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.