Re: Unreachability detection at tunnels servers WAS: RE: Comments onzeroconf draft

[Radhakrishnan Suryanarayanan <rkrishnan.s@samsung.com>]

> Yes, mech-v2 is saying that IPv4 ICMPs should be translated, but it also
> says, Section 3.8, that IPv6 NUD SHOULD be performed.

mech-v2 says IPv4 ICMP error messages other than "packet too big" MAY be
translated.
But "packet too big" translation should be done as it is used for
determining IPv6 PMTU when IPv4 acts as a link-layer for IPv6.

ICMPv4 Destination unreachable (particularly Host & network unreachable)
errors do help the last-hop IPv6 router (tunnel server ) in determining the
reachability of end-node's IPv4 address which is the tunnel's end-point. So
translation helps in such cases to speed up the unreachability detection.

If IPv6 NUD is also supported then we can either translate the ICMPv4 error
messages (faster) or cache out the NUD entry if address resolution fails.
The tunnel server must support "packet too big" translation anyway for IPv6
PMTU. so as well have a couple of other error messages translated as well
which can be helpful.

IMHO, ICMPv4 error message translation & IPv6 NUD both should be supported.

Regards
Radhakrishnan