WDIFF

draft-ietf-ngtrans-isatap-03.txt --> draft-ietf-ngtrans-isatap-04.txt

NGTRANS Working Group F. Templin
INTERNET-DRAFT SRI International
T. Gleeson
Cisco Systems K.K.
M. Talwar
D. Thaler
Microsoft Corporation

Expires 30 July 18 October 2002 30 January 18 April 2002

Intra-Site Automatic Tunnel Addressing Protocol (ISATAP)

draft-ietf-ngtrans-isatap-03.txt

draft-ietf-ngtrans-isatap-04.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.

Abstract

This document specifies the Intra-Site Automatic Tunnel Addressing
Protocol (ISATAP) that connects IPv6 hosts and routers (nodes) within
IPv4 sites. ISATAP is a transition mechanism that enables incremental
deployment of IPv6 by treating the site's IPv4 infrastructure as a
Non-Broadcast Multiple Access (NBMA) link layer. layer for IPv6. ISATAP
mechanisms use a new an IPv6 interface identifier format that embeds an
IPv4 address - this enables automatic IPv6-in-IPv4 tunneling within a
site, whether the site uses globally assigned or private IPv4
addresses. The new interface identifier format can be used with both
local and global unicast IPv6 prefixes - this enables IPv6 routing
both locally and globally. ISATAP mechanisms introduce no impact on

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routing table size and require no special IPv4 services (e.g., IPv4
multicast).

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

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The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html.

1. Introduction

This document presents a simple, scalable approach that enables
incremental deployment of IPv6 within IPv4-based sites in a manner
that is compatible with inter-domain transition mechanisms, e.g.,
[6TO4]. We refer to this approach as the Intra-Site Automatic Tunnel
Addressing Protocol, or ISATAP (pronounced: "ice-a-tap"). ISATAP
allows dual-stack nodes that do not share a common 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 an
NBMA link layer.

This document specifies details for the transmission of IPv6 packets
over ISATAP links (i.e., automatic IPv6-in-IPv4 tunneling), including
a new EUI-64 [EUI64] based interface identifier [ADDR][AGGR] format
that embeds an IPv4 address. This format supports configuration of
global, site-local and link-local addresses as specified in [AUTO] as
well as simple link-layer address mapping. Simple validity checks for
received packets are given. Also specified in this document is the
operation of IPv6 Neighbor Discovery for ISATAP, as permitted for
NBMA links by [DISC]. The document finally presents deployment and
security considerations for ISATAP.

2. Applicability Statement

ISATAP provides the following features:

- treats site's IPv4 infrastructure as an NBMA link layer using
automatic IPv6-in-IPv4 tunneling (i.e., no configured tunnel state)

- enables incremental deployment of IPv6 hosts within IPv4 sites with
no aggregation scaling issues at border gateways

- requires no special IPv4 services within the site (e.g., multicast)

- supports both stateless address autoconfiguration and manual
configuration

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- supports networks that use non-globally unique IPv4 addresses (e.g.,
when private address allocations [PRIVATE] are used), but does not
allow the virtual ISATAP link to span a Network Address
Translator [NAT]

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- compatible with other NGTRANS mechanisms (e.g., [6TO4])

3. Terminology

The terminology of [IPv6] applies to this document. The following
additional terms are defined:

link:
same definition as [AUTO][DISC].

underlying link:
a link layer that supports IPv4 (for ISATAP), and MAY also support
IPv6 natively.

ISATAP link:
one or more underlying links used for IPv4 tunneling. The IPv4
network layer addresses of the underlying links are used as
link-layer addresses on the ISATAP link.

ISATAP interface:
a node's attachment to an ISATAP link.

ISATAP prefix:
a prefix used to configure an address on the ISATAP interface. This
prefix is administratively assigned to the ISATAP link and MUST NOT
be duplicated on native IPv6 links.

ISATAP address:
an IPv6 address with an ISATAP prefix and an ISATAP format interface
identifier constructed as specified in section 4.

ISATAP router:
an IPv6 node that has an ISATAP interface over which it forwards
packets not explicitly addressed to itself.

ISATAP host:
any node that has an ISATAP interface and is not an ISATAP router.

