BROCADE IP PRIMER

Chapter 1: Networking BasicsThis connector is called a BNC connector. To have multiple machines connectedto the network, you needed to have T-connectors to allow a coaxialcable to be connected from the computer into the main line. At the end of themain line, you had a terminator. This was a terminating resistor that reflectedthe signal back through the cable.This is called a bus topology. This signal travels back and forth along the mainline. Every machine that is attached to the main line sees the frames thatevery other machine sends, but it only pays attention to the ones addressed toitself. This topology has plenty of weaknesses.For one, the bus topology doesn't expand very well. A single length of coaxialcable is only rated for 185 meters. If the cable is longer than that, the signalwill experience attenuation. This is the distance beyond which the electricalsignal will be so weak that it won't be properly detected. When an electrical signalis sent along the copper, it will immediately start “losing steam.” The signalwill become weaker and weaker the farther it goes. After 185 meters on acoaxial line, the signal will become so weak, other devices in the chain won'treally be sure there's a signal there. It becomes unreliable beyond that point.Another weakness in the bus topology is that if there's a break anywhere in themain line, the whole network is down. Think of an electrical circuit. If there's abreak in the cable, there's a break in the circuit. Now, no computer is talking toanybody. Network Administrators in yon days of yore will likely reflect on the ol'coaxial network days and shudder. Compared to what we have now, they werea nightmare to maintain.Twisted PairWhat do we have now? Well, the most common medium is called twisted pair.This comes in many varieties. On the high level, there's Unshielded TwistedPair (UTP) and Shielded Twisted Pair (STP). STP is expensive, and the shieldingcan make it difficult to bend or shape. On the other hand, the additionalshielding does a better job of preventing outside interference. UTP is, by far,the most common. They both come in different grades called categories. Someof the most common categories include category 3, category 5, category 5e,and category 6. These are most commonly abbreviated to CAT3, CAT5, CAT5e,and CAT6. CAT5 uses thicker cables inside than CAT3. It also has more twistsper meter. Likewise with CAT5e and CAT6, the higher the number, the thickerthe copper cables and the more twists per meter. Also, the higher the category,the greater the performance. CAT3 is only rated for 10 Mbps Ethernet, whileCAT5e and CAT6 are required for gigabit. There are many more than these, butthese are the categories you're most likely to deal with.22 Brocade IP Primer