PC Hardware —

Specifying the Right Network Cable

In order to ensure trouble-free operation, network cabling must match the system requirements. Cable specifications are based on three factors: speed, bandwidth, and length. Cables are designated with names like 10Base5. Speed is the first number in the identification¾representing the maximum transmission speed (bandwidth) in Mbps. This will be 1, 5, 10, or 100. Band is the second part of the identification. It is either base or broad depending upon whether the cable is baseband or broadband. The last part of the identification refers to the cable length or cable type. If the unit is a number, it is the maximum length of the cable segments in hundreds of meters (1 meter is approximately 3.3 feet). In some cases, it can refer to 50-meter increments (1Base5 is five 50-meter increments-250 meters). In other cases, it represents cable type: T (twisted-pair) or F (fiber-optic). The following table shows the common types of cables and their specifications.

Name Description Type Segment Speed
10BaseT Common UTP twisted-pair .5 to 100 meters 10 Mbps
10Base2 Ethernet ThinNet Coaxial 185 meters 10 Mbps
10Base5 Thick Ethernet Coaxial 500 meters 10 Mbps
100BaseT Becoming common Twisted-pair .5 to 100 meters 100 Mbps

The preceding table covers the basic cable requirements for the A+ networking objective; however, there are many other forms of network connections. For example, you'll find microwave links; forms of radio; and, for small offices and homes, power-line networks (whose NICs have connectors that plug into wall sockets, allowing regular wiring to carry the signal), and telephone-line networks that use standard phone jacks to plug into existing lines. These have relatively short ranges (generally limited to one office or one floor of a building).

LAN Communication

A LAN is similar to a telephone system with one party line-not everyone can talk at the same time. The difference is that, with a LAN, the speed is so fast that it fosters the perception that many transactions are taking place at the same time. But just like a one-lane road, the heavier the traffic, the slower it moves.

Ethernet

Ethernet uses a system known as carrier sense multiple access with collision detection (CSMA/CD). It also uses the bus topology discussed earlier in this lesson. The term "carrier sense" means that the network card listens to the cable for a quiet period during which it can send messages. "Multiple access" refers to the fact that more than one computer can be connected to the same cable. And "collision detection" is the ability to detect whether messages have collided in transit (in which case neither message will arrive at its destination and both will be retransmitted).

Fast Ethernet was developed to meet the increasing demands on networks. Fast Ethernet works on the same principals as the original Ethernet, but operates at 10 times the speed. Ethernet transmits at 10 Mbps, and Fast Ethernet transmits at 100 Mbps.

Token Ring

As described earlier, a token ring network uses a "token" as the basis for deciding who can communicate on the network. Token rings transmit at 4 or 16 Mbps.