Network Working Group                                         F. Templin
Internet-Draft                                                Consultant
Expires: July 31, 2005                                        T. Gleeson
                                                      Cisco Systems K.K.
                                                               M. Talwar
                                                               D. Thaler
                                                   Microsoft Corporation
                                                        January 27, 2005

        Intra-Site Automatic Tunnel Addressing Protocol (ISATAP)

Status of this Memo

   This document is an Internet-Draft and is subject to all provisions
   of Section 3 of RFC 3667.  By submitting this Internet-Draft, each
   author represents that any applicable patent or other IPR claims of
   which he or she is aware have been or will be disclosed, and any of
   which he or she become aware will be disclosed, in accordance with
   RFC 3668.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF), its areas, and its working groups.  Note that
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   Internet-Drafts are draft documents valid for a maximum of six months
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   The list of current Internet-Drafts can be accessed at

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   This Internet-Draft will expire on July 31, 2005.

Copyright Notice

   Copyright (C) The Internet Society (2005).


   The Intra-Site Automatic Tunnel Addressing Protocol (ISATAP) connects
   IPv6 hosts/routers over IPv4 networks.  ISATAP views the IPv4 network

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   as a link layer for IPv6 and views other nodes on the network as
   potential IPv6 hosts/routers.  ISATAP supports an automatic tunneling
   abstraction similar to the Non-Broadcast Multiple Access (NBMA)

Table of Contents

   1.   Introduction . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.   Requirements . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.   Terminology  . . . . . . . . . . . . . . . . . . . . . . . .   3
   4.   Domain of Applicability  . . . . . . . . . . . . . . . . . .   4
   5.   Node Requirements  . . . . . . . . . . . . . . . . . . . . .   4
   6.   Addressing Requirements  . . . . . . . . . . . . . . . . . .   4
   7.   Automatic Tunneling  . . . . . . . . . . . . . . . . . . . .   5
   8.   Neighbor Discovery for ISATAP Interfaces . . . . . . . . . .   7
   9.   Site Administration Considerations . . . . . . . . . . . . .   9
   10.  Summary of Impact on Routing . . . . . . . . . . . . . . . .   9
   11.  Security considerations  . . . . . . . . . . . . . . . . . .  10
   12.  IANA Considerations  . . . . . . . . . . . . . . . . . . . .  11
   13.  Acknowledgments  . . . . . . . . . . . . . . . . . . . . . .  11
   14.  References . . . . . . . . . . . . . . . . . . . . . . . . .  12
     14.1   Normative References . . . . . . . . . . . . . . . . . .  12
     14.2   Informative References . . . . . . . . . . . . . . . . .  12
        Authors' Addresses . . . . . . . . . . . . . . . . . . . . .  13
   A.   Modified EUI-64 Addresses in the IANA Ethernet Address
        Block  . . . . . . . . . . . . . . . . . . . . . . . . . . .  14
   B.   Changes since -22  . . . . . . . . . . . . . . . . . . . . .  14
        Intellectual Property and Copyright Statements . . . . . . .  16

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1.  Introduction

   This document specifies a simple mechanism called the Intra-Site
   Automatic Tunnel Addressing Protocol (ISATAP) that connects IPv6
   hosts/routers over IPv4 networks.  Dual-stack (IPv6/IPv4) nodes use
   ISATAP to automatically tunnel IPv6 packets in IPv4, i.e., ISATAP
   views the IPv4 network as a link layer for IPv6 and views other nodes
   on the network as potential IPv6 hosts/routers.

   ISATAP enables automatic tunneling whether global or private IPv4
   addresses are used, and presents a Non-Broadcast Multiple Access
   (NBMA) abstraction similar to [RFC2491][RFC2492][RFC2529][RFC3056].

   The main objectives of this document are to: 1) describe the domain
   of applicability, 2) specify addressing requirements, 3) specify
   automatic tunneling using ISATAP, 4) specify the operation of IPv6
   Neighbor Discovery over ISATAP interfaces, and 5) discuss Site
   Administration, Security and IANA considerations.

2.  Requirements

   SHOULD NOT, RECOMMENDED, MAY, and OPTIONAL, when they appear in this
   document, are to be interpreted as described in [RFC2119].

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

3.  Terminology

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

      a connected, self-contained, single administrative domain network
      surrounded by zero or more border-filtering routers and containing
      interior routers and links with their attached interfaces.

