ISDN & FDDI

ISDN (Integrated Services Digital Network) ISDN is an all-digital, circuit-switched network system that was originally designed by the world's telephone companies and service providers as a replacement for the aging analog telephone system. There are three different ISDN implementations:   1. BRI (Basic Rate ISDN) This is the ISDN version that is most interest to customers because it operates over the existing copper wire local loop to provide digital voice and data channels. BRI is sold as two channels of 64 Kbps each (called the B channels) and one 16-Kbps channel (called the D channel) used for signaling, such as call setup. The B channels can be used for either voice or data and combined to form a 128-Kbps data channel.   2. PRI (Primary Rate ISDN) Organizations with a need for ISDN at higher data rates (for network connections) get involved with PRI. It basically provides additional channels as required up to a total of 23 B channels and one 64-Kbps D channel for a total bandwidth that is equivalent to T1 (1.544 Mbps).

Network Introduction Network Cabling Wireless Network Network Interface Card OSI Model Protocols Ethernet - Network architecture Token Ring - Network architecture AppleTalk and ArcNet - Network architectures Repeaters, Bridges, Routers, and Gateways E-mail Standards Modem & Async Comm. T1, T3, and Switched 56 Digital Connectivities Packet-Switching Network,Frame Relay and ATM ISDN & FDDI

3. B-ISDN (Broadband ISDN)

B-ISDN service rate is above 155 Mbps. It was developed in anticipation of future video and multimedia services. The B-ISDN architecture defines ATM at roughly the data link layer and SONET (Synchronous Optical Network) at the physical layer.

SONET is a fiber-optic network implemented primarily by the carriers on an international scale. The carriers use B-ISDN technology to connect their own systems. End users can take advantage of it through prior other high-data-rate links such as DSL (Digital Subscriber Line).
 

There is one outstanding diference between BRI/PRI and B-ISDN. B-ISDN is an ATM-based cell-switching service. In contrast, BRI and PRI are circuit-switching services. However, B-ISDN can implement virtual circuits in its cell streams.

FDDI (Fiber Distributed Data Interface)

FDDI is a specification that describes a high-speed (100 Mbps) token-passing ring network that uses fiber-optic media. It was developed by the ANSI X3T9.5 commitee, and released in 1986. FDDI was designed for high-end computers that did not find enough bandwidth in existing 10 Mbps Ethernet or 4 Mbps Token Ring architecture.

FDDI can be used for metropolitan area networks (MANs) to connect networks in the same city with a high-speed fiber-optic cable connection. It is limited to a maximum ring length of 100 kilometers, so it is not really designed to be used as a WAN technology.

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