On Thu, 29 Oct 2009, apetlund@simula.no wrote:

I apologise that some of you received this mail more than once. My email
client played a HTML-trick on me.

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+	/* If a thin stream is detected, retransmit after first
+	 * received dupack */
+	if ((tp->thin_dupack || sysctl_tcp_force_thin_dupack) &&
+	    tcp_dupack_heurestics(tp) > 1 && tcp_stream_is_thin(tp))
+		return 1;
+
 	return 0;
 }

Have you tested it? ...I doubt this will work like you say and

retransmit

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something when the window is small. ...Besides, you should have built

this

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patch on top of the function rename you submitted earlier as after DaveM

applied that this will no longer even compile...

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--
 i.

We have performed extensive tests mapping the effect of the patch you
commented on some months ago. Since then, the only change was the one you
requested of switching tcp_fackets_out() with tcp_dupack_heurestics().
After inspecting the code, I believed the effect should be equal to the
previous, only making considerations for SACK and FACK availability.
Please tell if this will break the intended effect, and I will modify the
patch accordingly.

Ah, you're of course right. FACK retransmits the head always but RFC3517 
mode doesn't. I think you'd need to artificially lower (ie., to calculate)
the dupthresh (from tp->reordering) to be 1 for it to work as intented.

Graphs from our tests of the original patch can be found at the location
linked to below.  I have tested the new one for functionality, but have
not et performed tests on this scope as the changes were minor. I will, of
course, fix the function rename in the next iteration. Sorry for that.

http://folk.uio.no/apetlund/lktmp/

You curiousity, have you run this more aggressive form of early retransmit 
against the one ID gives? ...I checked your results but if I understood 
them correctly the IDish early retransmit wasn't among the variants used.

-- 
 i.