4. Transmission of IPv6 Packets on ISATAP Links

ISATAP links transmit IPv6 packets via automatic tunneling using the

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site's IPv4 infrastructure as an NBMA link layer. Automatic tunneling
for ISATAP uses the same mechanisms specified in [MECH,3.1-3.6],
i.e., IPv6 packets are automatically encapsulated in IPv4 using 'ip-
protocol-41'
'ip-protocol-41' as the payload type number. Specific considerations
for ISATAP links are given below:

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4.1. ISATAP Interface Identifier Construction

IPv6 unicast addresses [ADDR][AGGR] include a 64-bit interface iden-
tifier
identifier field in "modified EUI-64 format", based on the IEEE
EUI-64 [EUI64] specification. (Modified EUI-64 format inverts the
sense of the 'u/l' bit from its specification in [EUI64], i.e.,
'u/l' = 0 indicates local-use.) ISATAP specifies an [EUI64]-format
address con-
struction 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 use
in 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 interpretation 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:

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

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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 (hence, other interpreta-
tions of TSE, TSD) are reserved for future
IANA use.

The above specification is compatible with all aspects of [EUI64],

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including support for encapsulating legacy EUI-48 interface identif-
iers
identifiers (e.g., an IANA EUI-48 format multicast address such as: '01-00-
5E-01-02-03'
'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 indicating
an IPv4 address is embedded. Thus, when the first four octets of a [ADDR]-
compatible an
[ADDR]-compatible IPv6 interface identifier are: '00-00-5E-FE'
(note: the 'u/l' bit MUST be 0) the interface identifier is said to
be in "ISA-
TAP "ISATAP format" and the next four octets embed an IPv4 address
encoded in network byte order (least significant octet first). order. Addresses con-
figured configured on the an ISATAP
interface MUST use the ISATAP interface iden-
tifier identifier format.

4.2. Stateless Autoconfiguration and Link-Local Addresses

ISATAP addresses are IPv6 unicast addresses [ADDR,2.5] that use with ISATAP
format interface identifiers as follows:

Link-local, site-local, and global ISATAP addresses can be created
exactly as specified in [ADDR], (e.g., by auto-configuration [AUTO]
or manual configuration). For example, the IPv6 address:

3FFE:1a05:510:1111:0:5EFE:8CAD:8108

3FFE:1A05:510:1111:0:5EFE:8CAD:8108

has a prefix of '3FFE:1a05:510:1111::/64' '3FFE:1A05:510:1111::/64' and an ISATAP format inter-
face
interface identifier with embedded IPv4 address: '140.173.129.8'.
The address is alternately written as:

3FFE:1a05:510:1111:0:5EFE:140.173.129.8

3FFE:1A05:510:1111:0:5EFE:140.173.129.8

The link-local and site-local variants (respectively) are:

FE80::0:5EFE:140.173.129.8
FEC0::1111:0:5EFE:140.173.129.8

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4.3. ISATAP Link/Interface Configuration

A node configures an ISATAP link over one or more underlying IPv4
links, i.e., the ISATAP link MAY be configured over one or more
link-layer (IPv4) addresses. Each link-layer address 'V4ADDR_LINK' is
used to configure a link-local address 'FE80::0:5EFE:V4ADDR_LINK' on
an ISATAP interface. ISATAP interfaces MAY be assigned one per link-
layer

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link-layer address, or as a single interface for multiple link-layer
addresses.

In the former case, the address of each ISATAP interface SHOULD be
added to the Potential Routers List. List (see section 5.2.1). In the
latter case, the inter-
face interface will accept ISATAP packets addressed to
any of the IPv4 link-
layer link-layer addresses, but will choose one as its
primary address, used for sourcing packets. Only this address need
be represented in the Poten-
tial Potential Routers List.

4.4. Sending Rules and Address Mapping

The IPv6 next-hop address for packets sent on an ISATAP link MUST be
an ISATAP address. Packets that do not satisfy this constraint MUST
be discarded and an ICMP destination unreachable indication with code
3 (Address Unreachable) [ICMPv6] MUST be returned. No other sending
rules are necessary.

The procedure for mapping unicast addresses into link-layer addresses
is to simply treat the last four octets of the ISATAP address as an
IPv4 address (in network byte order). No multicast address mappings
are specified.

