Subject: AODV Simulation with Moderate to Large Traffic Load

From: Wang Qiang <[email-masked]>
Date: Wed, 9 Jan 2002 22:53:02 +0800

Dear ns users:

I'm trying different levels of loading to a 50-node ad hoc network in
1500mx300m area.  Since default ns2 wireless media link capacity is 2Mbps,
the following loading levels results from calculation:

1. Light loading:   20 CBR conneections sending 64-byte packets at 4 packet
per sec
   Loading factor = 20 x 64 x 8 x 4 / 2M = 0.03 erlang = 3%

2. Moderate loading:  30 CBR connections sending 512-byte packets at 8
packet per sec
   Loading factor = 30 x 512 x 8 x 8 / 2M = 0.49 erlang = 49%

3. Heavy loading:  30 CBR connections sending 1024-byte packets at 8 packet
per sec
   Loading factor = 30 x 1024 x 8 x 8 / 2M = 0.98 erlang = 98%

However given moderate loading at above, NO single scenario has ever
complete successful so far!  Not to mention the case of heavy loading.  The
simulation ALWAYS core dump halfway with a "eval.c 41: no such file or
directory" error.  This error did happen with even the light loading case,
but much less frequently and could be bypassed by replacing a new scenario
file. However this method apparently doesn't work with moderate loading and
heavy loading!

Has anyone experienced similar problem or tried to simluate large traffic
before?
All comments are welcome!

Thank you.

wangq

---

From: Jim Kaba <[email-masked]>
Date: Wed, 09 Jan 2002 13:52:18 -0500

Wang,
  If you're creating output packet trace files to be used analysis tools,
watch their size as the simulation progresses.  In some NS2 simulations
we've run with high packet loads, we've seen the tracefiles grow to 2
gigabytes, which was the maximum file size on the Linux machine we were
using.  You may find that the core dumps occur when the output file reaches
the maximum limit supported by your OS.

Jim

-- 
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James T. Kaba                   
Sarnoff Corporation      Time flies like an arrow...
[email-masked]                ...Fruit flies like a banana!
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