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Date:      Sun, 25 Oct 1998 00:43:05 +0930 (CST)
From:      Kris Kennaway <kkennawa@physics.adelaide.edu.au>
To:        Brian Somers <brian@awfulhak.org>
Cc:        current@FreeBSD.ORG
Subject:   Re: Improper sharing of modem bandwidth 
Message-ID:  <Pine.OSF.4.05.9810250042340.197-100000@mercury.physics.adelaide.edu.au>
In-Reply-To: <199810211031.LAA01095@woof.lan.awfulhak.org>

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On Wed, 21 Oct 1998, Brian Somers wrote:

> > If you're interested, you could try doing a ``s/20/100/'' in bundle.c 
> > in src/usr.sbin/ppp and rebuilding & installing ppp.  Perhaps the 
> > ``20'' is a bit light.

Making the suggested change from 20 to 100 in bundle.c didnt seem to have
a noticeable effect; to recap my problem, if I start up a binary transfer
which runs at full throttle (~1.65k/s on my 14.4k modem, usually), then it
starves all other network connections to the point of exclusion. I've done
some more checking and perhaps some of this will be helpful.

If I ^Z the ftp (or http, or whatever the binary transfer is that's
hogging the modem) process, the modem continues to transfer for ~11
seconds (~18k) before coming to a stop; immediately thereafter my other
network sessions (telnet, ping, etc) "unfreeze" and I get normal
performance from them. Restarting the FTP transfer immediately excludes
everything else again.

If I start a ping of a host which is ~400ms away at normal usage,
restarting the FTP transfer will cause no further packets to be returned.

Doing a 'tcpdump ip and not host <ftphost>' where <ftphost> is the host
I'm downloading from shows the icmp echo requests going out, but nothing
at all coming in.

Similarly, DNS requests to the machine on the other side of the modem link
go out, but nothing comes back. In the 10 minutes I've been watching this,
I've not seen a single packet come back in response to the DNS queries and
other stuff I have running - in the meantime, the FTP transfer continues
to run at full speed. It seems I cannot get a single packet in other than
from the FTP data stream.

Kris


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