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 evenimpressive working knowledge of PCs, operating systems, applications,and common problems and solutions. Many of these people are wizards withdesktop computers.
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Networking: A Beginner’s Guide Fifth Edition- P1342 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 their name all you need to know about what they do. The first portion—the number—can be 10, 100, or 1000, and this number indicates the data rate (in Mbps) that the standard carries. The word Base means the network is baseband rather than broadband. (A baseband connection carries only one signal at a given instant; a broadband connection carries multiple signals at any time.) The terminating letter or number indicates what sort of cable is used: T for twisted pair, 2 for thin coaxial, 5 for thick coaxial, and F or X usually indicating fiber-optic cable. Here’s a quick reference guide to the different standards commonly seen: 10Base-2 10 Mbps, coaxial (RG-58) cable 10Base-5 10 Mbps, coaxial (RG-8) cable 10Base-T 10 Mbps, twisted-pair (two pairs, Cat-3 or higher) cable 100Base-T 100 Mbps, twisted-pair (two pairs, Cat-5) cable; a variant called 100 Base-T4 designates four pairs 100Base-TX 100 Mbps, twisted-pair (two pairs, Cat-5) cable 100Base-FX 100 Mbps, fiber-optic cable 1000Base-T 1 Gbps, twisted-pair (four pairs, Cat-5) cable 10GBase-X 10 Gbps, fiber-optic cable Are not limited in the number of nodes in a single logical segment Use RJ-45 connectors for all connections (this type of connector is similar to a modular telephone connector, but the RJ-45 is larger) 100Base-T networks are similar to 10Base-T networks and have these characteristics: Require four actual wires (two twisted pairs in a single sheath) Must use Cat-5 cable or better Are limited to a length of 100 meters (328 feet) for each node connection Are not limited in the number of nodes in a single logical segment Use RJ-45 connectors for all connections 1000Base-T networks are notable in that they can run over existing Cat-5 cable, butat ten times the speed of 100Base-T networks. Running over Cat-5 cable is a significantadvantage for 1000Base-T, because over 75 percent of installed network cabling today44 Networking: A Beginner’s Guide is Cat-5, and rewiring an entire building for a new networking standard is an extremely expensive proposition. 1000Base-T over Cat-5 networks have these characteristics: Require eight actual wires (four twisted pairs in a single sheath) Must use Cat-5 cable or better Are limited to a length of 100 meters (328 feet) for each node connection Are not limited in the number of nodes in a single l ...