Intelligence Network Services

The evolution of stored program control switching and common channel signaling has facilitated the development of several new public network based services--e.g., 800 Service, Automatic Calling Card Service, etc. As an application of these capabilities to private network service, Virtual Private Network (VPN) has emerged as a state-of-the-art alternative to meet private customers' networking needs. VPN service--a software-based virtual network service--simulates a private network using public network switching and transmission facilities. This paper describes the motivation and evolution of VPNs as well as their typical features and capabilities. Due to the author's familiarity with the products, more detailed examples of specific implementation on AT&T products are presented to help the reader gain insight into the applications of the VPN concept.