By far the most common architecture today is Ethernet, which first appeared in 1975. Today its the de facto standard in almost every corporate network but there are other factors to consider, such as
By far the most common architecture today is Ethernet, which first appeared in 1975. Today its the de facto standard in almost every corporate network but there are other factors to consider, such as cabling. The most esoteric, 10Base5, can be ignored for our office network since its intended for remote installations. This leaves 10Base2 and 10BaseT.The wiring used for 10Base2, or Thinnet, is simple coaxial cable. Its a linear bus system, in other words each client machine is connected to a single run of cable (or segment) via a BNC T-piece which connects to a BNC connector on the network card. 10Base2 is by far the easiest system to set up for a small network. Just install network cards in all your machines, get yourself n T-pieces and n 10Base2 leads (where n is the number of client machines) and string them together, terminating each end of the network with 50-ohm terminators to absorb reflections. But be aware that if the cable suffers from an internal breakage or one of the T-piece connections fails, the network will grind to a halt.Aside from the potential reliability problems, once you have more than a few machines connected it makes more sense to have each client connected to a central point in whats known as a star topology. That way you can install neat conduits and network connection points and move machines around and connect them at will, without affecting the rest of the network. This is what 10BaseT gives you.10BaseT uses UTP (unshielded twisted pair) cabling with RJ-45 telephone-style connectors. There are two Ethernet speeds available: 10BaseT (10Mbits/sec) and 100BaseTX (100Mbits/sec), or Fast Ethernet.
Its important to get the appropriate cable quality rating for the speed of the network. There are five official quality categories for UTP cable, but only two are relevant for the speeds of 10/100BaseTX networks. CAT 3 cabling supports speeds of up to 10Mbits/sec, and CAT 5 up to 100Mbits/sec. But its a false economy to go for less than CAT 5 cabling even if you dont need 100Mbits/sec just yet.
For our network, the central focus of the star topology is a hub. Hubs are powered, offering another benefit of 10BaseT - the hub acts as a signal repeater, boosting its power so that the length of cable from each networked machine to the hub can be up to 100m. For 10Base2, the maximum length of the whole network segment - from one terminator to the other, via all machines - is 185m.
There arent too many options to consider when youre choosing a hub: the number of ports are usually in multiples of four, and extend up to 24-way. If you start out with a smaller hub, of say eight ports, its easy to expand the network further using another and chaining the two, which is done by setting one of the ports as an uplink. If theres no uplink option on the hub, you can still chain them by using a UTP crossover cable. Our network is being built from scratch, so we dont need to consider any legacy hardware. But if theres an older 10Base2 network you need to interface with, many hubs have Thinnet BNC connectors for that purpose. If you do chain hubs, however, you need to be aware of the hop-count rule. This states that to maintain reliability in a 100BaseTX network, there should be no more than two hubs between any two computers. With a 10BaseT network, there should be no more than four. So, if you anticipate eventually having to cater for 30 machines, buy at least a 16-port hub to start with.
With our 20 clients, running a cable across the floor from each one to the hub isnt practical, so well want to install proper network points and conduit, letting us jack machines in as necessary. For that we need a patch panel located beside the hub. A patch panel is nothing more than a rack, with a row of RJ-45 connectors at the front connected to a row of wiring terminals at the back. The UTP cables are wired into the terminals, and then all we have to do when a machine is disconnected from one network point and connected to another, or a new machine is added, is connect a patch lead from the appropriate socket on the patch panel to a port on the hub.