RE: The state of IPv6 multihoming development

["Tony Hain" <alh-ietf@tndh.net>]

Tony Li wrote:
> ...
> Ok, if apps (or the underlying transport) can use more than 
> one address, 
> then that implies that the host has to make a decision about 
> WHICH address to use, which is what Craig was objecting to in 
> the first place.  If the host has to decide, then it's making 
> a routing decision and it certainly shouldn't have enough 
> information to make that decision.

I know Craig said the host is making a routing decision, but it isn't.
Even if it tried it could be overruled by the routers for the outbound
packets. The only thing the host can decide that might even come close
to a routing decision is the address that the remote node will use to
talk back toward it. This is not a routing decision, but for those who
are into fine-grained TE, it might be considered a policy decision. 

Even if the origin node chooses an address that is overwritten by a
border router, there is absolutely nothing the origin AS can do to
enforce/influence the routing policy of the foreign network manager. As
the packet gets closer, there might be an opportunity to create a
localized gravity well, but only if there is no filtering going on
between the providers. Since the origin network can't enforce reverse
path routing decisions, the idea that the origin host is making any kind
of routing decision is completely bogus. 

Tony