draft-ietf-ngtrans-isatap-02.txt   draft-ietf-ngtrans-isatap-03.txt 
NGTRANS Working Group Fred L. Templin NGTRANS Working Group F. Templin
INTERNET-DRAFT SRI International INTERNET-DRAFT SRI International
Expires 21 May 2001 21 November 2001 T. Gleeson
Cisco Systems K.K.
M. Talwar
D. Thaler
Microsoft Corporation
Expires 30 July 2002 30 January 2002
Intra-Site Automatic Tunnel Addressing Protocol (ISATAP) Intra-Site Automatic Tunnel Addressing Protocol (ISATAP)
draft-ietf-ngtrans-isatap-02.txt draft-ietf-ngtrans-isatap-03.txt
Abstract Abstract
This document specifies an intra-site automatic tunneling protocol This document specifies the Intra-Site Automatic Tunnel Addressing
(ISATAP) for connecting IPv6 hosts and routers (nodes) within Protocol (ISATAP) that connects IPv6 hosts and routers (nodes) within
predominantly IPv4-based networks. This method is based on an IPv6 IPv4 sites. ISATAP is a transition mechanism that enables incremental
aggregatable global unicast address format (described herein) that deployment of IPv6 by treating the site's IPv4 infrastructure as a
embeds the IPv4 address of a node within the EUI-64 format interface Non-Broadcast Multiple Access (NBMA) link layer. ISATAP mechanisms
identifier. This document assumes that, during the IPv4 to IPv6 co- use a new IPv6 interface identifier format that embeds an IPv4
existence and transition phase, many sites will deploy IPv6 address - this enables automatic IPv6-in-IPv4 tunneling within a
incrementally within their IPv4 interior routing domains; especially site, whether the site uses globally assigned or private IPv4
those sites which have large and complex pre-existing IPv4 addresses. The new interface identifier format can be used with both
infrastructures. Within such sites, the address format and methods local and global unicast IPv6 prefixes - this enables IPv6 routing
described in this document will enable IPv6 deployment for nodes that both locally and globally. ISATAP mechanisms introduce no impact on
do not share a common link with an IPv6 gateway for their site. routing table size and require no special IPv4 services (e.g., IPv4
multicast).
While other works in progress in the NGTRANS working group propose
mechanisms for assigning globally-unique IPv6 address prefixes to
sites and methods for inter-domain routing between such sites, the
approach outlined in this memo enables large-scale incremental
deployment of IPv6 for nodes within a site's pre-existing IPv4
infrastructure without incurring aggregation scaling issues at the
border gateways nor requiring site-wide deployment of special IPv4
services such as multicast. The approach proposed by this document
supports IPv6 routing within both the site-local and global IPv6
routing domains as well as automatic IPv6 in IPv4 tunneling across
portions of a site's IPv4 infrastructure which have no native IPv6
support. Additionally, this approach supports automatic tunneling
within sites which use non globally-unique IPv4 address assignments,
such as when Network Address Translation [NAT] is used.
Status of this Memo Status of this Memo
This document is an Internet-Draft and is in full conformance with This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026. all provisions of Section 10 of RFC2026.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that Task Force (IETF), its areas, and its working groups. Note that
other groups may also distribute working documents as Internet- other groups may also distribute working documents as Internet-
Drafts. Drafts.
skipping to change at page 2, line 12 skipping to change at page 2, line 4
other groups may also distribute working documents as Internet- other groups may also distribute working documents as Internet-
Drafts. Drafts.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet- Drafts as reference time. It is inappropriate to use Internet- Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
The list of current Internet-Drafts can be accessed at The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt http://www.ietf.org/ietf/1id-abstracts.txt
The list of Internet-Draft Shadow Directories can be accessed at The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html. http://www.ietf.org/shadow.html.
Copyright Notice Copyright Notice
Copyright (C) The Internet Society (2001). All Rights Reserved. Copyright (C) The Internet Society (2001). All Rights Reserved.
1. Introduction 1. Introduction
The IETF NGTRANS working group anticipates an heterogeneous IPv4/IPv6 This document presents a simple, scalable approach that enables
infrastructure in the near future and thus is chartered to develop incremental deployment of IPv6 within IPv4-based sites in a manner
mechanisms to support IPv4/IPv6 coexistence and transition toward that is compatible with inter-domain transition mechanisms, e.g.,
global IPv6 deployment. For the most part, existing NGTRANS [6TO4]. We refer to this approach as the Intra-Site Automatic Tunnel
approaches focus on inter-domain routing between IPv6 islands using Addressing Protocol, or ISATAP (pronounced: "ice-a-tap"). ISATAP
the existing global IPv4 backbone as transit. But, these islands may allows dual-stack nodes that do not share a common link with an IPv6
themselves comprise complex heterogeneous IPv4/IPv6 networks (e.g. router to automatically tunnel packets to the IPv6 next-hop address
large academic or commercial campus intranets) that require intra- through IPv4, i.e., the site's IPv4 infrastructure is treated as an
domain IPv4 to IPv6 transition mechanisms and strategies as well. In NBMA link layer.
order to address this requirement, this document presents a simple
and scalable approach that enables incremental deployment of IPv6
nodes within predominantly IPv4-based intranets. We refer to this
approach as the Intra-Site Automatic Tunnel Addressing Protocol, or
ISATAP (pronounced: "ice-a-tap").
