With Packet-Radio you can built a inexpensive but powerful data network.
Within a net, we talk about the users, who transmit and receive data and the nodes, which forward the data in direction to the receiver.
Nodes are intelligent systeme, which know the current strukture of the network and which manage to transport the data packets through the net in the most efficient way.
The users need just a simple Packet-Radio-Controller or a plug-in modem (30-200 $) to participate the amateur radio data network. As node controller, a more powerful computer or TNC3S with X-Net Software is required.
All nodes in a net have to exchange information about the link quality between the adjacent stations. A complex software can now calculate, which way from A to B would be the fastest and most efficient. It is important to re-evaluate the situation every now and then, as it may happen that a certain node station fails and the data traffic has to be routed on new ways to find alternative ways not using the failed node. Due to varying traffic load, some links may be congested and other (maybe slower) ways have to be used in parallel. A data net in general (especially the amateur net with its home-built and amateur-operated stations) is not a static thing but it changes from moment to moment.
Network node software has to decide, in which direction a given data packet is to be forwarded. The decision varies depending on the situation and load of the net. Poor software may cause oscillations by changeing traffic from congested links to other links and causing congestions there, which causes the routing algorithm to switch to and fro. With the X-Net software (available free on the internet) for TNC3 and PC, the radio amateurs have an excellent platform for very reliable, fast and inexpensive nodes.