Buck Rogers K4ABT Handbook page 26

; Packet Radio "The Basics"
Section 1
Suppose you are a user with access to a local node, and you want to contact another user station who is also within range of
the same node. You can, of course, connect to the other station "the old way" by using the node as a digipeater. To take
advantage of the store-and-forward capabilities of the node, however, you would use this two-step procedure: (1) connect to
the node ("uplink"); then, (2) issue a CONNECT command with the callsign or identifier of the other user station
("downlink").
UPLINK-DOWNLINK CONNECTIONS:
All AX.25 frames include the callsigns of both the originating station and the destination station. When you request a
downlink, the node "adopts" your callsign as the originating station (rather than using its own callsign). This is necessary
so the destination station can properly identify you as the connecting user station. The node does NOT use your "exact"
callsign, but if it did, and, if there happened to be a direct path between your station and the destination station, that station
would then see two stations using the same callsign. This can create confusion at the destination station or on the
network... BIG-TIME!
To avoid this problem, the down linking node "adopts" your basic callsign, by changing the SSID (or adding a callsign
suffix) from N to 15-N. For example, if your callsign is NT4XXX, the downlink uses NT4XXX-15; if your callsign is
W4KGS-2, the downlink uses W4KGS-13; and so forth. To utilize the full store-and-forward capability of the nodes, you
would use a three-step procedure:
(1) Connect to your local node; then.
(2) Issue a CONNECT command with the callsign or node identifier of the distant node.
(3) Issue a CONNECT command with the callsign of the other user station.
UPLINK, CROSSLINK, AND DOWNLINK, CONNECTIONS:
When you perform step (2) of this procedure, you are asking your local node to create a "circuit" for you between your local
node and the distant node. If the two nodes are sufficiently far apart, the circuit may have to pass through several
intermediate nodes. In any case, the routing is performed automatically by the node. Your circuit is carried by a series of
AX.25 "crosslinks" between pairs of adjacent nodes.
USING THE "CQ" FEATURE:
The CQ command is used to broadcast a short text message from a node, and to enable other user stations that receive the
broadcast to connect to the station that originated the broadcast. An example is:
CQ This is George, Connect to me at the CALL & SSID displayed
All text after the CQ is optional and can be any string up to 77 characters long.
In response to a CQ command, the node broadcasts the specified message in "unproto" mode, using the callsign of the
originating user (with a translated SSID) as the source and "CQ" as the destination. The broadcast is made in the form of
an AX.25 UI-frame.
If WA4GSO in Wadesboro, North Carolina sent the CQ through several nodes to a node in Macon, Georgia, the display at
the Macon node would appear similar to the following:
WA4GSO-15>CQ: George in Wadesboro, NC
Section II
"2 N 1" Handbook
The Packet Radio
Section 2
Chapter Eight
Using the advanced features of the X1J4 Node
; TheNET X1J4 System Node Operators Handbook __ Page 26
Buck Rogers K4ABT
by
; The X1J4 System Node Operator's (SNO) Handbook