ISATAP is based on an aggregatable global unicast address format that This document specifies details for the transmission of IPv6 packets
carries a standard 64-bit IPv6 address prefix [ADDR][AGGR] with a over ISATAP links (i.e., automatic IPv6-in-IPv4 tunneling), including
specially-constructed 64-bit EUI-64 Interface Identifier [EUI64]. a new EUI-64 [EUI64] based interface identifier [ADDR][AGGR] format
This address format is fully compatible with both native IPv6 and that embeds an IPv4 address. This format supports configuration of
NGTRANS routing practices (e.g. [6to4],[6BONE]). But, the interface global, site-local and link-local addresses as specified in [AUTO] as
identifier in an ISATAP address employs a special construction that well as simple link-layer address mapping. Simple validity checks for
encapsulates an IPv4 address suitable for automatic IPv6-in-IPv4 tun- received packets are given. Also specified in this document is the
neling. Since tunneling occurs only within the site-level prefix of operation of IPv6 Neighbor Discovery for ISATAP, as permitted for
the ISATAP address, the embedded IPv4 address NEED NOT be globally NBMA links by [DISC]. The document finally presents deployment and
unique; rather, it need only be topologically correct for (and unique security considerations for ISATAP.
within) the context of the site.
ISATAP allows dual-stack nodes that do not share a common link with 2. Applicability Statement
an IPv6 gateway to join the global IPv6 network by automatically tun-
neling IPv6 messages through the IPv4 routing infrastructure within
their site. Two methods for automatic discovery of an IPv6 gateway
for ISATAP address autoconfiguration are provided. This approach
allows large-scale intra-site deployment without incurring aggrega-
tion scaling issues at border gateways, since only a single global
IPv6 address prefix need be used for the entire site. (Multiple pre-
fixes are, however, supported and may be used for site renumbering
and simliar purposes.) Finally, this approach supports networks which
use non-globally unique IPv4 addresses, such as when private address
allocations [PRIVATE] and/or Network Address Translation [NAT] are
used.
2. Changes ISATAP provides the following features:
Major changes from version 01 to version 02: - treats site's IPv4 infrastructure as an NBMA link layer using
automatic IPv6-in-IPv4 tunneling (i.e., no configured tunnel state)
- Cleaned up text and tightened up terminology. Changed "IPv6 destination - enables incremental deployment of IPv6 hosts within IPv4 sites with
address" to "IPv6 next-hop address" under "sending rules". Changed no aggregation scaling issues at border gateways
definition of ISATAP prefix to include link and site-local. Changed
language in sections 4 and 5
- Updated status of Linux implementation - requires no special IPv4 services within the site (e.g., multicast)
Major changes from version 00 to version 01: - supports both stateless address autoconfiguration and manual
configuration
- 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]
- Revised draft to require *different* /64 prefixs for ISATAP - compatible with other NGTRANS mechanisms (e.g., [6TO4])
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 3. Terminology
identifier to indicate "local scope", since ISATAP interface
identifiers are unique only within the scope of the ISATAP
prefix. (See section 4.)
Major changes from personal draft to version 00: The terminology of [IPv6] applies to this document. The following
additional terms are defined:
- Title change to provide higher-level description of field of link:
use addressed by this draft. Removed other extraneous text. same definition as [AUTO][DISC].
- Major new section on automatic discovery of off-link IPv6 routers underlying link:
when IPv6-IPv4 compatibility addresses are used. a link layer that supports IPv4 (for ISATAP), and MAY also support
IPv6 natively.
3. Terminology 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.
The terminology of [IPv6] applies to this document. Additionally, the ISATAP interface:
following terms are used extensively throughout this document: a node's attachment to an ISATAP link.
ISATAP prefix: ISATAP prefix:
Any link-local, site-local or globally aggregatable IPv6 prefix declared a prefix used to configure an address on the ISATAP interface. This
as such. An ISATAP prefix configures ONLY ISATAP addresses within its prefix is administratively assigned to the ISATAP link and MUST NOT
scope; native IPv6 addresses SHOULD NOT be configured on an ISATAP prefix. be duplicated on native IPv6 links.
ISATAP address: ISATAP address:
An IPv6 address with an ISATAP prefix and an IPv4 address embedded in an IPv6 address with an ISATAP prefix and an ISATAP format interface
the interface identifier in the manner described in section 4 below. identifier constructed as specified in section 4.
Native IPv6 address:
An IPv6 address constructed using a non-ISATAP prefix.
ISATAP pseudo-interface:
ISATAP encapsulation of IPv6 packets inside IPv4 packets occurs
at a point that is logically equivalent to an IPv6 interface,
with the link layer being the IPv4 unicast network. This point
is referred to as a pseudo-interface. An ISATAP pseudo-interface
is assigned an ISATAP address through address autoconfiguration.
ISATAP router: ISATAP router:
An IPv6 router supporting an ISATAP pseudo-interface. It is normally an IPv6 node that has an ISATAP interface over which it forwards
an interior router within an heterogeneous IPv6/IPv4 network. packets not explicitly addressed to itself.
ISATAP host: ISATAP host:
An IPv6 host which has an ISATAP pseudo-interface. any node that has an ISATAP interface and is not an ISATAP router.
4. ISATAP Address Format
In the following sections, we will motivate our proposed extensions
of the existing IEEE OUI reserved by the Internet Assigned Numbers
Authority [IANA] to support IEEE EUI-64 format addresses as well as
the ISATAP address format itself.
