WDIFF

draft-ietf-ngtrans-isatap-15.txt --> draft-ietf-ngtrans-isatap-16.txt

Network Working Group F. Templin
Internet-Draft Nokia
Expires: March 10, April 14, 2004 T. Gleeson
Cisco Systems K.K.
M. Talwar
D. Thaler
Microsoft Corporation
September 10,
October 15, 2003

Intra-Site Automatic Tunnel Addressing Protocol (ISATAP)
draft-ietf-ngtrans-isatap-15.txt
draft-ietf-ngtrans-isatap-16.txt

Status of this Memo

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.

This Internet-Draft will expire on March 10, April 14, 2004.

Abstract

This document specifies an Intra-Site Automatic Tunnel Addressing
Protocol (ISATAP) that connects IPv6 hosts and routers within IPv4
sites. ISATAP treats the site's IPv4 unicast infrastructure as a
Non-Broadcast, Multiple Access (NBMA) link layer for IPv6. IPv6 with no
requirement for IPv4 multicast. ISATAP enables intra-site automatic IPv6-in-IPv4
tunneling whether globally assigned or private IPv4 addresses are
used.

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Table of Contents

1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Requirements . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
4. Basic IPv6 Operation . . . . . . . . . . . . . . . . . . . . . 4
5. Automatic Tunneling . . . . . . . . . . . . . . . . . . . . . 5 6
6. Neighbor Discovery . . . . . . . . . . . . . . . . . . . . . . 6 8
7. Address Autoconfiguration . . . . . . . . . . . . . . . . . . 9 12
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9 12
9. Security considerations . . . . . . . . . . . . . . . . . . . 9 12
10. Acknowledgements Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 10 12
Normative References . . . . . . . . . . . . . . . . . . . . . 10 13
Informative References . . . . . . . . . . . . . . . . . . . . 11 14
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 12 15
A. Major Changes . . . . . . . . . . . . . . . . . . . . . . . . 12 15
B. Rationale for Interface Identifier Construction . . . . . . . 14
C. Deployment Considerations . . . . . . . . . . . . . . . . . . 15
D. Other Considerations . . . . . . . . . . . . . . . . . . . . . 15 16
Intellectual Property and Copyright Statements . . . . . . . . 17 18

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1. Introduction

This document presents specifies a simple approach mechanism called the Intra-Site
Automatic Tunnel Addressing Protocol (ISATAP) that enables
incremental deployment of IPv6 [RFC2460] within IPv4 [RFC0791] sites.
ISATAP allows dual-stack nodes that do not share a link with an IPv6
router to automatically tunnel packets to the IPv6 next-hop address
through IPv4, i.e., the site's IPv4 infrastructure is treated as a
link layer for IPv6.

Specific

The main objectives of this document are to: 1) specify operational
details for the operation of IPv6 and automatic tunneling of IPv6 over IPv4 using ISATAP are given, including an interface identifier ISATAP, 2)
specify the format that
embeds of IPv6 interface identifiers using an embedded
IPv4 address. This format supports IPv6 address
configuration and simple link-layer address mapping. Also specified
is address, 3) specify the operation of IPv6 Neighbor Discovery and deployment/security
Address Autoconfiguration, and 4) discuss security considerations.

The specification in this document is very similar to [RFC2529], with
the primary distinction that ISATAP does not require IPv4 multicast
support within the site.

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 [RFC2119].

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. Terminology

The terminology of [RFC2460] [RFC2460][RFC2461][RFC2462] applies to this
document. The following additional terms are defined:

site:
same as defined in [RFC3582], which is intended to be equivalent
to "enterprise" as defined in [RFC1918].

link, on-link, off-link:
same as defined in ([RFC2461], section 2.1).

underlying link:
a link layer that supports IPv4 (for ISATAP),

ISATAP interface:
an interface used for automatic IPv6-in-IPv4 tunneling and MAY also support
IPv6 natively.
configured over one or more IPv4 addresses assigned to one or more
of the node's IPv4 interfaces that belong to the same site.

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ISATAP interface:
an interface configured over one or more underlying links.

advertising ISATAP interface:
same meaning as "advertising interface" advertising interface in ([RFC2461], section
6.2.2).

ISATAP address:
an address with an on-link prefix assigned on an ISATAP interface
and with an interface identifier constructed as specified in
Section 4.1.

4. Basic IPv6 Operation

ISATAP interfaces automatically tunnel IPv6 packets in IPv4 using the
site's IPv4 infrastructure as a link layer for IPv6, layer, i.e., IPv6 treats the
site's IPv4 infrastructure as a Non-Broadcast, Multiple Access (NBMA)
link layer, layer with properties similar to [RFC2491]. The following
ISATAP-specific considerations are noted
sections specify details for basic IPv6 operation: operation on ISATAP
interfaces:

4.1 Interface Identifiers and Unicast Addresses

ISATAP interface

Interface identifiers use "modified EUI-64" for ISATAP are constructed in Modified EUI-64
format ([RFC3513], as specified in ([ADDR-ARCH], section 2.5.1) and 2.5.1). They are formed
by appending an a 32-bit IPv4 address assigned
to an underlying link to the 32-bit string '00-00-5E-FE'. Appendix B
includes non-normative rationale for this construction rule.

