From: steve@wattres.SJ.CA.US (Steve Watt -- KD6GGD)
Newsgroups: rec.radio.amateur.packet,rec.radio.info,rec.answers,news.answers
Subject: rec.radio.amateur.packet Frequently Asked Questions
Summary: Common quesions and answers about Packet Radio.
Date: 22 Jan 93 12:12:16 GMT
Expires: 02/26/93
Reply-To: packet-faq@wattres.SJ.CA.US (Packet Radio FAQ Coordinators)
Followup-To: rec.radio.amateur.packet
Organization: Steven Watt, Consultant   San Jose, CA, USA
Supersedes: <packet-radio-faq-1-725693899@wattres.SJ.CA.US>

Posted-By: auto-faq 1.20
Archive-name: packet-radio-faq


Frequently Asked Questions for Amateur Packet Radio

Version 1.11 - Last modified 1/21/93

This document is for unlimited distribution.

Please send corrections and additions to:
   packet-faq@uts.amdahl.com
Which will expand to a list of people who are familiar with most packet
issues.  I hope. ;-)

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.


Table of contents:

1  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  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  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  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 bursts, 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.  A copy
of that FAQ is also available from ftp.cs.buffalo.edu.


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, two
amateurs can talk to each other from long distances using the packet
radio network.

Packet BBS operations:

Many cities have one or more packet Bulletin Board System (BBS) available
on the local packet network.  Amateurs can check into the BBSes and read
messages from other packet users on almost any topic.  BBSes are
networked together over the packet network to allow messages to reach a
broader audience than just your local BBS users.  Private messages may also
be sent to other packet operators, either locally or who use other
BBSes.  BBSes have the latest ARRL, AMSAT, and propagation bulletins.
Many BBSes 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 as 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 BBSes
(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 use the same frequency channel simultaneously.


1.5  What elements make up a packet station?

TNC (Terminal Node Controller):  A TNC contains a modem, a CPU, and the
associated circuitry required to convert between RS-232 and the packet
radio protocol in use.  It assembles a packet from some of the data on
the serial line, computing an error check (CRC) for the packet, modulates
it into audio frequencies, and puts out appropriate signals to transmit
that packet over the connected radio.  It also reverses the process,
translating the audio that the connected radio receives into a byte
stream on the RS-232 port.

Most TNC's currently use 1200 BPS (bits per second) for local VHF and UHF
packet, and 300 BPS for longer distance, lower bandwidth HF
communication.  Higher speeds are available for use in the VHF, UHF, and
especially microwave region, but they often require unusual hardware and
drivers.

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

A radio:  For 1200 BPS UHF/VHF packet, commonly available narrow band FM
voice radios are used.  For HF packet, 300 BPS data is used over
single side band modulation. For high speed packet (anything greater
than 1200 BPS), 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 TNC keys up the radio, and sends its
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 sender's and
recipient's amateur radio callsign, thus providing station identification
with every transmission.


1.8  Definitions:  Commonly used terms in 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
44.xxx.xxx.xxx.

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

AMPR - Amateur Packet Radio.

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

AX.25 - Amateur X.25 protocol.  The basis of most packet systems.
See section 1.7 for more information.

CRC - Cyclic Redundancy Check. The error detection scheme included
in each packet.  Verify that the packet was received error free.

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

digi - Short name for a digipeater

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

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.

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

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

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.

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

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.

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.

modem - MODulator/DEModulator.  Converts the analog signals into
a binary data stream (a series of ones and zeros) for the TNC or a
micro-computer.  First step in decoding packets.  It also converts
binary data to analog, which is the last step in encoding packets.

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

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

PPP - Point to Point Protocol.  PPP is another protocol used for moving
IP frames over a serial line.  It supports host authentication, and non-
transparent serial lines.  It also has a standard way of negotiating
header (and potentially data) compression over the line.  See also SLIP.

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

RS-232 (RS-323C) - A (more or less) 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.

SLIP - Serial Line Internet Protocol.   A trivial protocol for putting
IP frames over a serial line to do (potentially) cheap TCP/IP networking.
Approximately the same as KISS, except over wireline networks.  See also
PPP.

SSB - Single Side Band.  The radio modulation scheme used for HF packet
and satellite packet communications.

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.

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

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


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.  -ed]

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 passed 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
ensure that rules of message content are followed.


  It's my license if I 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 licensee's responsibility, one illegal message sent
over the packet radio network could literally jeopardize the licenses
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  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 policies 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 of 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 in the /hamradio/packet subdirectory.

wsmr-simtel20.army.mil

Very large collection of amateur radio software.

wuarchive.wustl.edu

Mirror site of Simtel20 archives.  Unix directory structure, which is
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.

akutaktak.andrew.cmu.edu

SoftKiss for the Mac, in /aw0g.  Requires NET/Mac.
SoftKiss is an init/cdev/driver that allows a MAC to do packet using
a Poor Man's Packet modem.

sumex-aim.stanford.edu

NET/Mac is the port of KA9Q's NET program.  It doesn't have nifty features
like scrolling or saving the windows, but the individual sessions can be
recorded into a file.

2.3  How do I contact the ARRL via electronic mail?

There are various addresses at ARRL HQ, but the most important one is
probably info@arrl.org.  That is where general information about the
ARRL can be acquired.  This address reaches a person, so you'll have
to specify what/who you're looking for.


2.4  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  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 its call was in the
digipeater field, 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 with fewer timeouts, because
acknowledgments are 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 station as if
connecting to any other packet station.  From there, he can issue
commands to instruct the station to connect to another user locally or
connect to another NET/ROM station.  This connect, then connect again,
means that to a user's TNC, you are connected to a local station only
and its transmissions do not have to be digipeated over the entire
network and risk loosing packets.  This local connection proved to be
more reliable.

NET/ROM doesn't use all of the AX.25 protocol.  Instead, it uses
special AX.25 packets called Unnumbered Information (UI) packets and
then puts its own special protocol on top of AX.25.  This is again
used to increase efficiency of its 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.  However, if
band conditions such as ducting occur, ordinarily unreachable nodes can
be 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.  Each ROSE node
has 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.

ROSE's use of static routing tables ensures that ROSE nodes don't attempt
to route packets through links that aren't reliably reachable, as NET/ROM
nodes often do.  However, ROSE suffers from the inability to automatically
update its routing tables as new nodes come online.  The operators must
manually update the routing tables, which is why ROSE networks require
more maintainance.

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 BBSes
use a special forwarding protocol developed originally by Hank Oredsen,
W0RLI.

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

-- 
Steve Watt               {news,steve}@wattres.San-Jose.CA.US
 ...!decwrl!gigo!wattres!{news,steve}       ...!apple!wattres!{news,steve}
Never trust a computer bigger than you can lift.
Newsgroups: rec.radio.amateur.packet