[150288] in North American Network Operators' Group
Re: Common operational misconceptions
daemon@ATHENA.MIT.EDU (Steven Bellovin)
Mon Feb 20 20:41:29 2012
From: Steven Bellovin <smb@cs.columbia.edu>
In-Reply-To: <4F42E275.50608@necom830.hpcl.titech.ac.jp>
Date: Mon, 20 Feb 2012 20:40:33 -0500
To: Masataka Ohta <mohta@necom830.hpcl.titech.ac.jp>
Cc: "nanog@nanog.org" <nanog@nanog.org>
Errors-To: nanog-bounces+nanog.discuss=bloom-picayune.mit.edu@nanog.org
>
>
>> The timer for Linux is 5 minute by default but you can change it.
>
> Timer timeouts do not affect TCP MSS.
>
RFC 2923:
TCP should notice that the connection is timing out. After
several timeouts, TCP should attempt to send smaller packets,
perhaps turning off the DF flag for each packet. If this
succeeds, it should continue to turn off PMTUD for the connection
for some reasonable period of time, after which it should probe
again to try to determine if the path has changed.
It's Informational, not standards track, but the problem -- and the fix
-- have been known for a very long time.
--Steve Bellovin, https://www.cs.columbia.edu/~smb
