For each of the factors that contribute to the time taken to transmit a message between two processes over a communication channel, state what measures would be needed to set a bound on its contribution to the total time. Why are these measures not provided in current general-purpose distributed systems?

What will be an ideal response?

Time taken by OS communication services in the sending and receiving processes - these tasks would need to be guaranteed sufficient processor cycles.
Time taken to access network. The pair of communicating processes would need to be given guaranteed network capacity.
The time to transmit the data is a constant once the network has been accessed.

To provide the above guarantees we would need more resources and associated costs. The guarantees associated with accessing the network can for example be provided with ATM networks, but they are expensive for use as LANs.
To give guarantees for the processes is more complex. For example, for a server to guarantee to receive and send messages within a time limit would mean limiting the number of clients.