Greg;
Our goal is to let IP run over (almost) all the link types
as efficiently as possible.
Right?
>> DAD?
> Duplicate Address Detection (from rfc2462).
I know. But, we are talking about address resolution, not DAD.
>> Address resolution of ND gives up after three NSes and
>> is not robust.
> As indicated in the State transition table in appendix C,
> The address unreachable message is sent in response to each of
> the queued packets and then the NC entry is deleted.
Yup.
Thus, ND gives up after three NSes and is not robust.
> Indeed, the address has been unreachable during the probe
> period, so this may be interpreted as correct behaviour.
It is correct to send a message that ND is performing poorly,
when ND is performing poorly.
However, it does not deny the fact that ND is poor.
> Newly arriving packets will cause a new NC entry to be
> created, and this may establish connectivity.
>
> This may have a significant cost in time and packet
> loss, though.
And, our goal is to let IP run over (almost) all the link types
as efficiently as possible.
It involves to make mechanisms of IP over some link type
actively make use of properties specific to the link type,
which means ND approach to ignore the diffeence of link
types was wrong and failed.
> We really can't rely upon deployed ipv6 hosts and
> routers being implemented with WLAN specific changes
> (unless these are good in every network).
We can and we must implement IP with lin specific mechanisms
and we can't and must not expect such mechanisms are good in
every network.
> If we can come up with some options (or generally useful
IP is generally useful. Forget to expect "generally useful"
for ND.
> but it's probably
> better to concentrate on the wireless hosts first.
ARP, for example, is better than ND, because it use
broadcast only for request and replies are unicast.
> It's possible that devices which know that they're using
> WLAN could adopt a better ND strategy. For example:
>
> * Send packets which are likely to be robustly transmitted
> (not multicast downstream to WLAN hosts).
You can't send packets, unless address resolution succeed.
> * attempt to set neighbour cache entries before a neighbour
> solicitation from the peer is sent.
> For WLAN the RS and the RA (if the RA is unicast) can be
> sent robustly (with retransmission) if the router is configured
> to send unicast RAs.
I'm afraid it's ARP and is not good enough.
> Unicast RAs are likely to increase the load
> in the case many devices configure simultaneously though.
It's not a problem of modern networks, which has broad enough
bandwidth for small number of hosts.
Masataka Ohta
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