FAQ Search Today's Posts Mark Forums Read
» Video Reviews

» Linux Archive

Linux-archive is a website aiming to archive linux email lists and to make them easily accessible for linux users/developers.


» Sponsor

» Partners

» Sponsor

Go Back   Linux Archive > CentOS > CentOS

 
 
LinkBack Thread Tools
 
Old 10-14-2008, 09:32 PM
mouss
 
Default Sendmail and pmtu discovery

Kai Schaetzl a écrit :
> Ralph Angenendt wrote on Tue, 14 Oct 2008 17:24:08 +0200:
>
>> If you don't know the smallest MTU on the path to the mail server, you
>> might not be able to send packets over that path, especially if DF is
>> set.
>
> But if it's not set? Shouldn't most devices have it not set?
>

It's not per device. It's a method to improve performances.
http://www.znep.com/~marcs/mtu/


_______________________________________________
CentOS mailing list
CentOS@centos.org
http://lists.centos.org/mailman/listinfo/centos
 
Old 10-15-2008, 01:50 AM
Chris Boyd
 
Default Sendmail and pmtu discovery

On Oct 14, 2008, at 1:59 PM, Sean Carolan wrote:


If you've ever dealt with with one of these paranoid Mordac-type
security managers you know exactly what I'm talking about. In our
case the path of least resistance was to disable pmtu discovery, and
tell the customer that we've done all we possibly can to alleviate the
issue on our end. Hopefully they come to their senses and allow ICMP
packets like every major ISP and mail provider on the Internet.


Yes, but then you have broken your equipment, and possibly lost the
ability to communicate with many more customers.


Yes, I've dealt with these people. If they turn off all ICMP, they
often drop fragments as well, making the problem even worse. You can
sometimes get them to listen by asking them if their Internet access
seems a little "weird" in that some sites work sometimes or downloads
are slow or they can't get some email :-)


They'll usually say yes and then you might be able to get them to
listen, and hopefully send them a bill.


--Chris
_______________________________________________
CentOS mailing list
CentOS@centos.org
http://lists.centos.org/mailman/listinfo/centos
 
Old 10-28-2008, 03:20 PM
"Sean Carolan"
 
Default Sendmail and pmtu discovery

> Yes, I've dealt with these people. If they turn off all ICMP, they often
> drop fragments as well, making the problem even worse. You can sometimes get
> them to listen by asking them if their Internet access seems a little
> "weird" in that some sites work sometimes or downloads are slow or they
> can't get some email :-)

What do you do when the receiving server is at Microsoft? (mx4.hotmail.com)

Oct 28 11:18:25 exmx2 sendmail[19190]: m9SGHXL4019186:
to=<some.user@hotmail.com>, delay=00:00:52, xdelay=00:00:52,
mailer=esmtp, pri=43523, relay=mx4.hotmail.com. [65.54.244.232],
dsn=4.0.0, stat=Deferred: Connection reset by mx4.hotmail.com.

I'm not surprised that Microsoft would make such a boneheaded decision
as to block all ICMP traffic to their hotmail servers, however would
this not cause a ton of customer email to simply be lost? Do they
just not care? I guess at this point my only choice may be to lower
my MTU size.
_______________________________________________
CentOS mailing list
CentOS@centos.org
http://lists.centos.org/mailman/listinfo/centos
 

Thread Tools




All times are GMT. The time now is 02:38 PM.

VBulletin, Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.
Content Relevant URLs by vBSEO ©2007, Crawlability, Inc.
Copyright ©2007 - 2008, www.linux-archive.org