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/ )