IPv6 global leading token
'0000:5EFE', then setting the universal/local ("u") bit as follows:

When the IPv4 address is globally unique (i.e., provider-assigned),
the "u" bit is set to 1 and the leading token becomes '0200:5EFE'.
When the IPv4 address is from a private allocation [RFC1918], the "u"
bit is set to 0 and the leading token remains as '0000:5EFE'.

Global and local-use ([RFC3513], link-local IPv6 unicast addresses ([ADDR-ARCH], sections
2.5.4, 2.5.6) for ISATAP
addresses are constructed as follows:

(Appendix B provides additional non-normative details.)

4.2 ISATAP Interface Configuration

ISATAP interfaces are configured over one or more underlying links
that support IPv4 Management

The IP Tunnel MIB [MIB] is used, with the following additions for tunneling within a site;
ISATAP interfaces:

o For each IPv4 address
assigned to an underlying link ISATAP interface is seen as configured over, a link-layer
tuple consisting of the IPv4 address for
ISATAP.

4.3 Multicast and Anycast

ISATAP interfaces recognize an IPv6 node's required addresses
([RFC3513], section 2.8), including certain multicast/anycast ifIndex for the

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addresses.

Mechanisms for multicast/anycast emulation on ISATAP interfaces
(e.g., MARS [RFC2022], etc.) are out of scope.

5. Automatic Tunneling

The common tunneling mechanisms specified

corresponding IPv4 interface ([RFC2863], section 3.1.5) is added
to ifRcvAddressTable ([MIB], section 3.1.2).

o tunnelIfRemoteInetAddress in ([MECH], sections 2 and
3) are used, with the following noted considerations tunnelIfEntry object ([MIB],
section 4) is set to 0.0.0.0 for ISATAP:

5.1 Tunnel MTU and Fragmentation ISATAP automatic tunnel interfaces may be configured interfaces.

When an IPv4 address over multiple
underlying links with diverse maximum transmission units (MTUs). The
minimum MTU for IPv6 interfaces which an ISATAP interface is 1280 bytes ([RFC2460], Section 5),
but configured is
removed from its IPv4 interface, the corresponding (IPv4 addres,
ifIndex)-tuple MUST be removed from the following considerations apply for ISATAP interfaces:

o Nearly all interface
ifRcvAddressTable. If the IPv4 nodes connect address is also used as
tunnelIfLocalInetAddress ([MIB], section 5) in the ISATAP interface
tunnelIfEntry, the interface MUST either set tunnelIfLocalInetAddress
to physical links with MTUs of 1500
bytes a different IPv4 address or larger (e.g., Ethernet)

o Sub-IPv4 layer encapsulations (e.g., VPN) may occur on some paths

o Commonly-deployed VPN interfaces be disabled.

When a new IPv4 address is added to an IPv4 interface an ISATAP
interface is configured over, a new (IPv4 address, ifIndex)-tuple MAY
be added to ifRcvAddressTable and tunnelIfLocalInetAddress MAY be set
to the new address.

4.3 Multicast and Anycast

ISATAP interfaces recognize an IPv6 node's required addresses
([ADDR-ARCH], section 2.8). The following multicast mappings are
defined for packets sent on ISATAP interfaces:

o When the IPv6 destination address is the 'All-Routers'
([ADDR-ARCH], section 2.7.1) or
'All_DHCP_Relay_Agents_and_Servers' ([RFC3315], section 1.2)
multicast address, it is mapped to V4ADDR(i) for one or more
PRL(i)'s (see: Section 6.1). The manner of selecting PRL(i)'s is
up to the implementation.

Other multicast mappings, and mechanisms for general-purpose
multicast/anycast emulation on ISATAP interfaces are beyond the scope
of this document.

4.4 Source/Target Link Layer Address Options

Source/Target Link Layer Address Options ([RFC2461], section 4.6.1)
for ISATAP have the following format:

+-------+-------+-------+-------+-------+-------+-------+--------+
| Type |Length | 0 | 0 | IPv4 Address |
+-------+-------+-------+-------+-------+-------+-------+--------+

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Type:
1 for Source Link-layer address.
2 for Target Link-layer address.

Length:
1 (in units of 8 octets).

IPv4 Address:
The 32 bit IPv4 address, in network byte order.

5. Automatic Tunneling

ISATAP interfaces use the basic transition mechanisms specified in
[MECH] with the following exceptions:

5.1 Tunnel MTU and Fragmentation

The specification in ([MECH], section 3.2) is not used; the
specification in this section is used instead.

The minimum MTU for IPv6 interfaces is 1280 bytes ([RFC2460], Section
5), but the following operational considerations are noted:

o Nearly all IPv4 nodes connect to physical links with MTUs of 1500
bytes or larger (e.g., Ethernet)

o Sub-IPv4 layer encapsulations (e.g., VPN) may occur on some paths

o Commonly-deployed VPN interfaces use an MTU of 1400 bytes

To maximize efficiency and minimize IPv4 fragmentation for the
predominant deployment case, LinkMTU ([RFC2461], Section 6.3.2) for
the ISATAP interface interfaces SHOULD be
set to no more than 1380 bytes (1400 minus 20 bytes for IPv4
encapsulation).

LinkMTU MAY be set to larger values when a dynamic link layer (IPv4)
MTU discovery mechanism is used used, or when a static MTU assignment is
used and the anticipated/measured level of fragmentation in the
site's IPv4 network is deemed acceptable.

