The Interface Message Processor Program.

The ARPA Network has been in operation for over four years and has become an international facility. The network has grown to over forty-five sites spread across the continental United States, plus satellite connections to Hawaii, Norway, and England, and is steadily growing over forty independent computer systems of varying manufacture are interconnected. Provision has been made for terminal access to the network from sites which do not enjoy the ownership of an independent computer system. Implementation of the IMPs required the development of a sophisticated computer program which has been previously described. As stated then, the principal function of the IMP program is the processing of packets, including the following segmentation of Host messages into packets receiving, routing, and transmitting store-and-forward packets retransmitting unacknowledged packets, reassembling packets into messages for transmission into a Host and generating RFNMs and other control messages., The program also monitors network status, gathers statistics, and performs on-line testing. Author