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1994-11-13
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Date: Thu, 14 Jul 94 04:30:07 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 #148
To: tcp-group-digest
TCP-Group Digest Thu, 14 Jul 94 Volume 94 : Issue 148
Today's Topics:
ARRL DIG COMM CONF. NEWS Rev 7/12/94
ARRL DIGITAL COMM CONF UPDATE BULLETIN 7/12/94
Bridge vs. Repeater
Managing MSS and Window; IP encapsulation (3 msgs)
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: Wed, 13 Jul 94 21:03:11 CST
From: edf@bbs.wd0hxt.ampr.org
Subject: ARRL DIG COMM CONF. NEWS Rev 7/12/94
To: tcp-group@UCSD.EDU
----- Forwarded message -----
When you think about it, unless you've got a clear freq of your own
and don't have to share it with lots of other packet stations, a beam
is discourtious UNLESS (!) it is also cophased with an omni. Why?
Beacuse the beam's back-door rejection will allow your station to keyup
on top of other stations, resulting not only in increased band congestion
but also avoidable interference that could lead to disconnections.
It's easy to cophase an omni to a beam. Just run a 1/4 wavelength of
75 ohm coax to each 50 ohm antenna and to the transmitter 50 ohm line.
Yes, beam (and omni) power output is 1/2 of what you get if just one
antenna were online, but a good beam will make up for that and the omni
will let you hear stations instead of keying up on top of them.
Just some Month of May Thoughts ... :)
73 de Ron KC6RCO@KC6RCO.#ECMN.MN.USA.NA Internet: ronm@kc6rco-nrom.ampr.org
----- End of forwarded message -----
-------------------------------------------------------------------------------
de Ed Fairbairn WD0HXT
internet/amprnet = edf@bbs.wd0hxt.ampr.org
pbbsnet = wd0hxt@wd0hxt.#msp.mn.usa.na
------------------------------
Date: Wed, 13 Jul 94 21:13:38 CST
From: tcp-info@bbs.wd0hxt.ampr.org
Subject: ARRL DIGITAL COMM CONF UPDATE BULLETIN 7/12/94
To: tcp-group@UCSD.EDU
----- Forwarded message -----
ARRL 13th ANNUAL DIGITAL COMMUNICATIONS CONFERENCE AUGUST 19-21
Do you operate a Digital mode (maybe Pactor, Packet, GTOR or AMTOR) now?
Do you find it difficult to keep up with the latest Digital technology?
Would you like to know more about Digital modes?
If you answered "yes" to any of these questions, then you should attend the
13th Annual ARRL Digital Communications Conference. Read on ...
The Conference will be held on August 19 - 21, 1994 at the Thunderbird
Convention Center, 2201 East 78th Street in Bloomington, Minnesota.
Accomodations are available at the adjacent Thunderbird Hotel, at the many
Hotels and Motels located within a short distance, and also at several area
RV\camper campgrounds.
Enjoy a weekend of fun learning about the latest developments in TCP/IP,
PACTOR, AMTOR, PACTOR-II, CLOVER, G-TOR, PACKET, DSP, and imaging. Participate
in the nine forums about DSP, new HF modes, TCP/IP, VHF/UHF networking, BBS
SYSOP issues and more. A glance at the program (attached) will show many
forums that will catch your interest!
One of the highlights of the conference will be the presentation of 18
technical papers on the many aspects of digital communications throughout the
day on Saturday. A list of papers is attached. You will receive a copy of
all papers presented.
Many demonstrations of the latest in hardware and software will be presented.
When you leave, you will have an in-depth understanding of the latest digital
communications advancements and techniques. The Saturday evening Technical
Showcase will feature TAPR Special Interest Group meetings for BBS SYSOPs
and on VHF/UHF network building and a nearly-mathless presentation of the
design and implementation of DSP software for a high-performance HF DSP
modem based on the $99 TI DSK DSP evaluation module by Johan Forrer, KC7WW.