4.1. IEEE EUI-64 Interface Identifiers in IPv6 Addresses
IPv6 aggregatable global and local-use unicast addresses [ADDR]
include a 64-bit interface identifier in IEEE EUI-64 format [EUI64],
which is specified as the concatenation of a 24-bit company_id value
(also known as the OUI) assigned by the IEEE Registration Authority
(IEEE/RAC) and a 40-bit extension identifier assigned by the address-
ing authority for that OUI. (Normally, the addressing authority is
the organization to which the IEEE has allocated the OUI). IEEE EUI-
64 interface identifiers are formatted as follows:
|0 1|1 3|3 4|4 6|
|0 5|6 1|2 7|8 3|
+----------------+----------------+----------------+----------------+
|ccccccugcccccccc|ccccccccmmmmmmmm|mmmmmmmmmmmmmmmm|mmmmmmmmmmmmmmmm|
+----------------+----------------+----------------+----------------+
Where 'c' are the company-specific bits of the OUI, 'u' is the 4. Transmission of IPv6 Packets on ISATAP Links
universal/local bit, 'g' is the individual/group bit and 'm' are the
extension identifier bits. (NOTE: [ADDR] specifies that the 'u' bit
is inverted from its normal sense in the IEEE context; therefore u=1
indicates global scope and u=0 indicates local scope).
In order to support encapsulation of legacy IEEE EUI-48 (24-bit) ISATAP links transmit IPv6 packets via automatic tunneling using the
extension identifier values, [EUI64] specifies that the first two site's IPv4 infrastructure as an NBMA link layer. Automatic tunneling
octets of the EUI-64 40-bit extension identifier (bits 24 through 39 for ISATAP uses the same mechanisms specified in [MECH,3.1-3.6],
of the EUI-64 address itself) SHALL BE 0xFFFE if the extension iden- i.e., IPv6 packets are automatically encapsulated in IPv4 using 'ip-
tifier encapsulates an EUI-48 value. [EUI64] further specifies that protocol-41' as the payload type number. Specific considerations for
the first two octets of the extension identifier SHALL NOT be 0xFFFF, ISATAP links are given below:
since this value is reserved by the IEEE/RAC. However, all other 40-
bit extension identifier values are available for assignment by the
OUI addressing authority.
4.2. An EUI-64 Interface Identifier Format for IANA 4.1. ISATAP Interface Identifier Construction
The IANA owns IEEE OUI: 00-00-5E, and [IANA] specifies EUI-48 format IPv6 unicast addresses [ADDR][AGGR] include a 64-bit interface iden-
(24-bit) interface identifier assignments within that OUI. But, tifier field in "modified EUI-64 format", based on the IEEE EUI-64
[IANA] does not specify how these legacy EUI-48 assignments will be [EUI64] specification. (Modified EUI-64 format inverts the sense of
written in EUI-64 format, nor does it specify a format for future the 'u/l' bit from its specification in [EUI64], i.e., 'u/l' = 0
40-bit extension identifier assignments. We propose the following indicates local-use.) ISATAP specifies an [EUI64]-format address con-
format for EUI-64 addresses within IANA's OUI reservation: struction 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 2|2 3|3 3|4 6|
|0 3|4 1|2 9|0 3| |0 3|4 1|2 9|0 3|
+------------------------+--------+--------+------------------------+ +------------------------+--------+--------+------------------------+
| OUI ("00-00-5E"+u+g) | TYPE | TSE | TSD | | OUI ("00-00-5E"+u+g) | TYPE | TSE | TSD |
+------------------------+--------+--------+------------------------+ +------------------------+--------+--------+------------------------+
Where the fields are: Where the fields are:
OUI IANA's OUI: 00-00-5E with 'u' and 'g' bits (3 octets) OUI IANA's OUI: 00-00-5E with 'u' and 'g' bits (3 octets)
TYPE Type field; indicates how (TSE, TSD) are interpreted (1 octet) TYPE Type field; specifies interpretation of (TSE, TSD) (1 octet)
TSE Type-Specific Extension (1 octet) TSE Type-Specific Extension (1 octet)
TSD Type-Specific Data (3 octets) TSD Type-Specific Data (3 octets)
And the following interpretations are defined based on TYPE: And the following interpretations are specified based on TYPE:
TYPE (TSE, TSD) Interpretation TYPE (TSE, TSD) Interpretation
---- ------------------------- ---- -------------------------
0x00-0xFD RESERVED for future IANA use 0x00-0xFD RESERVED for future IANA use
0xFE (TSE, TSD) together contain an embedded IPv4 address 0xFE (TSE, TSD) together contain an embedded IPv4 address
0xFF TSD is interpreted based on TSE as follows: 0xFF TSD is interpreted based on TSE as follows:
TSE TSD Interpretation TSE TSD Interpretation
--- ------------------ --- ------------------
0x00-0xFD RESERVED for future IANA use 0x00-0xFD RESERVED for future IANA use
0xFE TSD contains 24-bit EUI-48 intf id 0xFE TSD contains 24-bit EUI-48 intf id
0xFF RESERVED by IEEE/RAC 0xFF RESERVED by IEEE/RAC
Essentially, if TYPE=0xFE, TSE is treated as an extension of TSD. If Thus, if TYPE=0xFE, TSE is an extension of TSD. If TYPE=0xFF, TSE is
TYPE=0xFF, TSE is treated as an extension of TYPE. Other values for an extension of TYPE. Other values for TYPE (hence, other interpreta-
TYPE (and hence, other interpretations of TSE, TSD) are reserved for tions of TSE, TSD) are reserved for future IANA use.
