Chapter 4, Problem 4Q

Explanation of Solution

Compare roll-call polling, hub polling, and contention as follows:

Roll-call polling	Hub polling	Contention
The front end processor works repeatedly through a list of clients until all are polled.	The computer passes the poll to the next computer until it reaches the first computer.	Whenever the data is transmitted, the computers wait until the circuit is free.
It can be altered to select clients in precedence such that some get polled more frequently than the others.	On the multipoint circuit, the poll starts from one computer and passes it to the next computer, which transmits its message and passes the poll to the next...