When a dynamic link layer MTU discovery mechanism is not used, the
ISATAP interface MUST NOT encapsulate IPv6 packets with the
Don't Fragment (DF) bit MUST NOT be set in the encapsulating IPv4 header.
header of packets sent on the ISATAP interface. In this case, black
holes may in rare instances occur along some paths even when the
tunnel interface uses the IPv6 minimum MTU of 1280 bytes. (This
concern is not specific to ISATAP interfaces, but applies to all
tunnels for which nested levels of sub link-layer encapsulation may

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occur.)

5.2 Handling IPv4 ICMP Errors

ARP failures and persistent ICMPv4 errors SHOULD be processed as
link-specific information indicating that a path to a neighbor has
failed ([RFC2461], section 7.3.3).

5.3 Local-Use IPv6 Unicast Link-Local Addresses

The specification in ([MECH], section 3.7) is not used; the
specification in Section 4.1 of this document is used instead.

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5.4 Ingress Filtering Neighbor Discovery over Tunnels

The specification in ([MECH], section 3.9) 3.8) is used.

Additionally, packets received on an ISATAP interface with an ISATAP
network-layer (IPv6) source address that does not embed used; the
link-layer (IPv4) source address
specifications in the interface identifier Section 6 and Section 7 of this document are
silently discarded.

6. Neighbor Discovery used
instead.

5.5 Decapsulation/Filtering

The specification specifications in ([MECH], section 3.8) applies only to configured
tunnels. [RFC2461] provides the following guidelines for
non-broadcast multiple access (NBMA) link support:

"Redirect, Neighbor Unreachability Detection and next-hop
determination should be implemented as described in this document.
Address resolution sections 3.6, 3.9 and 4.1) are used.

In addition, the mechanism for delivering Router
Solicitations and Advertisements on NBMA links is not specified in
this document."

ISATAP interfaces SHOULD implement Redirect, Neighbor Unreachability
Detection, and next-hop determination exactly as specified in
[RFC2461]. Address resolution and decapsulator MUST determine the mechanisms correct tunnel
interface to receive each IPv4 protocol-41 packet via a table lookup
for delivering
Router Solicitations and Advertisements are not specified by
[RFC2461]; instead, they are specified in the following sections tuple consisting of
this document.

6.1 Address Resolution the packet's IPv4 source and Neighbor Unreachability Detection destination
address, and ifIndex for the receiving IPv4 interface. (Note that
ISATAP addresses are resolved to link-layer (IPv4) interfaces match all IPv4 source addresses by default; if a
static computation, i.e.,
tunnel interface with a more-specific match on the last four octets are treated IPv4 source
address exists, it is selected to receive the packet as for
longest-prefix-match.) Packets for which the correct tunnel interface
cannot be determined are discarded; in this case, the decapsulator
MAY also send an IPv4
address.

Hosts SHOULD perform an initial reachability confirmation by sending
Neighbor Solicitation (NS) message(s) and receiving a Neighbor
Advertisement (NA) ICMPv4 Destination Unreachable message as specified in ([RFC2461], with code 3
(Port Unreachable) ([RFC1122], section 7.2).
Unless otherwise specified in a future document, solicitations are
sent 3.2.2.1) to the target's unicast IPv4 source
address in the packet's outer header.

After determining the correct tunnel interface, the decapsulator MUST
also verify that the packet's link-layer (IPv4) source address is
correct for the network-layer (IPv6) source address.

Hosts SHOULD additionally perform Neighbor Unreachability Detection
(NUD) as specified For ISATAP
interfaces, the packet's link-layer source address is correct if one
(or more) of the following are true:

o the network-layer source address is an ISATAP address that embeds
the link-layer source address in ([RFC2461], section 7.3). Routers MAY perform
these reachability confirmation its interface identifier.

o the network-layer source address is an IPv6 neighbor within the
same site as the receiving ISATAP interface, and NUD procedures, but this might
not scale the link-layer
source address matches the link layer address in all environments.

All ISATAP nodes MUST send solicited the neighbor advertisements
([RFC2461], section 7.2.4).

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6.2 Duplicate Address Detection

Duplicate Address Detection ([RFC2462], section 5.4) is not required
for ISATAP addresses, since duplicate

cache.

o the link-layer source address detection is assumed to
have been already performed a member of the Potential Router
List for the IPv4 addresses from site (see: Section 6.1).

Packets for which they
derive.

6.3 Router and Prefix Discovery

The following sections describe mechanisms to support the router link-layer source address is incorrect are
discarded, and
prefix discovery process ([RFC2461], an ICMPv6 Destination Unreachable message ([ICMPV6],
section 6):

6.3.1 Conceptual Data Structures

ISATAP nodes use 3.1) SHOULD be sent to the conceptual data structures Prefix List and
Default Router List exactly IPv6 source in the inner header of
the encapsulated packet (subject to rate limiting as in ([RFC2461], [ICMPV6],
section 5.1). 2.4, paragraph f).

6. Neighbor Discovery

ISATAP
adds a new conceptual data structure "Potential Router List" (PRL)
and interfaces use the following new configuration variable:

PrlRefreshInterval
Time neighbor discovery mechanisms specified in seconds between successive refreshments of
[RFC2461] with the PRL after
initialization. It SHOULD be no less than 3,600 seconds. The
designated value of all 1's (0xffffffff) represents infinity.

