Mumbai University > Computer Engineering > Sem 8 > parallel and distributed systems

Marks: 5M

The first middle ware model has started with the distributed file system, where the files were stored and distributed over the network.

Models of middle ware are as follows:

Remote Procedure call:

It is one of the succesful middle ware models used in modern distributed applications for communication.

It uses local call to call a procedure resides on the remote machine to get the result.

Hidden communication is done between client and server.

For eg If a user wants to get the sum of two numbers stored on remote server by using local method call, the user calls method with parameters, in turn server receives a RPC call from the client and returns the appropriate result to the client.

Therefore, though the method was executed remotely it appears like a local to the called machine.

This is a synchronous technology where both the client and server should be present during the communication.

Message oriented Middleware(MOM):

It is another model used to send and receive the communication messages between clients and servers.

It uses data structures like queue to store and retrieve messages.

When the client is sending the messages faster than the receiver receiving it or the client is sending the message when the receiver is not available. So it uses queuing mechanism between the client and server to avoid the message been misplaced.

It is asynchronous mechanism where messages can be sent even though the receiver is not available

For eg Email system

Distributed Object Technology

The distributed object technology has changed the scope of middleware technologies to one step up where objects are distributed to the remote server to facilitate the client.

Eg RMI and CORBA

The distributed object mechanism hides the communication interfaces and their details to provide access to the remote object efficiently.

Remote Method Invocation

In this objects are distributed and located by using the RMI registry.

The client can access remote objects by using the interfaces.

Disadvantage

It didnt support the concept of hetrogeneity and is compatible with java platform only. Common object request broker architecture(CORBA)-

It is one of the most popular distributed object technologies where objects can be accessible from remote location through ORB.

Server and client communicate with each other through object request broker bus.

To map the semantics of objects and fetch the appropriate object an interface definition language is used.

It is evolved with service based middle ware where service models are used.

In service model, the services are published by the service providers and consumed by the service consumer.

eg Service oriented Architecture (SOA)