From: Shawn Ostermann (ostermann@eecs.ohiou.edu)
Date: 03/08/04
From: "Shawn Ostermann" <ostermann@eecs.ohiou.edu> Subject: Re: number of connections in tcptrace Date: Mon, 08 Mar 2004 10:50:40 -0500 Message-Id: <20040308155040.4946611A53D@picard.cs.ohiou.edu>
> I'm going to analyze the RTT samples per connection by using a large
> tcpdump file,
> (The tcpdump file size is around 280 GB.)
OK, that's certainly a big file. I don't know what the current record
would be, but I would suspect that you'd be a contender!
> I'm wondering how many connections are supported with tcptrace.
> Is there any limit on the number of connections ?
The internal mechanics are supposed to scale to any number of
connections. At least I don't know of any internal problems at
present.
> I mean the number of files generated when I run with "tcptrace -Z
> sample.dump".
Tcptrace uses an LRU scheme to close inactive files in cases like this
to avoid running out of file descriptors. It actually seems to work
pretty well.
Where you will run into trouble is in the VM requirements. Tcptrace was
written to create a big data structure of everything that it saw and
then report about it. The data structures were rewritten several years
ago to make it more friendly to VM. Inactive connection records should
get dumped out to swap space by the VM subsystem and shouldn't need to
get pulled back in until final processing. In practice, that works
well, but I've never tried it on anything the size of the problem that
you're looking at.
You might need to look into 'continuous' (real-time) mode in which it
expects to run 'forever'. It throws away connection records after some
threshold (either total count or inactive time). There's a sample
module, mod_realtime, that shows how to use it.
Shawn
-------------------------------------------------------------------------------
Dr. Shawn Ostermann - EECS Department Chair - Ohio University
330 Stocker Center, Ohio University, Athens, Ohio 45701-2979
ostermann@eecs.ohiou.edu -- FAX: (740)593-0007 -- Voice: (740)593-1566
http://www.eecs.ohiou.edu/faculty/ostermann.html http://www.eecs.ohiou.edu
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