Default: 3,600 seconds following exceptions:

6.1 Conceptual Model Of A PRL is associated with every Host

To the list of Conceptual Data Structures ([RFC2461], section 5.1),
ISATAP interface and supports interfaces add:

Potential Router List
A set of entries about potential routers for the site; used to
support the mechanisms specified in Section 6.3.4. 6.2.3. Each entry in the PRL
("PRL(i)") has an associated timer ("TIMER(i)"), and an IPv4
address ("V4ADDR(i)") that represents a site border router's advertising
ISATAP interface.

When a node enables an ISATAP interface, it initializes

6.2 Router and Prefix Discovery

6.2.1 Message Validation

6.2.1.1 Validation of Router Solicitation Messages

To the PRL with
IPv4 addresses. The addresses MAY be discovered via a DHCPv4
[RFC2131] option for ISATAP, manual configuration, or an unspecified
alternate method (e.g., DHCPv4 vendor-specific option, etc.).

When no other mechanisms are available, a DNS fully-qualified domain
name (FQDN) [RFC1035] established by an out-of-band method (e.g.,
DHCPv4, manual configuration, etc.) MAY be used. The FQDN is resolved
into IPv4 addresses list of validity checks for Router Soliciation messages
([RFC2461], section 6.1.1), ISATAP interfaces add:

o If the PRL through a static host file, a
site-specific name service, querying message includes a DNS server within Source Link Layer Address Option, the site, or
message also includes an unspecified alternate method. There are no mandatory rules for the
selection IP authentication Header.

6.2.1.2 Validation of a FQDN, but manual configuration MUST be supported. When
DNS is used, client resolvers use the IPv4 transport.

After initialization, nodes periodically refresh Router Advertisement Messages

To the PRL (i.e., using
one or more list of the methods described above) after PrlRefreshInterval. validity checks for Router Advertisement messages
([RFC2461], section 6.1.1), ISATAP interfaces add:

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6.3.2 Validation of Router Advertisements Messages

The specification in ([RFC2461], section 6.1.2)

o IP Source Address is used.

6.3.3 Router Specification

Routers with advertising an ISATAP interfaces behave link-local address that embeds
V4ADDR(i) for some PRL(i).

o If the same as
described in ([RFC2461], section 6.2). message includes a Source Link Layer Address Option, the
message also includes an IP authentication Header.

6.2.2 Router Specification

As permitted by ([RFC2461], section 6.2.6), advertising ISATAP
interfaces SHOULD send unicast RA Router Advertisement messages to a the
soliciting host's unicast address when the solicitation's source address is
not the unspecified address.

6.3.4

6.2.3 Host Specification

Hosts behave

6.2.3.1 Host Variables

To the same as described in list of host variables ([RFC2461], section 6.3) with
the following additional considerations for ISATAP:

6.3.4.1 Soliciting Router Advertisements

Hosts solicit Router Advertisements (RAs) by sending Router
Solicitations (RSs) to advertising 6.3.2), ISATAP
interfaces add:

PrlRefreshInterval
Time in seconds between successive refreshments of the PRL. PRL after
initialization. It SHOULD be no less than 3600 seconds. The
manner
designated value of selecting PRL(i)'s for solicitation is up to the
implementation. Hosts add the following variable to support the
solicitation process: all 1's (0xffffffff) represents infinity.

Default: 3600 seconds

MinRouterSolicitInterval
Minimum time in seconds between successive solicitations of the
same advertising ISATAP interface. It SHOULD be no less than 900
seconds. The designated value of alll 1's (0xffffffff) represents
infinity.

Default: 900 seconds

RS messages use a link-local unicast address from

6.2.3.2 Interface Initialization

The host joins the all-nodes multicast address on ISATAP
interface interfaces,
as the IPv6 source address.

6.3.4.2 Router Advertisement Processing

RAs received from a member of the PRL (i.e., RAs with an ISATAP IPv6
source address that embeds V4ADDR(i) for some PRL(i)) are processed
exactly as specified in multicast-capable interfaces ([RFC2461], section 6.3.4). 6.3.3).

Additionally,
hosts reset TIMER(i) to schedule the next solicitation event (see:
Section 6.3.4.1). Let "MIN_LIFETIME" be the minimum value in host provisions the
Router Lifetime ISATAP interface's PRL with
IPv4 addresses it discovers via manual configuration, a DNS
fully-qualified domain name (FQDN) [RFC1035], a DHCPv4 option for
ISATAP [ISDHCP], a DHCPv4 vendor-specific option, or the lifetime(s) encoded in options included in the
RA message. Then, TIMER(i) an unspecified
alternate method. (Support for manual configuration is reset as follows:

TIMER(i) = MAX((0.5 * MIN_LIFETIME), MinRouterSolicitInterval)

RAs received from a router REQUIRED;
other than a member of the PRL methods are OPTIONAL.)

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processed

When FQDNs are used, the host establishes the FQDN via manual
configuration or an unspecified alternate method. (Support for manual
configuration is REQUIRED; other methods are OPTIONAL.) The host
resolves the FQDN into IPv4 addresses through lookup in a static host
file, a site-specific name service, querying the site's DNS service,
or an unspecified alternate method. When DNS is used, client
resolvers use the IPv4 transport.

