[tg] IP fragmentation issue.

[Arthur de Castro Callado]

What network technology are you using? Ethernet?

Ethernet frames must have up to 1500 bytes, no more. This limits the size
of the packet in a way that when one wants to transmit segments with more
than is allowed (bytes 1500 - headers), the segment will be divided into
pieces before sending.

Arthur.

On Thu, 15 Apr 2004, Hugues VAN PETEGHEM wrote:

> Hi all,
>
> I got an IP fragmentation problem using 'tg'. Here is the problem statement :
>
> ---------                                      ---------
> | pc10 |--------------------------------| pc6 |
> ---------10.0.0.10               10.0.2.2--------
>
> I'm trying to generate a simple data flow from pc10 (10.0.0.10) to pc6
> (10.0.2.2). Here are the 'tg' input files :
>
> # pc10
> on 0:15 tcp 10.0.2.2.80
> at 5 setup
> at 6 arrival 0.5 length 2000
> packet 300
>
> # pc6
> on 0:15 tcp 0.0.0.0.80 server
> at 1 wait
>
> After a couple of minutes, I use 'dcat' to transform the log files in text
> files and here are the first lines of both files :
>
> # pc10
> (...)
> Event Time      Type            Address         Id      Length
> -----------------------------------------------------------------
>
> 5.010170        Setup
> 6.509204        Transmit        10.0.2.2.80     0       2000
> 7.009049        Transmit        10.0.2.2.80     2000    2000
> 7.508948        Transmit        10.0.2.2.80     4000    2000
> 8.008956        Transmit        10.0.2.2.80     6000    2000
> (...)
>
> >From the client side, everything goes perfectly. Each packet is sent to
> 10.0.2.2:80 every 0.5 second. These packet have a 2000 bytes length.
>
> # pc6
> (...)
> Event Time      Type            Address         Id      Length
> -----------------------------------------------------------------
>
> 0.004769        Setup
> 19.742468       Accept          10.0.0.10.1207  Association 5
> 21.238312       Receive         10.0.0.10.1207  0       2000
> 21.737539       Receive         10.0.0.10.1207  2000    1448
> 21.737888       Receive         10.0.0.10.1207  3448    552
> 22.237457       Receive         10.0.0.10.1207  4000    1448
> 22.237830       Receive         10.0.0.10.1207  5448    552
> (...)
>
> >From the server side, the first packet is well received, but after that,
> everyhing is "wrong". I mean, it receive the data, but fragmented.
>
> I think it is a 'tg' (or 'dcat') problem. Have someone faced this before ? If
> not, could you try it and tell me if you have the same problem.
>
> Thanking you in advance :
>
> H
> --
> Hugues VAN PETEGHEM
> Institut d'Informatique - FUNDP
> ---------------------------------------------
> Web : http://www.info.fundp.ac.be/~hvp/
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