Re: Node throughput and packet delay

[Tarik Alj <aljtarik@ozias.inrs-telecom.uquebec.ca>]

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> Date: Sat, 9 Oct 1999 18:54:57 +0100 (BST)
> From: Lloyd Wood <L.Wood@surrey.ac.uk>
> X-Sender: eep1lw@petra.ee.surrey.ac.uk
> To: Sean Murphy <murphys@teltec.dcu.ie>
> cc: Poyuen Cheng <Poyuen_Cheng@symmetrycomm.com>, 
"'ns-users@mash.CS.Berkeley.EDU'" <ns-users@mash.cs.berkeley.edu>
> Subject: Re: Node throughput and packet delay
> X-url: http://www.ee.surrey.ac.uk/Personal/L.Wood/
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> 
> On Sat, 9 Oct 1999, Sean Murphy wrote:
> 
> > >  I am new in ns. Several questions:
> > >  1. How to simulate the throughput of the node? For example, I have $n1 
and
> > >     $n2, the link between them is with bandwidth 2M bps. But $n1 can only
> > >     process data at 500kps (the $n1 throughput). How to simulate that?
> > 
> > Complete guess - you could just install an artificial link and an
> > artificial node to model the 500kb/s bottleneck within the node. So the
> > real node would then be modelled by 2 simulation nodes joined by a 500kb/s
> > link.
> > 
> > >  2. How to trace the packet delay time and variation?
> > 
> > I wrote some code to do this - I implemented another c++ object to log
> > packet transmission and arrival times to a file. It involves slightly
> > modifying ns and recompiling ns, which is not ideal if you're a new user,
> > but it's not that hard to do especially if you're familiar with makefiles.
> > Let me know if you want more info.
> > 
> > Another solution that doesn't involve modifying ns is to create trace
> > files for your simulation and perform filtering on the trace file using
> > awk, for example to obtain the info you want. I've never done this, so I
> > don't know exactly what it entails.

Ignorance maybe a bliss... but awk (or Perl) really isn't that hard to learn 
(besides you can find a lot of example scripts in the test and ex directories0. 
You can learn more about the tracefiles in ns: notes & documentation, chapter 16 
in the Support section (as of april 1 99). And instprocs like trace-all and 
trace-queue.

> 
> Something like the script in:
> http://www-mash.cs.berkeley.edu/dist/archive/ns-users/9907/0350.html
> 
> L.
> 
> some people's idea of 'hard' is just weird.
some people work on saturdays!
> 
> > If you plan on pursuing this, I think
> > you should probably use different flows and use these to perform your
> > filtering.
> > 
> > Sean.
> > -----
> > Sean Murphy,			Email: sean.murphy@teltec.dcu.ie
> > Teltec Ireland,			Phone: +353-1-7045080
> > DCU, Dublin 9,			Fax:   +353-1-7045092
> > Ireland.
> 
> <L.Wood@surrey.ac.uk>PGP<http://www.ee.surrey.ac.uk/Personal/L.Wood/>

Tarik