4.5. Validity Checks for Received Packets

ISATAP interfaces MUST silently discard any received packets that do
not satisfy ONE OF at least one of the following validity checks:

- the network-layer (IPv6) source address has a prefix configured on
the ISATAP interface and an ISATAP-format interface identifier that
embeds the link-layer (IPv4) source address, i.e., source is on-link

- the link-layer (IPv4) source address is in the Potential Routers List
(see section 5.2), 5.2.1), i.e., previous hop is an on-link ISATAP router

5. Neighbor Discovery for ISATAP Links

Section 3.2 of [DISC] ("Supported Link Types") provides the following

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guidelines for non-broadcast multiple access (NBMA) link support:

"Redirect, Neighbor Unreachability Detection and next-hop determi-
nation
determination should be implemented as described in this
document. Address resolution and the mechanism for delivering
Router Solicitations and Advertisements on NBMA links is not
specified in this docu-
ment." document."

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ISATAP links SHOULD implement Redirect, Neighbor Unreachability
Detection, and next-hop determination exactly as specified in [DISC].
Address resolution and the mechanisms for delivering Router Solicita-
tions
Solicitations and Advertisements for ISATAP links are not specified
by [DISC]; instead, they are specified in this document. (Note that
these mechanisms MAY potentially apply to other types of NBMA links
in the future.)

5.1. Address Resolution

Protocol addresses (IPv6) in on ISATAP links are resolved to link-layer
addresses (IPv4) by a static computation, i.e., the last four octets
are treated as an IPv4 address. Thus the functions and conceptual
data structures used by [DISC] for the purpose of address resolution
are not required. The conceptual "neighbor cache" described in [DISC]
is still needed for other functions, such as neighbor unreachability
detection, but it is not used for address resolution.

The link-layer address option used in [DISC] is not needed. Implemen-
tations SHOULD NOT send link-layer
Link-layer address options SHOULD NOT be sent in any Neighbor
Discovery packets, and MUST be silently ignore any such options ignored in any received
Neighbor Discovery packets which are received. packets.

5.2. Router and Prefix Discovery

Since the site's IPv4 infrastructure is treated as an NBMA link
layer, unsolicited Router Advertisements do not provide sufficient
means for router discovery on ISATAP links. Thus, alternate mechan-
isms
mechanisms are required and specified below:

5.2.1. Conceptual Data Structures

ISATAP nodes use the conceptual data structures Prefix List and
Default Router List conceptual
data structures exactly as specified in [DISC,5.1]. ISATAP links
add a new conceptual data structure "Potential Router List" and the fol-
lowing
following new configuration variable:

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ResolveInterval Time between name service resolutions.
Default and suggested minimum: 1hr

A Potential Router List (PRL) is associated with every ISATAP link.
The PRL provides context for router discovery and a trust basis for
router validation (see security considerations). Each entry in the
PRL has an IPv4 address and an associated timer used for polling. The
IPv4 address represents a router's ISATAP interface (likely to be an

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"advertising interface"), and is used to construct the ISATAP link-
local
link-local address for that interface.

When the a node enables an ISATAP link, it initializes the PRL with
IPv4 Potential
Router List (PRL) for that link. Unless other information is
available (e.g., manual address configuration, a vendor-specific
DHCP option, etc.) the following method (similar to the [SIP, 1.4.2]
procedure) SHOULD be used:

1. The site administrator maintains address records for ISATAP
router interfaces, and makes these available in the site's
name service. Nodes attempt to find one or more addresses discovered through
for the PRL by querying the name service lookups service.

2. There are no mandatory rules on the selection of domain name
to be used within a site for this purpose, but administrators
are encouraged to use the Well-
Known Service "isatap.domainname" convention
(e.g., isatap.example.com), as specified in [RFC2219]. Nodes
can construct this domain name "ISATAP" (see "IANA Considerations"). by prepending the label "isatap"
to their parent domain name, which is established by other
means. Nodes then query this domain name for address records
(e.g., DNS 'A' resource records), and initialize the PRL with
the IPv4 addresses in the replies.

3. After initialization, nodes periodically repeat this process after the above
procedure every ResolveInterval seconds to detect
additions/deletions for the PRL. Initialization of update the PRL through
static with
any IPv4 address assignments and/or an alternate name for lookups
is a supported configuration option, but addresses added/deleted since the method described above previous iteration.
When DNS is preferred. used, nodes MUST follow the procedures in [RFC1035]
regarding cache invalidation when the DNS time-to-live expires.

