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NGTRANS Working Group                                  Fred L. Templin
INTERNET-DRAFT                                         SRI International
Expires 21 May 2001                                    21 November 2001

        Intra-Site Automatic Tunnel Addressing Protocol (ISATAP)

                    draft-ietf-ngtrans-isatap-02.txt

Abstract

   This document specifies an intra-site automatic tunneling protocol
   (ISATAP) for connecting IPv6 hosts and routers (nodes) within
   predominantly IPv4-based networks. This method is based on an IPv6
   aggregatable global unicast address format (described herein) that
   embeds the IPv4 address of a node within the EUI-64 format interface
   identifier.  This document assumes that, during the IPv4 to IPv6 co-
   existence and transition phase, many sites will deploy IPv6
   incrementally within their IPv4 interior routing domains; especially
   those sites which have large and complex pre-existing IPv4
   infrastructures. Within such sites, the address format and methods
   described in this document will enable IPv6 deployment for nodes that
   do not share a common link with an IPv6 gateway for their site.

   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

   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.




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   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.



   Copyright Notice

   Copyright (C) The Internet Society (2001).  All Rights Reserved.


1.  Introduction

   The IETF NGTRANS working group anticipates an heterogeneous IPv4/IPv6
   infrastructure in the near future and thus is chartered to develop
   mechanisms to support IPv4/IPv6 coexistence and transition toward
   global IPv6 deployment. For the most part, existing NGTRANS
   approaches focus on inter-domain routing between IPv6 islands using
   the existing global IPv4 backbone as transit. But, these islands may
   themselves comprise complex heterogeneous IPv4/IPv6 networks (e.g.
   large academic or commercial campus intranets) that require intra-
   domain IPv4 to IPv6 transition mechanisms and strategies as well. In
   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
   carries a standard 64-bit IPv6 address prefix [ADDR][AGGR] with a
   specially-constructed 64-bit EUI-64 Interface Identifier [EUI64].
   This address format is fully compatible with both native IPv6 and
   NGTRANS routing practices (e.g. [6to4],[6BONE]). But, the interface
   identifier in an ISATAP address employs a special construction that
   encapsulates an IPv4 address suitable for automatic IPv6-in-IPv4 tun-
   neling. Since tunneling occurs only within the site-level prefix of
   the ISATAP address, the embedded IPv4 address NEED NOT be globally
   unique; rather, it need only be topologically correct for (and unique
   within) the context of the site.

   ISATAP allows dual-stack nodes that do not share a common link with



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   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

   Major 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

     - Updated status of Linux implementation



   Major 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.)


   Major 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.




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


3.  Terminology

   The terminology of [IPv6] applies to this document. Additionally, the
   following terms are used extensively throughout this document:

   ISATAP prefix:
     Any link-local, site-local or globally aggregatable IPv6 prefix declared
     as such. An ISATAP prefix configures ONLY ISATAP addresses within its
     scope; native IPv6 addresses SHOULD NOT be configured on an ISATAP prefix.

   ISATAP address:
     An IPv6 address with an ISATAP prefix and an IPv4 address embedded in
     the interface identifier in the manner described in section 4 below.

   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:
     An IPv6 router supporting an ISATAP pseudo-interface. It is normally
     an interior router within an heterogeneous IPv6/IPv4 network.

   ISATAP host:
     An IPv6 host which has an ISATAP pseudo-interface.


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],



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   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
   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)
   extension identifier values, [EUI64] specifies that the first two
   octets of the EUI-64 40-bit extension identifier (bits 24 through 39
   of the EUI-64 address itself) SHALL BE 0xFFFE if the extension iden-
   tifier encapsulates an EUI-48 value. [EUI64] further specifies that
   the first two octets of the extension identifier SHALL NOT be 0xFFFF,
   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

   The IANA owns IEEE OUI: 00-00-5E, and [IANA] specifies EUI-48 format
   (24-bit) interface identifier assignments within that OUI. But,
   [IANA] does not specify how these legacy EUI-48 assignments will be
   written in EUI-64 format, nor does it specify a format for future
   40-bit extension identifier assignments. We propose the following
   format for EUI-64 addresses within IANA's OUI reservation:













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    |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; indicates how (TSE, TSD) are interpreted (1 octet)

      TSE     Type-Specific Extension (1 octet)

      TSD     Type-Specific Data (3 octets)


   And the following interpretations are defined 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
                   0xFF         RESERVED by IEEE/RAC

   Essentially, if TYPE=0xFE, TSE is treated as an extension of TSD. If
   TYPE=0xFF, TSE is treated as an extension of TYPE. Other values for
   TYPE (and hence, other interpretations of TSE, TSD) are reserved for
   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

   would be written in the IANA EUI-64 format as:

       01-00-5E-FF-FE-01-02-03

   But, this proposed format also provides a special TYPE (0xFE) for
   embedding IPv4 addresses within the IANA 40-bit extension identifier.
   This special TYPE forms the basis for the ISATAP address format as



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   described in the following sections.


