I've used 14.4 modems, nullmodems locked at 38400, and a 56kbps modem with
my NetBSD box, all without a hint of problem.  I have used both PPP and
SLIP.  I've also used NetBSD 1.3, 1.3.3, and 1.4.  I have only run NetBSD
on i386 hardware.  I haven't needed to set anything out of the ordinary;
and although I have some experience setting up networking connections with
TCP/IP (with Amigas), all of my UNIX networking experience has been in the
setting up of these dial-up (and nullmodem) connections.  There were no
speedbumps or headaches for me.  I have connected to 2 or 3 different
ISP's, as well as across the room to an Amiga.  ``It just works.''

With the 56kbps modem, locked at 115kbps raw serial speed, I have seen
throughput up to around 10K/sec (with fairly comrpessible data).

So, you say that it's definitely a NetBSD problem; I say that it probably
isn't, because it shouldn't be that hard to get good performance out of
NetBSD.  Even I did it.  (^&

Things (perhaps obvious things) to try:

.) Switch modems and/or phone lines (you said that you had a LINUX box,
   and imply that the LINUX box performs better).

.) Install LINUX where you have NetBSD, and/or vice versa.  See if the
   problems stick to the hardware, or follow the OS.

.) Do a clean NetBSD install on the original machine.

.) Try using SLIP, just for giggles.  (Note, until recently, NetBSD's SLIP
   was a little brain-dead about MTU's, but that's fixed as of 1.4, I
   believe---I haven't used SLIP in some time, though.  The brain-damage
   wouldn't hurt in most cases, but caused me some grief when & where I
   needed SLIP.)

.) Try a lower serial rate; even if your modem is rated to handle 115kbps
   serial speeds.  This is grasping at straws, but you never know...

.) Try nullmodeming the two computers together.  See how fast you can get
   it to go; see if the connection is faster one way than the other.

.) Completely delete your NetBSD box's PPP configuration (but save a
   backup for comparison, especially in case this idea leads you
   anywhere).  Then try redoing it from scratch.  Only use 
   examples/references that are installed as part of NetBSD, and make a
   completely straightforward config (don't turn on any extra options, no
   matter how innocuous or beneficial they may seem).

   (IN PARTICULAR, you might try for a fairly minimal modem-init string.)


NetBSD should be able to get just about every bit of speed that your modem
supports, and it shouldn't be hard to do.  If you are experienced with
setting up dialup accounts & with UNIX, then whatever you're missing is
probably right under your nose, and you'll slap your forehead when you
find it.  (^&

Good luck, and please post to the NetBSD-help@netbsd.org mailing list when
you find out what's wrong.


  "I probably don't know what I'm talking about."  --rkr@rkr.kcnet.com