Topic: sending large messages breaks internet surfing

[Laurent DINCLAUX]

When i send large messages (from 1Mo) using e-smith smtp server all work stations of the network behind the server can not surf over internet anymore.

We have an ADSL connection (64kbits/s up and 256 kbits/s down).

Looking at TCP/UDP port trafic on pppo using iptraf when sme is sending the email, I can see that only TCP/25 has activity. Data rates are 50kbits/s in and 1 to 5 kbits/s out.

Any Idea of what is happening .?
Any  tip to continue normal surfing while sending large messages?

Thanks in advance

[Nathan Fowler]

You could adjust the QOS/TOS flags for SMTP traffic, it appears you're consuming all your available bandwidth sending messages.

What version of E-Smith?

[Laurent DINCLAUX]

SME 5.6

I have qos installed but don't know how to configure it...

[benja]

Hi Nathan,

I've got the same probleme with a SME 5.5U6 box. When a user send large email, all upload bandwith is taken by the smtp server an no other Internet services is usable.

Is it possible to limit upload SMTP traffic ? Thanks.

benja

[Nathan Fowler]

I just stumbled across this thread, this looks like something you guys would want to implement and should accomplish the bandwidth limitation for SMTP (TCP 25):

http://forums.contribs.org/index.php?topic=17814.msg69672#msg69672

[KeVin M]

Hi

I suspect the issue isn't QOS but fixing something the email system. I see the problem - and have since SME5.0 on several different gateways - in large mails or if sending say 100em's each of 250KB plus (ie, from an Outlook maillist). Say goodbye to the link until a reboot. The gateway doesn't use the available bandwidth, it just slows the gatway to a crawl, no remote access (since it timesout) and *VERY* frustrated users. We find if an email exceeds 15MB then we will need to interveen within a day or so (adsl) and the message won't have sent. On a modem gateway the size is about 5MB.  Also if a large (say 15MB) email is received expect to see an error in the mail file with a memory allocation error, followed immediately by a delivery OK line showing the message took 1 second. I have tried reducing the qmail queue to 3 and that helps for the mail list mailouts (this is a 1.7Ghz, 80GB hdd, 256Mb Ram, adsl etc etc machine). About the only thing I have yet to try is different network cards (try other than 8139).

I have now moved the mailout requirement to a dos based command line mailout program using a different mail server and that works fine. The big emails we have fixed by installing the modindex addon and allowing remote access to the files.  

Funnily enough sendmail on my main servers has no problems with either situation. Guess who isn't going to put qmail on my main servers.

Kevin

[Laurent DINCLAUX]

>The gateway doesn't use the available bandwidth, it just slows the
>Qgatway to a crawl, no remote access (since it timesout) and *VERY*
>frustrated users.

That is what I was thinking about

> I have now moved the mailout requirement to a dos based command
> line mailout program using a different mail server and that works fine. > The big emails we have fixed by installing the modindex addon and
> allowing remote access to the files.

Well, I rather fix the problem instead of finding any DOS or HTTP downloads work around...

I think that sould be repported to bugs@e-smith.org...
What do you think?

[benja]

Hi all,

Strange bug ... Anyway, we need to accommodate while there's no patch to solve this issue. I look at the thread given by Nathan.

I create a file /etc/sysconfig/cbq/cbq-0025.upload
DEVICE=ppp0,128Kbit,12Kbit
RATE=15Kbit
WEIGHT=2Kbit
PRIO=5
RULE=,:25

The goal is to limit the upload smtp stream (,:25) to 15kbit/s on my very slow adsl link (ppp0). I activate cbq with the command # /sbin/cbq start No effect except that the cpu utilization increase ... Any idea of what is missing ???

Thanks,
benja

[Gordon Rowell]

Laurent DINCLAUX wrote:
>  [...]
> Well, I rather fix the problem instead of finding any DOS or
> HTTP downloads work around...
>
> I think that sould be repported to bugs@e-smith.org...
> What do you think?

The issue here is that there is no bandwidth prioritization. The mail
server (qmail) will use the link as heavily as possible, which may
swamp incoming packets - remember ADSL is highly asymmetric. Any efficient TCP client can do similar things to the external link.

The fix is bandwidth prioritization (or a bigger link). Have a look at  the WonderShaper:
   http://www.lartc.org/wondershaper/

Naturally, I'm sure lots of people would be interested if you properly
integrate this, taking into account the various external lines sizes supported by the server.

Gordon

[Laurent DINCLAUX]

Wondershaper was last released on 16th of April 2002...

Why CBQ can't do the job ??

[Cyrus Bharda]

Gordon,

Will wondershaper work on versions less than 5.6 though? I thought that the 5.5 and less kernals did not support wondershaper, am I wrong?

Thanks,

Cyrus Bharda

[Guck Puppy]

You're not wrong. From http://www.lartc.org/wondershaper/ :

"Works on Linux 2.4 & higher."

G