On Sun, 04 Sep 2011 09:14:45 -0300, D G Teed wrote: > On Wed, Aug 31, 2011 at 1:09 PM, Camaleón <[email protected]> wrote: > >> I've been busy on these days trying to solve a problem with Postfix >> that drove me nuts. >> >> Sporadically (let's say one in hundred e-mails) my Postfix had problems >> for delivering messages with ~3 MiB of attachment to some e-mail hosts. >> DSN service returned the final notice of delivery to the user and logs >> displayed an error like "timed out while sending message body".
(...) >> Googling around I found some posts and articles¹ pointing to the MTU >> value (my bonded interface was set by default to 1500) and as I had >> nothing to lose, I changed this and lowered to 1400. (...) > You might want to try the postfix mailing list and see if they have any > ideas. > Be prepared for cold, hard, terse answers. They don't chat much - busy > I guess. :-) Should I couldn't solve the problem, sure, I would had to post in there. The fact is I like Postfix so much, I find it very flexible and easy to deal with but in specific case, I didn't think the app was the culprit but as Osamu has pointed out, a router or a filter (firewall) in between our hosts making noise. > Was the previous MTU of 1500, a value you had set, or the default when > queried? 1500 was the default MTU value for the bonded interfaces. I thinks is the system default for ethernet devices nowadays. > I'm wondering because of a recent experience I had tweaking MTU. I > wanted to try jumbo frames to improve samba throughput on large video > files. With MTU set to 9000 on Linux and Windows, throughput increased > about 8 times. But it caused problems with the web service on Linux, > which was running a domain under dyndns. I set the MTU on Linux back to > unspecified, but left the jumbo frame active on Windows side. The > performance was still very good in large samba file transfers. I might > remember this wrong, but it seemed it was worse performance when Linux > side specified 1500, so I left it as unspecified and it has worked well. > I still get high transfer speeds in samba with unspecified MTU on Linux > but jumbo of 9000 MTU on Windows side. That was exactly the kind of problems I would like to avoid :-) But as you said, lower values for MTU are not prone to errors or conflicts but higher ones (like jumbo frames). I hope performance is not badly penalized for having a low value, though... > BTW, 1492 is a common MTU seen in FAQs. You might get just as good with > that. MTU is now set at 1400. The host I was trying to contact seemed to be fine with that setting so I kept it so. Greetings, -- Camaleón -- To UNSUBSCRIBE, email to [email protected] with a subject of "unsubscribe". Trouble? Contact [email protected] Archive: http://lists.debian.org/[email protected]
