Here are some of the mechanisms which are used to send messages in multicomputers:
Packet switching: Packet switching is a type of switching mechanism in multicomputers where each message is divided in to a number of packets. Then, a packet is delivered to the first switch. After the packet is transferred fully to the first switch, then it is transferred to the next switch and so on until the destination has arrived. Advantage of packet switching mechanism is that it is a very efficient. However a major disadvantage is that it takes a considerable amount of time to send packets to the destination.
Circuit switching: In this process the path from the source to destination is determined. Then, data in the form of bits is sent all at once from source to destination. The transfer of data is very fast in this process.
Blocking or synchronous calls: Messages are sent by using “send” calls and received by using “receive” calls. In blocking mechanism, when a “send” is called, the sending process is blocked and it waits until the “send” is finished. Similarly when “receive” is called then the receiving process is blocked until the “receive” is finished.
Non-blocking or asynchronous calls: In this mechanism, the sending and receiving processes are not blocked and they keep working in parallel with the “send” and “receive” calls. Thus, by this method the communication is faster.