5.2.2. Validation of Router Advertisement Messages

A node MUST silently discard any received Router Advertisement mes-
sages
messages that do not satisfy the validity checks in [DISC,6.1.2] as
well as the following additional validity check for ISATAP:

- the network-layer (IPv6) source address is derived from
an IPv4 address in the PRL

5.2.3. Router Specification

Advertising ISATAP interfaces of routers behave the same as advertis-
ing
advertising interfaces described in [DISC,6.2]. However, periodic
unsolicited multicast Router Advertisements are not required, thus
the "interval timer" associated with advertising interfaces is not
used for that purpose.

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When an ISATAP router receives a valid Router Solicitation on an
advertising ISATAP interface, it replies with a unicast Router Adver-
tisement
Advertisement to the address of the node which sent the Router Solicita-
tion.
Solicitation. The source address of the Router Advertisement is a
link-local unicast address associated with the interface. This MAY
be the same as the destination address of the Router Solicitation.

By default, ISATAP routers will not receive Router Advertisements
from other ISATAP routers. Thus, Router Advertisement consistency
verification [DISC,6.2.7] is not supported by default. Routers MAY

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ISATAP 30 January 2002

OPTIONALLY routers MAY engage in the exchange of router advertisements with other
members of the PRL to enable polling process described under
Host Specification below (e.g. if Router Advertisement consistency
verification [DISC,6.2.7] is desired), but this function. is not required.

5.2.4. Host Specification

Hosts periodically poll each entry in the PRL ("PRL(i)") by sending
unicast Router Solicitation messages using the IPv4 address
("V4ADDR_PRL(i)") and associated timer in the entry. Hosts add the
following variable to support the polling process:

MinRouterSolicitInterval
Minimum time between sending Router Solicitations
to any router. Default and suggested minimum: 15min

When PRL(i) is first added to the list, the host sets its associated
timer to MinRouterSolicitInterval.

Entries are polled when they are created (following a short delay as
for initial solicitations [ND,6.3.7]), and when the associated timer
expires.

Polling consists of sending Router Solicitations to the ISATAP link-
local
link-local address constructed from the entry's IPv4 address, i.e.,
they are sent to 'FE80::0:5EFE:V4ADDR_PRL(i)' instead of 'All-Routers mul-
ticast'.
multicast'. They are otherwise sent in the same manner described in
[DISC,6.3.7].

When the host receives a valid Router Advertisement (i.e., one that
satisfies the validity checks in sections 4.5 and 5.2.2) it processes
them in the same manner described in [DISC,6.3.4]. The host addition-
ally
additionally resets the timer associated with the PRL entry that
matches the network-layer source address in the Router Advertisement.
The timer is reset to either 0.5 * (the minimum value in the router
lifetime or valid lifetime of any on-link prefixes advertised) or MinRouterSoli-
citInterval;
MinRouterSolicitInterval; whichever is longer.

6. ISATAP Deployment Considerations

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6.1. Host And Router Deployment Considerations

For hosts, if an underlying link supports both IPv4 (over which ISA-
TAP
ISATAP is implemented) and also supports IPv6 natively, then ISATAP
MAY be enabled if the native IPv6 layer does not receive Router Adver-
tisements
Advertisements (i.e., does not have connection with an IPv6 router).
After a non-link-local address has been configured and a default
router

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'Router Polling Process' process specified in section 5.2.4 and allow exist-
ing
existing ISATAP address configurations to expire as specified in
[DISC,5.3][AUTO,5.5.4]. In this way, ISATAP use will gradually dimin-
ish
diminish as IPv6 routers are widely deployed throughout the site.

Routers MAY configure a native link to simultaneously support both
native IPv6, and also ISATAP (over IPv4). Routing will operate as
usual between these two domains. Note that the prefixes used on the
ISATAP and native IPv6 interfaces will be distinct.

When an ISATAP router is configured, the The IPv4 address used for its
address(es) configured on a router's ISATAP interface interface(s) SHOULD be
added (either automatically or manually) to the site's name service address
records for the "ISATAP" Well-Known Ser-
vice name (e.g., by adding an A record in DNS), so it will be added
to the ISATAP Potential Router list of all nodes on the link. router interfaces (see section 5.2.1).

6.2. Site Administration Considerations

The following considerations are noted for sites that deploy ISATAP:

- ISATAP links are administratively defined by a set of router
interfaces, and set of nodes which have those interface addresses
in their potential router lists. Thus, ISATAP links are defined by
administrative (not physical) boundaries.

