Re: [tcpm] I-D Action:draft-hkchu-tcpm-initcwnd-00.txt

Hi,

I've skimmed your paper hoping to see big improvements in loading  times 

However, the reductions in download times you find are below 10% - and this is the best case only a subset of traffic is increasing the initial cwnd.  
The experiments in 4.2 show that using Maps in the slowDC scenario can negatively affect the download time too for some users, by roughly the same amount. When all traffic uses the initial cwnd of 10 I expect to see 
smaller improvements or even increases in download times for all web traffic.

Thus, the 10% average improvement does not seem very compelling to me. Have you tested upload speeds? As DSL uploads are 128-256Kbps, I expect using an initial cwnd of 10 packets will result in increased loading times for web uploads, for instance, in the best case. As DSL lines have buffers roughly of that length, causing burst of 10 packets will negatively affect all other ongoing connections.

So it seems to me this may be a good idea to standardize for servers, and not for regular hosts. And even for servers, it is hard to understand the effects when everybody uses this large init_cwnd.

Cheers,
Costin

On 9 Mar 2010, at 00:35, Jerry Chu wrote:

> The link to the paper below has been fixed. Sorry for the delay.
> 
> Jerry
> 
> On Tue, Mar 2, 2010 at 2:50 PM, Jerry Chu <hkchu@google.com> wrote:
> Our first draft proposal to raise the initial congestion window was submitted
> a couple of days ago and is available at
> 
> http://www.ietf.org/id/draft-hkchu-tcpm-initcwnd-00.txt
> 
> A paper with the title "An Argument for Increasing TCP’s Initial Congestion
> Window" detailing our large scale experiments will soon be available at
> 
> http://code.google.com/speed/articles/tcp_initcwnd_paper.pdf
> (The link is not there yet due to a last minute snag. Hopefully it
> will be fixed asap.)
> 
> Comments are welcome.
> 
> Jerry
> 
> -----------------------------------------------------------------------------------------------------------
> From: Internet-Drafts@ietf.org
> To: i-d-announce@ietf.org
> Reply-to: Internet-Drafts@ietf.org
> Subject: I-D Action:draft-hkchu-tcpm-initcwnd-00.txt
> X-RSN: 1/0/935/28943/32298
> X-HREF: http://www.ietf.org/ibin/c5i?mid=6&rid=49&k1=935&k2=32298
> 
> A New Internet-Draft is available from the on-line Internet-Drafts directories.
> 
> Title : Increasing TCP's Initial Window
> Author(s) : J. Chu, et al.
> Filename : draft-hkchu-tcpm-initcwnd-00.txt
> Pages : 16
> Date : 2010-02-28
> 
> This document proposes an increase in the permitted TCP initial
> window (IW) from between 2 and 4 segments, as specified in RFC 3390,
> to 10 segments. It discusses the motivation behind the increase, the
> advantages and disadvantages of the higher initial window, and
> presents results from several large scale experiments showing that
> the higher initial window improves the overall performance of many
> web services without risking congestion collapse. Finally, it
> outlines a list of concerns to be addressed in future tests.
> 
> A URL for this Internet-Draft is:
> http://www.ietf.org/internet-drafts/draft-hkchu-tcpm-initcwnd-00.txt
> 
> Internet-Drafts are also available by anonymous FTP at:
> ftp://ftp.ietf.org/internet-drafts/
> 
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