Inter-process Communication Concepts

Two Primitives:

• send(destination, message)

• receive(source, message)

Addressing

Direct addressing or Indirect addressing

Direct Addressing

With symmetric direct addressing, both the sender and the receiver processes must name the other to communicate.

send(P, message)
receive(Q, message)

With asymmetric direct addressing, only the sender names the recipient, the recipient is not required to name the sender.

send(P, message) // Send a message to process P
receive(id, message) // Receive a message from any process; the id is set to the name of the sender

Indirect Addressing

Messages are sent to a shared data structure consisting of queues. Such queues are generally called mailboxes.

Benefit of indirect addressing: (more flexibility) The relationship between senders and receivers can be one-to-one, many-to-one, one-to-many, or many-to-many.

The ownership of a mailbox：

• Process mailbox ownership: Only the owner process may receive messages from the mailbox, and other processes may send to this mailbox.

• System mailbox ownership

Synchronization

Sender and receiver may or may not be blocking.

• Blocking send, blocking receive: Both sender and receiver are blocked until message is delivered. Called a rendezvous.

• Nonblocking send, blocking receive: Sender continues processing such as sending messages as quickly as possible; Receiver is blocked until the requested message arrives.

• Nonblocking send, nonblocking receive: Neither party is required to wait.

Buffering

• Zero capacity: the sender must block until the recipient receive the message

• Bounded capacity: the queue has finite length n; full or not-full?

• Unbounded capacity: the queue length is potentially infinite.The sender never blocks.