Preferential Service in the PSTN

This chapter has presented an existing preferential communications system that is deployed in the U.S. PSTN. It operates in tandem with the general public and is designed to increase the probability that a call with get through the PSTN when it, or parts of it, are experiencing congestion. The service requires an authorization code from the user. This represents a distributed authorization system, which can be contrasted against the organizational and centralized system of AUTODIN (discussed in chapter 4).