Hi,
No, Droptail does not have an infinite queue. The size is limited by the limit_ parameter. I think the default is 20.
As far as why you can't get 500 Mbps. Your maximum obtainable bandwidth in TCP is limited by your RTT and window size (a configurable parameter in ns).
max bandwidth = (packet size * window size)/RTT
Assuming you are using the default packet and window size, this should limit you to about 3 to 4 Mbps for your particular topology.
The default packet size for ns is 1000 bytes and the default window size is 20.
Hope this helps.
Cheers!
Mandeep
-----Original Message-----
From: guru0109 [SMTP:[email protected]]
Sent: Monday, March 27, 2000 7:21 AM
To: [email protected]
Subject: [ns] Does Droptail have infinite queue?
Hi.
I found some strange things... in NS 2.1b6
Here is my network configuration
Sender-----link1-----router-----link2-----receiver
router use droptail both sides.
link1: 500Mbps 20msec RTT
link2 : 10Mbps 0.1msec RTT
Sender use TCP/Reno(all parameter default)
simulation time 100sec
throughput : about 3.9Mbps
link1's RTT 100msec(same bandwidth 500Mbps) throughput : 0.8Mbps
link1's RTT 20msec and bandwidth 500Mbps link2's RTT 0.1msec, 1Mbps :
throughput 1Mbps
and both simulation router doesn't discard any packet.
I think if router packet discarding occurs, low throughput is
reasonalble.
but no packet discard why tcp can't sends upto about 500Mbps?
I attach my tcl script..
Did I miss something?
Any information helpful.
Thx << File: 1node.tcl >>