   ISATAP node:
      a node that implements the specifications in this document.

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   ISATAP interface:
      an ISATAP node's non-broadcast multi-access (NBMA) IPv6 interface
      used for automatic tunneling of IPv6 packets in IPv4.

   ISATAP interface identifier:
      an IPv6 interface identifier with an embedded IPv4 address
      constructed as specified in Section 6.1.

   ISATAP address:
      an IPv6 unicast address that matches an on-link prefix on an
      ISATAP interface of the node, and includes an ISATAP interface

      an IPv4 address-to-interface mapping, i.e., a node's IPv4 address
      and its associated interface.

   locator set:
      a set of locators associated with an ISATAP interface, where each
      locator in the set belongs to the same site.

4.  Domain of Applicability

   The domain of applicability for this technical specification is
   automatic tunneling of IPv6 packets in IPv4 for ISATAP nodes within
   sites that observe the Security Considerations found in this
   document, including host-to-router, router-to-host, and host-to-host
   automatic tunneling in certain enterprise networks and 3GPP/3GPP2
   wireless operator networks.  (Other scenarios with sufficient trust
   basis ensured by the mechanisms specified in this document also fall
   within this domain of applicability.)

   Extensions to the above domain of applicability (e.g., by combining
   the mechanisms in this document with other technical specifications)
   are out of scope.

5.  Node Requirements

   ISATAP nodes observe the common functionality requirements for IPv6
   nodes found in [NODEREQ] and the requirements for dual IP layer
   operation found in ([MECH], section 2).  They also implement the
   additional features specified in this document.

6.  Addressing Requirements

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6.1  ISATAP Interface Identifiers

   ISATAP interface identifiers are constructed in Modified EUI-64
   format ([RFC3513], section 2.5.1 and appendix A) by concatenating the
   24-bit IANA OUI (00-00-5E), the 8-bit hexadecimal value 0xFE, and a
   32-bit IPv4 address in network byte order as follows:

   |0              1|1              3|3                              6|
   |0              5|6              1|2                              3|

   When the IPv4 address is known to be globally unique, the "u" bit
   (universal/local) is set to 1; otherwise, the "u" bit is set to 0.
   "g" is the individual/group bit, and "m" are the bits of the IPv4

6.2  ISATAP Interface Address Configuration

   Each ISATAP interface configures a set of locators consisting of IPv4
   address-to-interface mappings from a single site, i.e., an ISATAP
   interface's locator set MUST NOT span multiple sites.

   When an IPv4 address is removed from an interface, the corresponding
   locator SHOULD be removed from its associated locator set(s).  When a
   new IPv4 address is assigned to an interface, the corresponding
   locator MAY be added to the appropriate locator set(s).

   ISATAP interfaces form ISATAP interface identifiers from IPv4
   addresses in their locator set and use them to create link-local
   ISATAP addresses ([RFC2462], section 5.3).

6.3  Multicast/Anycast

   It is not possible to assume the general availability of wide-area
   IPv4 multicast, so (unlike 6over4 [RFC2529]) ISATAP must assume only
   unicast capability in its underlying IPv4 carrier network.  Support
   for IPv6 multicast over ISATAP interfaces is not described in this

   Similarly, support for Reserved IPv6 Subnet Anycast Addresses is not
   described in this document.

7.  Automatic Tunneling

   ISATAP interfaces use the basic tunneling mechanisms specified in
   ([MECH], section 3).  The following additional specifications are

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   also used:

7.1  Encapsulation

   ISATAP addresses are mapped to a link-layer address by a static
   computation, i.e., the last four octets are treated as an IPv4

7.2  Handling IPv4 ICMP Errors

   ISATAP interfaces SHOULD process ARP failures and persistent ICMPv4
   errors as link-specific information indicating that a path to a
   neighbor may have failed ([RFC2461], section 7.3.3).

7.3  Decapsulation

   The specification in ([MECH], section 3.6) is used.  Additionally,
   when an ISATAP node receives an IPv4 protocol 41 datagram that does
   not belong to a configured tunnel interface, it determines whether
   the packet's IPv4 destination address and arrival interface match a
   locator configured in an ISATAP interface's locator set.

   If an ISATAP interface that configures a matching locator is found,
   the decapsulator MUST verify that the packet's IPv4 source address is
   correct for the encapsulated IPv6 source address.  The IPv4 source
   address is correct if:

   o  the IPv6 source address is an ISATAP address that embeds the IPv4
      source address in its interface identifier, or:

   o  the IPv4 source address is a member of the Potential Router List
      (see: section 8.1).