After the host provisions the ISATAP interface's PRL with IPv4
addresses, it sets PrlRefreshIntervalTimer to PrlRefreshInterval
seconds. The host re-initializes the PRL (i.e., as specified above)
when PrlRefreshIntervalTimer expires, or when an asynchronous
re-initialization event occurs. When the host re-initializes the PRL,
it resets PrlRefreshIntervalTimer to PrlRefreshInterval seconds.

6.2.3.3 Processing Received Router Advertisements

Router Advertisements (RAs) are processed exactly as specified in
([RFC2461], section 6.3.4) except that any
RA contents ([RFC2461], section 6.2.3) that would alter ISATAP link
parameters are silently ignored. In particular, non-zero values in
the Router Lifetime, M and O flags, Cur Hop Limit, Reachable Time,
and Retrans Timer as well as prefix options with the L and/or A bits
set are ignored. If that, if the MTU option is present,
the option's value SHOULD be stored in a per-neighbor cache entry for
the source of the RA; it MUST NOT be copied into LinkMTU for the
ISATAP link.

7. Address Autoconfiguration

Hosts invoke stateless address autoconfiguration under interface.

Additionally, hosts reset TIMER(i) to schedule the conditions
specified next solicitation
event (see: Section 6.2.3.4). Let "MIN_LIFETIME" be the minimum value
in ([RFC2462], sections 5.5).

Hosts invoke stateful address autoconfiguration under the conditions
specified Router Lifetime or the lifetime(s) encoded in options included
in ([RFC2462], section 5.5). When DHCPv6 [RFC3315] is used,
hosts send messages to the "All_DHCP_Relay_Agents_and_Servers"
multicast address ([RFC3315], sections 1.2 and 1.3). RA message. Then, TIMER(i) is reset as follows:

TIMER(i) = MAX((0.5 * MIN_LIFETIME), MinRouterSolicitInterval)

6.2.3.4 Sending
implementations map Router Solicitations

To the "All_DHCP_Relay_Agents_and_Servers" multicast
address list of events after which RSs may be sent ([RFC2461], section
6.3.2), ISATAP interfaces add:

o TIMER(i) for some PRL(i) expires.

Additionally, hosts MAY send Router Solicitations to a link-layer (IPv4) an ISATAP
link-local address by selecting that embeds V4ADDR(i) for some PRL(i).

When the site supports the DHCPv6 service, PRL(i) instead of
the server/relay function
MUST be deployed equally on each router that is a member All-Routers multicast address.

6.3 Address Resolution and Neighbor Unreachability Detection

6.3.1 Message Validation

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6.3.1.1 Validation of Neighbor Solicitations

To the PRL.

8. IANA Considerations

The IANA is advised to specify construction rules list of validity checks for IEEE EUI-64
addresses formed from Neighbor Solicitation (NS)
messages ([RFC2461], section 7.1.1), ISATAP interfaces add:

o If the Organizationally Unique Identifier (OUI)
"00-00-5E" in message includes a Source Link Layer Address Option, the IANA "ethernet-numbers" registry. The non-normative
text in Appendix B is offered as
message also includes an example specification.

9. Security considerations

ISATAP site border routers MUST implement IPv6 and IPv4 ingress
filtering and in particular MUST discard any packets originating from
outside IP authentication Header.

6.3.1.2 Validation of Neighbor Solicitations

To the site that use an IP address from list of validity checks for Neighbor Advertisement (NA)
messages ([RFC2461], section 7.1.2), ISATAP interfaces add:

o If the site as message includes a Target Link Layer Address Option, the
source address. Additionally, site border routers MUST implement
ip-protocol-41 filtering by not allowing packets for that protocol
message also includes an IP authentication Header.

6.3.2 Address Resolution

The specification in ([RFC2461], section 7.2) is used. NS and out of NA
messages MAY omit the site. Finally, site border routers MUST NOT forward
any packets with local-use source or destination addresses outside of source/target link layer address option when
the site ([RFC3513], section 2.5.6).

Even with IPv4 and IPv6 ingress filtering, reflection attacks can
originate from compromised nodes within source/target is an ISATAP site that spoof
IPv6 source addresses. Security mechanisms address. ISATAP addresses for reflection attack
mitigation SHOULD which
the neighbor's link-layer address cannot otherwise be used in routers with advertising ISATAP
interfaces. At determined
(i.e., from the neighbor cache or a minimum, site border routers SHOULD log potential

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source link layer address spoofing cases.

Site administrators maintain option in a list of IPv4
received packet) are resolved to link-layer addresses representing
advertising ISATAP interfaces by a static
computation, i.e., the last four octets are treated as an IPv4
address.

Hosts SHOULD perform an initial reachability confirmation by sending
NS message(s) and make them available via one or more receiving a NA message; NS messages are sent to the
target's unicast address. Routers MAY perform an initial reachability
confirmation, but this might not scale in all environments.

As specified in ([RFC2461], section 7.2.4), all nodes MUST send
solicited neighbor advertisements on ISATAP interfaces.

6.3.3 Neighbor Unreachability Detection

Hosts SHOULD perform Neighbor Unreachability Detection as specified
in ([RFC2461], section 7.3). Routers MAY perform neighbor
unreachability detection, but this might not scale in all
environments.

