What is RPC?- RPC in Operating System

Updated April 6, 2023

Overview of Remote Procedure Call (RPC)

A remote Procedure Call or RPC is used in distributed computing, and this call occurs when a procedure is executed in a different address space. This protocol is helpful when the process does not know other computer’s network details and the service is requested in a different computer. This is also called a subroutine call or function call. This has a client-server model. The arguments are passed to a remote procedure and the call is sent to the server by the client. RPC can be used in Windows, Apple, and UNIX. The authentication of RPC is DES so that the application can be made secure.

RPC in Operating System

A Remote Procedure Call (in short RPC) is a protocol used by operating systems to allow processes to communicate across a network. RPC allows a process running on one computer to call a procedure on another computer, as if the procedure was running locally.

When a process makes an RPC call, it sends a message containing the procedure name and any necessary arguments to the remote computer. The remote computer receives the message, executes the procedure, and returns the results back to the calling process. The calling process then continues execution as if the procedure had been executed locally.

RPC provides a high-level abstraction for communication between processes, allowing developers to write distributed applications without having to worry about the underlying networking details. RPC is often used in client-server architectures, where a client process makes RPC calls to a server process to access its services.

Some common implementations of RPC include Sun RPC (used in Unix-based systems), Microsoft’s DCOM (Distributed Component Object Model), and CORBA (Common Object Request Broker Architecture).

Key takeaway

• RPC clients possess a broadcast function, so they can transfer messages to multiple servers and get the corresponding replies
• RPC can make a nonblocking server call or client call. The call can be completed by procedure related to the client.
• The function to send many nonblocking client calls is referred to as a single batch.

What does RPC do?

When a program that uses the RPC framework is compiled, the compiler generates a stub for each remote procedure that the program can call. The stub is a piece of code that represents the remote procedure and handles the communication with the remote server.

When the program is executed, and a remote procedure call is made, The stub intercepts the remote procedure call request from the client program and forwards it to the client runtime program, which is responsible for handling network communication and sending the request across the network to the server application. When the client stub is first invoked, it queries a name server to obtain the transport address of the server application, which it then uses to send the remote procedure call request across the network.

Once the client runtime program knows the address of the server, it sends the request message containing the name of the remote procedure and any arguments to the server over the network. The server receives the request and passes it to its own runtime program and stub that interfaces with the remote procedure.

The remote procedure is executed on the server, and the results are sent back to the client using the response-request protocol. The server runtime program and stub package the results into a response message, which is sent back to the client through the network.

Upon receiving the response message, the client runtime the program and stub unpack the results and return them to the calling program. This allows the calling program to access the results of the remote procedure call as if it had been executed locally.

How does RPC Work? (Working of RPC)

Once the remote procedure call is raised, the present environment is halted, the parameters of the procedures are sent through the network to the current environment where the RPC is executed and then the requested procedure takes place in that environment. Once the procedure is completed, the output is transferred back to the current environment, somewhere, the execution is continued as if it is executing from the standard procedure call.

The working of RPC is described in the below steps:

Client stub, client, and RPC run-time are executed on the client machine

A client initiates the process of client stub by passing the parameters in the standard method. The package of procedure parameters is known as marshaling. The client stub saves the data within the own address space of the client and requests the local RPC runtime to transfer again to the server stub.

Then the user can work on RPC by following the standard procedural calls. Now the RPC runtime works on the message transmission in the network connection between the client and server. It manages the retransmission of jobs, routing, acknowledgment, and encryption.

Once the server procedure is completed, it comes back to the server stub that packs or marshalls the output values to a message which is then sent back to the transport layer by the server stub.

Here the transport layer transfers the result message to the transport layer of the client, which is transferred back as a message into the client stub.

In this final stage, the output parameters are unpacked by the client stub from the resulting packet, and finally, the execution process is returned to the caller.

Types of RPC:

Here are some types of RPC:

1. Synchronous RPC: In synchronous RPC, the client program makes a request to the server and waits for a response before proceeding. This means that the client program is blocked until it receives a response from the server.
2. Asynchronous RPC or Callback RPC: In asynchronous RPC, the client program sends a request to the server and continues executing without waiting for a response. After the server receives the remote procedure call request from the client, it executes the requested procedure and sends the response back to the client through the network when it is ready. Asynchronous RPC is often used when the server may take a long time to acknowledge or when the client needs to continue executing without blocking.
3. Broadcast RPC: In broadcast RPC, the client sends a message to all servers on the network, and each server that is able to handle the request responds. Broadcast RPC is often used when multiple servers can handle a request and the client wants to receive responses from all of them.
4. Batch-mode RPC: In batch-mode RPC, the client sends a batch of requests to the server, and the server processes them all before sending back a batch of responses. This can be more efficient than sending individual requests and responses, as it reduces the overhead of network communication. Batch-mode RPC is often used when the client needs to make multiple requests to the server, but does not need to receive immediate responses.

   Issues of Remote Procedure Calls (RPC) 

1. RPC Runtime

The RPC runtime is a software component that manages the communication and execution of remote procedure calls in an RPC system. The runtime is responsible for handling multiple requests from clients, dispatching them to the server application, and returning the results to the client. Issues related to the RPC runtime can include performance bottlenecks due to high request volume or network latency, as well as security concerns related to authentication and encryption of the network communication.

