RE: The state of IPv6 multihoming development

["J. Noel Chiappa" <jnc@ginger.lcs.mit.edu>]

    > From: Iljitsch van Beijnum <iljitsch@muada.com>

    > If we look at a huge enterprise as one example of someone who needs
    > multihoming, and at a single host with two interfaces or one interface
    > with two addresses as another .. they could both use a multi address
    > solution.

This is an excellent point, part of one I was about to make myself, actually,
as a result of my previous message mentioning the difference between "site
multi-homing" and "host multi-homing".

If you have a host which is multi-homed to widely spaced points in the
topology, there's unlikely to be a routing-based solution, i.e. one where that
host has only one address.


    > For the host, this could be something like Marcelo Bagnulo's extension
    > header, modified mobility, Peter Tattam's modified TCP or my own
    > "BALTS" idea. These all boil down to a host having several addresses
    > and being able to receive packets on a secondary address and trick the
    > transport layer into thinking it's still using the primary address.

Two points. First, Craig Huegen seems to think that any solution involving
multiple addresses is infeasible for a large organization. What's your reply
to him?

Second, I seem to recall some people objecting to multiple addresses because
it's too much code/complexity. It would seem to me that once you have
multiple addresses, the details on exactly how they are used are somewhat in
the noise; whether one tricks the transport layer, or gets it to understand
the possibility of multiple addresses, there's a certain amount of code
involved.

About the only way I could see it making a difference is if you can figure out
some way to do all on the multi-homed end. Some multiple-address schemes
involve both ends, which is obviously more perturbing. The downside, of
course, is that then there are probably things you can't do it you only
involve the multi-homed end. (Too tired to figure them all out right at the
moment - although I suppose you could use the "aliasing/tunneling devices"
at the non-multi-homed end to get around this.)

Of couse, then it starts to get ugly pretty quickly... lots of different hacks
and kludges.

	Noel