MBOX-Line: From imap at tlinx.org  Mon Aug  8 12:11:03 2005
To: imap-protocol@u.washington.edu
From: Linda Walsh <imap@tlinx.org>
Date: Fri Jun  8 12:34:36 2018
Subject: [Imap-protocol] Protocol Q: IMAP(s) svr (want tcp)-> IMAP client
In-Reply-To: <Pine.OSX.4.63.0508072357050.477@pangtzu.panda.com>
References: <42F6B7FD.2000408@tlinx.org> <8764uhgp3l.fsf@windlord.stanford.edu>
	<Pine.OSX.4.63.0508072357050.477@pangtzu.panda.com>
Message-ID: <42F7AE47.7080403@tlinx.org>

I'll check the session timeout -- I should have thought of that as my
"client" starts fetchmail in "poll" mode, and I believe that involves
not closing the connection.

It's actually a regular HW firewall box, not NAT, but this is likely
the problem as the fw-box has "default TCP session timeoutssame problem
likely exists as TCP sessions are set with 'default' timeouts of 30 minutes.

Thank you for pointing out the obvious likely problem. (*sigh*)

Linda

Mark Crispin wrote:

> On Sun, 7 Aug 2005, Russ Allbery wrote:
>
>> Linda Walsh <imap@tlinx.org> writes:
>>
>>> I notice (have for a long time) entries in my firewall' "denied" 
>>> traffic
>>> log that my ISP's imap server is attempting to initiate an inbound TCP
>>> connection from server port 993 to a high numbered (>50000) client 
>>> port.
>>
>> This is generally caused by confused firewalls that terminate a 
>> connection
>> too quickly and then deny the final TCP ack from the server.  Check 
>> to see
>> if these denied packets happen immediately after the end of a legitimate
>> connection.
>
>
> Note as well that a NAT box that times out a session too quickly can 
> do this.  An IMAP session in IDLE can stay open for up to 30 minutes 
> without any traffic, and the server can break the inactivity.
>
> Most NAT boxes are stupid and assume that only clients break inactivity.
>
> -- Mark --
>
> http://staff.washington.edu/mrc
> Science does not emerge from voting, party politics, or public debate.
> Si vis pacem, para bellum.