future IANA use. This format conforms to all requirements specified
in [EUI64] and supports encapsulation of EUI-48 interface identifiers
in the manner described by that document. For example, an existing
IANA EUI-48 format multicast address such as:
01-00-5E-01-02-03 The above specification is compatible with all aspects of [EUI64],
including support for encapsulating legacy EUI-48 interface identif-
iers (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 a [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 format" and the next four octets embed an IPv4 address encoded in
network byte order (least significant octet first). Addresses con-
figured on the ISATAP interface MUST use the ISATAP interface iden-
tifier format.
would be written in the IANA EUI-64 format as: 4.2. Stateless Autoconfiguration and Link-Local Addresses
01-00-5E-FF-FE-01-02-03 ISATAP addresses are unicast addresses [ADDR,2.5] that use ISATAP
format interface identifiers as follows:
But, this proposed format also provides a special TYPE (0xFE) for | 64 bits | 32 bits | 32 bits |
embedding IPv4 addresses within the IANA 40-bit extension identifier. +------------------------------+---------------+----------------+
This special TYPE forms the basis for the ISATAP address format as | link-local, site-local or | 0000:5EFE | IPv4 Address |
described in the following sections. | global unicast prefix | | of ISATAP link |
+------------------------------+---------------+----------------+
4.3. ISATAP Address Construction 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:
Using the proposed IANA-specific method for interface identifier con- 3FFE:1a05:510:1111:0:5EFE:8CAD:8108
struction discussed in sections 4.1 and 4.2 (with TYPE=0xFE), and
with reference to [ADDR], we can construct an ISATAP address as fol-
lows:
| 3| 13 | 8 | 24 | 16 | 8 | 8 | 8 | 8 | 32 bits | has a prefix of '3FFE:1a05:510:1111::/64' and an ISATAP format inter-
+--+-----+---+--------+--------+---+---+---+---+---+---+---+----+ face identifier with embedded IPv4 address: '140.173.129.8'. The
|FP| TLA |RES| NLA | SLA | 0x| 0x| 0x| 0x| IPv4 Address | address is alternately written as:
| | ID | | ID | ID | 00| 00| 5E| FE| of Endpoint |
+--+-----+---+--------+--------+--------------------------------+
(NOTE: since ISATAP address interface identifiers are interpreted 3FFE:1a05:510:1111:0:5EFE:140.173.129.8
only within the local scope of the /64 ISATAP prefix, we set the u/l
bit in the least significant octet of the OUI to '0' to indicate
local scope.)
By way of example, an existing node with IPv4 address 140.173.129.8 The link-local and site-local variants (respectively) are:
might be assigned an IPv6 64-bit prefix of 3FFE:1a05:510:200::/64. We
can then construct an ISATAP address for this node as:
3FFE:1a05:510:200:0:5EFE:8CAD:8108 FE80::0:5EFE:140.173.129.8
FEC0::1111:0:5EFE:140.173.129.8
or (perhaps more appropriately) written as the alternative form for 4.3. ISATAP Link/Interface Configuration
an IPv6 address with embedded IPv4 address found in [ADDR]:
3FFE:1a05:510:200:0:5EFE:140.173.129.8 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 address, or as a single interface for multiple link-layer
addresses.
Similarly, we can construct the link-local and site-local variants In the former case, the address of each ISATAP interface SHOULD be
(respectively) of the ISATAP address as: added to the Potential Routers List. In the latter case, the inter-
face will accept ISATAP packets addressed to any of the IPv4 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 Routers List.
FE80::0:5EFE:140.173.129.8 4.4. Sending Rules and Address Mapping
FEC0::200:0:5EFE:140.173.129.8
4.4. Advantages 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.
By embedding an IPv4 address in the interface identifier portion of The procedure for mapping unicast addresses into link-layer addresses
an IPv6 address as described in section 4.3, we can construct aggre- is to simply treat the last four octets of the ISATAP address as an
gatable global unicast IPv6 addresses that can either be routed glo- IPv4 address (in network byte order). No multicast address mappings
bally via the IPv6 infrastructure or automatically tunneled locally are specified.
across portions of a site's IPv4 infrastructure which have no native
IPv6 support. Additionally, a node with both an ISATAP link and a
native IPv6 link could act as a router for nodes that share its
native link, since the ISATAP node could automatically tunnel mes-
sages across a site's IPv4 domain on behalf of the native IPv6 nodes.
An example would be deployment of IPv6 on a workgroup LAN. In this
case, one host could configure an ISATAP address and act as a router
for other hosts which use native IPv6 addresses on the LAN.
An additional advantage for our proposed method of embedding an IPv4 4.5. Validity Checks for Received Packets
address in the interface identifier portion of an IPv6 address not
found in other approaches such as [6TO4] is that large numbers of
ISATAP addresses could be assigned within a common IPv6 routing pre-
fix, thus providing maximal aggregation at the border gateways. For
example, the single 64-bit IPv6 prefix:
3FFE:1a05:510:2412::/64 ISATAP interfaces MUST silently discard any received packets that do
not satisfy ONE OF the following validity checks:
could include literally millions of nodes with ISATAP addresses. - the network-layer (IPv6) source address has a prefix configured on
This feature would allow a "sparse mode" IPv6 deployment such as the the ISATAP interface and an ISATAP-format interface identifier that
deployment of sparse populations of IPv6 hosts on large numbers of embeds the link-layer (IPv4) source address, i.e., source is on-link
independent links throughout a large corporate Intranet.
