Who invented rpc

RPC, a procedure, is loaded with additional semantics. IPC assumes nothing, except allocate the resources for communication, transparently transfer data perhaps many RPCs , and deallocate those resources when finished. That one should build networking from RPC, rather than the other way around.

As evidence, the supporters pointed to the paper by Spector that Tanenbaum cites. Spector [] developed a taxonomy for the semantics for remote operations: maybe once, at least once, only once, etc. This is based on the number of messages exchanged and the range of failures that might be encountered, i. Spector ignores or assumes that the fundamental conditions for this to work are all unstated assumptions.

He assumes that it will not be necessary to fragment messages, have sequencing, acknowledgements other than the response of the RPC , or flow control. All RPC models will not only have to obey these rules, but will also need in addition to a request-id that can be matched to the response: sequence numbers to order requests and responses that are longer than the maximum packet size, to detect lost or duplicate messages, detect corrupted messages, fragment and reassemble requests and responses, retransmission control, and flow control.

RPC has enough problems to handle which are ignored rather taking on the complicating issues of providing IPC with an error and flow control protocol. Furthermore, it has been shown that the class of error and flow control protocols have a very different structure than RPC [Day, ]. Their only interaction is for the control side to impose flow control by turning off a queue once in a while. They always result in an overly complex cumbersome to use solutions.

The asymmetry is a prime contributor to these problems. It is not an uncommon occurrence that looking at a problem in a distributed environment uncovers assumptions that were not apparent in the single system environment. To truly understand something, it is often very illuminating to consider how it would be done in a distributed environment. If we go back to our previous question: do these terms refer to processes or boxes?

The ARPANET developers were careful to ensure that hosts could be both clients and servers, and there are many examples of processes that receive requests from another process, perform some function on the data and pass it on to another function, etc.

In fact, Tanenbaum provides an example from Unix pipes:. And asks who is the client and who is the server? The key to this answer goes back to our 2nd comment: the lack of the infrastructure of the language. This construct uses a push down stack, so that the output of what is inside the angle-brackets is the input to sort.

More generally, RPC does not support recursion. No surprise,. Tanenbaum ignores the question of where did the command line come from in the first place, i. Once these are identified, it is clear who is doing what. And some processes do act as both client and server. Why not?

Why should this be a big deal? What is good for the goose is good for the gander! This is like preventing a procedure from calling another procedure. Overall, in the world of system design, symmetry is highly desirable and asymmetry is tolerated when necessary.

RPC is at best tolerated and best only used in the corner of the world, where it is applicable. Its advocates have been trying to generalize from a special case that is too restrictive. I was excited to learn what this bold new networking concept was all about. That has always been the case. To my shock, there was nothing beyond that. And to add insult to injury, all of the peer-to-peer protocols were client-server, not peer protocols at all.

If there is a message the application understands, then it was expected. Some models have kludged this by having a request with multiple replies, which might never have a final response. Interrupts are part of any operating system.

If RPC is more fundamental, then it must handle interrupts. Polling fits the RPC model. For this problem, Tanenbaum describes two situations: a terminal concentrator and sharing a file server. He indicates that RPC can work nicely for the terminal server with the concentrator requesting input from the terminal, in other words, polling. Not really. I have written this code. It really needs to be interrupt driven, otherwise too much time is lost polling terminals with nothing to send and it severely limits how many terminals can be supported.

Even with a fast typist and echoing every character remotely some systems do that , terminals are very slow devices. Tanenbaum should look at Telnet more closely. Contrary to what most textbooks say, Telnet is not a remote log-in protocol, but a terminal device driver protocol. And while most terminal-to-host protocols were asymmetric and would seem to lean toward RPC, Telnet is symmetric.

Making it a character-oriented IPC facility. This brilliant insight greatly increased its flexibility and created a model that made other issues simple. Again, not all problems are symmetric but the solutions are better when they are. Telnet did have to solve the half-duplex terminal problem and here again they found a brilliant way to see both cases as extremes of the same problem. Because of limited kernel memory, Telnet had to be a user process. Telnet can expect input at any time from either the network or from the user.

