Question

Explain different communication protocol used for rpcs.

Answer 1

The Request/Reply protocol



This protocol is also known as RR(request/reply) protocol.
It is useful for designing systems which involve simple RPCs.
In a simple RPC all the arguments and result fit in a single packet buffer while the call duration and intervals between calls are short.
This protocol is based on the idea of using implicit acknowledgement to eliminate explicit acknowledgement messages.
In this protocol a server reply is considered as an ACK for a clients request and a subsequent call from a client is considered as ACK of the client’s previous call.
Timeout-and-retires technique is used with RR protocol for failure handling. Retransmission of request message is done when there is no response.
RR protocol and timeout technique provides at-least-once call semantics on if duplicate requests are not filtered out.
Exactly once semantics are supported by servers using reply cache which stores replies.