   Packets for which the IPv4 source address is incorrect for this
   ISATAP interface are checked to determine whether they belong to
   another tunnel interface.

7.4  Link-Local Addresses

   ISATAP interfaces use link local addresses constructed as specified
   in section 6 of this document.

7.5  Neighbor Discovery over Tunnels

   ISATAP interfaces use the specifications for neighbor discovery found
   in section 8 of this document.

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8.  Neighbor Discovery for ISATAP Interfaces

   ISATAP interfaces use the neighbor discovery mechanisms specified in
   [RFC2461] and also implement the following specifications:

8.1  Conceptual Model Of A Host

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

   Potential Router List
      A set of entries about potential routers; used to support router
      and prefix discovery.  Each entry ("PRL(i)") has an associated
      timer ("TIMER(i)"), and an IPv4 address ("V4ADDR(i)") that
      represents a router's advertising ISATAP interface.

8.2  Router and Prefix Discovery - Router Specification

   Advertising ISATAP interfaces send Solicited Router Advertisement
   messages as specified in ([RFC2461], section 6.2.6) except that the
   messages are sent directly to the soliciting node, i.e., they might
   not be received by other nodes on the link.

8.3  Router and Prefix Discovery - Host Specification

   The Host Specification in ([RFC2461], section 6.3) is used.  ISATAP
   interfaces add the following specifications:

8.3.1  Host Variables

   To the list of host variables ([RFC2461], section 6.3.2), ISATAP
   interfaces add:

      Time in seconds between successive refreshments of the PRL after
      initialization.  The designated value of all 1's (0xffffffff)
      represents infinity.

      Default: 3600 seconds

      Minimum time in seconds between successive solicitations of the
      same advertising ISATAP interface.  The designated value of all
      1's (0xffffffff) represents infinity.

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8.3.2  Potential Router List Initialization

   ISATAP nodes initialize an ISATAP interface's PRL with IPv4 addresses
   discovered via manual configuration, a DNS fully-qualified domain
   name (FQDN) [RFC1035], a DHCPv4 option, a DHCPv4 vendor-specific
   option, or an unspecified alternate method.  FQDNs are established
   via manual configuration or an unspecified alternate method.  FQDNs
   are resolved into IPv4 addresses through a static host file lookup,
   querying the DNS service, querying a site-specific name service, or
   an unspecified alternate method.

   After initializing an ISATAP interface's PRL, if the PRL is empty the
   node SHOULD disable the interface.  Otherwise, the node sets a timer
   for the interface to PrlRefreshInterval seconds and re-initializes
   the interface's PRL as specified above when the timer expires.  When
   an FQDN is used, and when it is resolved via a service that includes
   TTLs with the IPv4 addresses returned (e.g., DNS 'A' resource records
   [RFC1035]), the timer SHOULD be set to the minimum of
   PrlRefreshInterval and the minimum TTL returned.  (Zero-valued TTLs
   are interpreted to mean that the PRL is re-initialized before each
   Router Solicitation event - see: section 8.3.4).

8.3.3  Processing Received Router Advertisements

   To the list of checks for validating Router Advertisement messages
   ([RFC2461], section 6.1.1), ISATAP interfaces add:

   o  IP Source Address is a link-local ISATAP address that embeds
      V4ADDR(i) for some PRL(i).

   Valid Router Advertisements received on an ISATAP interface are
   processed as specified in ([RFC2461], section 6.3.4).

8.3.4  Sending Router Solicitations

   To the list of events after which Router Solicitation messages may be
   sent ([RFC2461], section 6.3.7), ISATAP interfaces add:

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

   Since unsolicited Router Advertisements may be incomplete and/or
   absent, ISATAP nodes MAY schedule periodic Router Solicitation events
   for certain PRL(i)'s by setting the corresponding TIMER(i).

   When periodic Router Solicitation events are scheduled, the node
   SHOULD set TIMER(i) such that the next event will refresh remaining
   lifetimes stored for PRL(i) before they expire, including the Router
   Lifetime, Valid Lifetimes received in Prefix Information Options, and

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   Route Lifetimes received in Route Information Options [DEFLT].
   TIMER(i) MUST be set to no less than MinRouterSolicitInterval seconds
   where MinRouterSolicitInterval is configurable for the node, or for a
   specific PRL(i), with a conservative default value (e.g., 2 minutes).

