[e2e] [SPAM] opening multiple TCP connections getting popular

Michael Welzl michael.welzl at uibk.ac.at
Wed Aug 29 23:18:15 PDT 2007

On Wed, 2007-08-29 at 22:44 +0100, Jon Crowcroft wrote:
> 1.  I think one good thing about Bob Briscoe's rant about the fairness religion 
> is that it does question if we should be worrying about it so much - 


> I personally think that the net mainly survives because
>  access links in most the world are slower than the core and servers 
> (and p2p systems) are balanced: if you like, 
> Van's idea of packet conservation applies at the higher level of 
> file transfer/upload v. download, explicitly so in bittorrent's tit-for tat
> system.

That raises an interesting question: given the fact that different
experimental high-speed TCP variants are already widely deployed,
and given the fact that the Window Scaling option is not widely
used (*), what would happen to the net in the scenario that you
sketched of Japan, where fibre to the home is becoming more common,
if people would start using the Window Scaling option?

Is the net only stable because either your personal access
link or the lack of this option limits your sending rate anyway?


(*) - cf. http://www.icir.org/tbit/TCPevolution-Mar2005.pdf - and
we also persistently saw this behavior in PlanetLab

Does anybody know if there's a generally known, agreed upon reason
for not using Window Scaling? Google tells me that some broken
routers can't handle it... but, interestingly, Wikipedia (via
google :-) ) tells me that, since kernel version 2.6.8, the option
is enabled in Linux by default, and that it's used (by default? don't
know) in Vista...  so what, are we already heading for trouble?

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