on 2007-02-20 23:56 Narayanan, Vidya said the following: ... >> If I recall correctly, the issue of piggybacking arbitrary >> data on signalling messages was deferred from MIPv6 >> specifications, and hasn't been solved in later extensions or >> other protocols either. This is likely to bring up issues >> with different application PDU sizes, PMTUD, etc. >> >> Maybe filter signalling is sufficiently more restricted case >> of piggybacking arbitrary data that devising framing, PMTUD, >> etc. for it is simpler. I might agree with that if the >> filters were restricted to be (say) less than 500 bytes so >> that no fragmentation was never needed. >> > > Maybe I am missing something here, but, how does UDP help with > fragmentation? The alternative proposed at the transport layer seems to > be UDP-based.
No. Jari raised the question of whether a more general filter
definition language would be a good idea (my paraphrasing), and
you proposed that IPv6 extension headers should be used as
transport for it. Nobody else has proposed a specific transport
yet in this discussion.
Personally I'd support something which uses an existing generic
transport protocol, such as UDP or SCTP; with DTLS security for
instance; but I'm not too concerned with the exact pick of such
a protocol. What I'm very concerned about is the idea of moving
something which can both easily and reasonably be carried by an
existing generic transport protocol down into IPv6 extension
headers, when there's no evidence or arguments that doing so would
be particularly sensible or beneficial.
(Now, if somebody here had indeed proposed UDP as transport in
this discussion, I'd like to repeat something which Magnus
already hinted at, which is that it's still quite a difference
between what you can fit into a UDP package, and what you can add
in an IP header to a package which already carries a payload,
before fragmentation of that package occurs.)
>> While solving the more general problem might be useful, it's
>> not clear to me yet whether the requirements in this mobility
>> space are strong enough to preclude using a more generic
>> transport protocol.
>>
>
> In a mobile environment, the mobile node is in the best position to
> determine the mapping of filter rules to addresses based on currently
> available interfaces and connection conditions. This could be fairly
> dynamic and I can see a need to exchange this upon handoff to
> communicating devices (such as the HA or VPN GW or even a CN).
You keep ignoring the information that an analysis of the origins
of filter rule changes show them to be uncorrelated with handover
events.
Henrik
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