Also, unlike packet-switched networks, once the circuit is established, all data flows over the same path through the network. In Figure 3-1, all data associated with the call passes through nodes A, B, and C; and follows the symetrical return path. Therefore, the parameters of the session, such as delay and bandwidth, are fixed—this is both an advantage and a limitation to
end-user applications. The advantage of fixed delay for real-time applications is guaranteed delivery at regular intervals. For example, in telephone calls, this is important for smooth reproduction of conversations. The limitation, in terms of bandwidth, is that some applications may use all of the available bandwidth within their circuit, whereas others may use much less. The application that consumes more bandwidth cannot contribute its spare bandwidth to the application that requires less bandwidth. The result of this limitation is poor performance in environments where bandwidth requirements change over time. For example, when you are downloading or reading Internet Web pages, the process becomes frustratingly slow. However, given their predictable delay and bandwidth characteristics, circuit-switched networks are a convenient choice for fixed-bandwidth, real-time applications such as telephone services.
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