     Frequently Asked Questions
     for
     Amateur Packet Radio

     Version 1.5
     4 October 1991

     This document is for unlimited distribution.

     Please send corrections and additions to Steve Schallehn
     (steve@matt.ksu.ksu.edu).  The Packet Radio FAQ's will be posted
     on a monthly basis to rec.radio.amateur.packet.  The current
     version of this document is available via anonymous FTP at
     ftp.cs.buffalo.edu.


1.0  Basic Packet Radio Information
     1.1  What is packet radio?
     1.2  What is amateur radio?
     1.3  What can I do on packet radio?
     1.4  Why packet over other digital modes?
     1.5  What elements make up a packet station?
               TNC (Terminal Node Controller)
               Computer or Terminal
               A radio
     1.6  What do you mean we can all use the same channel?
     1.7  What is AX.25 ?
     1.8  Definitions:  Commonly used terms in Amateur Packet
          Radio
     1.9  Do's and Don'ts : Rules and Regulations

2.0  Computing Network Resources for Amateur Packet radio
     2.1  What Newsgroups/mailing lists are available?
     2.2  What anonymous FTP sites are available
     2.3  Are there any gateways for mail or news
               Internet / Packet Radio BBS Gateway
               LAN Gateways (Packet wormholes via Internet)

3.0  Networking and special packet protocols
     3.1  Are there any other protocols in use other than AX.25?
     3.2  What is TCP/IP?
     3.3  Networking Schemes
               What are some of those other networking schemes?
               Digipeaters
               KA-Nodes
               NET/ROM
               ROSE
     3.4  BBS message transfer






1.0  Basic Packet Radio Information

1.1  What is packet radio?

     Packet radio is digital communications via amateur radio.  Packet
     radio takes any digital data stream and sends that via radio to
     another amateur radio station.  Packet radio is so named because
     it sends the data in small burst, or packets.


1.2  What is amateur radio?

     Amateur Radio (sometimes called Ham Radio) is individuals using
     specified radio frequencies for personal enjoyment,
     experimentation, and the continuation of the radio art.  Amateur
     radio operators must be licensed by their government.  In the
     United States, the Federal Communications Commission issues
     amateur radio licenses.  Normally, a test on operating practices,
     radio theory, and in some cases morse code proficiency test is
     administered.  Amateur radio is not to be used for commercial
     purposes.  Also, amateur radio operators are restricted from
     using profanity and using amateur radio for illegal purposes.

     For more information on Amateur Radio in general, see the monthly
     frequently asked questions posting in rec.radio.amateur.misc.


1.3  What can I do on packet radio?

     Keyboard-to-Keyboard contacts:
          Like other digital communications modes, packet radio can be
          used to talk to other amateurs.  For those who cannot use HF
          frequencies, 2 amateurs can talk to each other from long
          distances using the packet radio network.

     Packet BBS operations:
          Many cities have a packet Bulletin Board System (BBS)
          attached to their local packet network.  Amateurs can check
          into the BBS's and read messages from other packet users on
          almost any topic.  BBS's are networked together over the
          packet network to allow messages to reach a broader audience
          than your local BBS users.  Private messages may also be
          sent to other packet operators, either locally or who use
          other BBSs.  BBS's have the latest ARRL, AMSAT, and
          propagation bulletins.  Many BBS's have a file section
          containing various text files full of information on amateur
          radio in general.

     DX Packet Cluster:
          A recent development is use of packet radio for DX spotting.
          HF operators connect to the local DX Packet Cluster for the
          latest reports on DX.  Often a user will 'spot' some hot DX
          and distribute the DX report real time.

     File Transfer:
          With special software, amateurs can pass any binary files to
          other amateurs.  Currently, this is done with TCP/IP
          communications, YAPP, and other specialized protocols.

     Satellite Communications:
          Many of the amateur radio satellites contain microcomputer
          systems that can provide special information to amateurs.
          Some satellites contain CCD cameras on board and you can
          download images of the earth and the stars.  Others provide
          store and forward packet mailboxes to allow rapid message
          transfers over long distances.  Some satellites use AX.25,
          some use special packet protocols developed for satellite
          communications.  A few transmit AX.25 packets over FM
          transmitters, but most use SSB transmissions.


