What is B-ISDN?

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  • Written By: Solomon Branch
  • Edited By: Allegra J. Lingo
  • Last Modified Date: 11 October 2019
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B-ISDN stands for Broadband Integrated Services Digital Network. It was designed to be the next step of the basic Integrated Services Digital Network (ISDN), which utilizes the public switched telephone system to transfer data. B-ISDN allows for the use of high-bandwidth applications, which was problematic for ISDN.

Integrated Services Digital Network (ISDN) was first introduced in the late 1980s. It was originally supposed to replace the analog signal used in the telephone system with a digital signal. This way it could be used for voice and data transmission. The idea was that if an agreement was obtained for a worldwide standard for ISDN usage, the price to produce the ISDN chips would be less expensive, thus leading to a high rate of user demand. It took years for an agreement to be reached and by the time it was finalized, the ISDN technology had been replaced by other modes of transmission.

The advantage of an ISDN network is that it uses the existing phone lines to transport data, video, voice, and other signals all at the same time, utilizing a digital signal. ISDN provides, depending on the signal type being transmitted and the specific interface type, anywhere from a rate of 64 kilobits per second (kbps) to 128 kbps, and technically it can go up to 2 megabits per second (mbps). B-ISDN, considered high-end ISDN, has a range of 155 mbps to 622 mbps.


A demand for higher bandwidth for use in video and voice transfer over the Internet was the primary driving force behind the development of a new system. Basic-rate ISDN, the standard interface that ISDN uses, lacks the required capacity to carry these signals in its channels. Businesses that used a local area network (LAN), which typically moved at 10 mbps, found the usual rate of 64 kbps slowed overall connectivity down a great deal. This prompted the introduction of B-ISDN, the broadband update for ISDN.

Despite its high speed and availability of use in fiber-optic networks, B-ISDN has not been widely implemented for use in networks or for Internet connectivity. For home networks, cable and DSL have been the primary technologies for network connections to the Internet. Businesses use a variety of connectivity types, primarily T1 and T3 lines, for Internet connectivity. Ethernet is still the main choice for LANs in both instances.

B-ISDN uses Asynchronous Transfer Mode (ATM). ATM utilizes small, same-sized data packets which create a more reliable signal than the typical variable-sized packets Ethernet networks use, which is an important thing for voice packets that need to be transferred in real-time. ATM is now used primarily in Digital Subscriber Lines (DSL) and in some wireless technologies.


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