PSN End-to-End functional specification

This memo is an updated version of BBN Report 5775, "End-to-End Functional Specification and describes important changes to the functionality of the interface between a Host and the PSN, and should be carefully reviewed by anyone involved in supporting a host on either the ARPANET or MILNET". The new End-to-End protocol (EE) is being developed in order to correct a number of deficiencies in the old EE, to improve its performance and overall throughput, and to better equip the Packet Switch Node (PSN, also known as the IMP) to support its current and anticipated host population.