Message Passing system is subsystem of Distributed System that provides a set of message based IPC protocol and does so by hiding details of complex network protocols and multiples heterogeneous platform from programmers.

2 Primitives: Send 2 Receive.

Features of Message Passing: - Simplicity: Simple and Ease to use. Simple and Clear Semantics of IPC Protocols of message passing makes it easier.

• Uniform Semantics: There are two types of communication :

  • Local

  • Remote

    1. Semantics of Remote should be as close as possible to local communication for ease of use.

• Efficiency :

  • It can be made efficient by reducing number of message exchange.

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

  • Minimizing the cost of maintaining connections.

  • Piggybacking.

• Reliability :

  • Distributed System is prone to node crashes or communication link failure resulting into loss of data.

  • Handling of lost message

• Duplicate messages, capable of detecting and handling duplicates.

• Generating and assigning appropriate sequences

• Correctness :

  • Issues

• Atomicity: Message to All of None.

• Order Delivery: Message in Order.

• Survivability: Message delivery despite of partial failure.

• Flexibility :

  • User may choose types and level of reliability

  • Synchronous/Asynchronous, Send/Receive Choice.

• Security:

  • It must provide secure end to end communication.
  • Necessary Steps:

• Authentication of receiver by sender.

• Authentication of sender by receiver.

• Portability:

  • Two Aspects:

• Message passing system should itself be portable.

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