Re: Neighbor Unreachability Detection is too impatient

[[e-mail]]

On (05/23/11 11:46), Erik Nordmark wrote:
> 
> 
> This draft proposes to change the requirement that NUD can not retransmit
> more than three times, so that NUD can be more robust against temporary
> network outages.
> 
> Comments?

I think the intention is to use impatient-NUD only when the unicast NS
has been triggered by a packet whose IP destination is offlink, i.e.,
the IP destination is different from the target of the NS, so
impatient-NUD should only be applied for router NCE's (and only when
the triggering packet has a different IP destination than the NCE target). 

But if the motivation is to avoid sending mcast NS where possible, it might
not be achieved in a few other cases that we can still catch. 
E.g., even for offlink IP destinations, the switch to an alternative
default router might also result in triggering mcast NS if the new
router itself has not been resolved yet.  If the objective is to avoid
sending multicast NS, impatient-NUD would only be useful in reducing
mcast traffic if the alternative NCE is in REACHABLE/STALE/PROBE/DELAY
state. Would it make sense to REQUIRE impatient-NUD only under that
specific circumstance?

--Sowmini