Re: Source address selection insufficient?

[Erik Nordmark <Erik.Nordmark@sun.com>]

> > Once you modify the hosts at both ends why not also provide connection
> > rehoming?
> 
> Sure. But how does this relate to the problem at hand currently?

I'm trying to understand whether we need ingress filtering avoidance
(such as the general case of source-based routing) even once we
have a connection rehoming solution.

One reason we might need that is when only one end of the communication
implements multi6.

> > (There seems to be a large class of connection rehoming mechanisms
> > that can live with source locator rewriting instead of ingress 
> > filtering,
> > but that's the subject of a different email.)
> 
> Unfortunately we still have to deal with the packets that can't be 
> rewritten and I'm not sure if expecting all routers to be upgraded to 
> support this is reasonable.

I guess the question is about timing and transition.
It might be reasonable to expect that over time all routers will be
upgraded, but we still need some approach to handle the interim.

> > I agree that source based routing and relaxed filtering both work.
> > What is tricky is the middle between the small and the large; too small
> > a site to be able to convince the ISPs to relax ingress filtering
> > and too large a site for source based routing to be trivial.
> 
> For mid-sized sites the "use a default only" policy wouldn't be ideal, 
> but it should at least make sure there is always a working path. For 
> small sites the default-only policy has the disadvantage that only one 
> external link will be used for outgoing traffic, but in a site that has 
> several routers and subnets, different routers/subnets could use 
> different external connections so rudimentary load balancing would 
> still happen.

But I suspect the mid-size sites would like to benefit from some level
of load balancing across their ISPs.

  Erik