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KA-Node
Overview
Most Kantronics TNCs (e.g., KPC-3 Plus, KPC-9612 Plus) include, as a part of their
firmware, the Kantronics KA-Node, a packet networking node. If you turn this node on,
others may use your station (unattended) not only as a digipeater, but as a node,
enabling them to find pathways to other stations and making those pathways more
efficient.
KA-Nodes, like other networking nodes such as NET/ROM, operate more efficiently
than do digipeaters as a link between two stations. End-to-end acknowledgement of
received packets is not required with the nodes; instead they handle errors between
each other, rather than from end to end (which can cause extra traffic when errors or
interference occurs). A KA-Node, however, is ―silent‖ in that it does not automatically
connect to and exchange routing data with adjacent nodes, as do fully-featured nodes
such as NET/ROM, X1J, or Kantronics‘ optional K-Net. Consequently, users cannot
issue a connect to a distant station without knowing the path - as they sometimes can
with a full-featured node. At the same time, KA-Nodes are useful in that they are more
efficient than digipeaters in using channel time, while not requiring the effort and time
required to maintain a full node.
When packet got started in the early 1980s, the initial packet units - terminal node
controllers (TNCs) - were designed and coded not only to accept station-to-station
connects, but to act as digipeaters for other stations. It was the first attempt at packet
radio networking, linking two stations together via several others. It soon became
evident, however, that digipeating, particularly through busy channels, was an inefficient
method of linking two stations via others. First of all, the station initiating the ―connect‖
had no way to know ahead of time whether or not the digipeating stations were
available. Second, the AX.25 protocol called for the station being connected to - at the
end of several digipeaters - to acknowledge each packet of the initiating station.
Packets not acknowledged (due to collisions) had to be retransmitted by the initiating
station AND ALL DIGIPEATERS in the communications chain. As a result,
communication often ground to a halt when channels were busy.
To solve these problems, NET/ROM, a PROM-based networking program that was
installed inside some TNC models, and a number of derivatives of NET/ROM (e.g.,
G8BPQ, X1J, KA-Node, K-Net) were developed. These networking programs provide
the user connecting to a station via one of these nodes with a choice of pathways to
other packet stations and with lists of stations heard.
NET/ROM and several of its derivatives provide for automatic routing of your connect
request - much like the phone system today routes your long distance calls. Others,
such as the KA-Node, assist you in building a pathway by allowing you to connect to
each node in turn through the pathway. All of the nodes correct the ―end-to-end‖
acknowledgment problem mentioned above. This is accomplished by building the
pathway with a number of individual ―local‖ connecting links; that is, each link in the
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