[128931] in North American Network Operators' Group
IPv6 PMTUD and OS-X
daemon@ATHENA.MIT.EDU (Franck Martin)
Fri Aug 20 17:27:14 2010
X-Barracuda-Envelope-From: franck@genius.com
Date: Sat, 21 Aug 2010 09:27:03 +1200 (FJT)
From: Franck Martin <franck@genius.com>
To: nanog@nanog.org
In-Reply-To: <8955944.577.1282339354317.JavaMail.franck@franck-martins-macbook-pro.local>
Errors-To: nanog-bounces+nanog.discuss=bloom-picayune.mit.edu@nanog.org
I'm trying to debug a pesky PMTUD issue with IPv6 on Mac OS-X 10.6.
It happens only from home, on wireless, when connected to a mac aiport that does an automatic tunnel (teredo) to IPv6 backbone. There are IPv6 web site that I cannot browse until I lower the MTU to 1400. My Linux desktop in similar config works fine...
With tracepath6, I see one end of the tunnel tells me MTU should be 1280, that's using linux tools.
On mac, tracepath6 does not seem to exist, and I don't know what tool to use... I have seen scamper, but no binary...
I have used wireshark (on mac) to detect the PTB packet, but don't see it either... I have not compared with my linux box...
I'm doing this testing on the side, slowly because it is fun to try to understand what's wrong here... and I wonder if others have had similar issues...
May be not fully on topic, but to bring it back to topic see this presentation:
http://www.ripe.net/ripe/meetings/ripe-60/presentations/Stasiewicz-Measurements_of_IPv6_Path_MTU_Discovery_Behaviour.pdf
Which states the PMTUD failure rate on IPv6 is about 1.9%
