karn@mouton.UUCP (09/29/84)
Gateway: The ARRL Packet-Radio Newsletter
Electronic Edition
Volume 1, Number 4
September 25, 1984.
ARRL DIGITAL COMMITTEE MEETING
The ARRL Ad Hoc Committee on Amateur Radio Digital Communication met
in Newington, Connecticut on September 14, 15 and 16. [See issue 3 of
Gateway for background on the Digital Committee.] Twenty packet-radio
enthusiasts (committee members and observers) were present for the
meeting. The group addressed the state of amateur packet radio; link-
layer protocols; and approaches to packet-radio networking.
The following items summarize the results of the weekend's meetings.
DIGITAL COMMITTEE APPROVES AX.25 SPECIFICATION
During its meeting on September 15, the ARRL Ad Hoc Committee on
Amateur Radio Digital Communication approved a specification of the
AX.25 link-level protocol. This clears the way for submission of the
protocol to the ARRL Board of Directors for their approval.
The approved specification of AX.25 was written by Terry Fox, WB4JFI.
The protocol is essentially the same as that implemented on all of the
TNCs now on the air. Major changes from previous versions of AX.25
concern the poll/final (P/F) bit and multiple digipeaters. The
specification includes the P/F bit resolution proposed by Phil Karn,
KA9Q [See July, 1984 QEX]. The use of multiple digipeaters, as
permitted on most available TNCs, is now part of the "official"
protocol. Neither of these changes will make the specified protocol
incompatible with existing implementations.
The ARRL Board of Directors will consider AX.25 at its next meeting,
in October of this year. Board of Directors' approval will create a
published, international standard protocol for amateur packet radio.
With such a standard in existence, commercial manufacturers will be
able to design products for packet radio, confident that their
products will be compatible with others'.
23-CM BAND PLAN COMMENTS
The Digital Committee also considered the matter of UHF band plans.
After some discussion, the committee endorsed the ARRL VHF/UHF
Advisory Committee (VUAC) band plans for both 23 cm and 33 cm. The
committee noted that the Southern California Repeater and Remote Base
Association (SCRRBA) 23-cm band plan also includes sufficient
frequency allocations for digital communication. The digital
allocation in the SCRRBA band plan is not on the same frequency as
that in the ARRL band plan, but this should only cause slight problems
on links going into and out of Southern California.
PACKET-RADIO NETWORKING
The next step in the development of amateur packet radio is the
specification and implementation of a network-layer protocol. The
network layer is responsible for routing packets from their originator
to their addressee through a number of intermediate stations. There
are currently two network protocols being proposed for amateur packet
radio. To help decide which of these protocols is better for
amateurs, the Digital Committee had a "brainstorming" session. The
session provided an interesting look at the future of amateur packet
radio. Some of the points made during the discussion follow:
o A user should need only a TNC to access the
network.
o The network should be easy to operate.
o The network should support a wide variety of
media (HF, VHF, microwaves, meteor scatter,
etc.).
o The network should remain amateur in spirit.
o The network should work when commercial
networks are down; in the event of
emergency, the network should still be
available.
o Network users should be able to specify their
needs (for example, a choice of speed over
reliability).
o The network should be able to resist jammers.
o The network should be able to take advantage
of new stations when they come on the air,
and should not be crippled by stations
leaving the air.
o The network should support traditional
amateur operating modes, rather than forcing
amateurs to change their habits.
o Both real-time and store-and-forward
operation should be supported.
o Controlled broadcast, or alert should be
available.
o Roundtable operation should be supported.
o There should be a network directory available
on the air.
o Fault detection and isolation should be easy.
o The network should function well in various
geographical regions.
o There should be a mechanism for monitoring
the performance of the network.
o There should be no user "passwords" or other
"authentication."
o The network should be data transparent;
whatever data is sent from the source should
be received unchanged by the destination.
o The network should be global.
o The goals set for the network should be
attainable within the limited, amateur
resources available.
This is an ambitious set of goals. The Digital Committee feels that,
given the proper approach and efficient use of available resources,
these goals are attainable.
After the brainstorming session, the committee heard tutorials on the
two proposed network approaches, datagrams and virtual circuits. A
very brief summary of each approach follows.
Each packet sent through a datagram network is routed independently of
any preceding or following packets. This routing system is very
robust; if stations join the network, they can be immediately taken
advantage of. If stations leave the network (as long as a path exists
from the source station to the destination station) communications
will not be interrupted. There is a price which must be paid for this
robustness: each packet must contain extensive information needed for
routing. The datagram protocol being advanced for amateur packet
radio is the Defense Advanced Research Projects Agency (DARPA)
Internet Protocol (IP).
In a virtual-circuit network, a route is established between the
calling station and the called station at the beginning of a QSO.
