Tcp: Increase Default Initial Receive Window.
Creators: name: Dukkipati, Nandita
name: Dumazet, Eric
name: Miller, David S.
Publisher: name: Zenodo
Year: 2010

description: author    Nandita Dukkipati &lt;nanditad@google.com&gt;    2010-12-20 14:15:56 +0000<br>
committer    David S. Miller &lt;davem@davemloft.net&gt;    2010-12-20 21:33:00 -0800<br>
commit    356f039822b8d802138f7121c80d2a9286976dbd (patch)<br>
tree    420c0da0f63f0e040ebf8b2ad5d30a0ad61c35bd<br>
parent    eda83e3b63e88351310c13c99178eb4634f137b2 (diff)<br>
download    linux-356f039822b8d802138f7121c80d2a9286976dbd.tar.gz

<br>
TCP: increase default initial receive window.

<br>
This patch changes the default initial receive window to 10 mss<br>
(defined constant). The default window is limited to the maximum<br>
of 10*1460 and 2*mss (when mss &gt; 1460).

draft-ietf-tcpm-initcwnd-00 is a proposal to the IETF that recommends<br>
increasing TCP's initial congestion window to 10 mss or about 15KB.<br>
Leading up to this proposal were several large-scale live Internet<br>
experiments with an initial congestion window of 10 mss (IW10), where<br>
we showed that the average latency of HTTP responses improved by<br>
approximately 10%. This was accompanied by a slight increase in<br>
retransmission rate (0.5%), most of which is coming from applications<br>
opening multiple simultaneous connections. To understand the extreme<br>
worst case scenarios, and fairness issues (IW10 versus IW3), we further<br>
conducted controlled testbed experiments. We came away finding minimal<br>
negative impact even under low link bandwidths (dial-ups) and small<br>
buffers.  These results are extremely encouraging to adopting IW10.

However, an initial congestion window of 10 mss is useless unless a TCP<br>
receiver advertises an initial receive window of at least 10 mss.<br>
Fortunately, in the large-scale Internet experiments we found that most<br>
widely used operating systems advertised large initial receive windows<br>
of 64KB, allowing us to experiment with a wide range of initial<br>
congestion windows. Linux systems were among the few exceptions that<br>
advertised a small receive window of 6KB. The purpose of this patch is<br>
to fix this shortcoming.

References:<br>
1. A comprehensive list of all IW10 references to date.<br>
http://code.google.com/speed/protocols/tcpm-IW10.html

2. Paper describing results from large-scale Internet experiments with IW10.<br>
http://ccr.sigcomm.org/drupal/?q=node/621

3. Controlled testbed experiments under worst case scenarios and a<br>
fairness study.<br>
http://www.ietf.org/proceedings/79/slides/tcpm-0.pdf

4. Raw test data from testbed experiments (Linux senders/receivers)<br>
with initial congestion and receive windows of both 10 mss.<br>
http://research.csc.ncsu.edu/netsrv/?q=content/iw10

5. Internet-Draft. Increasing TCP's Initial Window.<br>
https://datatracker.ietf.org/doc/draft-ietf-tcpm-initcwnd/

Signed-off-by: Nandita Dukkipati &lt;nanditad@google.com&gt;<br>
Acked-by: Eric Dumazet &lt;eric.dumazet@gmail.com&gt;<br>
Signed-off-by: David S. Miller &lt;davem@davemloft.net&gt;
description: Linux Kernel contribution
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=356f039822b8d802138f7121c80d2a9286976dbd