice: +1-508-875-3162
Fax: +1-508-875-3018
E-mail: bernie.volz@ericsson.com

Ralph Droms
Cisco Systems
300 Apollo Drive
Chelmsford, MA 01824
USA
Voice: +1 978 479 4733
E-mail: rdroms@cisco.com

Droms (ed.) (ed.), et al. Expires 30 May 1 Aug 2002 [Page 77] 78]

Internet Draft DHCP for IPv6 (-22) 21 Dec 2001

B. (-23) 1 Feb 2002

A. Appearance of Options in Message Types

The following table indicates with a "*" the options are allowed in
each DHCP message type:

DUID

Client Server IA RTA ORO Option Pref Time Client Server DSTM DSTM
ID ID Request Forw. Forw. Addr Tunn
Solicit * * * *
Advert. * * * * * * *
Request * * * * *
Confirm * * * *
Renew * * * * *
Rebind * * * *
Decline * * * * *
Release * * * *
Reply *
Reply * * * * * *
Reconf. * * *
Inform. * (see note) *
R-forw. * *
R-repl. * *

NOTE:

Only included in Information-Request messages that are sent
in response to a Reconfigure (see section 20.3.3).

Auth Server Domain Domain Status Circ. User Vendor
Unica. Search Server Code ID Class Class
Solicit * * *
Advert. * * *
Request * * *
Confirm * * *
Renew * * *
Rebind * * *
Decline * * * *
Release * * * *
Reply * * * * *
Reconf. *
Inform. * * *
R-forw. * *
R-repl. * *

Bound, Carney, Perkins, Droms (ed.) Expires 30 May 2002 [Page 78]

Internet Draft DHCP for IPv6 (-22) 21 Dec 2001

C. Appearance of Options in the Options Field of DHCP Messages

The following table indicates with a "*" where options can appear in
the options field or encapsulated in other options:

Option IA IAADDR RTA DSTM Client Server
Field Addr Forw. Forw.
Client msg. * *
Server msg. * *
DUID *
IA * *
IAADDR *
RTA *
ORO *
Pref *
Time *
Client Forw. *
Server Forw. *
DSTM Addr. *
DSTM Tunnel *
Authentic. *
Server Uni. *
Dom. Srch. *
Dom. Server *
Status Cod. * * *
Circ. ID * *
User Class *
Vend. Class *

References

[1] B. Aboba. DHCP Domain Search Option. Internet Draft, Internet
Engineering Task Force, December 2000. Work in progress.

[2] S. Alexander and R. Droms. DHCP Options and BOOTP Vendor
Extensions, March 1997. RFC 2132.

[3] J. Bound, L. Toutain, F. Dupont, O. Medina, A. Hossam, and
A. Durand. Dual Stack Transition Mechanism (DSTM). Internet
Draft, Internet Engineering Task Force, November 2001. Work in
progress.

[4] S. Bradner. Key words for use in RFCs to Indicate Requirement
Levels, March 1997. RFC 2119.

[5] S. Bradner and A. Mankin. The Recommendation for the IP Next
Generation Protocol, January 1995. RFC 1752.

Bound, Carney, Perkins, Droms (ed.) Expires 30 May 2002 [Page 79]

Internet Draft DHCP for IPv6 (-22) 21 Dec 2001

[6] W.J. Croft and J. Gilmore. Bootstrap Protocol, September 1985.
RFC 951.

[7] S. Deering and R. Hinden. Internet Protocol, Version 6 (IPv6)
Specification, December 1998. RFC 2460.

[8] R. Droms. Dynamic Host Configuration Protocol, March 1997. RFC
2131.

[9] R. Droms, Editor, W. Arbaugh, and Editor. Authentication for
DHCP Messages, June 2001. RFC 3118.

[10] R. Hinden and S. Deering. IP Version 6 Addressing Architecture,
July 1998. RFC 2373.

[11] S. Kent and R. Atkinson. Security Architecture for the Internet
Protocol, November 1998. RFC 2401.

[12] H. Krawczyk, M. Bellare, and R. Canetti. HMAC: Keyed-Hashing
for Message Authentication, February 1997. RFC 2104.

[13] David L. Mills. Network Time Protocol (Version 3)
Specification, Implementation, March 1992. RFC 1305.

[14] P.V. Mockapetris. Domain names - concepts and facilities,
November 1987. RFC 1034.

[15] P.V. Mockapetris. Domain names - implementation and
specification, November 1987. RFC 1035.

