| Integrated services of voice, data, teleconferencing and other applications are receiving wider attention and acceptance with the data and digital communications counimunity. The growth of the Internet is one area in which integrated services are in demand. Transporting text, graphics and multimedia data across the "Net" efficiently has become a big concern for network designers. ISDN is supplying one method for accessing the Internet and delivering these integrated services. For applications that require higher data transfers or larger bandwidth allocations, a second form of ISDN, known as broadband ISDN or BISDN, is being made available.
The original specification is being renamed N-ISDN which stands for narrowband ISDN Within internal inter-networks, routing protocols, ATM, and frame relay continue the job of routing these services through networks to their destination user. ATM is a cell based service that encapsulates packet data into fixed units known as cells and transports them across numerous networks. Frame relay contrasts with ATM in the use of variable size frames to handle the traffic across the networks. Table 8.1 shows a comparison of routing protocols for ISDN, ATM and frame relay.
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Table 8.1 |
Protocol Comparisons |
Parameter |
ISDN |
ATM |
Frame relay |
Bandwidth |
64-128 Kbps |
1.544 Mbps |
64 Kbps-1.544 Mbps |
|
BRI |
|
|
|
1.544 Mbps |
|
|
|
2.048 Mbps |
|
|
|
PRI |
|
|
Type |
Packet/circuit switch |
Cell switch |
Packet-switched frames. |
Features |
Integrated services: |
Integrated services; |
Variable packets; |
|
secure, reliable, |
QoS, reliable secure, |
bandwidth on demand; |
|
bursty traffic |
all types of traffic. |
point-to-point connectivity. |
Weak points |
Variable tariff rate; |
Lack of standards. |
Expensive; requires |
|
difficult to install |
|
dedicated lines; |
|
and configure |
|
complicated to make |
|
|
|
moves and changes. |
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