   When TIMER(i) expires, the node sends Router Solicitation messages as
   specified in ([RFC2461], section 6.3.7) except that the messages are
   sent directly to PRL(i), i.e., they might not be received by other
   routers.  While the node continues to require periodic Router
   Solicitation events for PRL(i), and while PRL(i) continues to act as
   a router, the node resets TIMER(i) after each expiration event as
   described above.

8.4  Neighbor Unreachability Detection

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

   After address resolution, hosts SHOULD perform an initial
   reachability confirmation by sending Neighbor Solicitation message(s)
   and receiving a Neighbor Advertisement message.  Routers MAY perform
   this initial reachability confirmation, but this might not scale in
   all environments.

9.  Site Administration Considerations

   Site administrators maintain a Potential Router List (PRL) of IPv4
   addresses representing advertising ISATAP interfaces of routers.

   The PRL is commonly maintained as an FQDN for the ISATAP service in
   the site's name service (see: section 8.3.2).  There are no mandatory
   rules for the selection of the FQDN, but site administrators are
   encouraged to use the convention "isatap.domainname" (e.g.,

   When the site's name service includes TTLs with the IPv4 addresses
   returned, site administrators SHOULD configure the TTLs with
   conservative values to minimize control traffic.

10.  Summary of Impact on Routing

   As stated in Section 4, this document focuses on connectivity to
   hosts.  Router-to-router protocols which rely on the use of multicast
   will not work over an ISATAP link, but this is not required for
   ISATAP's domain of applicability.  For router-to-host communication,
   the impact on Neighbor Discovery/Router Discovery is covered in
   Section 8.

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   Finally, there is no impact on existing routing protocols outside of
   the ISATAP link, as any arbitrary prefix can be used, as with most
   other link-layer protocols.

11.  Security considerations

   Implementors should be aware that, in addition to possible attacks
   against IPv6, security attacks against IPv4 must also be considered.
   Use of IP security at both IPv4 and IPv6 levels should nevertheless
   be avoided, for efficiency reasons.  For example, if IPv6 is running
   encrypted, encryption of IPv4 would be redundant except if traffic
   analysis is felt to be a threat.  If IPv6 is running authenticated,
   then authentication of IPv4 will add little.  Conversely, IPv4
   security will not protect IPv6 traffic once it leaves the ISATAP
   domain.  Therefore, implementing IPv6 security is required even if
   IPv4 security is available.

   There is a possible spoofing attack in which an attacker outside the
   IPv4 site spoofs an IPv6 source address which appears to be an
   on-link ISATAP address, and encapsulates it to an ISATAP node.  Since
   an ISATAP link spans an entire IPv4 site, restricting access to the
   link can be achieved by restricting access to the site, i.e., by
   having site border routers implement IPv4 ingress filtering and
   ip-protocol-41 filtering.

   Another possible spoofing attack involves spurious ip-protocol-41
   packets injected from within an ISATAP link by a node pretending to
   be a router.  The Potential Router List (PRL) provides a list of IPv4
   addresses representing advertising ISATAP interfaces of routers that
   hosts use in filtering decisions.  Site administrators should ensure
   that the PRL is kept up to date, and that the resolution mechanism
   (see: section 9) cannot be subverted.  ISATAP SHOULD NOT be used when
   the PRL is empty (see: section 8.3.2).

   ISATAP has unique characteristics that do not exist in other
   tunneling solutions such as 6to4 [RFC3056] and result in avoiding
   most security issues that exist in those protocols.  Unlike such
   protocols, ISATAP is only to be used within a site with border
   routers which filter ip-protocol-41 packets, as noted above.  This
   reduces the scope of spoofing attacks to other attackers inside the
   site.  Also unlike such protocols, ISATAP will not accept packets
   from arbitrary routers, only from routers in the Potential Router
   List it knows, as noted above.  This avoids spoofing attacks that
   would otherwise be possible by an attacker pretending to be a router,
   but relies on the security of the PRL resolution method used.
   Together, these characteristics mean that spoofing an IPv6 source
   address requires either spoofing the IPv4 address embedded in an
   ISATAP address, or spoofing an IPv4 address in the PRL.  This is

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   hence no worse than IPv4 without ISATAP in this respect.

