In your letter dated Tue, 3 Jan 2012 07:32:17 -0500 you wrote: >Of course an adaptation layer has various costs >beyond a single bit, but please also consider the >case where there are no unused bits at hand.
Well, Van Jacobson made his header compression work with SLIP. And everybody was happy. >The choice of minimum IPv6 Link MTU is necessarily >somewhat arbitrary. Different numbers are optimal >for different deployments. It is merely sad that >the IETF chose such a large number. > >The other approach I've heard about being taken >for working over small MTU links is simply to >perform (one-way) IPv6->IPv4 protocol translation, >since IPv4 works natively on links that small. >It seems sad that the IETF decision is pushing >people towards a protocol translation approach. What I see in IPv4 PMTU and also IPv6 PMTU is: - it just doesn't work reliably. - for IPv4 MSS clamping is widespread to make TCP work. and UDP just gets fragmented. - For IPv6, given that the host has to do the fragmentation, a big minimum MTU is required. Otherwise, too much stuff will end up being fragmented at 576. My guess is, that anybody who is running a links at less than 1280 is just going to get a lot of trouble. That applies both to the links you mentioned and any IPv6-to-IPv4 translators. Most IPv4 links are bigger than 1280. So, those translators will seem to work in most cases. IPv4 links smaller than 1280 will just see failures that are quite hard to debug. -------------------------------------------------------------------- IETF IPv6 working group mailing list [email protected] Administrative Requests: https://www.ietf.org/mailman/listinfo/ipv6 --------------------------------------------------------------------
