Dan,
>> On the other hand, the difference between 1500 and 1280 is so small, I >> wonder if breaking things just because you want to send packets >> at 1500 bytes makes a lot of sense. >> >> One other thing, if this makes the IPv6 experience worse than industry >> standard for IPv4, then maybe it is also not a good idea. > > The IPv6 headers are 20 bytes bigger than IPv4 headers, so a fairer > comparison is 1500 against 1260 (1260=1280-20). That is, with a 1500 > byte MTU with IPv4, the effective data payload is 1480 bytes (assuming > no IP options, which is a reasonable assumption with IPv4); with a > 1280 byte MTU with IPv6, the effective data payload is 1240 bytes > (assuming no IPv6 extensions). That's a 16.2% reduction in data > payload size from IPv4 to IPv6, with a commensurate increase in > number of packets to send the same data (assuming MTU-sized packets). I am a little confused by the comparisons being made in this thread. There is no guarantee that an 1500 IPv4 packet won't be fragmented, so a path that drops ICMPv4 packet too big messages will cause PMTU to fail. The 1280 number is the size of an MTU that IPv6 traffic can go on with out a need to be fragmented (that is, no PMTU issue). If a path can deliver 1500 byte IPv4 packets, it can also deliver 1500 byte IPv6 packets. The resulting payloads will be 20 byte less for IPv6, but that less than a 2% difference in payload size. I doubt middle boxes are going to let ICMPv4 packet too big messages through, and drop ICMPv6 packet too big messages. Am I missing something here? Bob > > This isn't quite "packets per second will increase by 16.2%", though, > as of course not all packets are 'full'. But there will be a pps > increase. > > -d > > > -------------------------------------------------------------------- > IETF IPv6 working group mailing list > ipv6@ietf.org > Administrative Requests: https://www.ietf.org/mailman/listinfo/ipv6 > -------------------------------------------------------------------- -------------------------------------------------------------------- IETF IPv6 working group mailing list ipv6@ietf.org Administrative Requests: https://www.ietf.org/mailman/listinfo/ipv6 --------------------------------------------------------------------
