ISDN
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Contents |
Overview
Integrated Services Digital Network (ISDN) is a type of circuit switched telephone network system, designed to allow digital transmission of voice and data over ordinary telephone copper wires, resulting in better quality and higher speeds than available with analog systems.
How It Works
With ISDN, there are two types of channels delivered. One is called the B Channel and the other is called the D Channel.
There are two kinds of ISDN bundles available:
Basic Rate Interface consists of two B channels, each with bandwidth of 64 kb and one D Channel with a bandwidth of 16 kbps. Together these three channels are known as 2B D. Available data bandwidth is 128Kb and the available voice lines is 2. Two B Channels are most commonly bonded together using MLPPP.
Primary Rate Interface
Contains 23 B channels and a D channel with a bandwidth of 64 kbps. Since the signaling has a dedicated channel the bandwidth is higher than the typical analog line's 56kb. Available data bandwidth is 1472Kb and the available voice lines is 23.
How Is It Installed?
A requirement of ISDN is that your office must be within 18,000 feet (about 3.4 miles or 5.5km) of the CO for BRI service; beyond that, expensive repeater devices are required, or ISDN service might not be available at all. PRI does not have the same distance limitations, though not all telecom providers offer PRI service.
Time Frame
PRIs and BRIs generally take from two weeks to 45 days to deliver based on carrier, network builds and complexity of service.
Uses
BRI
Generally used for video conferencing and for companies or residents not able to get DSL or cable access. With the expansion of DSL networks and the move to IP for video conferencing, most customers are moving away from BRIs.
PRI
Very common in the enterprise. Business use their advanced feature sets and control capabilities to power their corporate PBXs. PRIs help offices provide direct dialing numbers to their workers.
Pros/Cons
Cons
The only negatives to PRIs are the costs associated with the circuit and the complexity in the PBXs necesary to run them. With the bursty nature of IP, VoIP has been targeting the same customers that would buy PRIs and are expected to be the suceeding technology.
Pros
On the positive side, give companies better quality phone service with advanced management and features than typical analog lines.
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