November 5th, 2009 | 
Author: Principle of ISDN:
The main feature of the ISDN concept is to support a wide range of voice and nonvoice applications in the same network using a limited number of standardized facilities. ISDNs support a wide variety of applications, including both switched connections. Switched connections include both circuit- and packet-switched connections and their concatenations. Whenever practical, new services introduced into an ISDN should be compatible with 64-kbps switched digital connections. The 64-kbps digital connection is the basic building block of ISDN.
Objectives of ISDN:
System standardization; ensure universal access to the network. Achieving transparency; allow customers to use a variety of protocols and applications. Separating functions; ISDN should not provide services that preclude and competitiveness. Variety of configurations; provide private-line and switched services, addressing cost-related tariffs; ISDN service should be directly related to cost and independent of the nature of the data. Migration; provide a smooth transition while evolving. Multiplexed support; provide service to low-capacity personal subscribers as well as to large companies.
Evolution of ISDN:
ISDNs will be based on the concepts developed for telephone ISDNs and may evolve by progressively incorporating additional functions and network features including those of any other dedicated networks such as circuit and packet switching for data so as to provide for existing and new services. In the evolution toward an ISDN, digital end-to-end connectivity will be obtained via plant and equipment used in existing networks, such as digital transmission, time-division multiplex, and/or space-division multiplex switching. During this period, arrangements must be developed for the internetworking of services on other networks.
Broad band ISDN:
Broad band ISDN is defined by the ITU-T as service that provides transmission channels capable of supporting transmission rates greater than the primary data rate. With BISDN, services requiring data rates of a magnitude beyond those provided by ISDN, such as video transmission, will become available. With the advent of BISDN, the original concept of ISDN is being referred to as narrowband ISDN. The broadband node is called a broadband network termination, which codes the data information into smaller packets used by the BISDN network. Data transmission within the ISDN network can be asymmetric of the network.
Posted in Digital Communication
