On 05/18/2011 12:53 AM, Digest of postfix-users list wrote:
Date: Tue, 17 May 2011 17:37:22 +0200
From: Mark Martinec<mark.martinec+post...@ijs.si>
Subject: Re: Timed out while sending message body
> Tomasz K. Jarzynka:
> > Finally, I ran a tcpdump on our origin mail server, our firewall
> > and the destinantion mail server (thanks to the help of its
> > administrator) but the output is inconclusive to me. On our side,
> > It looks like transmission stalls after a couple hundred bytes +
> > subsequent retransmissions eventually leading to a timeout. On
> > the destination side, it looks like the connection is ended
> > immediately after the start of transmission.
>
> Google for
> 1 - IP path MTU discovery.
> 2 - TCP window scaling.
This doesn't look like a PMTU discovery problem, more like a NAT screwup.
A duplicate ACK packet #78 in mnisw-fw.dump seems to get translated
into a packet #81 in mnisw-mailhub.dump with a wrong sequence number
and with no NAT translation. This causes your mailer to RST the seemingly
new session, this RST is then seen by the remote side as an original
session reset.
Thanks, I didn't figure that out. I think I'll try bypassing the firewall
entirely to confirm the source of the problem.
--
Tomasz Krzysztof Jarzynka / tel. +48 22 597 07 45 / mob. +48 601 706 601
Network Information Systems Administrator / tomee(at)genesilico(d-o-t)pl
Laboratory of Bioinformatics and Prot. Engineering | iimcb.genesilico.pl
International Institute of Molecular and Cell Biology | www.iimcb.gov.pl