   4.3.  ISATAP Address Construction

   Using the proposed IANA-specific method for interface identifier con-
   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     |
    +--+-----+---+--------+--------+---+---+---+---+---+---+---+----+
    |FP| TLA |RES|  NLA   |  SLA   | 0x| 0x| 0x| 0x|  IPv4 Address  |
    |  | ID  |   |  ID    |  ID    | 00| 00| 5E| FE|   of Endpoint  |
    +--+-----+---+--------+--------+--------------------------------+

   (NOTE: since ISATAP address interface identifiers are interpreted
   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
   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

   or (perhaps more appropriately) written as the alternative form for
   an IPv6 address with embedded IPv4 address found in [ADDR]:

      3FFE:1a05:510:200:0:5EFE:140.173.129.8

   Similarly, we can construct the link-local and site-local variants
   (respectively) of the ISATAP address as:

      FE80::0:5EFE:140.173.129.8
      FEC0::200:0:5EFE:140.173.129.8


   4.4.  Advantages

   By embedding an IPv4 address in the interface identifier portion of
   an IPv6 address as described in section 4.3, we can construct aggre-
   gatable global unicast IPv6 addresses that can either be routed glo-
   bally via the IPv6 infrastructure or automatically tunneled locally
   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



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   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
   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

   could include literally millions of nodes with ISATAP addresses.
   This feature would allow a "sparse mode" IPv6 deployment such as the
   deployment of sparse populations of IPv6 hosts on large numbers of
   independent links throughout a large corporate Intranet.

   A final important advantage is that this method supports both sites
   that use globally unique IPv4 address assignments and those that use
   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

   Hosts should only use ISATAP on interfaces which do not share a com-
   mon link with a native IPv6 router. Routers may configure both ISATAP
   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
   regular IPv6 peers. The source address of such packets will be in



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   ISATAP format. Replies sent to this address can thus be automatically
   tunneled over the last IPv6 hop, which occurs on the ISATAP network.
   While nodes may optionally use stateful configuration to set an ISA-
   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

   As described in [AUTO], a node that does not share a common link with
   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
       (as described in section 4.) as:

         FE80::0:5EFE:V4ADDR_NODE

     - The node discovers the IPv4 address for an ISATAP router
       as: V4ADDR_RTR (**)

     - The node sends an Rtsol to the IPv6 "all-routers-multicast" address
       tunneled through the IPv4 infrastructure to the ISATAP router's
       IPv4 address. The addresses used in the IPv6 and IPv4 headers are:

         ipv6_src:  FE80::0:5EFE:V4ADDR_NODE
         ipv6_dst:  FF02::2
         ipv4_src:  V4ADDR_NODE
         ipv4_dst:  V4ADDR_RTR

     - Upon receiving the tunneled Rtsol, the ISATAP router sends
       a unicast Rtadv to the unicast address of the node which sent the
       Rtsol; again, by tunneling the Rtadv through IPv4. The addresses
       used in the IPv6 and IPv4 headers are:

         ipv6_src:  FE80::0:5EFE:V4ADDR_RTR
         ipv6_dst:  FE80::0:5EFE:V4ADDR_NODE
         ipv4_src:  V4ADDR_RTR
         ipv4_dst:  V4ADDR_NODE



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     - 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
         for an ISATAP pseudo-interface

       - a default route that points to the ISATAP router

   Note (**) that the above procedure assumes a means for discovering
   V4ADDR_RTR. We present two alternative methods for the automatic
   discovery of V4ADDR_RTR:


5.2.  DNS Well-Known Service Name

   The first method for discovering V4ADDR_RTR employs a new DNS Well-
   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

   [6TO4ANY] proposes an IPv4 anycast prefix for 6to4 relay routers.
   The proposal suggests an IPv4 prefix assignment '192.88.99.0/24'
   where the single address '192.88.99.1' is assigned as the "6to4 IPv6
   relay anycast address". We propose analogous assignments for the pur-
   pose of an "ISATAP router anycast address". (Whether the reservation
   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
   the intra-domain IPv4 routing infrastructure. Isolated IPv6 nodes
   would then use the ISATAP router anycast address as the V4ADDR_RTR
   IPv4 destination for off-link Rtsol's. This approach has the signifi-
   cant advantages that:

