Flow Control: A Comparative Survey

Packet switching offers attractive advantages over the more eonventional circuit-switched scheme, namely, flexibility in setting up user connections and more efficient use of resources after the connection is established. However, if user demands are allowed to exceed the system capacity, unpleasant congestion effects occur which rapidly neutralize the delay and efficiency advantages. Congestion can be eliminated by using an appropriate set of traffic monitoring and control procedures called flow control procedures. Flow control can be exercised at various levels in a packet network. The following levels are identified and discussed in this paper: hop level, entry-to-exit level, network access level, and transport level. For each level, the most representative techniques are surveyed and compared. Furthermore, the interaction between the different levels is discussed.