1.4  Why packet over other digital modes?

     Packet has three great advantages over other digital modes:
     transparency, error correction, and automatic control.

     The operation of a packet station is transparent to the end user;
     connect to the other station, type in your message, and it is
     sent automatically.  The Terminal Node Controller (TNC)
     automatically divides the message into packets, keys the
     transmitter and sends the packets.  While receiving packets, the
     TNC automatically decodes, checks for errors, and displays the
     received messages.  In addition, any packet TNC can be used a
     packet relay station, sometimes called a digipeater.  This allows
     for greater range by stringing several packet stations together.

     Packet radio provides error free communications because of built
     in error detection schemes.  If a packet is received, it is
     checked for errors and will be displayed only if it is correct.

     With VHF/UHF packet, many countries allow packet operators to
     operate in automatic control mode.  This means that you can leave
     your packet station on constantly.  Other users can connect to
     you at any time they wish to see if you are home.  Some TNC's
     even have Personal BBS's (sometimes called mailboxes) so other
     amateurs can leave you messages if you are not at home.

     Another advantage of packet over other modes is the ability for
     many users to be able to simultaneously use the same frequency
     channel simultaneously.


1.5  What elements make up a packet station?

     TNC (Terminal Node Controller)
          A TNC contains a modem to decode the audio signals into
          digital signals.  It also contains a modem and a micro-
          computer to convert the digital signals into text that can
          be sent over a RS-232 port to the computer.  The CPU also
          handles the protocol overhead of the packet station.  When
          you send data, it takes the text, puts error checking on it
          (CRC) and also puts it in an envelope for sending.  When
          receiving a signal, it takes it out of the envelope, and
          sends the message to the computer.

          Most TNC's use 1200 baud for local UHF/VHF packet and 300
          baud for long distance HF packet communications.  For
          VHF/UHF packet, higher speeds modems are available, but
          often are harder to interface.

     Computer or Terminal
          This is the user interface.  A computer running a terminal
          program or just a dumb terminal can be used.  For computers,
          any phone modem communications program can be adapted for
          packet use or customized packet radio programs are
          available.

     A radio
          For 1200 baud UHF/VHF packet, commonly available narrow band
          FM voice radios are used.  For HF packet, 300 baud data is
          used over single side band modulation. For high speed packet
          (anything greater than 1200 baud), special radios or
          modified FM radios must be used.


1.6  What do you mean we can all use the same channel?

     Packet radio uses a protocol called AX.25.  AX.25 specifies
     channel access (ability to transmit on the channel) to be handled
     by CSMA (Carrier Sense Multiple Access)  If you need to transmit,
     your TNC monitors the channel to see if someone else is
     transmitting.  If no one else is transmitting, then the radio
     keys up and the TNC sends it's packet.  All the other stations
     hear the packet and do not transmit until you are done.
     Unfortunately, 2 stations could accidentally transmit at the same
     time.  This is called a collision.  If a collision occurs,
     neither TNC will receive a reply back from the last packet it
     sent.  Each TNC will wait a random amount of time and then
     retransmit the packet.

     In actuality, a more complex scheme is used to determine when the
     TNC transmits.  See the "AX.25 Protocol Specification" for more
     information.


1.7  What is AX.25 ?

     AX.25 (Amateur X.25) is the communications protocol used for
     packet radio.  A protocol is a standard for how two computer
     systems are to communicate with each other, somewhat analogous to
     using business format when writing a business letter.  AX.25 was
     developed in the 1970's and based of the wired network protocol
     X.25.  Because of the difference in the transport medium (radios
     vs wires) and because of different addressing schemes, X.25 was
     modified to suit amateur radio's needs.  AX.25 includes a
     digipeater field to allow other stations to automatically repeat
     packets to extend the range of transmitters.  One advantage of
     AX.25 is that every packet sent contains the senders and
     recipients amateur radio callsign, thus providing station
     identification with every transmission.


1.8  Definitions:  Commonly used terms in Amateur Packet Radio

     HDLC :  (High-Level Data Link Control Procedures) A standard for
     high level link control. (ISO 3309)

     AX.25 : Amateur X.25 protocol.  The basis of most packet systems.
     See section 1.7.