The Hospitality Room will provide the place to meet old friends ... and make
new ones. At the Saturday luncheon you will get to know "who's who" in
digital communications. Meet the Engineering staff of manufacturers like
Kantronics and Timewave Technologies. The optional Saturday evening diner
will provide another opportunity to make new friends.
If you want a break from the Conference, the Mall of America, with hundreds
of unique stores, is located within easy walking distance. Your family will
enjoy Knott's Camp Snoopy theme park inside the Mall. The renowned Minnesota
Zoo is only a short drive away.
The Conference registration fee is $45 per person, which includes admission to
all Conference activities, a luncheon buffet and a copy of the technical
papers. An optional Saturday evening buffet is $20 per person additional.
Registration deadline is August 12th.
For more information about the Conference or special Airline and Motel
discounts call or write:
ARRL Digital Communications Conference
C/O Paul Ramey WG0G
16266 Finland Avenue
Rosemount, MN 55068
Packet: WG0G@WA0CQG.#MSP.MN.USA.NA
Telephone: (612) 432-1640
Internet: PRAMEY@RAM.NET
The host organization for the 1994 ARRL Digital Communications Conference is
the TwinsLAN Amateur Radio Club.
See YOU at the Digital Communications Conference August 19-21!
------------------------------------------------------------------------------
13th ANNUAL ARRL DIGITAL COMMUNICATIONS CONFERENCE
PRELIMINARY PROGRAM
Friday, August 19
TIME ROOM EVENT
Noon - 6 PM TBD ARRL "Future Modes"
Committee meeting.
Noon - 6 PM TBD ARRL "219-MHz" Committee
meeting.
4 - 10 PM Menominee Conference check-in.
6 PM - 11 PM Menominee Hospitality & Demo area open
Saturday, August 20
TIME ROOM EVENT
6:30 - Noon Menominee Hospitality & Demo area open
7:00 - Noon Menominee Conference Check-in.
8:00 - 8:15 AM Miami Conference "Welcome"
8:30 - 10:00 AM Miami Technical Paper Presentation
8:30 - 10:00 AM Yakima Forum - Developments in DSP
For the Amateur.
8:30 - 10:00 AM Shoshone Forum - TCP/IP - What's next?
10:00 - 10:15 AM All Break
10:15 - 11:45 AM Miami Technical Paper Presentation
10:15 - 11:45 AM Yakima Forum - ARRL Committee
Updates: "Future Modes":
Moderator - Paul Rinaldo W4RI
and "219-MHz Networking":
Moderator - Tod Olson K0TO"
10:15 - 11:45 AM Shoshone Forum - Digital Data (Voice
and Image) Transmission
Method Developments.
11:45 - Noon AM All Break
Noon - 1:00 PM Miami Buffet Luncheon (Included)
1:00 - 5:30 PM Menominee Hospitality & Demo area open
1:15 - 2:45 PM Miami Technical Paper Presentation
1:15 - 2:45 PM Yakima Forum - High-Speed (above
1200 baud) data transfer
methods and networking
techniques.
1:15 - 2:45 PM Shoshone Forum - HF Data Transmission
Methods - An Over-view of
Current Modes and What's
Coming Next.
2:45 - 3:00 PM All Break
3:00 - 4:30 PM All Continuation of all sessions
5:30 - 6:30 PM Miami Buffet Diner (Optional)
7:00 - 11:00 PM Menominee Hospitality & Demo area open
7:00 - 10:00 PM Miami Tucson Amateur Packet Radio
(TAPR) Presents Special
Interest Groups:
- Packet BBS SYSOPs
- VHF/UHF Network Building
7:00 - 10:00 PM Yakima American Digital Radio
Society (ADRS)presents a
technical presentation:
"A Low Cost DSP Modem for HF Digital
Experimentation" by
Johan Forrer, KC7WW
Sunday, August 21
TIME ROOM EVENT
8:30 - Noon Menominee Hospitality & Demo area open
10:00 - 11:00 Menominee Conference wrap-up and close.
