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....