Chapter15.Leasing a (Network) Roadway Between Lots of Places


Chapter 15. Leasing a (Network) Roadway Between Lots of Places

What You Will Learn

After reading this chapter, you should be able to

  • Compare and contrast point-to-point WAN link's physical layer with Frame Relay physical topologies

  • Compare and contrast HDLC and PPP with Frame Relay

  • Explain the basic forwarding process in Frame Relay using DLCIs

  • Explain the concept behind the term virtual circuit

  • List several reasons why Frame Relay is a widely used WAN technology

The U.S. Department of Transportation (DOT) could plan to build a road directly between your house and every other place to which you might want to drive. It could do the same for everyone else as well. That would be ridiculous, of course, because the DOT would end up paving practically the entire country! Instead, the DOT built one road to your house, which is in turn connected to other roads, ultimately allowing you to drive anywhere you want to drive.

Chapter 14, "Leasing a (Network) Roadway Between Two Points," covered the basics of how a serial link could be used between two routers, which can be compared to paving a road directly between. This chapter covers a WAN technology called Frame Relay. Frame Relay uses one physical WAN link connected to each site, while allowing each site to send data to each other site. That's a lot like the DOT paving one road to your house, and you driving anywhere you want, always leaving your house by driving over that one road.

When you want to build a network to connect multiple remote sites, you could just order a lot of serial links. However, Frame Relay requires less work and less new hardware, making Frame Relay a much more cost-effective solution compared to leased lines.

In many ways, Frame Relay acts like a network built with an Ethernet switch. With an Ethernet switch, more than two devices can be cabled to the switch. To send an Ethernet frame to any of the other devices, the sender just needs to put the right destination Ethernet address in the frame. As you'll read in this chapter, a Frame Relay network acts like a big WAN switch, with routers connecting to it. To send data to another router, the sending router just needs to send a frame with the right address in it.




Computer Networking first-step
Computer Networking First-Step
ISBN: 1587201011
EAN: 2147483647
Year: 2004
Pages: 173
Authors: Wendell Odom

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