   The threats associated with IPv6 Neighbor Discovery are described in

   The use of temporary addresses [RFC3041] and Cryptographically
   Generated Addresses [CGA] on ISATAP interfaces is outside the scope
   of this specification.

12.  IANA Considerations

   The IANA is requested to specify the format for Modified EUI-64
   address construction ([RFC3513], Appendix A) in the IANA Ethernet
   Address Block.  The text in Appendix B of this document is offered as
   an example specification.  The current version of the IANA registry
   for Ether Types can be accessed at:

13.  Acknowledgments

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

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

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

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

14.  References

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14.1  Normative References

   [MECH]     Gilligan, R. and E. Nordmark, "Basic Transition Mechanisms
              for IPv6 Hosts and Routers",
              Internet-Draft draft-ietf-v6ops-mech-v2-00, February 2003.

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

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

   [RFC2434]  Narten, T. and H. Alvestrand, "Guidelines for Writing an
              IANA Considerations Section in RFCs", BCP 26, RFC 2434,
              October 1998.

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

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

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

   [RFC3513]  Hinden, R. and S. Deering, "Internet Protocol Version 6
              (IPv6) Addressing Architecture", RFC 3513, April 2003.

14.2  Informative References

   [CGA]      Aura, T., "Cryptographically Generated Addresses (CGA)",
              Internet-Draft draft-ietf-send-cga, April 2004.

   [DEFLT]    Draves, R. and D. Thaler, "Default Router Preferences and
              More-Specific Routes",
              Internet-Draft draft-ietf-ipv6-router-selection-06.txt,
              October 2003.

   [NODEREQ]  Loughney, J., "IPv6 Node Requirements",
              Internet-Draft draft-ietf-ipv6-node-requirements, August

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

   [RFC2492]  Armitage, G., Schulter, P. and M. Jork, "IPv6 over ATM

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              Networks", RFC 2492, January 1999.

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

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

   [RFC3056]  Carpenter, B. and K. Moore, "Connection of IPv6 Domains
              via IPv4 Clouds", RFC 3056, February 2001.

   [RFC3756]  Nikander, P., Kempf, J. and E. Nordmark, "IPv6 Neighbor
              Discovery (ND) Trust Models and Threats", RFC 3756, May

Authors' Addresses

   Fred L. Templin


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


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

   Phone: +1 425 705 3131

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

   Phone: +1 425 703 8835

Appendix A.  Modified EUI-64 Addresses in the IANA Ethernet Address

   Modified EUI-64 addresses ([RFC3513], section 2.5.1 and Appendix A)
   in the IANA Ethernet Address Block are formed by concatenating the
   24-bit IANA OUI (00-00-5E) with a 40-bit extension identifier and
   inverting the "u" bit, i.e., the "u" bit is set to one (1) to
   indicate universal scope and it is set to zero (0) to indicate local

   Modified EUI-64 addresses have the following appearance in memory
   (bits transmitted right-to-left within octets, octets transmitted

   0                       23                                        63
   |        OUI            |            extension identifier         |
   000000ug00000000 01011110xxxxxxxx xxxxxxxxxxxxxxxx xxxxxxxxxxxxxxxx

   When the first two octets of the extension identifier encode the
   hexadecimal value 0xFFFE, the remainder of the extension identifier
   encodes a 24-bit vendor-supplied id as follows:

   0                       23               39                       63
   |        OUI            |     0xFFFE     |   vendor-supplied id   |
   000000ug00000000 0101111011111111 11111110xxxxxxxx xxxxxxxxxxxxxxxx

   When the first octet of the extension identifier encodes the
   hexadecimal value 0xFE, the remainder of the extension identifier
   encodes a 32-bit IPv4 address as follows:

   0                       23      31                                63
   |        OUI            |  0xFE |           IPv4 address          |
   000000ug00000000 0101111011111110 xxxxxxxxxxxxxxxx xxxxxxxxxxxxxxxx

Appendix B.  Changes since -22

   NOTE: This section to be removed before publication as an RFC.

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   o  added definition for the term "site"

   o  added new section on summary of impact on routing

   o  added 6to4 comparision paragraph in Security Considerations

   o  clarified security considerations statement on possible spoofing
      attacks from a node outside the site

   o  added "ISATAP SHOULD NOT be used when the PRL is empty" to section
      8.3.2 and security considerations

   o  mentioned Nokia internal project work under acknowledgements

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