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| The first decision that you have to make when selecting NICs for your computers is what data link layer protocol you want to use on your network. The protocol you select determines what NICs, hubs, and cables you purchase, because all of the systems on your network must use the same protocol. Most of the tutorials in this topic assume that you're using Ethernet. |
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| Ethernet is the most popular data link layer protocol in the world, and there are several reasons why this is so. Because it has been around for more than 20 years, Ethernet hardware, such as NICs and hubs, is inexpensive and easy to find. The popularity of the protocol also means that experienced Ethernet technicians are common and their time is also relatively inexpensive. Standard Ethernet is also tolerant of faults like overlong cable segments and loose connections. |
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| Token Ring, running at 16 Mbps, is the primary alternative to Ethernet on typical LAN installations. Although it uses a ring topology internally, the cable installation is a star. Token Ring controls access to the network medium by using a small packet called a token, which is passed around the ring to each system. Only the PC possessing the token is permitted to transmit. For this reason, there are no collisions on a Token Ring network, and heavy traffic does not degrade performance, as in Ethernet. |
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| Although it is faster than Ethernet and better at handling high traffic levels, Token Ring is still far less popular than Ethernet. One of the reasons for this is that Token Ring is substantially more expensive than Ethernet. Implementing the logical ring requires a more complex hub called a multistation access unit (MSAU) and NICs are approximately twice as expensive as equivalent Ethernet adapters. |
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| Fiber Distributed Data Interface (FDDI) is a 100 Mbps protocol designed for use on backbone networks, that is, networks that connect a series of other networks together. FDDI uses fiber optic cable in a double-ring topology, which all but eliminates several of the problems common to copper-based networks. Because signals on fiber optic cable don't weaken as quickly as those on copper, cable segments can be up to 100 kilometers long. Fiber cable is also completely resistant to electromagnetic interference. |
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| Despite its speed and efficiency, FDDI and other protocols that use fiber optic cable are not practical for small networks. Apart from the high cost of the NICs and hubs needed, installing and maintaining fiber optic cable is not a job for a beginner. Because it uses pulses of light instead of electrical signals, fiber optic cable uses completely different installation procedures. Specialized tools and testing equipment are required, as are special skills. |
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| Fast Ethernet increases the speed of the standard Ethernet protocol to 100 Mbps with only a small additional expense. If you are building a new network, you can purchase Ethernet NICs that support both 10 and 100 Mbps Ethernet for only a little more than a single speed card. The cables and hubs required for Fast Ethernet are similarly priced. Even if you don't have any real need for the additional bandwidth today, time moves very fast in the networking industry and you might need it in the near |
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