Subject :- Data Structures

Topic :- Communication

Difficulty :- Low

Message Passing system (MPS) of Distributed System provides a set of message based IPC protocols. It hides the details of complex network protocols and multiples heterogeneous platforms from programmers.

A typical Message passing system uses two Primitives for communication: SEND ( Data, Receivers Address), RECEIVE(Data)

Features of Message Passing: -

Simplicity: A MPS should be Simple and Easy to use. It must have Simple and Clear Semantics of IPC Protocols which makes message passing easier.

Uniform Semantics: There are two types of communication :Local and Remote Semantics of Remote should be Same or at least as close as possible to local communication for ease of use.

Efficiency : A Message Passing System Should be efficient and it can be made efficient by,
Reducing the total number of message exchange.

Avoiding cost of setting and terminating connections between the same pair. Minimizing the cost of maintaining connections.

Piggybacking the acknowledgments with next message to same receiver.

Reliability :

Distributed System is prone to node crashes or communication link failure resulting into loss of data. MPS can be made reliable by designing the algorithms which deal with the problems like : Handling of lost message, Duplicate messages.

A MPS should be capable of detecting and handling duplicates, Generating and assigning appropriate sequences.

Atomicity: The atomicity property tells that message in the distributed system must be sent to All intended receivers or None.

A good MPS delivers the messages in a proper Order.

It also offers the Survivability: Means ability of Message delivery despite of partial failure.

Flexibility :

User may choose types and level of reliability.

Synchronous/Asynchronous, Send/Receive Choice.

Security:

A good MPS must provide secure end to end communication. TO achieve security the possible ways are :Authentication of receiver by sender, Authentication of sender by receiver, Encryption and Decryption.

Portability:

A good MPS should be portable with respect to Two Aspects:

Message passing system should itself be portable.

Applications written by using primitives of IPC Protocols of Message Passing System should be Portable.