     TAPR : Tucson Amateur packet Radio.  Was the first group to
     create a packet radio TNC using AX.25.  Soon a TAPR TNC became
     cloned by many others.  TAPR continues development of packet
     radio equipment.

     digipeater : A packet radio station used for repeating packets.
     See section 3.3.1 for more information.

     digi : Short name for a digipeater

     NET/ROM : A scheme for packet radio networking.  See section
     3.3.3 for more information.

     TCP/IP : Transmission Control Protocol/Internet Protocol.  A set
     of utility programs used over AX.25.  See sections 3.2 for more
     information.

     KA9Q NOS : (KA9Q Network Operating System)  A TCP/IP program
     originally developed by Phil Karn, KA9Q.  Currently there are
     many different versions available.  See section 3.2 for more
     information.

     NODE : A network node.  Often a network node running NET/ROM.

     KA-Node : A simple networking scheme developed by TNC maker
     Kantronics.  See section 3.3.2 for more info.

     CSMA : Carrier Sense Multiple Access.  A system allowing many
     stations to use the same radio frequency simultaneously for
     packet communications.

     TNC : Terminal Node Controller.  See section 1.5 for more
     information.

     AMPR : Amateur Packet Radio.

     44 net : The class A network designator for TCP/IP amateur packet
     radio.  All numerical TCP/IP addresses are in the format of
     44.xxx.xxx.xxx .

     ampr.org : The high level domain recognized on Internet for
     amateur packet radio TCP/IP.

     RS-232 : (RS-323C)  A standard for interconnection of serial
     peripherals to small computer systems.  In packet radio, RS-232
     is the most common interface between TNC's and the
     Computer/Terminal.

     protocol : A standard used for intercommunications between
     different computer systems.

     CRC : Cyclical Redundancy Code. The error detection scheme
     included in each packet.  Verify that the packet was received
     error free.

     KISS : Keep It Simple Stupid.  A simple interface developed for
     communications between TNCs and computers.  This allows for most
     of the packet processing to be handled by the computer.  Commonly
     used with packet TCP/IP software.

     modem : Modulator/Demodulator.  Converts the analog signals into
     binary data stream (a series of ones and zeros) for the TNC or a
     micro-computer .  First step in decoding packets.

     FCC : Federal Communications Commission.  Regulates and issues
     licenses for amateur radio in the United States.

     FM : Frequency Modulation.  The radio modulation scheme used for
     VHF and UHF packet communications.

     SSB : Single Side Band Modulation.  The radio modulation scheme
     use for HF packet and satellite packet communications.

     AFSK : Audio Frequency Shift Keying.  A method of representing
     digital information by using different audio frequencies
     modulated on a carrier.

     FSK : Frequency Shift Keying.  A method of representing digital
     information by shifting the radio carrier different amounts to
     represent ones and zeros.

     LAN : Local Area Network.  A packet network developed for
     communications throughout a city or region.  Often, the LAN uses
     separate frequencies from inter-city packet links.


1.9  Do's and Don'ts : Rules and Regulations

     NOTE: These regulations apply only to amateurs regulated by the
     FCC (United States), but often are similar to regulations in
     other countries.
     [Since I have no experience with amateur radio in other
     countries, I cannot make any comments.  Please bring any notable
     exceptions to my attention. -Steve]


     Although there are no specific rules that apply to amateur packet
     radio, the general amateur radio rules force some restrictions on
     packet usage.


     Can I set up a TNC at home and one at work so I can check my
     Electronic mail via packet?

          This cannot be done without special restrictions.  Amateur
          radio rules prohibit any business.  Since you could have
          mail from your boss (or maybe even someone selling you
          something over Internet), that would constitute business
          activity and is specifically prohibited.

          Profanity can also be a complication.  Since you have no
          control over the language used in E-mail, proper filtering
          is required.  Since no filter scheme can catch every
          offense, it is best to say every message must be hand
          filtered.


     I would like to set up a packet radio gateway between a land line
     computer network and the packet network.  Is this possible?