2. Stub

In an RPC system, a stub is a software component that acts as a proxy on the client side for a remote procedure located on the server side. In an RPC system, stubs can be present on both the client side and the server side.

• On the client side, the stub is generated by the client’s RPC runtime system, which provides a set of API functions that the client program uses to call the remote procedure. The stub marshals the arguments of the remote procedure call into a format that can be transmitted over the network to the server, and sends the message to the server. After the server returns the results, the stub unmarshals the results and passes them back to the client program.
• On the server side, the stub is generated by the server’s RPC runtime system, which provides a set of API functions that the server program uses to register the remote procedure and respond to client requests. The stub unmarshals the remote procedure arguments sent by the client, calls the actual remote procedure implemented by the server, and marshals the return values or output parameters back to the client.

3. Binding

In an RPC system, binding refers to the process of associating a client program’s remote procedure call with a specific server program that provides the implementation of the remote procedure. Binding can involve two main processes: naming and locating.

• Naming: Naming involves assigning a name or identifier to the remote procedure that the client program wants to call. The name can be a human-readable name or a machine-readable identifier, and can be used by the client program to reference the remote procedure when making the remote procedure call.
• Locating: Locating involves determining the network address or location of the server program that provides the implementation of the remote procedure. This can involve querying a name server or directory service that maintains a mapping between remote procedure names or identifiers and network addresses or locations.

4. The calling semantics associated with RPC.

The calling semantics associated with RPC refers to the way in which client programs make remote procedure calls and handle potential errors or failures during the RPC process. Some common calling semantics include:

• Retry request message: If a client program does not receive a response from the server after making a remote procedure call, it may retry sending the request message a certain number of times before giving up. This can help ensure that the remote procedure call is successfully processed, even if there are network or server issues that initially prevent the call from completing.
• Duplicate filtering: To avoid processing the same remote procedure call multiple times, the server may use a technique called duplicate filtering, where it checks incoming requests to see if they are duplicates of requests, it has already processed. If a request is found to be a duplicate, the server can simply return the same results it returned for the original request rather than processing the call again.
• Retransmission of results: In some cases, the client program may need to retransmit the results of a remote procedure call back to the server for additional processing or validation. This can involve resending the results over the network using the same RPC framework used for the original remote procedure call.

RPC features

The features of RPC in os are as follows,

• RPC hides the difficulties in the message transmission procedure from the user
• RPC involves particular layers in OSI models
• Clients can interact with the server by means of higher-level languages
• RPC operates effectively in local and remote environments
• RPC program is compiled in simple code which is easy to understand
• The threads and processes in the operating system can be easily managed by RPC

RPC characteristics:

The standard attributes of RPC are listed below,

• Transparency: RPC provides a transparent mechanism for calling remote procedures, allowing client programs to invoke procedures on remote servers as if they were local.
• Encapsulation: RPC encapsulates the details of network communication, allowing client programs to call remote procedures without having to worry about the complexities of low-level network protocols.
• Heterogeneity: RPC supports heterogeneous environments, allowing programs running on different operating systems and hardware architectures to communicate with each other.
• Interoperability: RPC provides a standardized interface that allows programs written in different programming languages to communicate with each other.
• Scalability: RPC can be used to build large, distributed systems, allowing programs to call remote procedures on servers located anywhere on the network.
• Security: RPC can be secured using various authentication and encryption mechanisms to ensure that only authorized clients can call remote procedures.
• Performance: The performance of RPC can be affected by factors such as network latency and server load, but optimized implementations can provide fast and efficient remote procedure calls.

Advantages and disadvantages of RPC

Advantages:

• Easy to use: RPC provides a simple and familiar programming model, allowing developers to call remote procedures in a similar way to local function calls.
• Encapsulation: RPC encapsulates the details of network communication, allowing developers to accentuate on the logic of their application rather than the complexities of low-level network protocols.
• Interoperability: RPC provides a standardized interface that allows programs written in different programming languages to communicate with each other, enabling developers to use the best tools for the job.
• Scalability: RPC can be used to build large, distributed systems, allowing programs to call remote procedures on servers located anywhere on the network.
• Security: RPC can be secured using various authentication and encryption mechanisms to ensure that only authorized clients can call remote procedures.

Disadvantages:

• Performance: The performance of RPC can be affected by factors such as network latency and server load, which can make it slower than local function calls.
• Complexity: RPC introduces additional complexity into the application, requiring developers to handle issues such as network failures and timeouts.
• Coupling: RPC can lead to tight coupling between the client and server, making it difficult to change the interface or migrate to a new system.
• Debugging: Debugging RPC-based applications can be more difficult than local applications, as issues may arise due to network communication or remote procedure invocation.
• Overhead: RPC introduces additional overhead in terms of network communication and serialization/deserialization of data, which can impact performance and scalability.

Conclusion

In conclusion, Remote Procedure Call (RPC) is a powerful mechanism for building distributed applications. It allows client programs to call remote procedures on servers located anywhere on the network, providing a transparent and standardized interface for inter-process communication. Remote Procedure Call is a strategy that is getting progressively significant in material science tests, with the abundance of circulated handling power. By understanding the different types and characteristics of RPC, developers can choose the most appropriate approach for their application and build reliable and efficient distributed systems.

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