INTROWAN - CHAPTER 3 Introduction to WAN Technologies This...

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CHAPTER Introduction to WAN Technologies 3-1 3 Introduction to WAN Technologies This chapter introduces the various protocols and technologies used in wide- area network (WAN) environments. Topics summarized here include point-to-point links, circuit switching, packet switching, virtual circuits, dialup services, and WAN devices. Later chapters in this book discuss WAN technologies in more detail. What is a WAN? A WAN is a data communications network that covers a relatively broad geographic area and often uses transmission facilities provided by common carriers, such as telephone companies. WAN technologies function at the lower three layers of the OSI reference model: the physical layer, the data link layer, and the network layer. Figure 3-1 illustrates the relationship between the common WAN technologies and the OSI model.
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Point-to-Point Links Internetworking Technology Overview, June 1999 3-2 Figure 3-1 WAN technologies operate at the lowest levels of the OSI model. Point-to-Point Links A point-to-point link provides a single, preestablished WAN communications path from the customer premises through a carrier network, such as a telephone company, to a remote network. A point-to-point link is also known as a leased line because its established path is permanent and fixed for each remote network reached through the carrier facilities. The carrier company reserves point-to-point links for the private use of the customer. These links accommodate two types of transmissions: datagram transmissions, which are composed of individually addressed frames, and data-stream transmissions, which are composed of a stream of data for which address checking occurs only once. Figure 3-2 illustrates a typical point-to-point link through a WAN. Figure 3-2 A typical point-to-point link operates through a WAN to a remote network. ith0301 OSI Layers MAC Sublayer WAN Specifications SDLC LAPB X.25 PLP X.21bis PPP HDLC Frame Relay Physical Layer Network Layer EIA/TIA-232 EIA/TIA-449 V.24 V.35 HSSI G.703 EIA-530 SMDS Data Link Layer 12323 WAN
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Introduction to WAN Technologies 3-3 Circuit Switching Circuit Switching Circuit switching is a WAN switching method in which a dedicated physical circuit is established, maintained, and terminated through a carrier network for each communication session. Circuit
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This note was uploaded on 03/01/2012 for the course LAN 340 taught by Professor Bryanjensen during the Spring '12 term at American Public University.

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INTROWAN - CHAPTER 3 Introduction to WAN Technologies This...

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