Subject: WG Review: Site Multihoming in IPv6 (multi6)

From: The IESG <[email-masked]>
Date: Fri, 23 Feb 2001 13:32:51 -0500

A new IETF working group has been proposed in the Operations and Management
Area. The IESG has not made any determination as yet. 

The following Description was submitted, and is provided for
informational purposes only:

Description of Working Group:
 
A multihomed site is a site that has more than one connection to the
public internet with those connections through either the same or
different ISPs. Sites choose to multihome for several reasons,
especially to improve fault tolerence, perform load balancing, etc.

Multihoming today is done largely by having a site obtain a block of
address space and then advertising a route for that prefix through
each of its ISP connections. The address block may be from the
so-called provider independent space, or may be a sub-allocation from
one of its ISPs.  A site's ISPs in turn advertise the prefix to some
or all of their upstream connections and the route for the prefix may
propagate to all of the routers connected to the default-free zone
(DFZ). As the number of sites multihoming in this manner increase, the
number of routes propagated throughout the DFZ increases and overall
routing stability decreases because of the burden on convergence
time. This WG will explore alternative approaches with better scaling
properties. Specifically, the WG will prefer multi-homing solutions
that tend to minimise adverse impacts on the end-to-end routing system
and limit the number of prefixes that need to be advertised in the
Default-Free Zone (DFZ).

This WG will consider the problem of how to multihome sites in
IPv6. The multihoming approaches currently used in IPv4 can of course
be used in IPv6, but IPv6 represents an opportunity for more scalable
approaches. IPv6 differs from IPv4 in ways that may allow for
different approaches to multihoming that are not immediately
applicable to IPv4. For example, IPv6 has larger addresses, hosts
support multiple addresses per interface, and relatively few IPv6
address blocks have been given out (i.e., there are no issues with
legacy allocations as in IPv4).

The WG will take on the following initial tasks:

Produce a document defining what site multihoming is, the requirements
for a multihoming solution (from both the end site and ISP
perspective).  This document will also include a taxonomy of different
ways that multihoming might be achieved.

Produce a document describing how multihoming is done today, including
an explanation of both the advantages and limitations of the
approaches.

The WG will also consider specific proposals to multihoming in IPv6
(both existing and new) and select a small number of them to work on
as formal WG items. Development of specific solutions will require
approval of the IESG (e.g., a recharter).