A final important advantage is that this method supports both sites - the link-layer (IPv4) source address is in the Potential Routers List
that use globally unique IPv4 address assignments and those that use (see section 5.2), i.e., previous hop is an on-link ISATAP router
non-globally unique IPv4 addresses, such as when private address
assignments and/or Network Address Translation are used. By way of
analogy to the US Postal system, inter-domain transition approaches
such as [6TO4] provide means for routing messages "cross-country" to
the "street address" of a distant site while the approach outlined in
this document provides localized routing information to reach a
specific (mailstop, apartment number, post office box, etc) WITHIN
that site. Thus, the site-level routing information need not have
relevance outside the scope of that site.
5. ISATAP Deployment Considerations 5. Neighbor Discovery for ISATAP Links
Hosts should only use ISATAP on interfaces which do not share a com- Section 3.2 of [DISC] ("Supported Link Types") provides the following
mon link with a native IPv6 router. Routers may configure both ISATAP guidelines for non-broadcast multiple access (NBMA) link support:
and Native IPv6 links on the same physical interface, but the pre-
fixes used will be distinct. An ISATAP router can be configured on
any ISATAP link to advertise the prefix(es) administratively assigned
to that link. Since ISATAP is NBMA, these advertisements are not
periodically multicast by the router, but are solicited by Rtsols
sent by hosts. Hosts will configure an ISATAP pseudo-interface and
assign it address(es) based on the ISATAP prefix(es) in the solicited
Rtadv messages.
Following ISATAP address configuration, ISATAP hosts communicate as "Redirect, Neighbor Unreachability Detection and next-hop determi-
regular IPv6 peers. The source address of such packets will be in nation should be implemented as described in this document. Address
ISATAP format. Replies sent to this address can thus be automatically resolution and the mechanism for delivering Router Solicitations
tunneled over the last IPv6 hop, which occurs on the ISATAP network. and Advertisements on NBMA links is not specified in this docu-
While nodes may optionally use stateful configuration to set an ISA- ment."
TAP prefix and a "default" route that points to an ISATAP router, a
greatly preferred alternative is to provide for automatic intra-site
IPv6 router discovery and stateless address autoconfiguration [DIS-
CUSS]. The following section presents a means for the automatic
discovery of ISATAP routers.
5.1. Automatic Discovery of ISATAP Routers 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 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.)
As described in [AUTO], a node that does not share a common link with 5.1. Address Resolution
an IPv6 router will NOT receive unsolicited Router Advertisements
(Rtadv's), nor will Router Solicitations (Rtsol's) from that node
reach an IPv6 router on the local link. But, the node may still be
able to connect to the global IPv6 Internet if an ISATAP router for
the site exists. Hence, a means for ISATAP router discovery is
required. We present the following procedure for a node to initiate
ISATAP router discovery (and for an ISATAP router to respond) when an
on-link IPv6 router is not available:
- The node constructs an ISATAP link local address for itself Protocol addresses (IPv6) in ISATAP are resolved to link-layer
(as described in section 4.) as: 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.
FE80::0:5EFE:V4ADDR_NODE The link-layer address option used in [DISC] is not needed. Implemen-
tations SHOULD NOT send link-layer address options in any Neighbor
Discovery packets, and MUST silently ignore any such options in
Neighbor Discovery packets which are received.
- The node discovers the IPv4 address for an ISATAP router 5.2. Router and Prefix Discovery
as: V4ADDR_RTR (**)
- The node sends an Rtsol to the IPv6 "all-routers-multicast" address Since the site's IPv4 infrastructure is treated as an NBMA link
tunneled through the IPv4 infrastructure to the ISATAP router's layer, unsolicited Router Advertisements do not provide sufficient
IPv4 address. The addresses used in the IPv6 and IPv4 headers are: means for router discovery on ISATAP links. Thus, alternate mechan-
isms are required and specified below:
ipv6_src: FE80::0:5EFE:V4ADDR_NODE 5.2.1. Conceptual Data Structures
ipv6_dst: FF02::2
ipv4_src: V4ADDR_NODE
ipv4_dst: V4ADDR_RTR
- Upon receiving the tunneled Rtsol, the ISATAP router sends ISATAP nodes use the Prefix List and Default Router List conceptual
a unicast Rtadv to the unicast address of the node which sent the data structures exactly as specified in [DISC,5.1]. ISATAP links add
Rtsol; again, by tunneling the Rtadv through IPv4. The addresses a new conceptual data structure "Potential Router List" and the fol-
used in the IPv6 and IPv4 headers are: lowing new configuration variable:
ipv6_src: FE80::0:5EFE:V4ADDR_RTR ResolveInterval Time between name service resolutions.
ipv6_dst: FE80::0:5EFE:V4ADDR_NODE Default and suggested minimum: 1hr
ipv4_src: V4ADDR_RTR
ipv4_dst: V4ADDR_NODE
- Upon receiving the Rtsol, the originating node performs address
autoconfiguration as described in [AUTO] and constructs:
- a fully-qualified ISATAP address for use as the source address A Potential Router List (PRL) is associated with every ISATAP link.
for an ISATAP pseudo-interface 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
"advertising interface"), and is used to construct the ISATAP link-
local address for that interface.
- a default route that points to the ISATAP router When the node enables an ISATAP link, it initializes the PRL with
IPv4 addresses discovered through name service lookups for the Well-
Known Service name "ISATAP" (see "IANA Considerations"). Nodes
periodically repeat this process after ResolveInterval to detect
additions/deletions for the PRL. Initialization of the PRL through
static IPv4 address assignments and/or an alternate name for lookups
is a supported configuration option, but the method described above
is preferred.