This route is called a virtual circuit or a virtual connection, and is
used by all of the packets in the QSO. Only the first or call-setup
packet must contain complete routing information. Once the virtual
circuit is established, subsequent packets need only include a
virtual-circuit number. If one of the stations in the virtual circuit
becomes unable to handle traffic, another call-setup packet must be
sent, and another virtual circuit set up. Note that most packets will
not be call-setup packets, and will contain minimal routing
information. This is one of the advantages of the virtual-circuit
approach to networking. The virtual circuit protocol proposed for
amateur use is called AX.25, and is set forth by Terry Fox, WB4JFI, in
the Third ARRL Amateur Radio Computer Networking Conference
proceedings.
These descriptions do not fully describe the protocols under
consideration, nor do they capture the scope of the discussions that
took place during the Digital Committee meeting. After almost two
days of discussion, there were still proponents of virtual circuits,
proponents of datagrams, and a number of undecided individuals.
The Digital Committee has no desire to force a protocol upon any
group. Because of the number of people in the undecided camp and the
number of points in favor of each type of protocol the committee
decided that the packet community would best be served by a period of
experimentation, during which both datagrams and virtual circuits
would be implemented and tested.
Several members of the committee stressed the importance of
implementing the protocols in a transportable high-level computer
language. This would allow the programs that are developed to be run
on many computers. The people who are going to be doing the
programming decided to use the "C" programming language. In order to
test the two protocol implementations, they must operate in the same
environment. The test environment chosen by the committee is the
Xerox 820 computer, modified to use an HDLC chip and run at 4 MHz.
These decisions are not meant to stifle network protocol experiments.
They were intended to foster program transportability, and to provide
a common environment for testing protocol performance.
The identification of network objectives, the discussion of protocols,
and the formulation of an experimental approach are the first steps
toward the implementation of a world-wide packet-radio network. If
you are interested in the network protocol experiments, contact a
member of the ARRL Digital Committee [See Gateway #3.] and get
started!
EUROPEAN PACKET ACTIVITY
Several European observers were present for the ARRL Digital committee
meeting. They were: Hanspeter Kuhlen, DK1YQ, from AMSAT-DL; Ian Wade,
G3NRW, from the British Amateur Radio Teleprinter Group (BARTG); John
Sager, G8ONH from the RSGB; and Alan Jones, G8WJM, from the Cambridge
Computer Labs. The primary duty of these observers was to learn about
the state of amateur packet radio in the U.S., but they also provided
us with some news about packet radio overseas.
Germany: In West Germany, several TAPR TNCs have made it through
customs into the hands of the new Bavarian Packet Radio Group. There
should be twenty or more packet stations on in West Germany by the
time you read this. Unfortunately, there are some German regulations
that will slow the development of packet networks; no two repeaters
may be linked together, and no third-party traffic may be passed.
Hanspeter was confident that these hurdles could be overcome. For
more information on the Bavarian Packet Radio Group, contact:
Thomas Kieselbach, DL2MDE
Narzissenweg 10
D-8031 WESSLING
W-Germany.
England: The RSGB, in conjunction with BARTG, has formed a Packet
Radio Working Party. The aims of the group, chaired by Dr. Dain
Evans, G3RPE, are : to clarify what is meant by Packet Radio in the
amateur context; to determine what form Packet Radio is likely to take
in the UK, and to compare this with activity in other countries; to
determine how packet repeater proposals are to be handled; and to
determine the requirements for possible changes of the license
regulations to exploit the capabilities of Packet Radio to the full.
The Working Party has held two meetings, and adopted AX.25 as a
standard for the UK. The BARTG newsletter Datacom is a good source of
information on packet radio in the UK. Write:
Ian Wade, G3NRW
7 Daubeney Close
Harlington
Dunstable
Bedfordshire
LU5 6NF
UK.
There are already thirteen stations running AX.25 packet radio in the
UK, and several dozen others are actively interested. Expect to hear
UK packet stations on Oscar-10 or HF any day now.
Via DATACOM
PACKET RADIO ON JAPANESE SATELLITE
Sometime between 1985 and 1987, the Japan Amateur Radio League (JARL)
and JAMSAT will be launching the first all-Japanese amateur satellite,
JAS-1. Along with a Mode-J transponder, JAS-1 will carry a store-and-
forward packet-radio transponder. The packet-radio transponder will
operate at 1200 bauds, FSK, with an uplink in the 2-meter band, and a
downlink in the 70-cm band. The designers of the satellite have
agreed to use the AX.25 link-layer protocol, strengthening the
protocol's standing as an international standard.
