On Thursday, 17. July 2008 15:55:25 Ilpo Järvinen wrote: > It would quite interesting to know more details about the mail server and > why the duplicate ACKs are not generated or don't ever reach the sender > but I guess the details are out of reach? It will be quite difficult to get more details as it's the SMTP relay sever of Germany's biggest ISP. There's a comment about them in Patrick's blog from 2008-06-23 if you are curious ;-) We see the same issue with a MX server from "United Internet". Normally they are pretty accurate about standards (they run GMX), so I guess this must be a problem of a router in between. This is also supported by the fact that 935 of our boxes already updated to kernel 2.6.24.7, yet the problem occured only at three sites and I guess there are more people out there using that SMTP relay server. Could you somehow "probe" the servers to see if they normally send duplicated ACKs by faking/forcing a retransmission? Though I guess this would invole writing some TCP "test" code. > One option would be to disable reentry to FRTO when some progress was > made... Please try with the patch below... Thanks for the patch. It seemed to help a bit. Here are two more traces: http://www.intra2net.com/de/download/tcpdump/tcp_frto_with_patch.tar.bz2 The first connection somehow made it after 400 seconds, the second one stalled and timed out :-( Hope they dumps are useful to you. Chers, Thomas -- To unsubscribe from this list: send the line "unsubscribe netfilter-devel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
