Subject: Re: draft-ietf-multi6-multihoming-requirements-06.txt

From: "J. Noel Chiappa" <[email-masked]>
Date: Mon, 16 Jun 2003 07:53:28 -0400

> From: S Woodside <[email-masked]>

    > Preferably there would be a way to automatically load balance

Load balancing is, fundamentally, a routing issue. You're selecting among one
of several alternate paths.

This is not a routing group, really - the basic consensus seems to be that we
can't efficiently support lots-and-lots of multi-homing in the routing, and
we're going to do it by having multiple addresses, and selecting among them.

So you're asking in the wrong place.

    > (or at least it would be easy to set up even for a naove user.)

You can do some load-balancing by ugly hacks like chosing addresses.

However, I'm afraid your stated goal (load-balancing for idiots) is in
fundamental conflict with one tool that people are currently using to do some
load-balancing, i.e. address selection - address selection is tricky and
doesn't work in all cases, and is therefore inappropriate for a "works for
idiots" mechanism.

Any general load-balancing scheme (i.e. one that would either work
semi-automagically in all cases, or at least one that had a fairly smart user
interface program that would take the user and lead them by the hand) would
have to be i) based on routing, and ii) based on a routing architecture
that's more powerful than the one we currently have deployed.

At which point, see Figure 1.

	Noel

---

From: Jay Ford <[email-masked]>
Date: Wed, 18 Jun 2003 10:20:07 -0500 (CDT)

> doesn't work in all cases, and is therefore inappropriate for a "works for

The problem I see is that (srcaddr,dstaddr) selection by a multihomed IPv6
host in the context of provider-based addressing can preempt the routing.
That means that the loading will be determined by clueless edge hosts, which
is about the worst place for such decisions to be made.  This feels like a
fundamental problem with the current direction of IPv6 deployment for which I
haven't yet seen a solution (except possibly a beefed up version of the NAROS
idea, which would effectively remove the address selection responsibility
from the host).

________________________________________________________________________
Jay Ford, Network Engineering Group, Information Technology Services
University of Iowa, Iowa City, IA 52242
email: [email-masked], phone: 319-335-5555, fax: 319-335-2951