RE: Preserving established communications (was RE: about draft-nordmark-multi6-noid-00)

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

> IMHO You would want to use the source address based routing when you don't
> want to use source address rewriting.
> There are some situations where you don't want the rewrite to take place and
> you want source address based routing. I can think of the following:
> - The external host don't support M6
> - The M6 context has not been established yet
> - An ULP hint made the M6 layer to select a different path, so you want to
> let the host select the ISP and not the routing system

I understand why the first bullet doesn't want source rewriting, but from
that it doesn't follow that source address based routing is needed.

The second case can be made to handle rewriting by carrying the
identifiers explicitly in those packets. This has the cost of
additional overhead during the M6 context establishment, but might have
benefits in terms of more quickly being able to detect failures during
that establishment; need to understand the details in that tradeoff.

> So a possible approach would be that if the rewrite ok bit is set, then you
> perform destination address routing and if the rewrite ok bit is not set you
> do source address based routing.
> Does this makes sense?

I don't understand what pieces of the total routing system
needs to be changed to support source address based routing, so I'm not
sure this makes any sense.

  Erik