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Packet Routing Services
Many organizations must communicate among several points. Leasing a line between each pair of points can prove too costly. Many services now are available that route packets between different sites. Some of the packet-routing services discussed in this chapter are as follows:
Each of these services has characteristics that suit it to particular uses, and all these services are available on a leased basis from service providers. An organization that must communicate among many sites simply pays to connect each site to the service, and the service assumes the responsibility of routing packets. The expense of operating the network is then shared among all network subscribers. Because the exact switching process is concealed from the subscriber, these networks frequently are depicted as a communication cloud, as shown in Figure 7.6.

These data rates can be compared to common LAN services such as Ethernet (10 Mbps) and Token Ring (4-16 Mbps).


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Many digital transmission methods use a technique called multiplexing. Multiplexing, described in Chapter 3, “Transmission Media,” enables broadband media to support multiple data channels.