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.
