Message switching was the precursor of packet switching, where message were routed in their entirely and one hop at a time. It was first introduced by Leonard Klein rock in 1961. Message switching systems are now days mostly implemented over packet switched or circuit switched data networks. Hop by top telex forwarding are example of message switching system. Email is another example of a message switching system. When this form of switching is used. No physical path is established in advance in between sender and receiver. Instead, when the sender has a block of data to be sent, it is stored in the first switching office then forwarded late at one hop at a time. Each block is receive in its entity form, inspected for errors and then forwarded or re transmitted. It is a form of store and forward network. Data is transmitted into the network and store in a switch. The network transfer the data from switch ti switch when it is convenient to do so , as such the data is not transferred in real time.