Chapter 15. Leasing a (Network) Roadway Between Lots of PlacesWhat You Will Learn After reading this chapter, you should be able to
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. |