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[SCTP-Discussion] Re: An error in the SCTPlib/SocketAPI


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  • From: Andreas Jungmaier <ajung AT exp-math.uni-essen.de>
  • To: Torbjörn Andersson <torbjorn.andersson AT kau.se>
  • Cc: discussion AT sctp.de, Thomas Dreibholz <dreibh AT exp-math.uni-essen.de>
  • Subject: [SCTP-Discussion] Re: An error in the SCTPlib/SocketAPI
  • Date: Fri Oct 31 15:17:01 2003
  • List-id: SCTP Discussions <discussion.sctp.de>
  • Organization: University Duisburg-Essen

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Torbjörn, all,

please find my comments below:

> > I tried the setup and compiled your applications. I had them run quite
> > many
> > times (~ 100 times) and they never failed, or stalled for me.
> > Note that this behaviour differs notably from what I had encountered
> > in version 1.0.0-rc2 (or 1.0.0-rc1 ?) !
>
> I'm using version 1.0.0 (no -rc*) and socketapi 1.3.1


That's what I meant: I saw the error you mentioned in rc1 and rc2 releases.
It disappeared, however, when I released the sctplib-1.0.0 version.
Are you sure (just to avoid any possible mixup) that all your applications
and socketapilib and sctplib were freshly installed ?

> > What happens actually is a unidirectional bulk-transfer of data, where
> > the client application lazily reads data (or rather the respective
> > thread of the socketapi does). When that happens, the arwnd drops from
> > about 32K to, essentially, 0. Then, when the application reads the
> > buffered
> > data, there is a 200ms "stall", after which an updated SACK (again with a
> > 32K window) is sent.
> >
> > If you can reproduce the problem, I will need an ethereal trace from
> > your side to help me find out what's going on.
>
> I have been able two create two tcpdump dumps from a run where
> everything goes well and one when it stalls. The stall seems to be due
> to rcwnd which goes down to zero in the runs where it goes wrong.

I suppose, that is advertised rwnd you mean ? Let me investigate that, and I
will report back with my results after the week-end.

> A secondary problem:
> Notice also that when everything goes well the client terminates but the
> server does not retrieve the SCTP_SHUT_COMP notification. The client
> retrieves its. The server will print its end-state and restart if it
> retrieves the SCTP_SHUT_COMP.

That may be an issue with the socket-api. Thomas, can you have a look
at this ?

Best regards,
Andreas

- --
Dipl.-Ing. Andreas Jungmaier
Computer Networking Technology Group
University of Duisburg-Essen
http://www.exp-math.uni-essen.de/~ajung
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  • [SCTP-Discussion] Re: An error in the SCTPlib/SocketAPI, Andreas Jungmaier, 10/31/2003

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