[3732] in linux-net channel archive
Re: PPP slow between Linux and Solaris - why is it so?
???@ATHENA.MIT.EDU (cs95rro@brunel.ac.uk)
Wed Jul 17 00:46:52 1996
From: cs95rro@brunel.ac.uk
To: jason@cygnus.com (Jason Merrill)
Date: Mon, 15 Jul 1996 12:53:42 +0100 (BST)
Cc: dave@edipost.auspost.com.au, linux-kernel@vger.rutgers.edu,
linux-net@vger.rutgers.edu
In-Reply-To: <199607140422.VAA04495@yorick.cygnus.com> from "Jason Merrill" at Jul 13, 96 09:22:19 pm
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Dave Cole <dave@edipost.auspost.com.au> wrote:
> I remember someone mentioned that Solaris was retransmitting packets too
> quickly or something causing >50% of bandwidth to be used up by duplicate
> packets. I got the impression that Solaris was to blame. Is this
> correct? In any case, I do not remember anyone ever mentioning a fix /
> trick / work around to get the throughput back up to what it should be.
The problem I had was exactly the opposite, AFAIK. The link was only going
about 1/3 of the time. I didn't have a copy of tcpdump for PPP at the time
and I've since moved and no longer use dialup.
- From what I managed to work out, the Xylogics box was buffering a quite
considerable amount of data. It then seemed to panic and send quite a few
ICMP slow-down messages[1] back to the SunOS/Solaris host. (Although not being
root on the box in question, I can't be sure) Exponential backoff would then
mean that the delay shot up to about 30s, before gradually coming down again.
The whole thing would then repeat.
The problem is a Solaris/SunOS one as far as I can work out: it overreacts to
the ICMP messages. The solution I found was to write a bit of code to feed FTP
data to the remote end at a certain speed. (1k per second) which increased
throughput quite dramatically.
I don't know if the patches will fix the problem: Next time I'm on a Linux
box with a modem, I'll dial up and use one of the Solaris 2.5 machines here
to ftp data back into my Linux box and see what performance I get
All the above could be rubbish, but it's what I *think* was going on.
[1] I forget the proper term, but I think you know the ones I mean.
* cs95rro@brunel.ac.uk ryan@bcs.org.uk * Ryan Richard O'Connell 0958 204802 *
* http://www.brunel.ac.uk:8080/~cs95rro * Finger: cs95rro@molnir.brunel.ac.uk *
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