PHASE III C AND PACKET RADIO
If the amateur satellite fraternity is able to fund the launch of a
Phase-III C satellite, that satellite might carry a packet radio
transponder. The ability of the satellite to carry such a transponder
will be regulated by three factors: kick motor capacity, space
available, and power available. If the proposed steam-propelled kick
motor is used, there should be both the motor capacity and space
available to launch a digital transponder. The power-consumption
limits placed on the design of the transponder would make most of the
existing technology useless, since existing high-level data link
control (HDLC) chips draw too much current for satellite application.
The use of software to transmit and receive packets through CMOS
serial I/O devices is under consideration. A packet transponder for
Phase-III C is not a high-priority item for AMSAT-DL, but it is under
consideration. Via DK1YQ
PACKET COLUMN IN RADIOSPORTING
Yuri Blanarovich, VE3BMV is hoping to start a new amateur-radio
magazine called Radiosporting. He plans to make it "for active
radioamateurs, filled with timely information that would be of
interest to many involved in operating and competitive aspects of
amateur radio." One of the columns in Radiosporting will be devoted
to RTTY, AMTOR and packet radio. If you are interested in subscribing
to Radiosport, or contributing to its packet column, contact:
RADIOSPORTING
Box 65
Don Mills, ON, M3C 2R6
CANADA.
MORE NEWS ON HIGH-SPEED PACKETS
We received the following letter from Richard Bisbey II, NG6Q:
"The Information Sciences Institute Amateur Radio Group (WB6MXZ) has
been on the air with a 56 Kb packet radio system since December, 1983.
The equipment consists of 8088-based controllers using the Zilog 8530
SCC chip and frequency agile 10-watt FSK transmitters and receivers.
The controller supports serial, parallel, and Ethernet connected
devices. Assembled controllers cost approximately $650. The system
uses standard INTERNET (IP/TCP) protocol, and in addition to
supporting simple link level connections, supports internetworking as
well as numerous high-level protocols such as TELNET, File Transfer
(FTP), Mail (SMTP), Multi-Media Mail (MMM,MPM), Graphics (GP), Packet
Voice (NVP), and Remote Virtual Disk (RVD). The hardware and software
can support data rates as high as 1 Mb, well in excess of the current
amateur limit of 56 Kb.
"Previous packet radio accomplishments by ISI amateurs include a March
1982 demonstration of transcontinental packet radio internetworking
between an aircraft flying above Los Angeles and a fixed station in
Virginia, and a November, 1982, demonstration of intercontinental
internetwork packet radio communications between Los Angeles,
California and The Hague, Netherlands using Intelsat-4A. The ISI
group is currently developing a low-cost spread-spectrum system with
capabilities similar to the current non-spread system."
SEATTLE, WA PACKET CLUB
The Seattle-Tacoma area packet radio users recently decided to become
a formal organization. The actual formation of the club will take
place October 13, 1984, at 1300 Pacific Time in the Boeing Employees'
Amateur Radio Society meeting house. The club constitution will be a
slightly modified version of the NEPRA constitution. The first large-
scale goal of the club will be linking of the Seattle-Tacoma-Everett
area to Vancouver, BC; Portland, OR; Spokane, WA; and Moscow, ID.
Via KD7UW
PACKET RADIO IN GEORGIA
The Georgia Radio Amateur Packet Enthusiasts (GRAPES) club was formed
on September 14. Their network name? GRAPEVINE, of course. They are
interested in setting up repeaters to link Georgia with the Carolinas,
Florida, Alabama and Tennessee. They would like to hear from
packeteers in those areas. One possibility that they are examining is
a repeater location on Brasstown Bald, a 4,784-ft mountain on the
northern Georgia border. For information, contact:
Dennis Barrow, WB4GQX
Rte 7 Heard Road
Cumming, GA 30130. Via W4RI
ABSTRACTS
As space permits, and interesting articles come to our attention,
Gateway will print abstracts of articles found in other journals and
newsletters. If you know of an article that should be abstracted,
drop us a note and a copy of the article.
"HF Packet Frequency Specification," by John
Langner, WB2OSZ; NEPRA Packetear, Issue 14. This
one-pager addresses the problem of frequency
specification for FSK stations on HF. It proposes
that the radio frequency midway between the mark
and space frequencies be used when discussing the
operating frequency of such stations.
"Routing Strategies in Computer Networks," by
Hsieh and Gitman; Computer, June, 1984. This
article addresses the question of routing. It
sets forth some algorithms for determining the
best route from one node to another, and discusses
the application of these algorithms to various
types of computer networks. Since it addresses
routing in both datagram and virtual-circuit
networks, this article is particularly interesting
to people concerned with amateur packet-radio
networking.
REPRODUCTION OF GATEWAY MATERIAL
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provided that the original contributor is credited and Gateway is
identified as the source.
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President
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