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Re: The next broadband killer: advanced operating systems?

  • From: Sam Stickland
  • Date: Tue Oct 23 05:38:01 2007

Adrian Chadd wrote:
On Tue, Oct 23, 2007, Sam Stickland wrote:

I'm concerned that if Microsoft were to post this as a patch to Windows XP/2003 then we would see the effects of this "all at once", instead of the gradual process of Vista deployment. Anyone agree?

You need both ends to have large buffers so TCP window sizes can grow.

So a few possibilities:

* you're running content servers but you're on training wheels and you're just
not aware of this. Windows default sizes are small, so you never notice
as you never grow enough TCP windows to fill your set buffer size.
These guys would notice if Windows XP was patched to use larger/adaptive
Yes. I was imagining a scenario where released patches mean that currently untuned servers and clients are suddenly adaptively tuning their TCP Window sizes. According to the Web100 website (, their automatic TCP buffer tuning has already been merged into mainline Linux kernels. If Microsoft release an XP patch that enabled all the Windows based clients out there to take advantage of this then there could be lot of surprised faces.
* .. caveat to the above: until Linux goes and does what Linux does best
and change system defaults; enabling adaptive socket buffers by default
during a minor version increment. Anyone remember ECN? :P Then even some
cluey server admins will cry in pain a little.
Is the adaptive buffer tuning in Linux not enabled by default?
* I don't think the proposals are changing TCP congestion avoidance/etc, are
Not as far as I know.
Its easily solvable - just drop the window sizes. In fact, I think the window
size increase/adaptive window size stuff would be much more useful for P2P over
LFN than average websites -> clients. General page HTTP traffic atm doesn't hit
window size before the reply has completed. Sites serving larger content
than HTML+images (say, Youtube, Music sites, etc) would've already given
this some thought and fixed their servers to not run out of RAM so easily.
Those are on a CDN anyway..
True. It would still be interesting to know if Microsoft were planning on patches all XP boxes to support this anytime soon though ;)