Re: Draft of updated WG charter

[Jay Ford <jay-ford@uiowa.edu>]

On Sat, 10 Jan 2004, Iljitsch van Beijnum wrote:
> > Path selection is only part of the multi-homing problem, & perhaps the
> > easier one.  In my realm of experience, most end systems have only a
> > single path out, so there is no path selection required.
>
> > The nastier problem is source & destination address selection.  In the
> > case of multiple addresses per host, the host is forced to make the
> > selection but the implications have to be handled in the rest of the
> > network (anti-spoof filtering, routing policy...).
>
> I'm not sure what you mean by "path" if you say that a host only has
> one. I think for the purpose of discussing multiaddress multihoming, a
> good definition of a path would be a combination of source and
> destination addresses.

From the host perspective, I mean "next hop", which is usually a single
router to which all packets get sent.  I shudder at the notion of host
address selection dictating an end-to-end path.

> The good part is that as soon as we implement mechanisms that allow
> transport sessions to jump addresses, the address selection problem
> isn't really a huge deal anymore: if you find yourself using
> unfortunate addresses, you simply jump to something more suitable.

More shuddering...

> > I'm not claiming that end systems should be completely stupid & the
> > network should do everything.  We might just disagree on where the
> > functionality dividing line should be.  I think address selection & path
> > selection shouldn't be on the end system side of the line, so an
> > architecture which causes every end system in every multi-homed network
> > to do those jobs seems broken to me.
>
> So what about having special boxes that sit between the hosts and the
> routers and handle multihoming? Obviously anything that can be
> implemented in an external box can also be integrated into a host when
> desired, so unless the drawbacks of allowing this functionality to be
> implemented in an external box are huge, this shouldn't take anything
> away from the people who actually like their hosts to handle this
> autonomously.

That sounds dangerously close to NAT, which I think most people would like to
avoid & eradicate.

For me, almost the entire IPv6 thing boils down to the issue of hosts having
multiple addresses.  That decision precipitated the rest of this mess.

________________________________________________________________________
Jay Ford, Network Engineering Group, Information Technology Services
University of Iowa, Iowa City, IA 52242
email: jay-ford@uiowa.edu, phone: 319-335-5555, fax: 319-335-2951