Kantronics KPC–3 Plus User Manual

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Kantronics KPC–3 Plus User Manual Manual pdf 112 page image

112Introduction to Basic Packet NetworkingA network node is a "collection point" in a packet network. It is at these node locationsthat packets are collected and routed to other nodes and end-users. Many networknodes operate at high data rates, usually at 9,600 or 19,200 baud. End-user access tothe network is usually at a lower baud (1200 baud) and on a different frequency. Theadvantage of a network system is two-fold: automatic routing of connections to othernetwork nodes and increased data throughput. A network node "knows" how toautomatically route data through neighboring nodes to distant nodes on the network.They do this by "hearing" other nodes broadcast this information. This means that auser connected to a node does not need to specify the particular route to take in orderto reach a distant node as long as the local node contains a listing for that distant node.Using a network node can also dramatically increase the data throughput to distantlocations. The packet data and the acknowledgments travel from node to node (ratherthan from end-to-end), greatly reducing the inevitable data collisions that will occurwhen attempting to communicate over long distances.The defacto standard networking protocol, NET/ROM, was developed in the late 1980'sby Software 2000, Inc. Since then, other node derivatives such as TheNET, TheNETPlus, TheNET X-1J, and G8BPQ have evolved. Although these variants differ in theirfeatures, they all utilize the same basic networking protocol.Some network nodes have more than one radio port in order to provide a high-speednetwork "backbone" on one frequency, as well as Local Area Network (LAN) access tothe high speed network at a lower data rate on a different frequency. This approach topacket networking makes good sense for a number of reasons. First, the high speedbackbone is free to pass large amounts of data without competing with end users for thechannel. Generators of large amounts of data are called servers. Many times serversare busy communicating with other servers, so dedicating a channel to this function isdesirable. Second, users are "shielded" from the server-to-server activity. Many userscould peacefully co-exist with a server if all the server did was to respond to userqueries. User input to a server generally consists of very small amounts of data thatgenerate fairly large responses. In a local area, this works quite well since all users candetect the presence of the server's data. Carrier Sense Multiple Access (CSMA) allowsthe channel to be shared nicely. However, servers, and in particular many BulletinBoard Systems (BBSs), spend much more time forwarding and receiving messagesfrom neighboring bulletin board systems than they do actually serving the local userpopulation! It is not unusual for a BBS to attempt forwarding (and reverse forwarding) onan hourly basis. This situation quickly evolves into quite a paradox - BBSs provide anextremely popular service that has been a boon to the growth and popularity of packetradio. As user numbers increase to take advantage of the services a BBS provides,BBS systems also increase in number in order to provide the service to more and moreusers. More and more BBS systems must now forward to each other, generating hugeamounts of data on the channel, leaving precious little time for the very source of theirexistence - the user community. User-to-user (keyboarding) QSOs become, at best, avery frustrating proposition. As a result, many users become ex-users, interest declines,and packet usage stagnates. With the K-Net function enabled in your KPC-3, cost-effective networking can benefit packet users in your area immediately.

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