- ISATAP hosts and routers can be deployed in an ad-hoc and independent
fashion. In particular, ISATAP hosts can be deployed with little/no
advanced knowledge of existing ISATAP routers, and ISATAP routers
can deployed with no reconfiguration requirements for hosts.

- ISATAP nodes periodically send Router Solicitations to all entries
in the Potential Router List. Worst-case control traffic is on the
order of (M x N), where 'M' is the number of routers in the Potential
Router List and 'N' is the total number of nodes on the ISATAP link.
The MinRouterSolicitInterval of 15min ([5.2.4]) bounds control traffic for
large numbers of nodes even in worst-case scenarios.

- Strategic ISATAP nodes periodically refresh the entries on the PRL, typically
by polling the DNS. Responsible site administration, along with
robust host and router protocol implementations, can provide significant reductions
in control traffic. At a minimum, site administrators SHOULD ensure that name
service
the site's address records for the "ISATAP" Well-Known Service name are well
maintained, and represent valid ISATAP routers. router interfaces (see

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section 5.2.1) are well maintained.

7. IANA considerations

We propose that IANA adopt the interface identifier construction
specified in section 4.1 for the existing IANA IEEE OUI registration
('00-00-5E'). Additionally, we request that the name "ISATAP" be
reserved in the IANA "Protocol and Service Names" assigned numbers
document.

8. Security considerations

Site administrators are advised that, in addition to possible attacks
against IPv6, security attacks against IPv4 MUST also be considered.
Many security considerations in [6OVER4,9] apply also to ISATAP.

Responsible IPv4 site security management is strongly encouraged. In
particular, border gateways SHOULD implement filtering to detect
spoofed IPv4 source addresses at a minimum; ip-protocol-41 filtering
SHOULD also be implemented.

If IPv4 source address filtering is not correctly implemented, the
validity checks in section 4.7 will not be effective in preventing
IPv6 source address spoofing.

If filtering for ip-protocol-41 is not correctly implemented, IPv6
source address spoofing is clearly possible, but this can be elim-
inated
eliminated if both IPv4 source address filtering, and the validity
checks in section 4.7 are implemented.

[DISC,6.1.2] implies that nodes trust Router Advertisements they
receive from on-link routers, as indicated by a value of 255 in the
IPv6 'hop-limit' field. Since this field is not decremented when ip-
protocol-41
ip-protocol-41 packets traverse multiple IPv4 hops [MECH,3.3], ISATAP
links require a different trust model. In particular, ONLY those
Router Advertisements received from a member of the Potential Routers
List are trusted; all others are silently discarded (see section
5.2.2). This trust model is predicated on IPv4 source address filter-
ing,
filtering, as described above.

The ISATAP address format does not support privacy extensions for
stateless address autoconfiguration [PRIVACY]. However, since the
ISATAP interface identifier is derived from the node's IPv4 address,
ISATAP addresses do not have the same level of privacy concerns as
IPv6 addresses that use an interface identifier derived from the MAC
address.

Acknowledgements

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Some of the ideas presented in this draft were derived from work at
SRI with internal funds and contractual support. Government sponsors
who supported the work include Monica Farah-Stapleton and Russell
Langan from U.S. Army CECOM ASEO, and Dr. Allen Moshfegh from U.S.
Office of Naval Research. Within SRI, Dr. Mike Frankel, J. Peter Mar-
cotullio,
Marcotullio, Lou Rodriguez, and Dr. Ambatipudi Sastry supported the
work and helped foster early interest.

The following peer reviewers are acknowledged for taking the time to
review a pre-release of this document and provide input: Jim Bound,
Rich Draves, Cyndi Jung, Ambatipudi Sastry, Aaron Schrader, Ole
Troan, Vlad Yasevich.

The authors acknowledge members of the NGTRANS community who have
made significant contributions to this effort, including Rich Draves,
Alain Durand, Nathan Lutchansky, Art Shelest, Margaret Wasserman, and
Brian Zill.

Finally, the authors recognize that ideas similar to those in this
document may have already been presented by others and wish to ack-
nowledge
acknowledge any other such contributions.

Normative References

[ADDR] Hinden, R., and S. Deering, "IP Version 6 Addressing
Architecture", RFC 2373, July 1998. (Pending approval
of "addr-arch-v3").

[AGGR] Hinden., R, O'Dell, M., and Deering, S., "An IPv6
Aggregatable Global Unicast Address Format",
RFC 2374, July 1998.

