RPC: Remote Procedure Call Protocol specification
RFC 1050
Document | Type |
RFC - Historic
(April 1988; No errata)
Obsoleted by RFC 1057
|
|
---|---|---|---|
Authors | |||
Last updated | 2013-03-02 | ||
Stream | Legacy | ||
Formats | plain text html pdf htmlized bibtex | ||
Stream | Legacy state | (None) | |
Consensus Boilerplate | Unknown | ||
RFC Editor Note | (None) | ||
IESG | IESG state | RFC 1050 (Historic) | |
Telechat date | |||
Responsible AD | (None) | ||
Send notices to | (None) |
Network Working Group Sun Microsystems, Inc. Request for Comments: 1050 April 1988 RPC: Remote Procedure Call Protocol Specification STATUS OF THIS MEMO This RFC describes a standard that Sun Microsystems and others are using and is one we wish to propose for the Internet's consideration. This memo is not an Internet standard at this time. Distribution of this memo is unlimited. 1. INTRODUCTION This document specifies a message protocol used in implementing Sun's Remote Procedure Call (RPC) package. The message protocol is specified with the eXternal Data Representation (XDR) language [9]. This document assumes that the reader is familiar with XDR. It does not attempt to justify RPC or its uses. The paper by Birrell and Nelson [1] is recommended as an excellent background to and justification of RPC. 2. TERMINOLOGY This document discusses servers, services, programs, procedures, clients, and versions. A server is a piece of software where network services are implemented. A network service is a collection of one or more remote programs. A remote program implements one or more remote procedures; the procedures, their parameters, and results are documented in the specific program's protocol specification (see Appendix A for an example). Network clients are pieces of software that initiate remote procedure calls to services. A server may support more than one version of a remote program in order to be forward compatible with changing protocols. For example, a network file service may be composed of two programs. One program may deal with high-level applications such as file system access control and locking. The other may deal with low-level file IO and have procedures like "read" and "write". A client machine of the network file service would call the procedures associated with the two programs of the service on behalf of some user on the client machine. Sun Microsystems, Inc. [Page 1] RFC 1050 Remote Procedure Call April 1988 3. THE RPC MODEL The remote procedure call model is similar to the local procedure call model. In the local case, the caller places arguments to a procedure in some well-specified location (such as a result register). It then transfers control to the procedure, and eventually gains back control. At that point, the results of the procedure are extracted from the well-specified location, and the caller continues execution. The remote procedure call is similar, in that one thread of control logically winds through two processes -- one is the caller's process, the other is a server's process. That is, the caller process sends a call message to the server process and waits (blocks) for a reply message. The call message contains the procedure's parameters, among other things. The reply message contains the procedure's results, among other things. Once the reply message is received, the results of the procedure are extracted, and caller's execution is resumed. On the server side, a process is dormant awaiting the arrival of a call message. When one arrives, the server process extracts the procedure's parameters, computes the results, sends a reply message, and then awaits the next call message. Note that in this model, only one of the two processes is active at any given time. However, this model is only given as an example. The RPC protocol makes no restrictions on the concurrency model implemented, and others are possible. For example, an implementation may choose to have RPC calls be asynchronous, so that the client may do useful work while waiting for the reply from the server. Another possibility is to have the server create a task to process an incoming request, so that the server can be free to receive other requests. 4. TRANSPORTS AND SEMANTICS The RPC protocol is independent of transport protocols. That is, RPC does not care how a message is passed from one process to another. The protocol deals only with specification and interpretation of messages. It is important to point out that RPC does not try to implement any kind of reliability and that the application must be aware of the type of transport protocol underneath RPC. If it knows it is running on top of a reliable transport such as TCP/IP [6], then most of the work is already done for it. On the other hand, if it is running on top of an unreliable transport such as UDP/IP [7], it must implement its own retransmission and time-out policy as the RPC layer does not Sun Microsystems, Inc. [Page 2] RFC 1050 Remote Procedure Call April 1988Show full document text