Re: The file that kills linux tcp

Matti Aarnio (matti.aarnio@tele.fi)
Wed, 5 Feb 1997 13:56:33 +0200 (EET)

...
> > Arnt> Here's the part of a packet trace. On one end
> > Arnt> (mail.linpro.no, 2.0.28), I did
> >
> > Arnt> $ ttcp -t -p 5007 -b 51200 thud.freebsd.org <
> > Arnt> xppp1B-x86-ELF.gz
> >
> > Arnt> and on the other (thud.freebsd.org, freebsd 3.0-current):
> >
> > Arnt> $ ./ttcp -r -p 5007 -b 51200 | tar ztf -
> >
> > Arnt> and the resulting output shows clearly that something is
> > Arnt> wrong, but not, to me, what. (I get essentially the same
> > Arnt> behaviour as this when both ends run linux 2.0.28, btw.)
> >
> > [snip]
...
>
> 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).

That was a timer problem in TCP code way back then.
I did notice it sometime around 1.3.5x, and gave enough
traces for Alan to figure it out. Arnt has 2.0.28, on
which the 16 second timeout horizon does not touble anymore.
The default connection timeout for TCP is (as I recall)
30 minutes (well, at least SEVERAL minutes.)

> This is important because wireless interfaces may be temporarily out of
> radio coverage and lose network connectivity for that time period.
>
> In Mobile-IP, a linux machine can move from one IP network to another IP
> network. Will the consequent change of routes affect linux TCP in any
> adverse way? (for instance timing, state of TCP connection)
>
> Is there any documentation on the net regarding the implementation of
> Linux's TCP/IP stack, particularly the TCP portion?

In the KHG ? Apparently not..

http://www.redhat.com:8080/HyperNews/get/khg.html

> Thanks,
> CCFoo
>
> More info about a Mobile-IP implementation for Linux can be obtained from
> http://mip.ee.nus.sg
> Another implementation is available in
> http://anchor.cs.binghamton.edu/~mobileip

/Matti Aarnio <matti.aarnio@tele.fi>