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

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

[EUI64] IEEE, "Guidelines for 64-bit Global Identifier (EUI-64)
Registration Authority",
http://standards.ieee.org/regauth/oui/tutorials/EUI64.html,
March 1997.

[ICMPv6] Conta, A. and S. Deering, "Internet Control Message
Protocol (ICMPv6) for the Internet Protocol Version 6
(IPv6) Specification", RFC 2463, December 1998.

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INTERNET-DRAFT ISATAP 30 January 18 April 2002

[IPV4] Postel, J., "Internet Protocol", RFC 791.

[IPV6] Deering, S., and R. Hinden, "Internet Protocol, Version 6
(IPv6) Specification", RFC 2460.

[MECH] Gilligan, R., and E. Nordmark, "Transition Mechanisms for
IPv6 Hosts and Routers", RFC 2893, August 2000.

[NAT] Egevang, K., and P. Francis, "The IP Network Address
Translator (NAT)", RFC 1631, May 1994.

[PRIVATE] Rekhter, Y., Moskowitz, B., Karrenberg, D., de Groot, G.,
and E. Lear, "Address Allocation for Private Internets",
RFC 1918, February 1996.

[SIP] Handley, M., Schulzrinne, H., Schooler, E., and
J. Rosenberg, "SIP: Session Initiation Protocol",
RFC 2543, March 1999.

Informative References

[6OVER4] Carpenter, B. and C. Jung, "Transmission of IPv6 over IPv4
Domains without Explicit Tunnels", RFC 2529.

[6TO4] Carpenter, B., and K. Moore, "Connection of IPv6 Domains
via IPv4 Clouds", RFC 3056, February 2001.

[IANA] Reynolds, J., and J. Postel, "Assigned Numbers", STD 2,
USC/Information Sciences Institute, October 1994.

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

[RFC1035] Mockapetris, P., "Domain Names - Implementation and
Specification", RFC 1035, November 1987.

[RFC2219] Hamilton, M., and R. Wright, "Use of DNS Aliases for
Network Services", RFC 2219 (BCP), October 1997.

Authors Addresses

Fred L. Templin
SRI International
333 Ravenswood Ave.
Menlo Park, CA 94025, USA
Phone: (650)-859-3144

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Email: templin@erg.sri.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

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INTERNET-DRAFT ISATAP 30 January 2002
Microsoft Corporation
One Microsoft Way
Redmond, WA 98052-6399
Phone: +1 425 705 3131
EMail: mohitt@microsoft.com

Dave Thaler
Microsoft Corporation
One Microsoft Way
Redmond, WA 98052-6399
Phone: +1 425 703 8835
EMail: dthaler@microsoft.com

APPENDIX A: Major Changes

changes from version 03 to version 04:

- Re-wrote section on Potential Router List initialization to
reference existing precedence in other documents

- several minor wording changes based on feedback from the
community

changes from version 02 to version 03:

- Added contributing co-authors

- RSs are now sent to unicast addresses rather than all-routers-multicast

- Brought draft into better alignment with other IPv6
standards-track documents

- Added applicability statement

changes from version 01 to version 02:

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- Cleaned up text and tightened up terminology. Changed "IPv6 destination
address" to "IPv6 next-hop address" under "sending rules". Changed
definition of ISATAP prefix to include link and site-local. Changed
language in sections 4 and 5

changes from version 00 to version 01:

- Revised draft to require different /64 prefixs for ISATAP
addresses and native IPv6 addresses. Thus, a node's ISATAP
interface is assigned a /64 prefix that is distinct from the
prefixes assigned to any other interfaces attached to the
node - be they physical or logical interfaces. This approach
eliminates ISATAP-specific sending rules presented in earlier
draft versions.

- Changed sense of 'u/l' bit in the ISATAP address interface
identifier to indicate "local scope", since ISATAP interface

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INTERNET-DRAFT ISATAP 30 January 2002
identifiers are unique only within the scope of the ISATAP
prefix. (See section 4.)

changes from personal draft to version 00:

- Title change to provide higher-level description of field of
use addressed by this draft. Removed other extraneous text.

- Major new section on automatic discovery of off-link IPv6 routers
when IPv6-IPv4 compatibility addresses are used.

Intellectual Property

The IETF has been notified of intellectual property rights claimed
in regard to some or all of the specification contained in this docu-
ment.
document. For more information consult the online list of claimed
rights.

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