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Chapter Summary

LANs are a critical component in computer networks today. While these structures come in many different sizes, they are always used to carry data at speeds as fast as possible over short geographic distances.

Ethernet is the most common type of LAN used today. Standards unique to Ethernet specify Ethernet LAN cabling and signaling at both the physical and data link layers of the OSI reference model. Bits that are transmitted over an Ethernet LAN are organized into frames. Ethernet LANs manage the signals on a network using a process called CSMA/CD.

A NIC or LAN adapter plugs into a motherboard and provides an interface for connecting to the network. The MAC address is burned onto each NIC by the manufacturer, providing a unique, physical network address that permits the device to participate in the network.

The cable and connector specifications used to support Ethernet implementations are derived from the EIA/TIA standards body. The categories of cabling defined for Ethernet are derived from the EIA/TIA-568 (SP2840) Commercial Building Telecommunications Wiring Standards. Several connection media are used for Ethernet, with RJ-45 and GBIC being the most common.

A GBIC is a hot-swappable I/O device that plugs into a Gigabit Ethernet port on a network device to provide a physical interface.

UTP cable is a four-pair wire. Each of the eight individual copper wires in UTP cable is covered by an insulating material, and the wires in each pair are twisted around each other. A crossover cable connects between similar devices like router to router, PC to PC, or switch to switch. A straight-through cable connects between dissimilar devices like switch to router or PC to switch.

This chapter also examined fiber-optic media. Optical fiber is a flexible, transparent fiber that is made of very pure glass (silica) and is not much bigger than a human hair. It acts as a waveguide, or “light pipe,” to transmit light between the two ends of the fiber. Optical fibers are widely used in fiber-optic communications, which permit transmission over longer distances and at higher bandwidths (data rates) than other forms of communication.

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