Question 1. (Both parts of this question require familiarity with the implementation of "at most once" RPC system discussed in lectures - e.g., see #rpc28.) a) Consider an RPC system in which clients initiate their calls with call sequence numbers which are also included when clients retry their calls after a timeout. The server maintains in its main memory the final results computed for the latest RPC received from each client and returns the results if a call is detected to be a retry. Assume that the clients never crash, (ii) the server can crash and a crashed server recovers after some time and (ii) no communication failure occurs. Identify the type of semantics guaranteed by this RPC system and explain the reasons for your answer. b) Suppose that communication failures do not permanently block inter-process communication and that any crashed node eventually recovers. Using the principles of the two- phase commit protocol, describe an RPC implementation scheme that would guarantee "exactly once" RPC semantics when both the server and the client nodes are prone to crashing. Hints: As in two-phase commit protocol, you can assume that each node has a recovery manager and maintains in its crash-proof store a 'log with atomic-write capability. You can also assume that an RPC involves only one server and does not lead to making another RPC in another server