ISDN (Integrated Service Digital Network) isa combination of CCITT standards for digital transmission over telephone copper wire as well as over media. They transfer analog as well as digital both on the same network.
N-ISDN architecture consists of various channels according to their speed. B channel provide speed up to 64kbs where d- channel provide 16/64 kbps. These are slow channels. But h channels are much faster than b or d channel. There are four h channels like ho=384 kbps, h10-1472 kbps, h11-1536, h12-1920 kbps.
They have two types of interfaces used BRI and PRI. BRI is slow as it has 2 b channels and one d channels (2B+D). Whereas PRI in some of the countries provide (23B+D) like USA and (30B-D) in EUROPE. B-ISDN h21 have speed 32.768 mbps, h22 43 to 45 mbps speed and h4 have 132 mbps to 138.24 mbps.
Signaling process: Meta signaling are bi-directional in nature and they use 1 SVCs per interface, whereas General broadcast are unidirectional in nature and they also 1 SVCs per interface but in case of Selective they may use several SVCs per user interface.
Protocol reference model: Consist of two high layers, second ATM adaption layerthen ATM layer and at last physical layer. Whereas OSI model as only 3 layers network layer, link layer and at last physical layer.
B-ISDN services; it provide facility of messaging services, conversational services, user controlled presentation, retrieval systems.
Applications: remote video surveillance, voice conferencing, data transfers, customer requirement, phone services, videotext, online services etc.
Conclusion: ISDN is better technology as it provides less cost consumptions over telephone. They have greater demand across the globe for computer to computer data communication, it provide multi service like image, video, integrating voice data and video over the networks.
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