[tg] IP fragmentation issue.

[Barbara Denny]

Hi,

TG is an application. You are seeing what the
application would get if it used TCP. TCP does 
affect the information bundling (Look more at 
how TCP works) and the OS gets involved here 
too. At the end of your data sending, you will
see TG at the sink got just as many bytes as 
what was sent. If you want to see what is going in and
out of the  network, use some type of sniffer 
(like tcpdump or etherfind).  The IP  fragmentation 
that goes on below is "invisible" to TG and TCP.

barbara

--- Arthur de Castro Callado <acc2 at cin.ufpe.br> wrote:
> 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/
> > _______________________________________________
> > tg mailing list
> > tg at postel.org
> > http://www.postel.org/mailman/listinfo/tg
> 
> _______________________________________________
> tg mailing list
> tg at postel.org
> http://www.postel.org/mailman/listinfo/tg


	
		
__________________________________
Do you Yahoo!?
Yahoo! Tax Center - File online by April 15th
http://taxes.yahoo.com/filing.html