[PATCH] Add a new TCP_IGNOREIDLE socket option

[John Baldwin]

On Wednesday, February 06, 2013 6:27:04 am Randall Stewart wrote:
> John:
> 
> A burst at line rate will *often* cause drops. This is because
> router queues are at a finite size. Also such a burst (especially
> on a long delay bandwidth network) cause your RTT to increase even
> if there is no drop which is going to hurt you as well.
> 
> A SHOULD in an RFC says you really really really really need to do it
> unless there is some thing that makes you willing to override it. It is
> slight wiggle room.
> 
> In this I agree with Andre, we should not be *not* doing it. Otherwise
> folks will be turning this on and it is plain wrong. It may be fine
> for your network but I would not want to see it in FreeBSD.
> 
> In my testing here at home I have put back into our stack max-burst. This
> uses Mark Allman's version (not Kacheong Poon's) where you clamp the cwnd at
> no more than 4 packets larger than your flight. All of my testing
> high-bw-delay or lan has shown this to improve TCP performance. This
> is because it helps you avoid bursting out so many packets that you overflow
> a queue.
> 
> In your long-delay bw link if you do burst out too many (and you never
> know how many that is since you can not predict how full all those
> MPLS queues are or how big they are) you will really hurt yourself even worse.
> Note that generally in Cisco routers the default queue size is somewhere between
> 100-300 packets depending on the router.

Due to the way our application works this never happens, but I am fine with
just keeping this patch private.  If there are other shops that need this they
can always dig the patch up from the archives.

-- 
John Baldwin