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Re: [ns] TCP source dropping packets

Hi

Yes.As you are setting the window size very big.And
the sender is thinking that reciever can accomodate
more and it keeps on pumping, but the link capacity is
small.Causing drops.
YOu have to set both the capacity and window size
accordingly to avoide the drops.

-Adeel

--- VJ VJ <[email protected]> wrote:

<HR>
<html><DIV>
<P>Hi Adeel,</P>
<P>&nbsp; Thanks for your reply. In my case the link
delay varies between 30 to 150ms, and the link bw is
100Mbps. So I wouldn't consider this as small delay,
but I have made my TCP window size extremely large. I
was thinking the reason for source to drop packets is,
when the cong window is increasing, the source may not
be able to pack more than BW*Delay bytes into the
link, if the window is bigger than the&nbsp;BW*Delay
product, it can drop packets at the source. Is my
argument valid ??</P>
<P>Thanks,</P>
<P>Vijay<BR></P></DIV>
<DIV></DIV>
<DIV></DIV>&gt;From: Adeel Baig <[email protected]>
<DIV></DIV>&gt;To: VJ VJ <[email protected]>,
[email protected] 
<DIV></DIV>&gt;CC: [email protected] 
<DIV></DIV>&gt;Subject: Re: [ns] TCP source dropping
packets 
<DIV></DIV>&gt;Date: Wed, 28 Mar 2001 16:23:31 -0800
(PST) 
<DIV></DIV>&gt; 
<DIV></DIV>&gt;Hi 
<DIV></DIV>&gt;About the drops at the source.It also
depends on the 
<DIV></DIV>&gt;link delay.If you keep the delay very
small then u 
<DIV></DIV>&gt;will observe the drops at the source. 
<DIV></DIV>&gt;About the default queue size .. yes
there is a default 
<DIV></DIV>&gt;queue size in the link which is 50.You
can manipulate 
<DIV></DIV>&gt;it by changing it in ns-default.tcl. 
<DIV></DIV>&gt; 
<DIV></DIV>&gt;Hope this will help. 
<DIV></DIV>&gt;Best of Luck 
<DIV></DIV>&gt; 
<DIV></DIV>&gt;-Adeel 
<DIV></DIV>&gt; 
<DIV></DIV>&gt;--- VJ VJ <[email protected]>wrote: 
<DIV></DIV>&gt; &gt; Hi, 
<DIV></DIV>&gt; &gt; Iam trying to simulate multiple
source nodes 
<DIV></DIV>&gt; &gt; (n0,n1,n2,n3) simultaneously 
<DIV></DIV>&gt; &gt; sending traffic to node n5
through a bottlneck node 
<DIV></DIV>&gt; &gt; n4. From the nam 
<DIV></DIV>&gt; &gt; simulation, I can see source node
dropping packets, 
<DIV></DIV>&gt; &gt; the 
<DIV></DIV>&gt; &gt; problem goes away when I
introduce a buffer to the 
<DIV></DIV>&gt; &gt; links attached to 
<DIV></DIV>&gt; &gt; nodes n0 to n4 or n1 to n4 or n2
to n4 or n3 to n4. 
<DIV></DIV>&gt; &gt; But I see the source 
<DIV></DIV>&gt; &gt; dropping packets with buffering
for some other link 
<DIV></DIV>&gt; &gt; bw/delay combination. 
<DIV></DIV>&gt; &gt; Does anyone have any insight to
this problem, how 
<DIV></DIV>&gt; &gt; does the ns-2 behave when 
<DIV></DIV>&gt; &gt; no buffer is attached to the link
? does it have any 
<DIV></DIV>&gt; &gt; default queue size 
<DIV></DIV>&gt; &gt; attached to the link ? Any help
will be of great use 
<DIV></DIV>&gt; &gt; to me. 
<DIV></DIV>&gt; &gt; 
<DIV></DIV>&gt; &gt; Thankyou very much, 
<DIV></DIV>&gt; &gt; Vijay 
<DIV></DIV>&gt; &gt; 
<DIV></DIV>&gt;_________________________________________________________________

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