Re: The file that kills linux tcp

Alan Cox (
Wed, 5 Feb 1997 22:32:11 +0000 (GMT)

> What happens to linux TCP if network connectivity is temporarily lost,
> let's say for a few seconds? Existing TCP connections seem to die off
> when network connectivity is lost for more than 15 seconds, and never
> recover onwards (tested with 1.3.55, not sure newer kernels exhibit this
> problem or not).

They will back off to up to 2 minutes. This is correct behaviour according
to the specs.

> This is important because wireless interfaces may be temporarily out of
> radio coverage and lose network connectivity for that time period.

There is a wireless extension someone has been playing with called SNOOP.
I dont have the paper handy, but the idea is basically to snoop on the
node before the radio hop to avoid long paths back when frames are lost
on an unreliable radio end node.

TCP itself doesnt do well above 10% packet loss and gets nasty above 30%.
This is mainly because it doesn't have any way to tell congestion from
other forms of loss. A radio link with 20%+ loss should be using a local
reliable transfer scheme or some kind of FEC such as golay or viterbi