computer network - Cable Properties
The reason we use so many different types of cables in a network is that each type has its own set of properties that specifically make it the best to use for a particular area or purpose. Different types vary in transmission speeds, distance, duplex, noise immunity, and frequency, and we are going to cover each of these next.
Based on the type of cable or fiber you choose and the network that it’s installed in, network administrator can control the speed of network to meet the network’s traffic demands. Admins usually permit, or would like to have, transmission speed of up to 10Gbps or higher on the core areas of their networks that connect various network segments. In the distribution and access areas, where users connect to switches, it’s typically 100Mbps per connection, but transmission speeds are creeping up because the traffic demand is getting higher.
Deciding factors used in choosing what cable type to use often come down to the topology of a network and the distance between its components. Some network technologies can run much further than others without communication errors, but all network communication technologies are disposed to decrease the degradation of a signal due to the medium itself and the distance signals have to travel. Some cable types suffer from decrease more than other. For instance, any network using twisted-pair cable should have a maximum segment length of only 328 feet (100 meters).
All communications are either half duplex or full duplex. The difference is whether the communication devices can “talk” and “listen” at the same time.
During half-duplex communication, a device can either send communication or receive communication, but not both at the same time. Think walkie-talkie when you press the button on the walkie-talkie, you turn the speaker off and you can’t hear anything the other side is saying.
In full-duplex communication, both devices can send and receive communication at the same time. This means that the effective throughput is doubled and communication is much more efficient. Full duplex is typical in most of today’s switched networks.
Any time electrons are pushed through two wires next to each other a magnetic current is created. And we can create a current in the wires. This is good because without magnetic flux we wouldn’t be using computers the power that surges through them is a result of it. The bad news is that it also creates two communications issues.
First, because the wire is creating a current based on the 1s and 0s coursing through it, with the right tools in hand, people can read the message in the wire without cutting it or even removing the insulation. You’ve heard of this it’s called tapping the wire, and it’s clearly a valid security concern.
The second magnetic-flux issue comes from the outside in instead of from the inside out. Because wires can take on additional current if they’re near any source of magnetism, you’ve got to be really careful where you run your cables. You can avoid EMI by keeping copper cables away from all powerful magnetic sources like electric motors, speakers, amplifiers, fluorescent light ballasts, and so on. Just keep them away from anything that can generate a magnetic field!
Each cable type has a specified maximum frequency that gives you the transmission bandwidth it can handle. Cat 5e cable is tested to 1OOMHz maximum frequency and can run 1Gbps signals for relatively short distances. That’s maxing it out, but it’s still good for connecting desktop hosts at high speeds. On the other hand, Cat 6 is a 250MHz cable that can handle 1Gbps data flow all day long with ease. Cat 6 has a lot more twists and thicker cables, so it’s best used when connecting floors of a building.