6.4 Redirect Function

To the list of validity checks for Redirect messages (([RFC2461],
section 8.1), ISATAP interfaces add:

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o If the message includes a Target Link Layer Address Option, the
message also includes an IP authentication Header.

7. Address Autoconfiguration

ISATAP interfaces use the address autoconfiguration mechanisms described
specified in Section 6.3.1. [RFC2462] with the following exceptions:

7.1 Address Lifetime Expiry

The list can include specification in ([RFC2462], section 5.5.4) is used, except that
an ISATAP address also becomes deprecated when the IPv4 anycast address(es) but administrators are advised address
embedded in its interface identifier is removed from an IPv4
interface over which the ISATAP interface is configured. (This
deprecation rule applies to consider
operational implications of anycast (e.g., see: [RFC1546]). all ISATAP addresses do not support privacy extensions for stateless addresses, including
link-local addresses.)

7.2 Stateful Address Autoconfiguration

When the site uses DHCPv6 [RFC3315] as the stateful address
autoconfiguration [RFC3041].

10. Acknowledgements

Portions mechanism, the server/relay function MUST be
deployed equally on each router that is a member of this work were derived the PRL.

8. IANA Considerations

The IANA is advised to specify construction rules for IEEE EUI-64
addresses formed from SRI International internal
funds and government contracts. the Organizationally Unique Identifier (OUI)
"00-00-5E" in the IANA "ethernet-numbers" registry. The non-normative
text in Appendix B is offered as an example specification.

9. Security considerations

The security considerations in [RFC2461][RFC2462][MECH] apply.

Additionally, site administrators MUST ensure that lists of IPv4
addresses representing the advertising ISATAP interfaces of PRL
members are well maintained.

10. Acknowledgments

Most of the basic ideas in this document are not original; the
authors acknowledge the original architects of those ideas. Portions
of this work were sponsored through SRI International internal
projects and government contracts. Government sponsors include Monica
Farah-Stapleton and Russell Langan (U.S. Army CECOM ASEO), and Dr.
Allen Moshfegh (U.S. Office of Naval Research). SRI International
sponsors include Dr. Mike Frankel, J. Peter Marcotullio, Lou

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Rodriguez, and Dr. Ambatipudi Sastry.

The following are acknowledged for providing peer review input: Jim
Bound, Rich Draves, Cyndi Jung, Ambatipudi Sastry, Aaron Schrader,
Ole Troan, Vlad Yasevich.

The following additional individuals are acknowledged for their significant contributions: Rich Draves,
Alain Durand, Hannu Flinck, Jason Goldschmidt, Nathan Lutchansky,
Karen Nielsen, Mohan Parthasarathy, Chirayu Patel, Art Shelest, Pekka
Savola, Margaret Wasserman, Brian Zill.

The authors also acknowledge the work of Quang Nguyen [VET] under the
guidance of Dr. Lixia Zhang that proposed very similar ideas to those
that appear in this document. This work was first brought to the
authors' attention on September 20, 2002.

Normative References

[ADDR-ARCH]
Hinden, R. and S. Deering, "IP Version 6 Addressing
Architecture", draft-ietf-ipv6-addr-arch-v4-00 (work in
progress), October 2003.

[ICMPV6] Conta, A. and S. Deering, "Internet Control Message
Protocol (ICMPv6) for the Internet Protocol Version 6
(IPv6) Specification", draft-ietf-ipngwg-icmp-v3 (work in
progress), November 2001.

[MECH] Gilligan, R. and E. Nordmark, "Basic Transition Mechanisms
for IPv6 Hosts and Routers", draft-ietf-v6ops-mech-v2-00
(work in progress), February 2003.

[MIB] Thaler, D., "IP Tunnel MIB", draft-thaler-inet-tunnel-mib
(work in progress), September 2003.

[RFC0791] Postel, J., "Internet Protocol", STD 5, RFC 791, September
1981.

[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.

[RFC2460] Deering, S. and R. Hinden, "Internet Protocol, Version 6
(IPv6) Specification", RFC 2460, December 1998.

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[RFC2461] Narten, T., Nordmark, E. and W. Simpson, "Neighbor
Discovery for IP Version 6 (IPv6)", RFC 2461, December
1998.

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Internet-Draft ISATAP October 2003

[RFC2462] Thomson, S. and T. Narten, "IPv6 Stateless Address
Autoconfiguration", RFC 2462, December 1998.

[RFC3513] Hinden, R. and S. Deering, "Internet

Informative References

[ISDHCP] Templin, F., "Dynamic Host Configuration Protocol Version 6
(IPv6) (DHCPv4)
Option for the Intra-Site Automatic Tunnel Addressing Architecture", RFC 3513, April
Protocol (ISATAP)", draft-templin-isatap-dhcp (work in
progress), October 2003.

Informative References

[RFC1035] Mockapetris, P., "Domain names - implementation and
specification", STD 13, RFC 1035, November 1987.

[RFC1546] Partridge, C., Mendez, T. and W. Milliken, "Host
Anycasting Service",

[RFC1122] Braden, R., "Requirements for Internet Hosts -
Communication Layers", STD 3, RFC 1546, November 1993. 1122, October 1989.

[RFC1918] Rekhter, Y., Moskowitz, R., Karrenberg, D., Groot, G. and
E. Lear, "Address Allocation for Private Internets", BCP
5, RFC 1918, February 1996.

