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From(Christoph Lameter)
SubjectRe: Slow PPP - caused by duplicate packets?
Date31 Mar 1996 07:59:49 -0800
: > > It _looks_ like the other end is ignoring our first ACK, so it times out, 
: > > and then sends the packet again. And then we ACK it twice (that's normal
: > > linux behaviour - there's the "normal" ACK, and then there is an extra
: > > one that comes from the fact that the linux TCP code decides we'd better
: > > ack again when we got a packet re-sent).
: > >
: > > Now, WHY is Solaris ignoring our first ACK?
: >
: > Is our first ack falling out of the cable, or not being sent or
: > something like that.
: >
: I have been listening to this thread for a while now. I'm running basically
: the same setup with no slow-downs seen from 1.3.57 through 1.3.80, which
: I am now running.
Could you post your exact configuration please?
: This sounds like a timing problem at the Solaris. I have seen this kind
: of problem over sdlc links before, where one side was always off building
: a buffer when the ack came, and missed it, causing an unnecessary retry
: of the buffer send.
I have the same problem with 1.3.81 dialin to 1.3.57 and 1.3.81....
This must be a linux problem. We dont use Solaris or anything else.

: BTW, did I hear that this is an external modem? It is possible that the
: handshaking problem is with your own modem (ie. the modem doesn't sent
: the ack because it never received it due to being busy on another task)
: and not between you and the Solaris. Have you tried other hosts?
I am running an Internal modem here. I tested the serial driver with
regular dialin and it works fine at high speeds etc. The problem
ONLY exists on a PPP/SLIP link.


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