Note (**) that the above procedure assumes a means for discovering 5.2.2. Validation of Router Advertisement Messages
V4ADDR_RTR. We present two alternative methods for the automatic
discovery of V4ADDR_RTR:
5.2. DNS Well-Known Service Name A node MUST silently discard any received Router Advertisement mes-
sages that do not satisfy the validity checks in [DISC,6.1.2] as well
as the following additional validity check for ISATAP:
The first method for discovering V4ADDR_RTR employs a new DNS Well- - the network-layer (IPv6) source address is from the PRL
Known Service (WKS) name [DNS1,DNS2]. With the establishment of a new
well-known service name (e.g. "ISATAPGW"), administrators could pub-
lish the IPv4 address of a gateway which implementations could use to
discover V4ADDR_RTR. This method has the advantage that it can be
deployed immediately using existing mechanisms. However, it requires
name service lookups and may not always provide the optimum
V4ADDR_RTR resolution for isolated hosts if multiple ISATAP routers
are available.
5.3. IPv4 Anycast for ISATAP routers 5.2.3. Router Specification
[6TO4ANY] proposes an IPv4 anycast prefix for 6to4 relay routers. Advertising ISATAP interfaces of routers behave the same as advertis-
The proposal suggests an IPv4 prefix assignment '192.88.99.0/24' ing interfaces described in [DISC,6.2]. However, periodic unsolicited
where the single address '192.88.99.1' is assigned as the "6to4 IPv6 multicast Router Advertisements are not required, thus the "interval
relay anycast address". We propose analogous assignments for the pur- timer" associated with advertising interfaces is not used for that
pose of an "ISATAP router anycast address". (Whether the reservation purpose.
of a second /32 assignment from the 6to4 IPv4 anycast prefix proposed
in [6TO4ANY] would be possible, or a separate prefix assignment would
be required is a matter of debate and TBD.)
ISATAP routers would advertise the ISATAP router anycast prefix via When an ISATAP router receives a valid Router Solicitation on an
the intra-domain IPv4 routing infrastructure. Isolated IPv6 nodes advertising ISATAP interface, it replies with a unicast Router Adver-
would then use the ISATAP router anycast address as the V4ADDR_RTR tisement to the address of the node which sent the Router Solicita-
IPv4 destination for off-link Rtsol's. This approach has the signifi- tion. The source address of the Router Advertisement is a link-local
cant advantages that: unicast address associated with the interface. This MAY be the same
as the destination address of the Router Solicitation.
- implementations could hard-code the well-known ISATAP By default, ISATAP routers will not receive Router Advertisements
anycast address, thus avoiding service discovery via DNS from other ISATAP routers. Thus, Router Advertisement consistency
verification [DISC,6.2.7] is not supported by default. Routers MAY
OPTIONALLY engage in the exchange of router advertisements with other
members of the PRL to enable this function.
- an optimum path to an ISATAP router would be ensured 5.2.4. Host Specification
by intra-domain IPv4 routing
As described above, the IPv4 anycast method for locating ISATAP
routers provides significant functional advantages over the DNS
approach, while the DNS approach can be implemented immediately pend-
ing the registration of a WKS name with IANA. While either method
will work, the decision of which to push for standardization is TBD
pending discussion at upcoming NGTRANS WG meetings.
6. Sending Rules and Routing Considerations 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:
Since each node will be assigned one or more ISATAP prefixes which MinRouterSolicitInterval
are administratively reserved for use ONLY by ISATAP nodes, no spe- Minimum time between sending Router Solicitations
cial sending rules are needed. In particular, correspondent nodes to any router. Default and suggested minimum: 15min
that share a common ISATAP prefix will always exchange messages using
their ISATAP pseudo-interfaces, whereas nodes that do not share a
common ISATAP prefix will always exchange messages via standard IPv6
routing. When sending a message on an ISATAP pseudo-interface, an
implementation SHOULD verify that the IPv6 next-hop address employs
the ISATAP address construction rules described in section 4 in order
to detect mis-configured addresses. No other sending rules are neces-
sary.
7. Address Selection When PRL(i) is first added to the list, the host sets its associated
timer to MinRouterSolicitInterval.
No special address selection rules are necessary. 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.
8. Automatic Deprecation Polling consists of sending Router Solicitations to the ISATAP 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'. They are otherwise sent in the same manner described in
[DISC,6.3.7].
ISATAP addresses are intended for use only by nodes which do not When the host receives a valid Router Advertisement (i.e., one that
receive native IPv6 Rtadv's due to not sharing a common link with an satisfies the validity checks in sections 4.5 and 5.2.2) it processes
IPv6 router. When native IPv6 Rtadv's become available (such as when them in the same manner described in [DISC,6.3.4]. The host addition-
an IPv6 router is deployed on a node's link), the node should con- ally resets the timer associated with the PRL entry that matches the
struct a non-ISATAP aggregatable global IPv6 unicast address using network-layer source address in the Router Advertisement. The timer
address auto-configuration [AUTO] for a non-ISATAP IPv6 prefix is reset to either 0.5 * (the minimum value in the router lifetime or
discovered through normal means [DISC]. After the node's native IPv6 valid lifetime of any on-link prefixes advertised) or MinRouterSoli-
address is populated in the DNS, the node should eventually cease citInterval; whichever is longer.
sending Rtsol's to the ISATAP router and discontinue use of its ISA-
TAP pseudo-interface. In this way, ISATAP addresses will gradually
(and automatically) disappear as IPv6 routers are widely deployed
within sites.
