Re: CWND CALCULATION

[Polly Huang <huang@catarina.usc.edu>]

> Hi:
>     I tried to figure out the cwnd calculation, but do not have
> any clue.  Please refer below:
> 
> TAHOE
> -----
> 0/cwnd=1.0000/ssthresh=15  \
> 1/cwnd=2.0000/ssthresh=15   > exponential increase of cwnd
> 2/cwnd=6.0000/ssthresh=15  /
> 
> 3/cwnd=15.0667/ssthresh=15  \  I can't figure out how cwnd
> 4/cwnd=15.1991/ssthresh=15  /  gets these values: 15.0667 , 15.1991 etc

The cwnd of TCP increases this way in ns-2 and also in Van's TCP paper I
think:

WHen receiving an ack:
	if cwnd < ssthresh
		cwnd+=1      /* multiplicative increase */
	else
		cwnd+=1/cwnd /* linear increase */

15.0667 is exactly 15+1/15.

Hope this make sense,
-Polly