Re: draft-baker-6man-multiprefix-default-route-00.txt is a newdraft

> > AFAIU, you are essentially proposing to perform source address  
> > based routing by the hosts and by the routers in a multiprefix  
> > site, is that correct?
>
> I don't like the term, because I first do a destination lookup and  
> only look up the source address in certain cases. Kind of like the  
> previous comment on source routing, which in IEEE 802.5, DSR, and RFC  
> 791 IP means that the source specifies all or part of the routing  
> path. I think the term mis-states the case.
>
> But yes, in certain cases where there is a multipath route, the point  
> is that if the datagram is handed to the wrong ISP and the ISP is  
> doing ingress filtering, the datagram will be dropped, and hence I  
> suggest that we direct it toward the right ISP.

But still, you appear to propose to fundamentally change the
forwarding process by inserting a relatively complex lookup
operation into per-packet forwarding, and I think such a change
needs quite a bit more in terms of justification.

Instead, my inclination would be to "solve" this problem in a
much simpler manner, simply by declaring it a configuration
error.  A site which receives prefixes from more than a single
provider is clearly multihomed, and needs to have its providers
make appropriate exceptions to a strict "I will only accept
packets with source addresses from within the prefix I delegate"
rule.  Either that, or the domain in question needs to ensure via
a combination of address selection and routing policy that one
avoids being subjected to (presumably unwanted) RPF failures.

Regards,

- Håvard

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