The AT&T Architecture: Evolving to an ISDN

Modern communications has evolved to a network architecture based on distributed intelligence. First introduced in the public network and later expanded by private network developments, out-of-band signaling has been used to achieve this distributed architecture. Integrated Services Digital Network takes this to the next step by linking private and public networks to each other and to terminals and hosts in a fully distributed processing achitecture that allows integrated support of voice, data, and video applications.