Re: Rewriting/ingress filtering/NAT/proxy, was: Re: Shim6 Agenda for IETF 71

[Sébastien Barré <sebastien.barre@uclouvain.be>]

Hi,

Iljitsch van Beijnum schreef:
> When packets return, routers don't rewrite the destination address. 
> Then, two things can happen: the packets end up at the host itself, 
> which recognizes the rewriting and from then on, sources packets with 
> the source address that was written in the first packet by the router. 
> Or hosts on the subnet are legacy and won't recognize the rewriting, 
> so a middlebox rewrites the destination address to the unique site 
> local prefix. 
This means that it is a requirement to have one of these three options 
(for packet return) :
- All hosts are legacy (and the middlebox always rewrites)
- All hosts recognize the rewriting (and the middlebox never rewrites)
- some hosts are legacy, other not, but the middlebox must be aware of 
the state of each host, so that it can selectively rewrite.

Is it right ?
> The host or middlebox can now start shim6 so that if there is a path 
> failure, the session/context can move to a different address.
Isn't there a possibility that a Shim6 context is established by both 
the middlebox and the host ? Or maybe this can be avoided by 
synchronizing the heuristics for Shim6 negotiation between the host and 
the middlebox  ?

regards,

Sébastien.