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


Chronological Thread 
  • From: Andreas Jungmaier <ajung AT exp-math.uni-essen.de>
  • To: Torbjörn Andersson <torbjorn.andersson AT kau.se>
  • Cc: <discussion AT sctp.de>
  • Subject: Re: [SCTP-Discussion] RETRY: An error in the SCTPlib/SocketAPI
  • Date: Tue Oct 28 12:57:04 2003
  • List-id: SCTP Discussions <discussion.sctp.de>
  • Organization: University Duisburg-Essen
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Torbjörn,

please see my answers inline, below:

On Thursday 23 October 2003 10:28, Torbjörn Andersson wrote:
> Hi all
>
> I'm writing to you again now because I still have problem with the SCTP
> layer. The 1.0.0 version did improve things but there is still a problem
> when one sends messages without intermediate delays.
>
> You can try it yourself if you compile my program and send 1000 messages
> with an interval of 0ms, each message containing 500 bytes. SCTP does
> not fail every time but it will eventually. I guess within 20 retries.
> The simplest network setup will do fine(2 hosts). What happens is that
> SCTP stalls somewhere as

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 ?) !

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.

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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