[e2e] TCP "experiments"

Joe Touch touch at isi.edu
Tue Jul 30 10:24:57 PDT 2013

On 7/30/2013 1:34 AM, Jon Crowcroft wrote:
> the nice thing about a lot of the big cloud/web service outfits
> is that they run a huge _range_ of applications so a point solution
> tcp optimised for just one thing that
> harmed the common case uses of TCP would be ruled out -

Large back-end stuff can run privately optimized TCP - or even opt out 
of TCP and use WDM (see the UCSD Sigcomm pubs).

My concern is that Google would easily trade 0.01% benefit from 1 
billion users over even a 10% decrease in performance internally if the 
economics demanded it.

IMO, too many mods to TCP are made in the name of "it's only 0.01% 
improvement, but that's important to X" (where X is Google, Netflix, 
etc.). And not enough of these mods are instrumented in a way that we 
can see their impact.

For the difference in approach, see RFC 6928 vs. 
draft-touch-automatic-iw. The former increases the IW as a fixed value 
because it helps Google's short connections. The latter is 
self-instrumented to react to whether the large IW works and adapt it 


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