I've put new header compression code on athos.rutgers.edu:/pub/linux.
slhc.readme will give details.  The code is in slhc.tar.  It contains
Van Jacobson header compression code, diffs to the original 0.99pl10
kernel to add the code, and also to fix various bugs and performance
problems in TCP that caused me trouble in using SLIP.

There's also a program for printing statistics from SLIP and the
header compression code: slipinfo.tar.Z.  This is based on code stolen
from ps to read from /dev/kmem.  It assumes that
/usr/src/linux/tools/system has symbols for your kernel.  I trust that
at some point people who know how to do so will put more network
statistics into /proc.  slipinfo gives only SLIP-specific statistics.
The base TCP code doesn't seem to maintain much in the way of
statistics.  A full array of error counters would have been helpful
for debugging.  slipinfo knows about the details of various kernel
structures, so it's only likely to be useful if you're using my
patches.  (Of course it wouldn't be hard to adjust to a standard SLIP
implementation.)

I'm not sure whether to put these on tsx-11, etc. or not.  It appears
that people are hard at work on a revised version of net-2.  I hope
all of this will appear there.  However for the moment if you want to
use SLIP, this will make a big difference to its usability.  (It also
improves retransmission and ack strategies, which could help for
Ethernet if you're having certain kinds of problems.  However I
haven't tried it with an Ethernet.  This is unlike the previous
version, where certain problems were hacked around in a way that would
be likely to cause trouble for Ethernet.)