Hi, On Dec 18, 2012, at 7:59 PM, Christopher J. Pilkington <cjp@0x1.net> wrote:

I'm looking for a simple tool to verify PMTUD is usable along a particular path. Ideally this tool would be cross-platform, or run on Linux or Windows.

I've done some testing of my own by hand, but hoping a tool would help the admin on the other side be able to test for themselves.

Scamper is a really cool tool, look at this example: job@Alice:~$ sudo scamper -c 'trace -P UDP-paris -M' -i 8.8.4.4 2001:67c:208c:10::1 traceroute from 2a02:d28:666::69 to 2001:67c:208c:10::1 1 2a02:d28:666::1 0.247 ms [mtu: 1500] 2 2a02:d28:5580:666::a 1.085 ms [mtu: 1500] 3 2a02:d28:5580:1::31 7.141 ms [mtu: 1500] 4 2a02:d28:5580:1::21 6.588 ms [mtu: 1500] 5 2a02:d28:5580::1:411 6.815 ms [mtu: 1500] 6 2001:7f8:1::a501:2414:2 7.612 ms [mtu: 1500] 7 2001:9e0:0:2::2 9.793 ms [mtu: 1500] 8 2001:9e0:0:3::2 8.277 ms [mtu: 1500] 9 2001:9e0:0:9::2 8.851 ms [mtu: 1500] 10 2001:9e0:411:1::10 9.015 ms [mtu: 1500] 11 2001:67c:208c:10::1 20.220 ms [mtu: 1464] traceroute from 78.152.42.69 to 8.8.4.4 1 78.152.42.65 0.230 ms [mtu: 1500] 2 78.152.42.1 0.253 ms [mtu: 1500] 3 78.152.44.89 6.693 ms [mtu: 1500] 4 78.152.34.14 6.906 ms [mtu: 1500] 5 78.152.44.95 6.705 ms [mtu: 1500] 6 195.69.144.247 7.207 ms [mtu: 1500] 7 209.85.248.116 7.183 ms [mtu: 1500] 8 209.85.255.60 7.416 ms [mtu: 1500] 9 216.239.49.28 12.922 ms [mtu: 1500] 10 * 11 8.8.4.4 10.481 ms [mtu: 1500] job@Alice:~$ Kind regards, Job