> -----Original Message----- > From: ipv6-boun...@ietf.org [mailto:ipv6-boun...@ietf.org] On Behalf Of > Philip Homburg > Sent: Saturday, April 16, 2011 3:44 AM > To: David Woodhouse > Cc: ipv6@ietf.org > Subject: Re: PMTU blackhole detection > > In your letter dated Sat, 16 Apr 2011 11:28:53 +0100 you wrote: > >On Sat, 2011-04-16 at 11:17 +0200, Philip Homburg wrote: > >> > >> PMTU blackhole detection seemed so obvious to me, that I never > bothered to > >> find out if there was an RFC specifying that it should be done. > > > >Conversely... > > > >It's always been *so* obvious to me that firewalling ICMP is broken, > >that I never bothered to find out of there was an RFC specifying that > it > >shouldn't be done. > > > >Perhaps *that* is what should be discussed, instead? > > I think that's fine. I can understand the argument that breaking things > causes > bugs to be resolved. > > 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). 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 --------------------------------------------------------------------
