tailieunhanh - Networking: A Beginner’s Guide Fifth Edition- P13

Networking: A Beginner’s Guide Fifth Edition- P13:I have run into many people over the years who have gained good even impressive working knowledge of PCs, operating systems, applications, and common problems and solutions. Many of these people are wizards with desktop computers. | 42 Networking A Beginner s Guide Figure 4-3. A star topology network other nodes must contend with that use for their own. In other words if you re using a network type with a capacity of 100 Mbps that s the total amount of bandwidth available to all of the nodes connected to the hub. NOTE Networks that are physically wired in a star topology are logically either a bus or a ring. This means that despite what the network looks like it still behaves as either a bus or a ring. Ethernet networks wired in a star fashion are logically a bus. Token Ring networks wired in a star fashion are logically a ring. Star topology networks can use one of several forms of Ethernet. The most common is 100Base-T Ethernet which provides 100 Mbps of bandwidth. Quite a few older networks use 10Base-T Ethernet which provides 10 Mbps of bandwidth. A newer standard called Gigabit Ethernet 1000Base-T offers 1 Gbps of bandwidth. Most recently a standard called 10 Gigabit Ethernet or alternately 10GBase-X which can run at 10 Gbps over fiber-optic cable has been approved. 10Base-T requires a type of twisted-pair cable called Category 3 Cat-3 cable. 100Base-T requires Category 5 Cat-5 cable. 10Base-T can also use Cat-5 but 100Base-T cannot use Cat-3. These days you should always use the most recent Cat-5 cable called Cat-5E even if it s intended for only a 10Base-T network. Cat-5 cable provides eight wires four twisted pairs and so can carry two connections in each cable if desired. If cost is not an issue consider even moving up to Cat-6. 10Base-T networks share the following wiring characteristics Require four actual wires two twisted pairs in a single sheath can be either unshielded twisted-pair or shielded twisted-pair Can be run on either Cat-3 or Cat-5 cable Are limited to a length of 100 meters 328 feet for each node connection Chapter 4 Understanding Network Cabling 43 10Base-What The various Ethernet standards referred to as for instance 10Base-2 10Base-T 100Base-T and so on contain in