Integrated Services Digital Network
Posted On Thursday, February 7, 2008 at at 11:06 PM by Murali SrinivasanIntegrated Services Digital Network
ISDN is a circuit-switched telephone network system, designed to allow digital transmission of voice and data over ordinary telephone copper wires, resulting in better voice quality than an analog phone. It offers circuit-switched connections (for either voice or data) in increments of 64 kbit/s. One of the major use cases is Internet access, where ISDN typically provides a maximum of 128 kbit/s.By combining your two B-channels you have access to up to 128 kbps more than four times as fast as a 28.8 kbps modem on a standard phone line. ISDN is a set of protocols for establishing and breaking circuit switched connections, and for advanced call features for the user.It is used for real-time videoconferencing. ISDN provides simultaneous voice, video, and text transmission between individual desktop videoconferencing systems and group videoconferencing systems.
The Basics
There are two types of ISDN channels or communication paths:
- B-channel
The Bearer ("B") channel is a 64 kbps channel which can be used for voice, video, data, or multimedia calls. B-channels can be aggregated together for even higher bandwidth applications.
- D-channel
ISDN Configurations
The user will get the ISDN connection in 2 configurations. They are,
- Basic Rate Interface (BRI)
BRI is the ISDN service most people use to connect to the Internet. An ISDN BRI connection supports two 64 kbps B-channels and one 16 kbps D-channel over a standard phone line. BRI is often called "2B+D" referring to its two B-channels and one D-channel. The D-channel on a BRI line can even support low-speed (9.6 kbps) X.25 data.BRI is the most common ISDN service for Internet access. A single BRI line can support up to three calls at the same time because it is comprised of three channels (2B+D). Two voice, fax or data "conversations," and one packet switched data "conversation" can take place at the same time.
- Primary Rate Interface (PRI)
ISDN PRI service is used primarily by large organizations with intensive communications needs. An ISDN PRI connection supports 23 64 kbps B-channels and one 64 kbps D-channel (or 23B+D) over a high speed DS1 (or T-1) circuit. The European PRI configuration supports 30B+D.
- Internet access
- Telecommuting/remote access to corporate computing
- Real-time Video conferencing
- Small and home office data networking