[70215] in North American Network Operators' Group
Re: Yahoo Mail problems ? (queue issues in general)
daemon@ATHENA.MIT.EDU (Valdis.Kletnieks@vt.edu)
Wed May 5 13:27:35 2004
To: Mike Tancsa <mike@sentex.net>
Cc: nanog@nanog.org
In-Reply-To: Your message of "Wed, 05 May 2004 10:59:55 EDT."
<6.0.3.0.0.20040505104644.03284a30@64.7.153.2>
From: Valdis.Kletnieks@vt.edu
Date: Wed, 05 May 2004 13:26:55 -0400
Errors-To: owner-nanog-outgoing@merit.edu
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On Wed, 05 May 2004 10:59:55 EDT, Mike Tancsa <mike@sentex.net> said:
> Anyone else seeing Yahoo mail queue up today ? Some of their servers
> respond in about 10secs with the HELO banner, most others take more than
> 2m. Because of the recent increase in SPAM, I was looking to reduce the
> wait time for the initial HELO to 2m from 5m. However, the RFC calls for 5m
> on the HELO and another 5m for the MAIL command.
Do you have a handle on whether the delay is between the first SYN packet and
finally completing the 3-packet handshake, or is it between that and when the
220 banner actually arrives? Or are both phases an issue?
> Having a process block like that for up to 10m seems a bit excessive to
> deliver one email (and its probably a bounce to boot!). What are others
> doing? This problem seems to becoming more and more acute.
What I do is the *first* attemt to deliver the mail has a highly-non-compliant
5 second timeout (which is just enough for an initial SYN, 2 retransmits, and a
few hundred ms budget for RTT for a SYN+ACK) for the 3-packet handshake, and
then subsequent retries in the background are given a longer 5-min timeout. (I
gathered some stats for quite sime time before deploying that - out of several
million connection attempts, I found less than a dozen that took over 5 seconds
that did in fact complete in under 5 minutes). Once the 3-packet handshake
succeeds, they then get a 5 minute timeout to get the 220 banner out. Probably
not perfect, but it's close enough to keep the queues manageable...
Also, YMMV, so gather your own stats....
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