Re: soft state (was Re: shim6 and bit errors in data packet headers

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

Iljitsch van Beijnum wrote:

> I would think that if one side triggers reachability testing, the  other 
> side would also do it. The probes in one direction can also  function as 
> replies in the other direction, cutting down on the  number of packets 
> exchanged.

I'm not sure we'd end up with both ends triggering reachability testing 
at about the same time, because that would seem to assume some form of 
periodic reachability testing even when there is no ULP traffic. Such 
background chatter seems undesirable.

Thus I think we'd want a packet driven trigger of reachability testing 
(much like NUD). When A sends a ULP packet to B, it checks whether it 
has current reachability information for B, and if not it triggers 
reachability testing.

With such an approach, only in the case that B receives the ULP packet 
and this makes it send a ULP packet back (e.g., a TCP ACK), might B 
trigger reachability testing.
But when B doesn't receive the packet it would not trigger reachability 
testing at the same time as A does.

   Erik