Kurose and Ross Edition 6 Exercise 1 Question P3 (Page No 71)

Question

Consider an application that transmits data at a steady rate (for example, the sender generates an N-bit unit of data every k time units, where k is small and fixed). Also, when such an application starts, it will continue running for a relatively long period of time. Answer the following questions, briefly justifying your answer:

1. Would a packet-switched network or a circuit-switched network be more appropriate for this application? Why?

2. Suppose that a packet-switched network is used and the only traffic in
   this network comes from such applications as described above. Furthermore,
   assume that the sum of the application data rates is less than the
   capacities of each and every link. Is some form of congestion control
   needed? Why?

Answer 1

a) A circuit-switched network would be well suited to the application, because the application involves long sessions with predictable smooth bandwidth requirements. Since the transmission rate is known and not bursty, bandwidth can be reserved for each application session without significant waste. In addition, the overhead costs of setting up and tearing down connections are amortized over the lengthy duration of a typical application session.
b) In the worst case, all the applications simultaneously transmit over one or more network links. However, since each link has sufficient bandwidth to handle the sum of all of the applications' data rates, no congestion (very little queuing) will occur. Given such generous link capacities, the network does not need congestion control mechanisms.