          Yes, and there are several such gateways in use, but they
          must be managed with caution.  Electronic mail may be pass
          FROM the packet network INTO the land line network without
          intervention.  However, mail passed TO packet radio is
          considered third party traffic (the sender is not an
          amateur) and these messages must be hand filtered to assure
          that rules of message content are followed.

     It's my license if I send use packet radio illegally anyway, so
     what does anyone else care!

          Packet radio is one of the few NETWORKED systems in amateur
          radio.  Many people have helped develop the network and
          there are many amateurs who own parts of the packet radio
          network.  Sending packet BBS mail, digipeating, and sharing
          the channel involves the licenses of MANY people.  Because
          of FCC rules stating that anything to come out of a
          transmitter (either in automatic mode or via your direct
          control) is the licensees responsibility, one illegal
          message sent over the packet radio network could literally
          jeopardize the license of thousands of other amateurs.  When
          in doubt, it is best to check with other amateurs about
          sending the message before it is sent.

     I have some ideas on how to use packet radio in a new way, but I
     don't know if it is legal.  Who could tell me if I can do it
     legally?

          The worst thing you can do is talk to the FCC about such an
          issue.  The FCC rules are written to be general enough to
          encompass but not restrict new radio activities.  In the
          past, any non-thought-out requests sent to the FCC have
          meant a reduction of privilege for all amateur radio
          operators.

          The best source for legal assistance is your national
          amateur radio association.  In the United States, that is
          the American Radio Relay League (ARRL).  Another good place
          for such conversations is over Usenet/packet mailing lists,
          or the amateur radio BBS network.







2.0  Computing Network Resources for Amateur Packet radio

     This section summarizes the resources available on Internet for
     amateur packet radio operators.


2.1  What Newsgroups/mailing lists are available?

     This is a list of all groups that regularly discuss amateur
     packet radio.  For newsgroups, join the group through use of your
     news reader.   For mailing lists, add a '-request' to the end of
     the list name to request subscriptions.  For listserv groups,
     send mail to 'listserv' at the node which contains the list.  The
     first line of the mail should be 'SUBSCRIBE groupname yourname'.
     Send the command 'help' for more information.


     rec.radio.amateur.packet (Newsgroup):
          General discussions involving Packet Radio.

     rec.radio.amateur.misc (Newsgroup):
          General amateur radio discussion.  Usually does not contain
          any particular information about Amateur Packet Radio.

     rec.radio.amateur.policy (Newsgroup):
          Discussion of regulation policies regarding every aspect of
          amateur radio.  Occasionally deals with polices of packet
          coordination and legal issues of packet radio.

     rec.radio.swap (Newsgroup):
          General For-Sale for any radio equipment.  Occasionally will
          have packet equipment for sale.  Recommended location for
          any amateur packet radio for-sale items.

     info-hams@ucsd.edu (Listserv group):
          A digest redistribution of the rec.radio.amateur.misc Usenet
          discussion.

     packet-radio@ucsd.edu (Listserv group):
          A digest redistribution of the rec.radio.amateur.packet
          Usenet discussion.

     ham-policy@ucsd.edu (Listserv group):
          A digest redistribution of the rec.radio.amateur.policy
          Usenet discussion

     hs-modem@wb3ffv.ampr.org (Mailing list):
          Discussion of high speed modems and radios available and
          future plans.  Also includes discussion of networking using
          high speed modems.

     tcp-group@ucsd.edu (Mailing list):
          Group discussion technical developments of TCP/IP over
          packet radio and use of the NOS TCP/IP programs.

     gateways@uhm.ampr.org (mailing list):
          Discussion of current gateways and future plans for
          gateways.  May deal with sensitive internetworking issues.


     For all lists at ucsd.edu, archives may be found via anonymous
     FTP at ucsd.edu.  Some listserv groups also have archives.  Send
     the command 'help' to the group's listserv for more information.
     Digest mailings for the ucsd.edu discussions are also available.
     Send mail to listserv@ucsd.edu with the first line being
     'longindex' for more information.