To implement it, they had to have two processes: one for incoming traffic; one for outgoing, and hack stty and gtty for the necessary coordination between them. The next thing that was done was to design and implement real IPC for Unix.

A similar experience occurred years later trying to do IPC on Apollo workstations, which only had an asymmetric RPC-like mailbox facility. The result was cumbersome, complex and a pain to build code on. The idea that a process can only be a client or only a server is religion, not engineering. Procedures do! Yea, okay, I remember: Fortran Function calls always have to return a value. Again the lack of the language infrastructure.

But most of the others are really more of the same: Not being precise and not defining a model, not making an RPC a procedure call, not providing the distributed OS support for the RPC, etc. Concluding Remarks. It has always seemed that what underlies the whole RPC phenomenon is a deep-seated fear among computer scientists of asynchrony.

They go to great lengths to keep everything very deterministic, very linear, when the problems are precisely the opposite. Many of the problems encountered are from trying to make an inherently asynchronous problem synchronous. Those 6 operations and the object model on which they operate are the intermediate language to be compiled to.

This makes the object model or perhaps restricted to a subset by an application connection available to an RPC program, the beginnings of the language model for a distributed program. How absurd! It is clearly part of a storage hierarchy and where it belongs in that hierarchy is determined by the access time. This does imply that the storage hierarchy is relative to a given member of the distributed application.

The same data stored in the same place will be at different levels of hierarchy relative to different processing. An interesting problem! Next, a process on the server side, which is dormant until the arrival of the call message, extracts the procedure parameters, computes the results, and sends a reply message. The server waits for the next call message. Finally, a process on the caller receives the reply message, extracts the results of the procedure, and the caller resumes execution.

Figure 2. In the RPC model, only one of the two processes is active at any given time. Furthermore, this model is only an example. The RPC protocol makes no restrictions on the concurrency model implemented, and others are possible.

For example, an implementation can choose asynchronous Remote Procedure Calls so that the client can continue working while waiting for a reply from the server. Additionally, the server can create a task to process incoming requests and thereby remain free to receive other requests. The client and server each have their own address spaces; that is, each has its own memory resource allocated to data used by the procedure. The following figure Figure 4.

Figure 4. The same marshalling engine is used on both the client and the server side, regardless of program architecture. There is a slight decline in performance when either the client or server uses an architecture different from the other because the marshalling engine must do additional translation during the communication.

The client stub then calls functions in the RPC client runtime library rpcrt4. If the server is located on a remote host, the runtime library specifies an appropriate transport protocol engine and passes the RPC to the network stack for transport to the server.

RPC Architecture [8] By replacing dedicated protocols and communication methods with a robust and standardized interface, RPC is designed to facilitate communication between client and server processes. The following figure Figure 3.

Figure 3. RPC Components [4] RPC includes the following major components: MIDL compiler Run-time libraries and header files Name service provider sometimes referred to as the Locator Endpoint mapper sometimes referred to as the port mapper In the RPC model, you can formally specify an interface to the remote procedures using a language designed for this purpose. The client application calls a local stub procedure instead of code implementing the procedure.

Stubs are compiled and linked with the client application during development. Instead of containing code that implements the remote procedure, the client stub code retrieves the required parameters from the client address space and delivers them to the client runtime library.

The client runtime library then translates the parameters as needed into a standard Network Data Representation NDR format for transmission to the server. Client: A process, such as a program or task, that requests a service provided by another program. Server: A process, such as a program or task, that responds to requests from a client. Endpoint: The name, port, or group of ports on a host system that is monitored by a server program for incoming client requests.

The endpoint is a network-specific address of a server process for remote procedure calls. The name of the endpoint depends on the protocol sequence being used. Endpoint Mapper EPM : Part of the RPC subsystem that resolves dynamic endpoints in response to client requests and, in some configurations, dynamically assigns endpoints to servers. Client Stub: Module within a client application containing all of the functions necessary for the client to make remote procedure calls using the model of a traditional function call in a standalone application.

The client stub is responsible for invoking the marshalling engine and some of the RPC application programming interfaces APIs. Server Stub: Module within a server application or service that contains all of the functions necessary for the server to handle remote requests using local procedure calls.