Re: please help: large topologies

[Lloyd Wood <L.Wood@surrey.ac.uk>]

On Mon, 3 May 1999, Kamil Sarac wrote:

> Hello all,
> 
> I am doing  multicast simulation using 250 node stub based
> network topology. I am using topology generator class (# Created May 98 by
> Ahmed Helmy; updated June 98) to generate my network topology. When I run
> the simulation, it gives an error that I have no clue about:
> 
> $> ns  dense250.tcl
> Creating hierarchical nodes..

Hmmm, the 'hierarchical' might be a hint here, if it's not your code
generating that message.

> creating node 100...
> creating node 200...
> Creating links 0...
> creating link 100...
> creating link 200...
> creating link 300...
> ns: _o10270 recv  386 5936: can't read "messages": no such variable
>     (Object set line 1)
>     invoked from within
> "Agent/Mcast/Control set messages($m)"
>     (procedure "_o10270" line 2)
>     (Agent/Mcast/Control recv line 2)
>     invoked from within
> "_o10270 recv  386 5936"
> 
> Interesting part is that I am doing a similar simulation with a network of
> size 100 nodes and it works, but for 250 node network it does not ( I use
> Node expandaddr to increase address space - I am using ns version  2.1b4a)

250 > 128; the upper limit of 'normal' addressing (with a bit reserved
for multicast.) So you're now in a 9, not 8, -bit address space. 

Since you're running over a byte's address space, try setting
hierarchical addressing. I've previously had the odd trouble with
hierarchical address spaces and multicast, so you'll also want to try
a unicast simulation and see what happens to narrow it down. 

Cheers,

L.

> Is it possible that topology generator does something wrong in generating
> large topologies or any other reasons about this error....
> 
> Thank you very much,
> 
> Kamil.

<L.Wood@surrey.ac.uk>PGP<http://www.ee.surrey.ac.uk/Personal/L.Wood/>