??: pppd and TCP/IP Window Size - Changing it?

??: pppd and TCP/IP Window Size - Changing it?

Post by Douglas E. Mitt » Sun, 26 Oct 1997 04:00:00

I have been having some performance problems with ppp.  There are
large pauses in data transfer, most noticable when in a
terminal/telnet/shell session.  I don't notice these pauses when
connected to my ISP's dialup servers, just when I make "private"
connections with other personal computers with Linux installed.

At home I've used the various suggestions posted here and all have
helped over-all through put via my ISP connection (asyncmap, etc) BUT
my personal type ppp connections still seem to need some work.  I've
even started using some of these suggestions in my Windows setups to
good effect!

I have set up a couple of Linux networks at work lately with slow
TCP/IP - Ethernet links and these same pauses were noticed.  There I
was able to modify the "window" size (via route command) to resolve
the problem.

What I understand from the Kernal docs, is that a window=0 defaults to
a 32k byte value which is only appropriate for very fast networks,
NICs and computers.  At work changing this from 0 to 4096 (or even
2048) resolved my problem.  It gave me a significant performance
increase as well as reducing the pauses.

Now for the million dollar question, how do I change the window size
on a ppp interface since it is established auto-magically by the
deamon?  I'm not assuming this will fix my "problem" but I'd like to
experiment with it.  I am currently using pppd V2.3.0 (?) which I
updated to when I installed V2.0.30 kernal.  (I'm not at my Linux
right now so that pppd version may not be right BUT its the minimal
update required for V2 kernals.)

Thanks in advance for any input, suggestions or discussions.
(positive or negative!  :-)   )

     Doug Mitton
      * In Brockville, Ontario, Canada
        (City of the Thousand Islands!)

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