Re: draft-ietf-multi6-multihoming-requirements-03

[Joe Abley <jabley@automagic.org>]

On Wed, Jul 03, 2002 at 12:22:29AM +0200, Iljitsch van Beijnum wrote:
> On Tue, 2 Jul 2002, Joe Abley wrote:
> 
> > > "Existing IPv4 multihoming practices can coexist with policy-based
> > > routing
> > > and forwarding mechanisms. An IPv6 multihoming architecture should
> > > retain this capability."
> 
> > As I said, I think that presupposes a solution.
> 
> I didn't have one in mind when I wrote it.

I was talking about the solution which involves "policy-based
routing and forwarding mechanisms". Seems to me that the requirement
in the document right now could be met without using those.

For example, suppose the pure aggregation/no hole-punching addressing
and route advertisement scheme is strictly adhered to, and the effect
of multi-homing is to number each interface with an address from each
transit provider. Further suppose that the TCP endpoint address
selection algorithm can be influenced by some hierarchical policy
signalling mechanism. In that case, inbound traffic towards a TCP
endpoint could be moved between transit providers without resorting
to CIDR abuse.

I'm not saying that such a scheme would feature in a multihoming
architecture v6, or that it is not without other substantial problems,
but it does sound to me like a solution to the specific requirement
in question which does not rely on advertising covering supernets
(or other disparate routes) to different transit providers in order
to achieve the desired goal.

More generally, you seem to be saying that the requirement as stated
reduces to something trivial, which of course should be supported by
any adequate multihoming architecture. If I have got that right, then
what's the harm in letting the requirement stand in the document?


Joe