2.2  What anonymous FTP sites are available for getting packet radio
     information and programs?

     This is a sampling of FTP sites that carry amateur packet radio
     related files.  Consult the Archie archive server for info on
     locating particular files.  For more information on using archie,
     send mail to archie@cs.mcgill.edu with the line 'help'.


     ucsd.edu
          Primary distribution site of KA9Q's derived TCP/IP packages.
          Also, general packet radio information.

     wsmr-simtel20.army.mil
          Very large collection of amateur radio software.

     wuarchive.wustl.edu
          Mirror site of Simtel20 archives.  Unix directory
          structure - Easier to use then the simtel20 archive.

     ftp.cs.buffalo.edu
          Supplimental archive site for amateur radio information.
          Contains current copies of all rec.radio.amatuer.* FAQ's.

     tomcat.gsfc.nasa.gov
          Packet software including Baycomm, Rose, G8BPQ, NOS, etc.


2.3  Are there any gateways for mail or news between Internet and
     Amateur Packet radio?

     Internet / Packet Radio BBS Gateway

     Jim Durham, W2XO, maintains a gateway between Internet and the
     Packet radio BBS system.

     To mail from Internet to Packet:
          1.   Mail to: "bbs@w2xo.pgh.pa.us"
          2.   Make the first line of the text a Packet BBS "send"
               command, ie:
                 SP TOCALL @ BBSCALL.ROUTING-HINTS < FROMCALL
          3.   The "subject" line of the Internet mail becomes the
               "title" line of the Packet BBS mail.

     NOTE:     Because of FCC regulations, Jim must hand filter each
               message sent FROM Internet TO the Amateur Packet Radio
               BBS system.  Messages should be of minimal length and
               appropriate content.  Read Section 1.9 (Do's and
               Don'ts: Rules and Regulations) regarding appropriate
               usage of packet radio for more information.  Always
               include the routing hints with the BBS callsign.

     To mail from Packet to Internet:
          1.   The amateur radio operator must have his callsign
               registered in the gateway alias list.  If you want to
               mail from packet to a specific amateur on Internet,
               send mail to 'durham@w2xo.pgh.ps.us' (Internet) or
               'W2XO @ W2XO.#WPA.PA.USA.NAOM' (Packet BBS mail) with
               his/her amateur callsign and their Internet address.
          2.   Once the above is accomplished, packet BBS mail should
               be sent to 'CALL @ W2XO.#WPA.PA.USA.NAOM'.  The mail
               will automatically be forwarded to the Internet address
               of the amateur with the 'CALL' callsign.


     Jim Durham's Internet address is 'durham@w2xo.pgh.ps.us'.


     LAN Gateways (Packet wormholes via Internet)

     Currently a group of amateurs are experimenting with connecting
     packet LANs together via Internet IP inside IP Encapsulation.
     Some of the gateways only accept TCP/IP packets, others AX.25
     packets.  These gateways uses the Internet as a transport medium,
     thus it is impossible to access the packet radio network from
     Internet.  For more information, join the Gateways mailing list
     by sending mail to "gateways-request@uhm.ampr.org".





3.0  Networking and special packet protocols

     This is a sample of some of the more popular networking schemes
     available today.  By far, there are more customized networking
     schemes used than listed.  Consult your local packet network guru
     for specific network information.


3.1  Are there any other protocols in use other than AX.25?

     AX.25 is considered the defacto standard protocol for amateur
     radio use and is even recognized by many countries as a legal
     operation mode.  However, there are other standards.  TCP/IP is
     used in some areas for amateur radio.  Also, some networking
     protocols use other packet formats than AX.25.

     Often, special packet radio protocols are encapsulated within
     AX.25 packet frames.  This is done to insure compliance with
     regulations requiring packet radio transmissions to be in the
     form of AX.25.  However, details of AX.25 encapsulation rules
     vary from country to country.


3.2  What is TCP/IP?

     TCP/IP stands for Transmission Control Protocol/Internet
     Protocol.  This is commonly used over the Internet wired computer
     network.  The TCP/IP suite contains different transmission
     facilities such as FTP (File Transfer Protocol), SMTP (Simple
     Mail Transport Protocol), Telnet (Remote terminal protocol), and
     NNTP (Net News Transfer Protocol)

     The KA9Q NOS program (also called NET) is the most commonly used
     version of TCP/IP in packet radio.  NOS originally was written
     for the PC compatible.  However, NOS has been ported to many
     different computers such as the Amiga, Macintosh, Unix, and
     others.  Smaller computers like the Commodore 64 and the Timex-
     Sinclar do not currently have version of NOS available.



