One document matched: draft-jabley-v6-anycast-clarify-00.txt

Network Working Group                                           J. Abley
Internet-Draft                                                       ISC
Expires: September 11, 2005                               March 10, 2005


                       Anycast Addressing in IPv6
                 draft-jabley-v6-anycast-clarify-00.txt

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Copyright Notice

   Copyright (C) The Internet Society (2005).

Abstract

   The IPv6 Addressing Architecture includes some restrictions on the
   use of anycast addresses.  These restrictions were intended to
   protect the nascient IPv6 Internet from possible harmful consequences
   that might result from widespread use of anycast as a mechanism to
   distribute services.

   Since then, anycast has been widely used to distribute services using



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   IPv4, and production use of anycast in IPv6 also exists.  While
   anycast as a service distribution mechanism requires care, and is not
   suitable for use in all situations, many useful applications of
   anycast exist and the restrictions in the IPv6 Addressing
   Architecture are no longer appropriate.

   This document seeks to remove the restrictions on the use of anycast
   addresses from the IPv6 Addressing Architecture.

Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3

   2.  General Applicability of Anycast . . . . . . . . . . . . . . .  3

   3.  Analysis of IPv6 Anycast Restrictions  . . . . . . . . . . . .  3
     3.1   Anycast Source Addresses . . . . . . . . . . . . . . . . .  3
     3.2   Anycast Addresses on Hosts . . . . . . . . . . . . . . . .  3

   4.  Anycast Addresses  . . . . . . . . . . . . . . . . . . . . . .  4

   5.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . .  4

   6.  Normative References . . . . . . . . . . . . . . . . . . . . .  4

       Author's Address . . . . . . . . . . . . . . . . . . . . . . .  4

       Intellectual Property and Copyright Statements . . . . . . . .  5























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1.  Introduction

   The IPv6 Addressing Architecture [2] includes some restrictions on
   the use of anycast addresses.  These restrictions were intended to
   protect the nascient IPv6 Internet from possible harmful consequences
   that might result from widespread use of anycast as a mechanism to
   distribute services.

   This document seeks to remove the restrictions on the use of anycast
   addresses from the IPv6 Addressing Architecture.

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY" and "OPTIONAL" in this
   document are to be interpreted as described in [1].

2.  General Applicability of Anycast

   Anycast has seen production deployment in distributing services over
   both IPv4 and IPv6.  However, anycast is not a suitable mechanism for
   all protocols, nor all routing systems.  A discussion of the design
   considerations of an anycast service distribution strategy can be
   found in [3].

3.  Analysis of IPv6 Anycast Restrictions

3.1  Anycast Source Addresses

   For many conventional services to be distributed using anycast, it is
   necessary for reply datagrams sent from servers to clients to be
   sourced from the same address that was used as the destination in
   request datagrams sent from clients to servers.  When such a service
   is distributed using anycast, the destination address used in request
   datagrams is necessarily an anycast address; corresponding reply
   packets must therefore use the same anycast address as their source
   address.

   Being able to use an anycast address as the source address in an IPv6
   datagram is a prerequisite for the distribution of many services
   using anycast over IPv6.

3.2  Anycast Addresses on Hosts

   Services are provided by hosts.  For a service to be distributed
   using anycast, datagrams directed at an anycast address must be
   routed to hosts so that client requests can be processed.  For such
   datagrams to be received on hosts, it must be possible to assign
   anycast addresses to interfaces on those hosts.




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   Being able to apply an anycast address to an interface on a host is a
   prerequisite for the distribution of services using anycast over
   IPv6.

4.  Anycast Addresses

   Section 2.6 of RFC2373 [2] is updated as follows:

   o  An anycast address MAY be used as the source address of an IPv6
      packet.
   o  An anycast address MAY be assigned to an IPv6 host.

5.  IANA Considerations

   This document requests no action from IANA.

6.  Normative References

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

   [2]  Hinden, R. and S. Deering, "IP Version 6 Addressing
        Architecture", RFC 2373, July 1998.

   [3]  Abley, J. and K. Lindqvist, "Operation of Anycast Services",
        Internet-Draft draft-ietf-grow-anycast-00, February 2005.


Author's Address

   Joe Abley
   Internet Systems Consortium, Inc.
   950 Charter Street
   Redwood City, CA  94063
   USA

   Phone: +1 650 423 1317
   Email: jabley@isc.org
   URI:   http://www.isc.org/












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Acknowledgment

   Funding for the RFC Editor function is currently provided by the
   Internet Society.




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