On 2012-06-04 14:55, Templin, Fred L wrote: >>> I just want to know if we can expect IPv6 to devolve into 1280 standard >>> mtu and at what gigabit rates. >> >> 1280 is the minimum IPv6 MTU. If people allow pMTU to work, aka accept >> and process ICMPv6 Packet-Too-Big messages everything will just work. >> >> This whole thread is about people who cannot be bothered to know what >> they are filtering and that they might just randomly block PtB as they >> are doing with IPv4 today. Yes, in that case their network breaks if the >> packets are suddenly larger than a link somewhere else, that is the same >> as in IPv4 ;) > > But, it is not necessarily the person that filters the PTBs > that suffers the breakage. It is the original source that > may be many IP hops further down the line, who would have > no way of knowing that the filtering is even happening.
It is not too tricky to figure that out actually: $ tracepath6 www.nanog.org 1?: [LOCALHOST] 0.078ms pmtu 1500 1: 2620:0:6b0:a::1 0.540ms 1: 2620:0:6b0:a::1 1.124ms 2: ge-4-35.car2.Chicago2.Level3.net 56.557ms asymm 13 3: vl-52.edge4.Chicago2.Level3.net 57.501ms asymm 13 4: 2001:1890:1fff:310:192:205:37:149 61.910ms asymm 10 5: cgcil21crs.ipv6.att.net 92.067ms asymm 12 6: sffca21crs.ipv6.att.net 94.720ms asymm 12 7: cr81.sj2ca.ip.att.net 90.068ms asymm 12 8: sj2ca401me3.ipv6.att.net 90.605ms asymm 11 9: 2001:1890:c00:3a00::11fb:8591 89.888ms asymm 12 10: no reply 11: no reply 12: no reply and you'll at least have a good guess where it happens. Not something for non-techy users, but good enough hopefully for people working in the various NOCs. Now the tricky part is where to complain to get that fixed though ;) Greets, Jeroen (tracepath6 is available on your favourite Linux, eg in the iputils-tracepath package for Debian, for the various *BSD's one can use scamper from: http://www.wand.net.nz/scamper/ )
