Re: [homenet] Redirect and source-specific routing

[Ole Troan <[e-mail]>]

Juliusz,

> I'm wondering if there isn't some interaction between Redirect messages and source-specific routing that we're overlooking.  RFC 4861 Section 8.3 says the following:
> 
>   Redirect messages apply to all flows that are being sent to a given
>   destination.  That is, upon receipt of a Redirect for a Destination
>   Address, all Destination Cache entries to that address should be
>   updated to use the specified next-hop, regardless of the contents of
>   the Flow Label field that appears in the Redirected Header option.
> 
> It does not speak of the source address, so I assume that this applies to all sources.  Consider the following topology:
> 
>   ---- A ---+--- B ----
>             |
>             H
> 
> If A and B advertise non-overlapping source-specific default routes and H is multiplexing its traffic over source addresses in both source prefixes (say, it's using MP-TCP), its Destination Cache entry will flap between A and B.
> 
> If I'm right, that argues in favour of an update to RFC 4861.

you are right. these issues are currently being discussed in 6man.
see http://tools.ietf.org/html/draft-sarikaya-6man-sadr-overview-07

we haven’t reached a conclusion if a source aware redirect is needed or not (if that’s what you had in mind). by the way, there is also ICMP unreachable code 5 (Source address failed ingress/egress policy), which I would think the router should send, rather than the redirect in this case.

cheers,
Ole