Direct Communicationand Indirect communication

Direct Communication

· Direct communication establishes a link between two processes. A communication link is a unidirectional path along which information flows.

· two processes use single communication link to share information.

· In this metod, there cannot be more that one link between two processes

direct communication

· Send and receive function used in direct communication are given below :

· Send(process name , message ,(receive(process name , message)

Send(A, message )- send a message to process A

Receive(A, message )-receive a message from process B

Indirect communication

· In indirect communication , no direct communication link exists between two processes.

· In this , messages are sent to and received from mailbox.

· A mailbox is a specialized repository where message can be placed by processes and from which message can be removed .

· In direct communication , more than two processes can shares a mailbox.

· No communication , more than two processes is possible if they do not share a mailbox.

· Each mailbox has a unique identification.

indirect communcation

· A process can communicate with some with other process via a number of different mailbox.

· The send and receive primitives in indirect communication are:

Send(mailbox,message)and receive(mailbox,message)

Send(P,message)-send a message to mailbox P

Receive (P,message)-receive a message from mailbox P

· A strength of the use of indirect addressing is that , by decoupling other sender and receiver , it allows for greater flexibility in the use of messages.

· The relationshipbetween sender and receiver processes can be one to one and many to one , one to many or many to many

· A oneto-one relationship allows a private communication link to be set up between two processes .in such a way , the interaction between these two processes is insulted from erroneous interfaces from other processes.

· A many-to-many relationship is used In client/ server interaction . one process provide service to number of other processes .in such a case , mailbox is called as port.

· A one-to-many relationship allows for one sender and multiple receive processes .it is useful for application where a message or some information is to be broadcast to set of processes.

· A mailbox may be owned either by a process or by the operating system.

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