Re: Node throughput and packet delay

[Sean Murphy <murphys@teltec.dcu.ie>]

>  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. 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.