On 5/24/11 6:21 AM, sowmini.varad...@oracle.com wrote:
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).
For an off-link destination, if there is only one choice (one default router) there is no need to be impatient.
Thus the applicability of patience is a bit broader.
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?
If a host has multiple default routers, it is likely (but not required by RFC 4861) that the host sends some flows to the different default routers. In that case there is an NCE for each default router. Thus declaring one of them as unreachable and moving those flows to use a different default router doesn't cause additional multicasts.
Erik -------------------------------------------------------------------- IETF IPv6 working group mailing list ipv6@ietf.org Administrative Requests: https://www.ietf.org/mailman/listinfo/ipv6 --------------------------------------------------------------------
