Messages in this thread | | | Date | Sun, 8 Sep 1996 06:44:20 -0700 (PDT) | From | Christoph Lameter <> | Subject | Re: Networking slowdowns |
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More details: - After the link is up a while the stoppages increase - You can boost the effect by having another linux box attached via ethernet to the box you are having the ppp connection with. Work on that other linux box.
I had stoppages that lasted minutes.
On Sun, 8 Sep 1996, Eric Schenk wrote:
> > Christoph Lameter <clameter@miriam.fuller.edu> writes: > >I think I found a way to demonstrate networking slowdown. > > > >Set the MTU/MRU of a PPP Link to 3000. Then telnet into your > >machine and cat a file of 10-20K. > >The session will stall while you still can telnet to the machine in a second > >session working just fine. > > > >Hope I did not shoot myself in the foot here... > > Ok. I tried this here with a test rig. Both ends running 2.0.15. > I see odd "stalling" patterns in the telnet test, in that output > is bursty. This is not entirely unexpected, since a 3000 byte packet > takes a second or so to pass through the link, but much less than > a second to display on the telnet screen. > I do not see a complete "stall", that is, at no time have I been able > to make the traffic stop completely. I have, however, observed pauses > that last a few (4-5) seconds. > Looking at the tcpdump I also see that the system is very rarely > sending a full sized packet, which is quite odd. This means that telnet > is not feeding characters to the PPP link fast enough to prevent > a Nagle timeout, and occasionaly appears to have to characters ready > to send for several seconds. > > As a test of this theory I ran FTP sessions across the same link. > All FTP sessions ran a full speed, no stalling, with a sequence of > full sized packets only. > > This makes me suspect something in either telnet, or the pty layer. > Further evidence of this: when running a tcpdump in parallel with a telnet > I observe that packets finish crossing the link several seconds before > they get displayed by telnet. > > I'd be interested to know if others see similar results with this test.. > If so, then perhaps we can narrow the range of inquery into this problem.
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