UNIVERSITY OF CALIFORNIA
                         College of Engineering
                  Department of Electrical Engineering
                          and Computer Sciences
                        Computer Science Division

    CS 162                                             Alan Jay Smith




                      Remote Procedure Call





    .   We’d like to make a "Call" to a procedure on another machine.

        .   We’ll call that a "remote procedure call".

        .   A "remote" call can be to another process on a  different

            machine or on this machine.



    .   Recommended  paper:  "Implementing  Remote  Procedure Calls",

        Birrell and Nelson, ACM TOCS, 2, 1, February 1984, pp. 39-59.

        .   "When a remote procedure is invoked, the calling environ-

            ment is suspended, the parameters are passed  across  the

            network to the environment where the procedure is to exe-

            cute (the callee), and the desired procedure is  executed

            there.   When the procedure finishes and produces its re-

            sults, the results are passed back to the  calling  envi-

            ronment,  where  execution resumes as if returning from a

            single machine call."



    .   Issues:

        .   How are arguments and results passed  when  there  is  no



                                 — 25.1 —









            shared address space?

            .   Must pass and return (effectively) by value.

                .   Could fake call by reference if necessary.

            .   Must be very careful about side effects.

        .   How is the callee located/identified?

            .   Static vs. Dynamic

        .   What  happens  if there are machine and/or communications

            failures?

        .   How are data integrity and security obtained  when  using

            an open communications channel?

        .   Overhead

        .   Would like semantics to be same or similar to normal pro-

            cedure call.



    .   Mechanism

        .   Five components:

            .   Caller (User)

            .   User-Stub - interface between the caller and the com-

                munications mechanism.

            .   Communications Package (RPCRuntime)

            .   Server-Stub  - interface between communications pack-

                age and callee.

            .   Server (callee)



    .   Call Steps:



    .   [ Caller - User-stub (pack arguments)  -  RPCRuntime  (trans-



                                 — 25.2 —









        mit)] -



    .   call packet -



    .   [  RPCRuntime  (receive)  -  Server Stub (unpack arguments) -

        callee -



    .   Server Stub (pack results) - RPC Runtime (transmit) ] -



    .   Result Packet -



    .   [ RPC Runtime(receive) - User-Stub (unpack result) - caller ]

































                                 - 25.3 -