[98319] in North American Network Operators' Group
Re: Seeking Comcast Contact: need to troubleshoot packet loss and/or
daemon@ATHENA.MIT.EDU (Jim Shankland)
Thu Aug 2 21:35:12 2007
Date: Thu, 02 Aug 2007 18:33:16 -0700
From: Jim Shankland <nanog@shankland.org>
Reply-To: nanog@shankland.org
To: Adrian Chadd <adrian@creative.net.au>
CC: nanog@merit.edu
In-Reply-To: <20070803010941.GA14587@skywalker.creative.net.au>
Errors-To: owner-nanog@merit.edu
Adrian Chadd wrote:
> On Thu, Aug 02, 2007, Jim Shankland wrote:
>
>> Linux has a nifty iptables option (clamp-mss-to-pmtu) to rewrite the
>> MSS in TCP SYN packets when forwarding a packet onto a link with
>> a lower MTU than the MSS in the packet. Works like a charm. If every
>> packet forwarding device on the Internet did this, PMTUD would not be
>> needed. As is, PMTUD is simply broken, due to widespread firewall
>> misconfiguration. As in so many other cases of Internet misbehavior,
>> you can avoid being part of the problem, but you can't be the solution.
>
> .. non-TCP traffic?
Hmm; I've never actually heard of anybody doing PMTUD on non-TCP
traffic, though it's possible. Does anybody actually do it?
Jim Shankland
