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SubjectRe: 1.3.89+Solaris+PPP - still lots of extra packets
Date
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> David Monro <davidm@gh.cs.usyd.edu.au> writes:
> >well, I have upgraded to 1.3.89, and I am still having ppp problems.
> >Interactive response to our Solaris server has improved - I no longer
> >get massive delays when attmepting to type-ahead into a shell. However,
> >I still have the duplicate packets problem with paging text files on
> >large xterms, and ftp transfers on a 68K (gzipped so no modem
> >compressions) file run at 240cps on a 14.4k modem. Below are the dumps
> >from both ends of the link for typing df on our server, which produces
> >85 lines of output. This time I have managed to include time stamps and
> >packet IDs at both ends.
> >
> It seems to me that SUNOS is choosing to retransmit packets much
> to early. Say a 1460 byte packet gets injected into the network by
> staff at time T, which then makes its way to your machine.
> Just counding transmission time over the modem I'd expect there to
> be a 1 second delay between the time staff sends the packet and the
> linux box can see it and ACK it. If the linux box waits another 1/2
> second to send the ACK (which is about what we are doing now),
> then sends it over the modem, you'd expected pretty much what
> you are seeing for the round trip delay on the ACK.
> Looking at staff's output log, it starts the first resend 1/2 second
> after the first packet is sent. There is no way that fuzzbox can
> even have the packet yet, never mind have responded.

I've had this problem, going via a Zylogics PPP box, on all versions of the
kernel I've used. (1.2.1, 1.2.13, 1.3.[lots]) I've not gone as far as packet
dumps (Mainly because tcpdump doesn't work on PPP and I haven't got time to
do it any other way) but it seems to me as if SunOS (Both 4 and 5) is overdoing
the source quench a bit. I generally get around 400cps on a good day (At 14.4k)
but for much of the time the transfer goes at full speed but then the CS drops
briefly and it waits for up to 30s. I hacked together a bit of C to spoon-feed
ftp data to the Linux box at 1.2k and it seems to work.

Hope this helps.

* cs95rro@brunel.ac.uk ryan@bcs.org.uk * Ryan Richard O'Connell *
* http://www.brunel.ac.uk:8080/~cs95rro * Finger: cs95rro@molnir.brunel.ac.uk *
The modern idiot is here and plain to see.

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