[RFC2022] Armitage, G., "Support for Multicast over UNI 3.0/3.1
based ATM Networks", RFC 2022, November 1996.

[RFC2131] Droms, R., "Dynamic Host Configuration Protocol", RFC
2131, March 1997.

[RFC2491] Armitage, G., Schulter, P., Jork, M. and G. Harter, "IPv6
over Non-Broadcast Multiple Access (NBMA) networks", RFC
2491, January 1999.

[RFC2529] Carpenter, B. and C. Jung, "Transmission of IPv6 over IPv4
Domains without Explicit Tunnels", RFC 2529, March 1999.

[RFC2827] Ferguson, P. and D. Senie, "Network Ingress Filtering:
Defeating Denial of Service Attacks which employ IP Source
Address Spoofing", BCP 38, RFC 2827, May 2000.

[RFC2863] McCloghrie, K. and F. Kastenholz, "The Interfaces Group
MIB", RFC 2863, June 2000.

[RFC3041] Narten, T. and R. Draves, "Privacy Extensions for
Stateless Address Autoconfiguration in IPv6", RFC 3041,
January 2001.

[RFC3315] Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C. and
M. Carney, "Dynamic Host Configuration Protocol for IPv6
(DHCPv6)", RFC 3315, July 2003.

[RFC3582] Abley, J., Black, B. and V. Gill, "Goals for IPv6
Site-Multihoming Architectures", RFC 3582, August 2003.

[VET] Nguyen, Q., "http://irl.cs.ucla.edu/vet/report.ps", spring
1998.

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Authors' Addresses

Fred L. Templin
Nokia
313 Fairchild Drive
Mountain View, CA 94110
US

Phone: +1 650 625 2331
EMail: ftemplin@iprg.nokia.com

Tim Gleeson
Cisco Systems K.K.
Shinjuku Mitsu Building
2-1-1 Nishishinjuku, Shinjuku-ku
Tokyo 163-0409
Japan

EMail: tgleeson@cisco.com

Mohit Talwar
Microsoft Corporation
One Microsoft Way
Redmond, WA> 98052-6399
US

Phone: +1 425 705 3131
EMail: mohitt@microsoft.com

Dave Thaler
Microsoft Corporation
One Microsoft Way
Redmond, WA 98052-6399
US

Phone: +1 425 703 8835
EMail: dthaler@microsoft.com

Appendix A. Major Changes

Major changes from version 14 earlier versions to version 15: 16:

o several editorial changes dropped "underlying link" from terminology.

o revised Security; IANA considerations specified multicast mappings.

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o revised Section 6.3.4.2

o added new section on ingress filtering

o revised stateful autoconfiguration and moved to new section

o removed overly-restrictive text at end of Section 6.3.4.1

changes from version 13 to version 14:

o removed applicability statement; applicability TBD by v6ops

o updated deployment/site admin sections; moved to appendices

o new text on "L" bit in prefix options in section 7.3.4.2

o removed extraneous text in Security Considerations

o fixed "layering bug" in section 7.3.4.3

o revised "ISATAP address" definition

o updated references for RFC 3315; 3513

changes from earlier versions to version 13:

o Revised ISATAP interface/link terminology

o Returned to using symbolic reference names

o Revised MTU section; moved non-normative MTU text to separate
document

o Added multicast/anycast subsection

o Revised PRL initialization

o Updated neighbor discovery, security consideration sections

o Rearranged/revised sections 5, 6, 7

o Added stateful autoconfiguration mechanism

o Normative references to RFC 2491, RFC 2462

o Moved non-normative MTU text to appendix C

o clarified address resolution, Neighbor Unreachability Detection

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o specified MTU/MRU requirements

o Addressed operational issues identified in 05 based on discussion
between co-authors

o Clarified ambiguous text per comments from Hannu Flinck; Jason
Goldschmidt

o Moved historical text in section 4.1 to Appendix B in response to
comments from Pekka Savola

o Identified operational issues for anticipated deployment scenarios

o Included reference to Quang Nguyen work

Appendix B. Rationale for Interface Identifier Construction

ISATAP specifies an EUI64-format address construction for the
Organizationally-Unique Identifier (OUI) owned by the Internet
Assigned Numbers Authority (IANA). This format (given below) is used
to construct both native EUI64 addresses for general use and modified
EUI-64 format interface identifiers for IPv6 unicast addresses:

|0 2|2 3|3 3|4 6|
|0 3|4 1|2 9|0 3|
+------------------------+--------+--------+------------------------+
| OUI ("00-00-5E"+u+g) | TYPE | TSE | TSD |
+------------------------+--------+--------+------------------------+

Where the fields are:

OUI IANA's OUI: 00-00-5E with 'u' and 'g' bits (3 octets)

TYPE Type field; specifies use of (TSE, TSD) (1 octet)

TSE Type-Specific Extension (1 octet)

TSD Type-Specific Data (3 octets)

And the following interpretations are specified based on TYPE:

TYPE (TSE, TSD) Interpretation
---- -------------------------
0x00-0xFD RESERVED for future IANA use
0xFE (TSE, TSD) together contain an embedded IPv4 address
0xFF TSD is interpreted based on TSE as follows:

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TSE TSD Interpretation
--- ------------------
0x00-0xFD RESERVED for future IANA use
0xFE TSD contains 24-bit EUI-48 intf id
0xFF RESERVED by IEEE/RAC

Thus, if TYPE=0xFE, TSE is an extension of TSD. If TYPE=0xFF, TSE is
an extension of TYPE. Other values for TYPE (thus, other
interpretations of TSE, TSD) are reserved for future IANA use.

