RFC 3178 (rfc3178) - Page 1 of 12

IPv6 Multihoming Support at Site Exit Routers

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Network Working Group                                          J. Hagino
Request for Comments: 3178                      Research Laboratory, IIJ
Category: Informational                                        H. Snyder
                                                            Vail Systems
                                                            October 2001


             IPv6 Multihoming Support at Site Exit Routers

Status of this Memo

   This memo provides information for the Internet community.  It does
   not specify an Internet standard of any kind.  Distribution of this
   memo is unlimited.

Copyright Notice

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

Abstract

   The document describes a mechanism for basic IPv6 multihoming
   support, and its operational requirements.  Unlike currently-
   practiced IPv4 multihoming, the technique does not impact the
   worldwide routing table size, nor IGP (Interior Gateway Protocol)
   routing table size in upstream ISPs.  The mechanism can be combined
   with more sophisticated (or complex) multihoming support mechanisms,
   and can be used as a foundation for other mechanisms.  The document
   is largely based on RFC 2260 by Tony Bates.

1.  Problem

   Routing table size has been a major issue for both IPv4 and IPv6.  As
   IPv6 addresses are 4 times larger in bit width than IPv4, the routing
   table size issue would have more serious negative effects on router
   memory usage, as well as routing table lookup performance.  To cope
   with this problem, the IPv6 addressing architecture [Hinden, 1998] is
   designed to take advantage of aggregated routing announcements to
   reduce the number of routes in default-free zone.  Also, 6bone
   operation guideline [Rockell, 2000] (which is the currently-practiced
   guideline for IPv6 network operation) suggests that ASes not announce
   non-aggregatable announcements to the default-free zone, if there is
   no special agreement with the peer.

   In IPv4, a multihomed site uses either of the following techniques to
   achieve better reachability:





Hagino & Snyder              Informational
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