Why is a Transparent Back Bone Important to a large amateur packet
network?

We have learned long ago that using Callsigns for network level devices
can lead to many problems.  In the early days of packet when we only had
digipeaters we could establish connects great distances (few users to
collide with!) with digipeaters, If you knew all the calls.  This lead to
the network maps, that needed to be continually updated as new stations
came on the air, as well as when old stations would move off to find a quite
frequency again.

The bottom line is that if I need to communicate with a station 200+ miles away
I (as a user) should not have to keep abreast of the networking (or political)
changes made by all the packet groups along the path.

As a network manager I should only have to worry about how connections are
established within my local network, and how my network interoperates with
the networks at my boarders (RF and geographical).

The ROSE X.25 Packet Switch was designed with these problems in mind.

The following is an example showing how flexible a ROSE X.25 Network is.

Problem:  Two switches are linked on the user channel and the traffic
          volume has increased to the point where a trunk link is needed.

Solution: Install dual port systems at each site and add second radios to
          link them.

Starting Network:
                                    2 m
                N2DSY-3  = = = = = X.25 = = = = = KA2VLP-3
                201744                              609426
                Little Falls                    Hightstown
         KD6TH-4                                          KB1BD-4

Note: KD6TH-4 and KB1BD-4 are BBS systems, but could just as well be two
          users.

The 70 cm band was chosen for the link, but we found out that we needed a
higher antenna than we already had for that band.  Some asking around
revealed a club (WB2JQR) tower that had a spare antenna, after some testing
we discovered the path would work, but we still needed to get connectivity
from JQR to VLP.  Another pair of radios needed to be found.  We then found
out that Russ, N2EVW had a dual-port cross band digipeater that was being
used to access the VLP switch from 70 cm already and he agreed to let us
use it to digipeat between the two towers (VLP and JQR).

Interim Network:
                            70 cm              WB2JQR-3
                     ...........................609443 ...
                    .                          Cranbury    \
                   .         2 m                          N2EVW-2
                 N2DSY-3   = = = = X.25 = = = KA2VLP-3  = = =
                 201744                       609426
                 Little Falls                 Hightstown
         KD6TH-4                                          KB1BD-4

Once the new radios are in hand, we are really waiting for crystals, we can
have the JQR tower and the VLP tower link directly.

Final Network:
                                      70 cm            WB2JQR-3
                      .................................609443
                      !                                Cranbury
                      !                2 m              !
                  N2DSY-3 = = = = = X.25 = = = = = KA2VLP-3
                  201744                             609426
                  Little Falls                   Hightstown
         KD6TH-4                                          KB1BD-4

In all of the above backbone changes, none of the users or BBS's needed to
be notified to make any changes, since the network access points maintained
identical connectivity.

The multi-port Switches were either DR-200's or TNC's connected via the RS-
232 port.

Each CPU (ie. TNC/DR-200) needs its own call sign since the RS-232 port is
assumed to be on a radio.  You can reuse a call sign if they are on
different frequencies or do not share another switch in the RF domain.

The DR-200 also has a daughter board that expands it to four ports.

I hope you find preceding example useful to show how flexible a network of
ROSE X.25 Packet Switches can be.

Thank you for your interest, and please...

                 "Try it, you'll like it!"

73, Tom
W2VY@KD6TH
(201) 478-7919