9. Multicast Considerations 6. ISATAP Deployment Considerations
Other works in progress [6TO4MULTI] are currently investigating mul- 6.1. Host And Router Deployment Considerations
ticast addressing issues for [6TO4]. The address format discussed in
this document is expected to be compatible with those emerging
approaches.
10. IANA considerations For hosts, if an underlying link supports both IPv4 (over which ISA-
TAP is implemented) and also supports IPv6 natively, then ISATAP MAY
be enabled if the native IPv6 layer does not receive Router Adver-
tisements (i.e., does not have connection with an IPv6 router). After
a non-link-local address has been configured and a default router
acquired on the native link, the host MAY discontinue the 'Router
Polling Process' process specified in section 5.2.4 and allow exist-
ing ISATAP address configurations to expire as specified in
[DISC,5.3][AUTO,5.5.4]. In this way, ISATAP use will gradually dimin-
ish as IPv6 routers are widely deployed throughout the site.
In order to support the EUI-64 address form described in this docu- Routers MAY configure a native link to simultaneously support both
ment, we propose that IANA adopt the EUI-64 Interface Identifier for- native IPv6, and also ISATAP (over IPv4). Routing will operate as
mat specified in section 4.2 for the existing 00-00-5E OUI owned by usual between these two domains. Note that the prefixes used on the
IANA. No other actions are required by the IANA. ISATAP and native IPv6 interfaces will be distinct.
11. Security considerations When an ISATAP router is configured, the IPv4 address used for its
ISATAP interface SHOULD be added (either automatically or manually)
to the site's name service 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.
The ISATAP address format does not support privacy extensions for 6.2. Site Administration Considerations
stateless address autoconfiguration [PRIVACY]. However, such privacy
extensions are intended primarily to avoid revealing one's MAC
address, and the ISATAP address format described in this document
accomplishes this same goal.
Additional security issues are called out in [6TO4] and probably The following considerations are noted for sites that deploy ISATAP:
apply here as well.
12. Implementation status - 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.
The author has implemented the mechanisms described in this draft - ISATAP hosts and routers can be deployed in an ad-hoc and independent
through modifications to the FreeBSD 3.2-RELEASE [FBSD] operating fashion. In particular, ISATAP hosts can be deployed with little/no
system with the INRIA [INRIA] IPv6 distribution. As of November 12, advanced knowledge of existing ISATAP routers, and ISATAP routers
2001, a Linux implementation is now integrated in the USAGI Linux can deployed with no reconfiguration requirements for hosts.
distribution [USAGI].
Additionally, Windows XP RC1 will implement elements of the mechanism - ISATAP nodes periodically send Router Solicitations to all entries
proposed in this paper. 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 bounds control traffic for
large numbers of nodes even in worst-case scenarios.
- Strategic site administration, along with robust host and router
implementations, can provide significant reductions in control
traffic. At a minimum, site administrators SHOULD ensure that name
service records for the "ISATAP" Well-Known Service name are well
maintained, and represent valid ISATAP routers.
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 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 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, 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 Acknowledgements
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, Lou Rodriguez, and Dr. Ambatipudi Sastry supported the work
and helped foster early interest.
The original ideas presented in this draft were derived from SRI con- The following peer reviewers are acknowledged for taking the time to
tractual work. The author recognizes that ideas similar to those in review a pre-release of this document and provide input: Jim Bound,
this document may have already been presented by others and wishes to Rich Draves, Cyndi Jung, Ambatipudi Sastry, Aaron Schrader, Ole
acknowledge any other such authors. The author also wishes to ack- Troan, Vlad Yasevich.
nowledge the government contract administrators who sponsored the
projects from which these works derived as well as his SRI colleagues
with whom he has discussed and reviewed this work, including Monica
Farah-Stapleton, Dr. Mike Frankel, J. Peter Marcotullio, Lou Rodri-
guez, and Dr. Ambatipudi Sastry.
The author acknowledges valuable input from numerous members of the The authors acknowledge members of the NGTRANS community who have
NGTRANS community which has helped guide the direction of the draft. made significant contributions to this effort, including Rich Draves,
The list of contributors is too long to enumerate, but the input from Alain Durand, Nathan Lutchansky, Art Shelest, Margaret Wasserman, and
the community has been vital to the draft's evolution. Alain Durand Brian Zill.
deserves special mention for contributing the title of this draft and
the ISATAP acronym. Additionally, Tim Gleenson and Nathan Lutchansky
numerous helpful suggestions for improvement.
The author finally wishes to provide special acknowledgement to Dave Finally, the authors recognize that ideas similar to those in this
Thaler, Art Shelest, Richard Draves, and others at Microsoft Research document may have already been presented by others and wish to ack-
for their ideas on automatic discovery of off-link IPv6 routers. Much nowledge any other such contributions.
of the text in section on deployment considerations derives directly
from discussions with Dave, Art, Rich and others.
References 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 [AGGR] Hinden., R, O'Dell, M., and Deering, S., "An IPv6
Aggregatable Global Unicast Address Format", Aggregatable Global Unicast Address Format",
RFC 2374, July 1998. RFC 2374, July 1998.
[ADDR] Hinden, R., and S. Deering, "IP Version 6 Addressing
Architecture", RFC 2373, July 1998.
