- ISDN refers to a collection of standards that define a digital architecture that provides an integrated voice/data capability to a location, utilizing the public switched network and includes benefits such as the ability to carry a variety of user-traffic feeds, faster call setup, and faster data transfer rate.
- The International Telecommunication Union Telecommunication (ITU-T) Standardization Sector defined three sets of standards for ISDN: E-series protocol for telephone network and ISDN, I-series protocol for ISDN concepts, aspects and interfaces, and the Q-series protocol for Switching and Signaling.
- ISDN specifies two standard access methods: BRI which uses two 64-kbps B channels and one 16 kbps D channel, and PRI which offers 23 B channels and one D channel.
- The ISDN BRI call establishment includes call initiation to local switch, path establishment and data transmission between switches, destination signal reception, and B channel connection.
- ISDN device types include Terminal Endpoints Network Termination points and a Terminal Adaptor.
- The ISDN reference points S, T, U, and R define connection types between two functions.
- To determine how to select a Cisco router for ISDN, check for an ISDN interface on the back of the router and then contact the service provider to see if the NT1 is provided.
- There are various switch types available for ISDN throughout the world, including AT&T 5ESS and 4ESS, Northern Telecom DMS-100, VN2 and 3, and Net3 and 5.
- The IOS command sequence is used for specifying the ISDN switch, selecting an ISDN BRI interface, and specifying the Service Provider Identification (SPID) numbers required to access the ISDN network.