Kantronics KPC–3 Plus User Manual
Also see for KPC-3 Plus: User guideUser guideManual
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Contents
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104KA-NodeOverviewMost Kantronics TNCs (e.g., KPC-3 Plus, KPC-9612 Plus) include, as a part of theirfirmware, 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 moreefficient.KA-Nodes, like other networking nodes such as NET/ROM, operate more efficientlythan do digipeaters as a link between two stations. End-to-end acknowledgement ofreceived packets is not required with the nodes; instead they handle errors betweeneach other, rather than from end to end (which can cause extra traffic when errors orinterference occurs). A KA-Node, however, is ―silent‖ in that it does not automaticallyconnect to and exchange routing data with adjacent nodes, as do fully-featured nodessuch as NET/ROM, X1J, or Kantronics‘ optional K-Net. Consequently, users cannotissue a connect to a distant station without knowing the path - as they sometimes canwith a full-featured node. At the same time, KA-Nodes are useful in that they are moreefficient than digipeaters in using channel time, while not requiring the effort and timerequired to maintain a full node.When packet got started in the early 1980s, the initial packet units - terminal nodecontrollers (TNCs) - were designed and coded not only to accept station-to-stationconnects, but to act as digipeaters for other stations. It was the first attempt at packetradio networking, linking two stations together via several others. It soon becameevident, however, that digipeating, particularly through busy channels, was an inefficientmethod 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 wereavailable. Second, the AX.25 protocol called for the station being connected to - at theend of several digipeaters - to acknowledge each packet of the initiating station.Packets not acknowledged (due to collisions) had to be retransmitted by the initiatingstation 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 wasinstalled 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 providethe user connecting to a station via one of these nodes with a choice of pathways toother packet stations and with lists of stations heard.NET/ROM and several of its derivatives provide for automatic routing of your connectrequest - 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 toeach node in turn through the pathway. All of the nodes correct the ―end-to-end‖acknowledgment problem mentioned above. This is accomplished by building thepathway with a number of individual ―local‖ connecting links; that is, each link in the |
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