3.3  Networking Schemes

     What are some of those other networking schemes?

     During the early days of amateur packet radio, it became apparent
     that a packet network was needed.  To this end, the following
     packet network schemes where created.


     Digipeaters

     The first networking scheme with packet radio was Digipeaters.
     Digipeaters would simply look at a packet, and if it's call was
     in the digipeater field, it would resend the packet.  Digipeaters
     allow the extension of range of a transmitter by retransmitting
     any packets addressed to the digipeater.

     This scheme worked well with only a few people on the radio
     channel.  However, as packet became more popular, digipeaters
     soon were clogging up the airwaves with traffic being repeated
     over long distances.  Also, if a packet got lost by one of the
     digipeaters, the originator station would have to retransmit the
     packet again, forcing every digipeater to transmit again and
     causing more congestion.


     KA-Nodes

     Kantronics improved on the digipeater slightly and created KA-
     Nodes.  As with digipeaters, KA-Nodes simply repeat AX.25 frames.
     However, a KA-Node acknowledges every transmission each link
     instead of over the entire route.  Therefore, instead of an end-
     to-end acknowledgement, KA-Nodes allow for more reliable
     connections because acknowledgments only carried on one link.
     KA-Nodes therefore are more reliable than digipeaters, but are
     not a true network.  It is similar like having to wire your own
     telephone network to make a phone call.


     NET/ROM

     NET/ROM was one of the first networking schemes to try to address
     the problems with digipeaters.  A user connects to a NET/ROM as
     if connecting to any other packet station.  From there, he can
     issue the NET/ROM commands to instruct it to connect to another
     user locally or connect to another NET/ROM.  This connect then
     connect again means that to a user's TNC, you are connected to a
     local station only and it's transmissions does not have to be
     digipeated over the entire network and risk loosing packets.
     This local connection proved to be more reliable.

     NET/ROM don't use all of the AX.25 protocol.  Instead, they use
     special AX.25 packet called Unnumbered Information (UI) packets
     and then put their own special protocol on top of AX.25.  This is
     again used to increase efficiency of it's transmissions.

     NET/ROM is a commercial firmware (software put on a chip) program
     that is used as a replacement ROM in TAPR type TNC's.  Other
     programs are available to emulate NET/ROM.  Among them are
     TheNet, G8BPQ node switch, MSYS, and some versions of NET.

     NET/ROM nodes, at regular intervals, transmit to other nodes
     their current list of known nodes.  This is good because as new
     nodes come on-line, they are automatically integrated in the
     network, but if band conditions such as ducting occur, often
     unreachable nodes are entered into node lists.  This causes the
     NET/ROM routing software to choose routes to distant nodes that
     are impossible.  This problem requires users to develop a route
     to a distant node manually defining each hop instead of using the
     automatic routing feature.


     ROSE

     Rose is another networking protocol derived from X.25.  Rose
     nodes have a static list of the nodes it can reach.  For a user
     to use a ROSE switch, he issues a connect with the destination
     station and in the digipeater field places the call of the local
     rose switch and the distant rose switch the destination station
     can hear.  Other then that, the network is completely transparent
     to the user.

     The static routing tables ROSE uses ensures that packet routing
     does not use unreliable links such as NET/ROM suffers from.
     However, ROSE suffers from it's inability to change it's routing
     table as new nodes come on line.  The operator must manually
     change every routing table, thus ROSE networks require greater
     maintenance times.


3.4  BBS message transfer

     Many of the BBS programs used in packet radio allow for mail and
     bulletins to be transferred over the packet radio network.  The
     BBS's use a special forwarding protocol developed originally by
     Hank Oredsen, W0RLI.

     Besides full service BBS's, many TNC makers have developed
     Personal BBS software to allow full service BBS to forward mail
     directly to the amateurs TNC.  This allows operators to receive
     packet mail at night and avoid tying up the network during busy
     hours.



     - End of Amateur Packet Radio Frequently Asked Questions -
