Re: HELP! Long ping times under Yellow Dog Linux

Subject: Re: HELP! Long ping times under Yellow Dog Linux
From: Gawain Reifsnyder (
Date: Mon Jan 22 2001 - 21:09:01 MST

This is a bit long so thanks in advance if you dare to read on. First
of all, I've successfully upgraded the kernel on my G4/400 to 2.2.18.
Thanks Chris and Bryan!

At first, the chronic long ping time problem seemed to get better,
but that now appears to simply have been due to reduced network
traffic over the weekend and ping times are back to 3500ms or so...
My whole network is practically unusable as far as the internet is
concerned.. :-( Here's a rundown of what's happening. I'm not
certain which items may be relevant, so I'll opt for overkill.

The patient --

Power Mac G4/400 with YDL 1.2.1 (spanking new 2.2.18 kernel)
Apache/1.3.14 (Unix) PHP/4.0.2 mod_ssl/2.7.1 OpenSSL/0.9.6

It's connected to the Internet via a cable modem with a 128k/sec upstream cap
The machine is set up as a server and handles approximately 30k pages/day
I have two IP addresses assigned by my provider, one for this
machine, the second for another Mac server running WebTen. The WebTen
machine is also running IPNetRouter and is the gateway for the other
machines on my LAN, (like the Mac I'm typing this message on.)

The network slowdown appears to spill over from the YDL machine and
affects any other Mac that tries to access the internet. Requests are
usually served, but performance feels about like a 14.4 modem instead
of cable. The big issue that I can't figure out is whether the
problem is due to a misconfiguration with the YDL server or is due to
issues with my ISP.

Occaisionally, (late at night or weekends) the problems seem to
nearly disappear. The server is still serving a fair amount of
requests and everything is zippy. That's usually not the way it is
though, and the problems have persisted for at least a couple of
weeks so I don't believe it's due to a DoS attack. Either way, there
doesn't seem to be a direct correlation between server activity and
the problem.

If I disconnect the YDL machine from the network I can ping other
outside machines (my ISP's DNS server for instance) at 50ms or less.
If I stop apache on the YDL machine, ping times seem to drop as well,
although I haven't taken the server down for long periods to prove
this. Load on the server itself seems to be very minimal, perhaps 90%
idle during peak times.

The server is generally not serving file downloads, just
html/php/database served pages, so I don't think I'm hitting my
upstream cap. Am I? Before I set up the YDL machine, the WebTen box
was handling a similar level of traffic on the same line without

Could it be some kind of DNS problem? I've checked and re-checked all
the settings on this machine, but there's one other niggling problem
that could be relevant. I'm getting DNS from my ISP. There seems to
be some servers that nslookup can't find. Others return proper
results. I discovered this when mail sent from a php script to a
client's address started getting returned:

For instance:


*** can't find Non-existent host/domain

However, this works fine:


Non-authoritative answer:

I don't know if this could have something to do with it or not. is definitely there, and mail sent from the WebTen machine
which gets its DNS from the same ISP gets there just fine.

Thanks for taking the time to read this diatribe. My network has
turned to molasses! ;-) Any ideas?


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