     - implementations could hard-code the well-known ISATAP
       anycast address, thus avoiding service discovery via DNS

     - an optimum path to an ISATAP router would be ensured
       by intra-domain IPv4 routing



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   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

   Since each node will be assigned one or more ISATAP prefixes which
   are administratively reserved for use ONLY by ISATAP nodes, no spe-
   cial sending rules are needed. In particular, correspondent nodes
   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

   No special address selection rules are necessary.


8.  Automatic Deprecation

   ISATAP addresses are intended for use only by nodes which do not
   receive native IPv6 Rtadv's due to not sharing a common link with an
   IPv6 router.  When native IPv6 Rtadv's become available (such as when
   an IPv6 router is deployed on a node's link), the node should con-
   struct a non-ISATAP aggregatable global IPv6 unicast address using
   address auto-configuration [AUTO] for a non-ISATAP IPv6 prefix
   discovered through normal means [DISC].  After the node's native IPv6
   address is populated in the DNS, the node should eventually cease
   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

   Other works in progress [6TO4MULTI] are currently investigating mul-
   ticast addressing issues for [6TO4]. The address format discussed in



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   this document is expected to be compatible with those emerging
   approaches.


10.  IANA considerations

   In order to support the EUI-64 address form described in this docu-
   ment, we propose that IANA adopt the EUI-64 Interface Identifier for-
   mat specified in section 4.2 for the existing 00-00-5E OUI owned by
   IANA. No other actions are required by the IANA.


11.  Security considerations

   The ISATAP address format does not support privacy extensions for
   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
   apply here as well.


12.  Implementation status

   The author has implemented the mechanisms described in this draft
   through modifications to the FreeBSD 3.2-RELEASE [FBSD] operating
   system with the INRIA [INRIA] IPv6 distribution. As of November 12,
   2001, a Linux implementation is now integrated in the USAGI Linux
   distribution [USAGI].

   Additionally, Windows XP RC1 will implement elements of the mechanism
   proposed in this paper.

Acknowledgements

   The original ideas presented in this draft were derived from SRI con-
   tractual work. The author recognizes that ideas similar to those in
   this document may have already been presented by others and wishes to
   acknowledge any other such authors. The author also wishes to ack-
   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



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   NGTRANS community which has helped guide the direction of the draft.
   The list of contributors is too long to enumerate, but the input from
   the community has been vital to the draft's evolution. Alain Durand
   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
   Thaler, Art Shelest, Richard Draves, and others at Microsoft Research
   for their ideas on automatic discovery of off-link IPv6 routers. Much
   of the text in section on deployment considerations derives directly
   from discussions with Dave, Art, Rich and others.

References

   [AGGR]     Hinden., R, O'Dell, M., and Deering, S., "An IPv6
              Aggregatable Global Unicast Address Format",
              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
              Autoconfiguration", RFC 2462, December 1998.

   [DISC]     Narten, T., Nordmark, E., and W. Simpson, "Neighbor
              Discovery for IP Version 6 (IPv6)", RFC 2461,
              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)
              Registration Authority",
              http://standards.ieee.org/regauth/oui/tutorials/EUI64.html,
              March 1997

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




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INTERNET-DRAFT   Intra-Site Automatic Tunnel Addressing 21 November 2001


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

   [IPV6]     Deering, S., and R. Hinden, "Internet Protocol, Version 6
              (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
              IPv6 Hosts and Routers", RFC 2893, August 2000.

   [SELECT]   Draves, R., Default Address Selection for IPv6, draft-
   ietf-
              ipngwg-default-addr-select-06.txt (work in progress)

   [FBSD]     http://www.freebsd.org

   [USAGI]    http://www.linux-ipv6.org

   [INRIA]    ftp://ftp.inria.fr/network/ipv6/

   [6BONE]    Rockell, R., and R. Fink, RFC 2772, February 2000.

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

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

      Fred L. Templin



Templin                            Expires 21 May 2001         [Page 14]

INTERNET-DRAFT   Intra-Site Automatic Tunnel Addressing 21 November 2001


      SRI International
      333 Ravenswood Ave.
      Menlo Park, CA 94025, USA

      Email: templin@erg.sri.com

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.  For more information consult the online list of claimed
   rights.







































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