Re: Slow Response for dial-up users

From: Ralf Hildebrandt (no email)
Date: Fri Mar 01 2002 - 09:49:34 EST


On Fri, Mar 01, 2002 at 04:36:40PM +0200, Warren Flemmer wrote:

> You seem a little sceptical so, heres a bit of the pop log

> Mar 1 15:50:44 unicorn pop3d[25633]: login:
> nas1-142.netlab.co.za[196.25.30.42] xxx plaintext
> Mar 1 15:50:51 unicorn pop3d[25633]: login:
> nas2-152.netlab.co.za[196.25.30.52] yyy plaintext

Looks ok.

> Errors
> Mostly reverse lookup errors.

Yup, I saw them in the pflogsumm output.

> MySQL

> Ahhhh.
> Full of these
> 020301 16:15:51 Aborted connection 152172 to db: 'yyyyy' user: 'xxxxxx'
> host: `unicorn.netlab.co.za' (Got an error reading communication packets)

Not good. I'm not a mySQL user, but that looks bad.

> This does not seem right.

Definitely.

> Could this be the source of my problem.

I'd think so.

> Where I come from bandwidth is extremely expensive. To prevent our
> modist bandwidth from being saturated by mail I use iproute2 to
> restict incoming and outgoing available bandwidth to port 25.

OK. I hope you also limit smtpd and smtp in master.cf to a VERYYYY LOW
value, like about 1-5 !

> Only connections from outside my network are limited. Dial-in users have a

This makes sense.

> direct path to the mail server that has no bandwidth restrictions.

Because it's not expensive (for you)

> >Is your DNS slow?
> >
> Never had an issue with them, in any way. Being small I rely on
> upstream providers for reverse lookups. Netsaint has been set to
> monitor that reverse lookups are functioning, and so far this year
> there has not been any problems.

OK. You could save bandwidth (and thus $$$) if you'd set up a caching
DNS.

> >Do you have a caching DNS?
> >
> They should also cache and the results of the dig below definitely
> implies they do.

OK. But still a local DNS could save you $$$

> On first query 800ms odd
> After that 4ms give or take
> Both servers responsed the same

So they're working fine.

> If I check the reverse lookups manually they are there.
> I had a few minites (4 or 5) of downtime yesterday which may
> explain some, but no all.

Maybe the lookups take too long, and thus Postfix reports them as
unresolvable.

> My mrtg on my internet wan interface shows there to be bandwidth
> available at all times yesterday, no saturation, but these are five minute
> averages.

Yup, hard to say.

-- 
Ralf Hildebrandt (Im Auftrag des Referat V A)   
Charite Campus Virchow-Klinikum                 Tel.  +49 (0)30-450 570-155
Referat V A - Kommunikationsnetze -             Fax.  +49 (0)30-450 570-916
Why you can't find your system administrators:
Went to Stop&Go to get ANOTHER case of insert favorite caffinated beverage here 
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