[AUTO] Thomson, S., and T. Narten, "IPv6 Stateless Address [AUTO] Thomson, S., and T. Narten, "IPv6 Stateless Address
Autoconfiguration", RFC 2462, December 1998. Autoconfiguration", RFC 2462, December 1998.
[DISC] Narten, T., Nordmark, E., and W. Simpson, "Neighbor [DISC] Narten, T., Nordmark, E., and W. Simpson, "Neighbor
Discovery for IP Version 6 (IPv6)", RFC 2461, Discovery for IP Version 6 (IPv6)", RFC 2461,
December 1998. December 1998.
[DNS1] Mockapetris, P. "Domain names - concepts and facilities",
STD 13, RFC 1034, November 1987.
[DNS2] Mockapetris, P. "Domain names - Implementation and Specif-
ication",
STD 13, RFC 1035, November 1987.
[DNSSRV] Gulbrandsen, A., Vixie, P., and L. Esibov, "A DNS RR for
specifying the location of services (DNS SRV)", RFC 2782,
February 2000.
[EUI64] IEEE, "Guidelines for 64-bit Global Identifier (EUI-64) [EUI64] IEEE, "Guidelines for 64-bit Global Identifier (EUI-64)
Registration Authority", Registration Authority",
http://standards.ieee.org/regauth/oui/tutorials/EUI64.html, http://standards.ieee.org/regauth/oui/tutorials/EUI64.html,
March 1997 March 1997.
[IANA] Reynolds, J., and J. Postel, "Assigned Numbers", STD 2, [ICMPv6] Conta, A. and S. Deering, "Internet Control Message
USC/Information Sciences Institute, October 1994. Protocol (ICMPv6) for the Internet Protocol Version 6
(IPv6) Specification", RFC 2463, December 1998.
[IPV4] Postel, J., "Internet Protocol", RFC 791 [IPV4] Postel, J., "Internet Protocol", RFC 791.
[IPV6] Deering, S., and R. Hinden, "Internet Protocol, Version 6 [IPV6] Deering, S., and R. Hinden, "Internet Protocol, Version 6
(IPv6) Specification", RFC 2460 (IPv6) Specification", RFC 2460.
[6TO4] Carpenter, B., and K. Moore, "Connection of IPv6 Domains
via IPv4 Clouds", RFC 3056, February 2001.
[6TO4ANY] Huitema, C., "An anycast prefix for 6to4 relay routers",
RFC 3068, June 2001.
[6TO4MULTI] Thaler, D., "Support for Multicast over 6to4 Networks",
draft-ietf-ngtrans-6to4-multicast-00.txt (work in pro-
gress)
[MECH] Gilligan, R., and E. Nordmark, "Transition Mechanisms for [MECH] Gilligan, R., and E. Nordmark, "Transition Mechanisms for
IPv6 Hosts and Routers", RFC 2893, August 2000. IPv6 Hosts and Routers", RFC 2893, August 2000.
[SELECT] Draves, R., Default Address Selection for IPv6, draft- [NAT] Egevang, K., and P. Francis, "The IP Network Address
ietf- Translator (NAT)", RFC 1631, May 1994.
ipngwg-default-addr-select-06.txt (work in progress)
[FBSD] http://www.freebsd.org [PRIVATE] Rekhter, Y., Moskowitz, B., Karrenberg, D., de Groot, G.,
and E. Lear, "Address Allocation for Private Internets",
RFC 1918, February 1996.
[USAGI] http://www.linux-ipv6.org Informative References
[INRIA] ftp://ftp.inria.fr/network/ipv6/ [6OVER4] Carpenter, B. and C. Jung, "Transmission of IPv6 over IPv4
Domains without Explicit Tunnels", RFC 2529.
[6BONE] Rockell, R., and R. Fink, RFC 2772, February 2000. [6TO4] Carpenter, B., and K. Moore, "Connection of IPv6 Domains
via IPv4 Clouds", RFC 3056, February 2001.
[PRIVATE] Rekhter, Y., Moskowitz, B., Karrenberg, D., de Groot, G. [IANA] Reynolds, J., and J. Postel, "Assigned Numbers", STD 2,
J., USC/Information Sciences Institute, October 1994.
and E. Lear, "Address Allocation for Private Internets",
RFC 1918, February 1996.
[PRIVACY] Narten, T., R. Draves, "Privacy Extensions for Stateless [PRIVACY] Narten, T., R. Draves, "Privacy Extensions for Stateless
Address Address Autoconfiguration in IPv6", RFC 3041,
Autoconfiguration in IPv6", RFC 3041, January 2001. January 2001.
[NAT] Egevang, K., and P. Francis, "The IP Network Address
Translator (NAT)", RFC 1631, May 1994.
[DISCUSS] private discussions with Dave Thaler, Art Shelest, et al.
Authors Addresses Authors Addresses
Fred L. Templin Fred L. Templin
SRI International SRI International
333 Ravenswood Ave. 333 Ravenswood Ave.
Menlo Park, CA 94025, USA Menlo Park, CA 94025, USA
Phone: (650)-859-3144
Email: templin@erg.sri.com 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
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 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:
- 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
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 Intellectual Property
The IETF has been notified of intellectual property rights claimed in The IETF has been notified of intellectual property rights claimed in
regard to some or all of the specification contained in this docu- regard to some or all of the specification contained in this docu-
ment. For more information consult the online list of claimed ment. For more information consult the online list of claimed
rights. rights.
 End of changes. 

This html diff was produced by rfcdiff 1.25, available from http://www.levkowetz.com/ietf/tools/rfcdiff/