[lwip-users] Re: [lwip] TCP Congestion Avoidance Bug

[Adam Dunkels]

Hi!

On Tue, 2002-07-02 at 15:26, yeoh yeow wrote:
> I came accross the following code and curious abt it:
> 
> /* Update the congestion control variables (cwnd and
>          ssthresh). */
> if(pcb->cwnd + pcb->mss * pcb->mss / pcb->cwnd > pcb->cwnd) {
>           pcb->cwnd += pcb->mss * pcb->mss / pcb->cwnd;
>         }
> 
> why ignore 1/8 of pcb->mss ?

RFC2001 "TCP Slow Start, Congestion Avoidance, Fast Retransmit, and Fast
Recovery Algorithms" says:

   Many implementations incorrectly add a small fraction of the segment
   size (typically the segment size divided by 8) during congestion
   avoidance.  This is wrong and should not be emulated in future
   releases.

So I guess that the 1/8 stuff is just an old approximation/optimization
made in older implementations.

/adam
-- 
Adam Dunkels <address@hidden>
http://www.dunkels.com/adam/

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