[ns] two equal UDP CBR flows in droptail queue get different bandwidths?

[Eduardo J. Ortega]

Hi there:

I've set up this experiment. I have two source nodes S1 and S2 directly 
connected to a node R1 and two destination nodes D1 and D2 also directly 
connected to a node R2. Nodes R1 and R2 are connected. All links are 1 Mb/s 
Full duplex with DropTail. Now, here's the thing. I set up two flows, one 
going from S1 to D1 and the other one form S2 to D2. Both flows are UDP CBR 1 
Mb/s. Flow 1 starts at t=0 and finishes at t=20.  flow 2 starts at t=10 and 
stops at t=15. Sim runs from t=0 to t=25.

I'd expect that at t=10 (when flow 2 starts), both flows would experience the 
same amount of packet losses, so that each one would use about 0.5Mb/s of the 
link between R1 and R2. But what really happens is that from t=10 to t=15, 
flow 2 uses all bandwidth while flow 1 loses all packets. Since both flows 
have the same parameters, shouldn't they receive the same share of bandwidth 
during that period? Or am i missing something here?

Thanks in advance.

-- 
Eduardo J. Ortega - Linux user #222873 
"No fake - I'm a big fan of konqueror, and I use it for everything." -- Linus 
Torvalds