----------------------------------------------------------------------------
13th ARRL Digital Communications Conference Proceedings
1. A Proposal for a Standard Digital Radio Interface
Jeffrey Austen, K9JA
2. Automatic Packet Reporting System (APRS)
Bob Bruninga, WB4APR
3. Broadcast, UI and un-connected protocols-the future of Amateur Packet Radio?
Paul Evans, W4/G4BKI
4. Packet, GPS, APRS and the Future
Paul Evans, W4/G4BKI
5. Computer Networks in Africa: From Utopian Discourse to Working Reality
Iain Cook
6. A Low Cost DSP Modem for HF Digital Experimentation
Johan Forrer, KC7WW
7. G-TOR: The Protocol
Mike Huslig, Phil Anderson, Karl Medcalf and Glenn Prescott
8. GMON-a G-TOR Monitoring Program for PC Compatibles
Richard Huslig and Phil Anderson, W0XI
9. A Theoretical Evaluation of the G-TOR Hybrid ARQ Protocol
Glenn E. Prescott, WB0SKX, And Phil Anderson, W0XI
10. On Fractal Compression of Images for Narrowband Channels and Storage
W. Kinsner, VE4WK
11. Fast CELP Algorithm and Implementation for Speech Compression
A. Langi, VE4ARM, W. Grieder, VE4WSG, and W. Kinsner, VE4WK
12. Wavelet Compression for Image Transmission Through Bandlimited Channels
A. Langi, VE4ARM, and W. Kinsner, VE4WK
13. ROSE X.25 Packet Switch Status Update
Thomas A. Moulton, W2VY
14. A Primer on Reliability as Applied to Amateur Radio Packet Networks
T.C. McDermott, N5EG
15. FSK Modem with Scalable Baud Rate
Wolf-Henning Rech, N1EOW, and Gunter Jost, KD7WJ
16. MacAPRS: Mac Automatic Packet Reporting System-A Macintosh Version of APRS
Keith Sproul, WU2Z, and Mark Sproul, KB2ICI
17. Formation of the TAPR Bulletin Board System Special Interest Group
David A. Wolf, WO5H
18. How Amateur Radio Operators Can Emulate an HF ALE Radio
David R. Wortendyke, N0WGC
19. A Preview of HF Packet Radio Modem Protocol Performance
Teresa Young, Stephen Rieman, David Wortendyke, N0WGC
---------------------------------------------------------------------------
Rev. 7/12/94
[EOF]
----- End of forwarded message -----
------------------------------
Date: Wed, 13 Jul 1994 10:57:18 -0500
From: David Rush <rush@erg.sri.com>
Subject: Bridge vs. Repeater
To: tcp-group@UCSD.EDU
Steve said:
>The argument that a router would be better than a repeater is off a
>bit, as it assumes the user wants to route. Some may just want to chat,
>or hook up with a (gulp) BBS... In this case the repeater attempts to
>solve the hidden node problem, but so could DAMA, for a lot less.
Well, isn't there a bit more than that? Even if two nearby users don't
care about routing, a router can keep two local users from sucking up
bandwidth... I'll share this with the group...
I said:
>> Yeah, presumably cross- or multi-banding would probably make the most
>> sense (easiest). All of the stations in a "mutually hearable area"
>> would share one freq on one band. The stations in a different
>> "mutually hearable area" (on the other side of the mountaintop
>> router) would share a different freq on a different band.
Then Gerry said:
>So, why not use a wide area machine on 2 in-band frequencies, using the
>regen? It's a "repeater" to the FM guys, simple to maintain, simple to
>build, simple to install. Find a good {tower/building top/mountain top}
>and put it up to cover as much of the are as possible. If you THEN have
>an area that's not adequately covered, put up another regen in that area
>on the reverse channel, or route over to that remote area.
Because traffic between two stations on the left side of the mountain would
generate useless traffic (thru the regen) on the right side of the mountain.
(Sucking up bandwidth.) A router could decide which packets need to cross
over the mountain, but otherwise stay quiet.