The above specification is compatible with all aspects of EUI64,
including support for encapsulating legacy EUI-48 interface
identifiers (e.g., an IANA EUI-48 format multicast address such as:
'01-00-5E-01-02-03' is encapsulated as: '01-00-5E-FF-FE-01-02-03').
But, the specification also provides a special TYPE (0xFE) to
indicate an IPv4 address is embedded. Thus, when the first four
octets of an IPv6 interface identifier are: '00-00-5E-FE' (note: the
'u/l' bit MUST be 0) the interface identifier is said to be in
"ISATAP format" and the next four octets embed an IPv4 specified layer address
encoded option format.

o specified setting of "u" bit in network byte order.

Appendix C. Deployment Considerations

Hosts can enable ISATAP, e.g., when native IPv6 service is
unavailable. When native IPv6 service is acquired, hosts can
discontinue the ISATAP router solicitation process (Section 6.3.4)
and/or allow associated state interface id's.

o removed obsoleted appendix sections.

o re-organized major sections to expire (see: [RFC2461], section 5.3
and [RFC2462], match normative references.

o revised neighbor discovery, address autoconfiguration, security
considerations sections. Added new subsections on interface
management, decapsulation/filtering, address lifetime expiry.

Appendix B. Interface Identifier Construction

This section 5.5.4). In this case, any associated provides an example specification for constructing EUI64
addresses
added to from the DNS should also be removed.

Routers can configure both native IPv6 and ISATAP interfaces over Organizationally-Unique Identifier (OUI) owned by
the
same physical link. The prefixes Internet Assigned Numbers Authority (IANA). It can be used on each to
construct both modified EUI-64 format interface will be
distinct, and normal IPv6 routing between the interfaces can occur.

Routers can obtain identifiers for IPv6 prefix delegations from a server via an
ISATAP interface
unicast addresses ([ADDR-ARCH], section 2.5.1) and advertise "native" EUI64
addresses for future use:

Where the delegated prefix(es) on other IPv6
interface(s).

Responsible administration can reduce control traffic overhead
associated fields are:

OUI IANA's OUI: 00-00-5E with router "u" and prefix discovery.

Appendix D. Other Considerations

The Potential Router List (PRL) contains the IPv4 addresses "g" bits (3 octets)

TYPE Type field; specifies use of
advertising ISATAP interfaces on site border routers, and the
specification mandates that nodes only accept Router Advertisement
(RA) parameters that alter (TSE, TSD) (1 octet)

TSE Type-Specific Extension (1 octet)

TSD Type-Specific Data (3 octets)

And the ISATAP link (e.g., default router
list, on-link prefix list, LinkMTU, etc.) if they following interpretations are sent by a specified based on TYPE:

TYPE (TSE, TSD) Interpretation
---- -------------------------
0x00-0xFD RESERVED for future IANA use
0xFE (TSE, TSD) together contain an IPv4 address
0xFF TSD is interpreted based on TSE as follows:

TSE TSD Interpretation
--- ------------------

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member

0x00-0xFD RESERVED for future IANA use
0xFE TSD contains 24-bit EUI-48 intf id
0xFF RESERVED by IEEE/RAC

Using this example specification, if TYPE=0xFE, then TSE is an
extension of the PRL. However, the specification allows any node on the
ISATAP link to send "other" parameters in RAs TSD. If TYPE=0xFF, then TSE is an extension of TYPE.
(Other values for TYPE, and also allows any
node on other interpretations of TSE, TSD are
reserved for future IANA use.) When TYPE='0xFE' the ISATAP link to act as a (non-default) EUI64 address
embeds an IPv4 address, encoded in network byte order.

For Modified EUI64 format interface identifiers in IPv6 router, e.g.,
if unicast
addresses ([ADDR-ARCH], Appendix A) using IANA's OUI, when TYPE=0xFE
and the node IPv4 address is configured as a router for its other IPv6 links.

These aspects of the specification allow useful functionality,
including globally unique (i.e., provider-assigned)
unicast address, the ability for ISATAP nodes other than PRL members "u" bit is set to
serve as routers for "stub" IPv6 networks, the ability for ISATAP
nodes 1 to send IPv6 packets with non-ISATAP source addresses (e.g.,
RFC 3401 privacy addresses), etc. But, allowing this functionality
prevents ISATAP nodes indicate universal scope.
When TYPE=0xFE and the IPv4 address is from perform effective ingress filtering for
IPv6 source addresses in packets they receive. Instead, a private allocation, the nodes
must trust that: 1) site border routers are performing ingress
filtering, and 2) malicious nodes are effectively denied access
"u" bit is set to 0 to indicate local scope. Thus, when the link.

Additionally, first
four octets of the specification expects that that IPv4 addresses interface identifier in an IPv6 unicast address
are
uniquely assigned within either: '02-00-5E-FE' or: '00-00-5E-FE', the ISATAP site. next four octets
embed an IPv4 address and the interface identifier is said to be in
"ISATAP format".

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The limited permissions granted above are perpetual and will not be
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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
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Acknowledgment

Funding for the RFC Editor function is currently provided by the
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----