What is ISDN and What is it's necessity?
Integrated service Digital network. ISDN is a circuit-switched
telephone network system, that also provides access to packet
switched networks, designed to allow digital transmission of voice
and data over ordinary telephone copper wires, resulting in better
voice quality than an analog phone. It offers circuit-switched
connections (for either voice or data), and packet-switched
connections (for data), in increments of 64 kbit/s. Another major
market application is Internet access, where ISDN typically
provides a maximum of 128 kbit/s in both upstream and downstream
directions (which can be considered to be broadband speed, since it
exceeds the narrowband speeds of standard analog 56k telephone
lines). ISDN B-channels can be bonded to achieve a greater data
rate, typically 3 or 4 BRIs (6 to 8 64 kbit/s channels) are
bonded.