As the name implies, networking is the connecting together of PC's and printers to allow resources to be shared. There are various methods of doing this, such as peer to peer, client/server, and main frames which serve dumb terminals. All of the examples on this page can be connected via Cat 5/5e/6 cabling by using adapters or baluns. Adapters convert whatever connectors are normally used to RJ45, and baluns also match the impedance to that of the systems normal cabling environment.
Peer to Peer
Peer to peer networking is usually found in small offices, shops, and nowadays even in homes. This method allows PC's to access information which is kept on any of the machines that are connected to the network, and to print to any of the printers on the network. This can become impractical however, when the amount of machines or the amount of traffic on the network starts to impact on the speed in which information can be accessed.
Another method is client/server networking, this system employs dedicated PC's or file server's which hold a companies information data bases in one location. Each of the users on the network can access files from the servers, and save files to the servers. This keeps all critical data in one place, and gives each user a dedicated link to that information. Keeping all of a company's data on one machine also has the added advantage making it easier to backup.
In the days before PC's, information was stored on a "main frame" and accessed by terminals which where connected to it. This was, in effect, like having one computer with lots of individual keyboards and screens all working the same machine. These "dumb terminals" had no processing power of their own and relied on the processing power of the main frame computer to do all the work. Some systems today are often mistakenly referred to as main frames, when in actual fact they are mini computers. They can however, have dumb terminals connected to them just as the main frames of the 60's and 70's did.Here are some of the obsolete older systems.
This was a main frame type system which used coaxial cable to connect dumb terminals to a controller. The topology was a hierarchical star configuration where the controllers were star wired from the 3270 and positioned around the building, the terminals were then star wired from the controllers. The controllers were beige coloured boxes which measured about 18" high and 24" wide. Baluns for the 3270 were needed to allow these terminals to connect over Cat 5 cabling.
IBM System 36 & 38
Again, a main frame type system but with a star/bus topology which used twinaxial cable (like coax but having two cores). The System 36 and 38 were large blue and white machines with built in consoles, each of their ports supported 7 devices which could be terminals or printers. The devices were daisy chained from the machines workstation controller ports, linking in and out of the terminals and printers. On sites where Type 1 or Cat 5 cable had been installed, it was usual to find 'star concentrators' or 'Loop Wiring Concentrators' (LWC), these simply carried out the daisy chaining of the terminals at the patch cabinet to enable the building to be star wired. This made it a more flexible system as the terminals didn’t need to be grouped in the same geographical area to be daisy chained. So if a person were to move to a different location in the building, they would simply plug their terminal into the nearest data outlet and re-patch the connection in the cabinet. Before this, such a move would have meant finding the nearest available line, diverting it in and out of the re-positioned terminal, and then re-addressing it.
This was the successor to the System 38 and its native environment was also a star/bus topology using twinaxial cable. However AS400's could also be connected over an Ethernet or Token Ring network just like a PC or a server. The advantage of this was the reliability of a main frame, with the speed and flexibility of a PC.AS400's used to be large boxes that filled the air conditioned computer rooms of only a few years ago. Each rack could contain disk drives, processors or tape backup devices and required dedicated three phase supplies to power them. The modern IBM servers are considerably smaller than their older counterparts, but with a lot more processing power.
The serial communications standard was defined by the Electronics Industries Association (EIA), and in 1969 it established the Recommended Standard number 232 version C (RS-232C) which is still the most widely used serial standard today.Some networks used a PC as a server and serial connections to attach other PC's which need access to the information stored on the server. These systems are becoming increasingly rare, usually found in small offices and shops where speed is not an issue. Each PC is connected via a screened multicore cable to what is sometimes referred to as a 'terminal server board'. These can also be wired with Category 5e cabling via an adapter, the adapter simply changes the serial connection from either a 25 or 9 way D type, to an RJ45 socket.
This was developed at about the same time as Ethernet (1970's) by the Datapoint Corporation, but due to its proprietary nature, it wasn't as widely accepted as Ethernet or Token Ring.ARCnet used a polling system whereby one machine became the master controller, and polled each of the other machines on the network to see if they had any data to transmit. Each machine had to wait for its turn before it could use the network and this made it quite a reliable system. The original ARCnet only had a signal speed of 2.5Mbps and although a 20Mbps version (ARCnet Plus) was introduced in 1992, it still didn't become very popular.This was quite a rare system but as it was once one of the main three, it is worth mentioning.