A short history lesson will help in understanding FidoNet. Tom Jennings was in San Francisco, and John Madill was in Baltimore, both working on the Fido BBS software. In the spirit of finding out if it could be done, they decided to add code to the system to support a dialup connection with no human intervention during the wee hours when the sysops were sleeping and the systems were free. This quickly became a useful function, since both systems and both sysops were busy and it was a convenient method of exchanging information.
From this chance beginning in May 1984, growth was phenomenal. By August 1984, there were 30 nodes. By September there were 50. By February 1985, there were 160 systems, and a group of sysops in St. Louis had taken over the administration of the list of systems. In June 1985 the network converted to the currently-used two-part addressing scheme to support the growth. As this is written in late 1987, the size of the network has passed 2000 nodes and change continues with a zone-based nodelist to facilitate communication with systems overseas. But we get ahead of the story . . .
Today's network is organized into geographical divisions of zones, regions, networks, individual systems, and points. A zone is a very large division. zone 1 is North America, zone 2 is Europe, and zone 3 is Australia, New Zealand, etc. Of more interest are regions, networks, and points.
North America is divided into regions. For example, the central region, region 11, includes Illinois, Indiana, Kentucky, Michigan, Ohio, and Wisconsin. Regions are assigned 2-digit numbers to differentiate them from networks. Regions are further broken down into networks. A network usually covers a rather small geographic area, such as a metropolitan area. Chicagoland is network 115. Individual systems are assigned a node number within the appropriate network or directly within the region if no network covers that specific location.
A point is a usually a one-person BBS. There is an analogy with telephone numbers. Think of the zone as the country code, the network as the area code, the node number as the telephone number, and the point as an extension for the individual. This is written as zone:network/node.point. For example, Chicago is covered by network 115, and is in zone 1. The specific BBS which has been assigned node 100 in the Chicago network would be 1:115/100. If there were point systems served by this BBS, they would be 1:115/100.1, 1:115/100.2, and so on.
The purposes of this organization are twofold. First, decentralization means that no one person has the task of administering the entire network. Since it is a volunteer and amateur operation and such an assignment would be a big job, it became obvious early in the life of FidoNet that decentralization was necessary to support growth of the network.
The second reason for such a hierarchy is to improve the flow of mail. One system in each network takes on the responsibility of Network Co-ordinator, and that BBS becomes node zero in the network. One of the tasks of the Network Co-ordinator is to forward incoming mail. Thus, if I have ten messages for different systems in the Chicagoland network, I need to make not ten telephone calls but only one -- to system 115/0, which is the NC for Chicagoland. The mailer software automatically routes messages for nodes in network 115 to 115/0, saving me money and making the network work better.