Subject: Re: NetBSD and cable modems
To: None <>
From: Wolfgang Rupprecht <>
List: tech-net
Date: 01/04/1999 11:36:02 (Matthias Scheler) writes:
> Which bandwidth do the modems offer? And are the acting as bridges or
> as routers?

The cable modem I have, a LanCity LCP does a claimed 10 Mbits/sec on
both the TV cable side and the ethernet side.  I've personally seen
over 5Mbits/sec ftp's.

The LanCity "modem" is a filtering bridge.  I wish they'd have taken
the extra effort to put in routing code.  On networks like here in
Fremont California we have > 8000 machines on one bridged ether.
There is an abundance of broadcast chatter.  I'm seeing >20 broadcasts
per sec during some parts of the day.  Real routing code would work
wonders at quieting this crap down.

Not all cable modems are bridges.  I understand cable modems like the
"*surfer" product from Motorola are real routers. (Although they use
different modulation techniques and are quite a bit slower.)

In regard to the original posters question about SMC de* TULIP cards
and overruns, I don't see any when talking to the cable modem.  The
only overruns I ever see is when I'm doing lots of disk I/O by
saturating the Adaptec card (wide/fast) and saturating the local
100base-TX ether.  Then I see the de driver shift into lower gear as

	Dec 18 21:33:07 capsicum /netbsd: de1: abnormal interrupt:
	      transmit underflow (raising TX threshold to 96|256)

	Nov 28 20:46:19 capsicum /netbsd: de1: abnormal interrupt:
	      transmit underflow (raising TX threshold to 128|512) 

       Wolfgang Rupprecht <>