     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 -