[16] T. Narten and H. Alvestrand. Guidelines for Writing an IANA
Considerations Section in RFCs, October 1998. RFC 2434.

[17] T. Narten and R. Draves. Privacy Extensions for Stateless
Address Autoconfiguration in IPv6, January 2001. RFC 3041.

[18] T. Narten, E. Nordmark, and W. Simpson. Neighbor Discovery for
IP Version 6 (IPv6), December 1998. RFC 2461.

[19] D.C. Plummer. Ethernet Address Resolution Protocol: Or
converting network protocol addresses to 48.bit Ethernet address
for transmission on Ethernet hardware, November 1982. RFC 826.

[20] J. Postel. User Datagram Protocol, August 1980. RFC 768.

[21] R. Rivest. * * *
Reconf. *
Inform. * * *
R-forw. * *
R-repl. * *

B. Appearance of Options in the Options Field of DHCP Messages

The MD5 Message-Digest Algorithm, April 1992. RFC
1321.

[22] H. Schulzrinne and J. Rosenberg. SIP: Session Initiation
Protocol -- Locating SIP Servers. Internet Draft, Internet
Engineering Task Force, March 2001. Work following table indicates with a "*" where options can appear in progress.

Bound, Carney, Perkins,
the options field or encapsulated in other options:

Droms (ed.) (ed.), et al. Expires 30 May 1 Aug 2002 [Page 80] 79]

Internet Draft DHCP for IPv6 (-22) 21 Dec 2001

[23] S. Thomson (-23) 1 Feb 2002

Option IA IAADDR RTA Client Server
Field Forw. Forw.
Client msg. * *
Server msg. * *
DUID *
IA *
IAADDR *
RTA *
ORO *
Pref *
Time *
Client Forw. *
Server Forw. *
DSTM Addr. *
DSTM Tunnel *
Authentic. *
Server Uni. *
Dom. Srch. *
Dom. Server *
Status Cod. * * *
Circ. ID * *
User Class *
Vend. Class *

C. Full Copyright Statement

This document and T. Narten. IPv6 Stateless Address
Autoconfiguration, December 1998. RFC 2462.

[24] P. Vixie, Ed., S. Thomson, Y. Rekhter, translations of it may be copied and J. Bound. Dynamic
Updates furnished to
others, and derivative works that comment on or otherwise explain it
or assist in its implementation may be prepared, copied, published
and distributed, in whole or in part, without restriction of any
kind, provided that the above copyright notice and this paragraph
are included on all such copies and derivative works. However,
this document itself may not be modified in any way, such as by
removing the copyright notice or references to the Internet Society
or other Internet organizations, except as needed for the purpose
of developing Internet standards in which case the Domain Name System (DNS UPDATE), April 1997. RFC
2136.

Chair's Address procedures
for copyrights defined in the Internet Standards process must be
followed, or as required to translate it into languages other than
English.

The working group can limited permissions granted above are perpetual and will not be contacted via
revoked by the current chair:

Ralph Droms
Cisco Systems
300 Apollo Drive
Chelmsford, MA 01824

Phone: (978) 244-4733
E-mail: rdroms@cisco.com

Bound, Carney, Perkins, Internet Society or its successors or assigns.

Droms (ed.) (ed.), et al. Expires 30 May 1 Aug 2002 [Page 81] 80]

Internet Draft DHCP for IPv6 (-22) 21 Dec 2001

Authors' Addresses

Questions about this memo can be directed to:

Jim Bound
Compaq Computer Corporation
ZK3-3/W20
110 Spit Brook Road
Nashua, NH 03062-2698
USA
Phone: +1 603 884 0062
Email: Jim.Bound@compaq.com

Mike Carney
Sun Microsystems, Inc
Mail Stop: UMPK17-202
901 San Antonio Road
Palo Alto, CA 94303-4900
USA
Phone: +1-650-786-4171
Email: mwc@eng.sun.com

Charles E. Perkins
Communications Systems Lab
Nokia Research Center
313 Fairchild Drive
Mountain View, California 94043
USA
Phone: +1-650 625-2986
Email: charliep@iprg.nokia.com
Fax: +1 650 625-2502

Ralph Droms
Cisco Systems
300 Apollo Drive
Chelmsford, MA 01824
USA
Phone: +1 978 244 4733
Email: rdroms@cisco.com

Bound, Carney, Perkins, (-23) 1 Feb 2002

BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.

Droms (ed.) (ed.), et al. Expires 30 May 1 Aug 2002 [Page 82] 81]
----