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1994-11-13
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Date: Fri, 3 Jun 94 04:30:01 PDT
From: Advanced Amateur Radio Networking Group <tcp-group@ucsd.edu>
Errors-To: TCP-Group-Errors@UCSD.Edu
Reply-To: TCP-Group@UCSD.Edu
Precedence: Bulk
Subject: TCP-Group Digest V94 #108
To: tcp-group-digest
TCP-Group Digest Fri, 3 Jun 94 Volume 94 : Issue 108
Today's Topics:
help with setting MSS
Linux SCC drivers
Send Replies or notes for publication to: <TCP-Group@UCSD.Edu>.
Subscription requests to <TCP-Group-REQUEST@UCSD.Edu>.
Problems you can't solve otherwise to brian@ucsd.edu.
Archives of past issues of the TCP-Group Digest are available
(by FTP only) from UCSD.Edu in directory "mailarchives".
We trust that readers are intelligent enough to realize that all text
herein consists of personal comments and does not represent the official
policies or positions of any party. Your mileage may vary. So there.
----------------------------------------------------------------------
Date: Thu, 2 Jun 94 13:46:13 PDT
From: Glenn Elmore <glenne@sr.hp.com>
Subject: help with setting MSS
To: tcp-group@ucsd.edu
Here in northern California, we are in the process of replacing 10
MHz KISS Tiny2 TNC2s with Ottawa PI2 cards to drive my higher speed 904
MHz radios. With some assistance from Dave Perry, VA3DP, I've been
successful in hacking PI.C to allow the cards to provide internal
RxClock recovery but to run the DPLL with an external clock input
instead of the BRG. This allows for an extra factor of 4 in speed. The
cards successfully drive the radios at 230.4 kbps when the DPLL is sourced
from the on-board oscillator.
Operation with JNOS 110C has been something of a problem though.
While I find that aggragate throughput of >200 kbps is possible with
long pings and a repetition rate just a bit longer than the RTT, data
throughput with FTP or SMTP is pretty disappointing. Increasing the
radio speed from 38.4 kbps to 230.4 kbps only results in best FTP
throughput numbers going from about 3.5 kchar/sec to 5.5 kchar/sec.
In order to better understand the problem, I went back to an Ethernet
card and compared JNOS to Clarkson FTP. On the same host&file that
Clarkson transfers at 50 and 140 kchar/sec kbps (386DX33 host) JNOS only
does 4.5kchar/sec and 7 kchar/sec for GET and PUT respectively.
In poking around, I notice that in spite of tcp mss=1540 and tcp
window of N*mss, n=1-8, and an attached card driver with an MTU of 2048,
the maximum packet size actually transmitted is 512 bytes. I've found
nothing that I can do from autoexec.nos that makes it larger. It
appears that 512 bytes is the negotiated value. I see in tcp.h:
#define DEF_MSS 512 /* Default maximum segment size */
What am I not doing right that is preventing larger than default MSS and
better throughput? Could someone with a well-performing Ethernet
configuration with JNOS give me some hints? I suspect that if I can
make Ethernet work well, I can also make the radios&PI cards work
well.
Thanks,
Glenn Elmore n6gn
amateur IP: glenn@SantaRosa.ampr.org
Internet: glenne@sr.hp.com
------------------------------
Date: Fri, 03 Jun 1994 12:53:36 +0100 (MET)
From: Joerg Reuter DL1BKE <DL1BKE@melaten.ihf.rwth-aachen.de>
Subject: Linux SCC drivers
To: tcp-group@UCSD.EDU
: I have a file of something that claims to be a beta of a generic SCC driver for
: the Linux kernel, written by PE1NNZ. The "INSTALL" notes say that it is
: implemneted as part of the kernel and was tested with several different
: software packages, including WAMPES and KA9Q Linux ports. However, the author
: says that he only tested it with the OptoSCC hardware.
:
You can get a newer version from me (1.4 <still> beta). It works
with the BayCom USCC card now and does not patch serial.c anymore
(serial.c changes with every kernel patchlevel, I hope tty_io.c does
NOT!). The code is based on the well-known PE1CHL-driver and ported
to Linux by Guido PE1NNZ. I added some modifications from
Rene DG0FT (for the BayCom USCC) and the KISS-mode settings.
I`ll try to upload the driver to the "incoming" directory on UCSD.EDU
next week.
vy 73,
--
Joerg Reuter Internet: dl1bke@melaten.ihf.rwth-aachen.de
ampr-net: dl1bke@db0pra
ax25 : DL1BKE @ DK0MWX.DEU.EU
------------------------------
End of TCP-Group Digest V94 #108
******************************