Subject: Re: TCP limited transmit
To: None <firstname.lastname@example.org>
From: venkat venkatsubra <email@example.com>
Date: 11/30/2000 09:46:57
Mark Allman wrote:
> > If i wanted to avoid adding the new field t_extra, won't the
> > following work too ?
> Um. I'm still thinking about it. I am not sure that it is the
> same... And, I am thinking of other's comments.
Let me know if you find any difference.
Also, i prefer the bumping the cwnd up, calling tcp_output
and then restoring it back method because it avoids adding code
in tcp_output that would be executed for every outgoing
packet if i understood it correctly.
> > Also, is there a simple way to count the number of times the
> > 'Limited Transmit' code helped avoid a retransmit timeout ? That
> > is, helped a fast retransmit to occur when otherwise it would have
> > resulted in a retransmit timeout ?
> As a heuristic, fast retransmit when cwnd is less than four packets
> would qualify.
This would work well unless the reason for less than four packet
cwnd is the arrival of a ICMP source quench just before the Fast
Retransmit. In which case the cwnd is reset to 1 segment.
> Hmm... Due to my current state of mind I can't come
> up with a concrete algorithm, but I would guess that you could
> cleverly count ACKs and figure it out. Why? Are you thinking of a
> counter or something?
Yes, i thought a counter that can be displayed through 'netstat -s'
could be useful.