What is the ROSE Switch ?

As a packet "user", you have a radio, computer, and TNC (Terminal Node
Controller) that lets you communicate with packet Bulletin Board Systems
(BBSs), Callbook servers, and other packet users.  The radio is just a way of
getting a signal from you to some other place, and the computer basically just
lets you see the information (bulletins or messages or whatever) that is
coming from (and that you send to) the "other" packet station.  That leaves
the TNC as the box that takes care of all the rest, like converting the
computer's information to a form that can be sent by radio (using a MODEM) and
making sure all the information gets from one end to the other without errors
and in the right order.  The process of getting the information sent without
errors, to the right place, dealing with other users on the frequency, and so
on, is handled by a computer inside the TNC.  This computer uses a software
program, which is inside an EPROM (Erasable-Programmable Read-Only Memory) IC
Chip, to perform all of these tasks in accordance with a special set of rules,
known as a "Protocol".  The protocol that Amateur Radio packet operators use
is named "AX.25" (Said "A X dot 25), which is a modified form of the X.25
protocol used in commercial digital networks.

Normally, you use the software on the EPROM that came with your TNC when you
bought it.  This software, which makes all TNCs act pretty much the same way,
lets you "connect" to another packet station and trade information.  It
doesn't matter whether the other station is a BBS, another user, or whatever.
For most users, this is all you'll ever need.

Some people, not happy with connecting only to other packet stations within
the range of their radio, use a regular TNC acting as a Digipeater (Digital
Repeater) to extend their range, much like a voice repeater extends the range
of a Handy-talkie.  A digipeater is just fine when you only want to go a
little bit farther than normal, and if there's not too many other users on the
frequency.  If you want to go really far - say, from Florida to Iowa -
digipeaters can't do it.

First, the protocol (rules) won't allow you to digipeat through more than 8
digipeaters.  Second, you would have to know the callsign of EVERY digipeater
along the path, which is not that easy.  Third (and most importantly), it is
nearly impossible to do in the "real" world - where errors can occur.  A
digipeater simply repeats what it hears correctly, passing it along on the
same frequency to the next digipeater in the string (of 8, lets say).  If each
digipeater "loses" one packet for every 20 sent (causing your station to send
it again), that means the digipeater has "a 95% path" (1/20 = 5%, 100% - 5% =
95%).  The "path" from one end of the string of digipeaters to the other is
the product (the result of multiplication) of each of the "paths".  Thus, the
effectiveness or quality of the path from one end of the string to the other
is 0.95 (same as 95%) multiplied by itself 8 (the number of digipeaters)
times, which equals 0.663, or about 2/3.  That means that about 2/3 of your
packets will reach the other end without getting lost.  Of course, the other
end has to send an acknowledgement packet for every one you send, so the
round-trip path "quality" becomes 0.663 x 0.663 = 0.439 -- meaning that less
than 1/2 (43.9%) of the packets you send get there and back.  This example
assumes very good (95%) paths all down the line.  In real life, the round-trip
"quality" for even a three digipeater path is about zero.

So, how do you get far, far away on packet ?  You use a "network"!  A network
is kind of like a string of digipeaters, but with special software in the
TNC's EPROM that lets the TNC behave a little differently.  The network
software allows the string of TNCs to give what is called a "hop-by-hop"
acknowledgement - this means that each TNC (running the special network
software) will acknowledge receiving the information directly.  Thus, the
first network TNC (Called a "Switch" or "Node") will send an "ack"
(acknowledgement) to you, the second will directly ack the first, and so on.
The advantage of this method - ack-ing each hop - is very important: the total
path quality equals only the worst path quality, not the PRODUCT of all of the
path qualities.  This makes for good communications over very long distances.

The other important feature that the special network software provides is the
possibility of "routing", sending your packets along a specific chain of
network switches.  That way, you don't have to know all of the callsigns of
the stations in-between.  Also, if the local experts (who put up the network
in the first place) get to choose which paths your packets get sent along,
they'll know which paths are the best and use THOSE instead of some poor
paths.  (You really can't tell how good a path a digipeater a few hundred
miles away might have).  Also, packet "links" between network stations can
work at speeds much faster than 1200 baud - 9600 baud is common, and some
links run at 2MBaud (2,000,000 Baud)!  The faster links allow more people to
use that link at the same time.

So, what is the ROSE switch ?  It is a piece of software, contained in an
EPROM, that replaces the normal TNC EPROM and allow the TNC to become a part
of a network.  As a user, you would never install a ROSE EPROM into your TNC,
because your computer couldn't talk to it the same way, and you couldn't use
your TNC to connect to anybody.  You would install a ROSE EPROM if you were
setting up a network, though.  There are a few different types of packet
network software, such as Net/Rom (or its clone, TheNet), TCP-IP, and ROSE.
You could put any one of these EPROMS into your TNC and become a part of a
network - but each type of network is different and uses different sets of
rules (protocols).

Why use the ROSE software to create a network, instead of one of the others ?
Well, the main advantage of ROSE is that the network managers decide on the
best routes between two points, not the users.  This allows the very best path
between two points to always be used.  Other network software lets the user
decide, and the user may not always know the best path, and unknowingly use a
very poor path, or even to create illogical and wasteful paths (like
connecting from New York City to New Jersey through Maine).  Another advantage
of ROSE is that the user issues only one simple command in order to go to any
other point, no matter the distance - just like the telephone network (and
all other commercial networks).  Other advantages include: Proper station
identification at all points in the network, at all times, according to
international standards (ROSE is the only software LEGAL in some countries!);
On-line HEARD, USERS and INFO features; True implicit addressing, where you
only have to know the exit point of the network, not all the steps in between;
Dynamic route selection, where the switch will automatically try other paths
if the best path is not working; Multi-port capability; Switch configuration
is done over the air, no need to visit the site; Security password to keep
unauthorized people from changing the configuration; All configuration and
routing information is retained when power is removed (battery backed); ROSE
software runs on any TNC-2 or clone, as well as some other TNCs; and lastly,
ROSE conforms with the Open Systems Interconnect (OSI) model recommended by
CCITT, providing international networking compatibility.

For more information about the ROSE X.25 Packet switch, contact the Radio
Amateur Telecommunications Society (RATS) at PO Box 93, Park Ridge NJ 07656
(USA).  The latest ROSE software, including all source code, is available on
CompuServe (Hamnet), or by sending a 720k PRE-FORMATTED floppy and a Self-
Addressed, postage-paid mailer to RATS.  Membership in the Radio Amateur
Telecommunications Society, which helps support further networking
development, is $20.00 per year, and includes the Society's quarterly journal.
Voting membership is $50.00 per year, and also includes the journal.  Each new
member receives a membership package which includes the latest ROSE software,
a ROSE User guide, and the latest version of ROSErver/PRMBS (a Packet Radio
MailBox System written by KA2BQE), which features a highly advanced user
interface as well as easy set-up and management.