Assuming that nobody even cares about routing in this case, what I'm
really proposing is a bridge (to use Ethernet terminology) between
the two sides of the mountain, rather than bit regenerator.
And when we say "bit regenerator", it's functionally equivalent to an
Ethernet repeater, aren't we?
David
---------------------------------------------------------------
David Rush, SRI International, Leavenworth, Kansas 913-682-9101
rush@erg.sri.com, david@n0oxh.ampr.org
------------------------------
Date: Wed, 13 Jul 1994 17:47:06 +0100
From: "Brian A. Lantz" <brian@lantz.cftnet.com>
Subject: Managing MSS and Window; IP encapsulation
To: TCP Group Mailing List <tcp-group@ucsd.edu>
On Wed, 13 Jul 1994, Phil Karn wrote:
> Can people tell me whether the receive-side change has made it yet to the
> NOS variants that people are using as wormhole gateways? Or do I need
> to keep 94 on the transmit end a little longer to avoid compatibility
> problems?
>
TNOS, based on an earlier version of JNOS, only checks for receiving 94.
It's funny that this came up today, since I was looking at a couple of
different IPIP listings (including xNOS) to see what differences there
were, since I'm looking into figuring out the patches needed to do it
under Linux.
Phil's is the only one I KNOW about that checks also for a '4'.
-----------------------------------------------------------
Brian A. Lantz/KO4KS brian@lantz.cftnet.com
REAL PORTION of Microsoft Windows code:
while (memory_available) {
eat_major_portion_of_memory (no_real_reason);
if (feel_like_it)
make_user_THINK (this_is_an_OS);
gates_bank_balance++;
}
------------------------------
Date: Thu, 14 Jul 1994 02:32:33 -0700
From: Phil Karn <karn@qualcomm.com>
Subject: Managing MSS and Window; IP encapsulation
To: A.Cox@swansea.ac.uk
IPNG is, in my opinion, years in the future. Beyond my current
horizon, anyway. And even if it wasn't, it's still worth doing for
IPv4. One situation in particular could really benefit: tunnel
encapsulation. A maximum sized packet being encapsulated could easily
generate two fragments, one maximum sized and the second very small.
Path MTU discovery could help avoid this.
What do you mean by MTU discovery breaking? I know that many routers
don't yet indicate the interface MTU when they bounce a too-large
packet with DF set. I plan to handle that by stepping through a table
of common MTU values.
My only concern about path MTU discovery is exactly how often I should
try to increase the MSS to probe for a possible route change after it
has been decreased. Given the relatively static routes on the net I
would probably say "rarely", but I don't like hard-coded values in
protocols that are supposed to be self-scaling.
Phil
------------------------------
Date: Thu, 14 Jul 1994 10:50:44 +0200 (BST)
From: A.Cox@swansea.ac.uk (Alan Cox)
Subject: Managing MSS and Window; IP encapsulation
To: karn@com.qualcomm (Phil Karn)
> What do you mean by MTU discovery breaking? I know that many routers
> don't yet indicate the interface MTU when they bounce a too-large
> packet with DF set. I plan to handle that by stepping through a table
> of common MTU values.
A measurable number of low grade routers simply 'lose' oversized packets. I've
had several network problems I have chased down to MTU discovery on SYS5.4
machines failing because routers on the way simply ate any oversized frames
without sending back an ICMP or sending back an icmp with a hop count of 16
that never arrives back. I suppose the answer to this is 'tcp discovery off'
as a KA9Q command 8).
> My only concern about path MTU discovery is exactly how often I should
> try to increase the MSS to probe for a possible route change after it
> has been decreased. Given the relatively static routes on the net I
> would probably say "rarely", but I don't like hard-coded values in
> protocols that are supposed to be self-scaling.
An off the cuff suggestion would be when you see a significant shift in
round trip time for a measurable duration being one. Another clue would be
the hop count on received tcp frames changing, and the third obvious one is
if your local route table shifts.
Alan
------------------------------
End of TCP-Group Digest V94 #148
******************************