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Chapter 14. Asynchronous Transfer Mode (... > 28. What kind of technology is neede...

28. What kind of technology is needed for data, voice, and video?

Data networking allows traffic characteristics that can be bursty in nature, and data can have variable-length packets or frames. Data traffic also can tolerate a certain amount of transmission delay, especially for non-real-time traffic. This implies that data arrival rates can be variable in nature, which suggests that variable-bit rate (VBR) transmissions are acceptable to data applications.

Voice traffic, on the other hand, is more sensitive to the arrival time of traffic. It’s a good idea for packets carrying part of a conversation to arrive quickly enough to avoid blank spots of time (“dead air”) in the conversation. This suggests a constant-bit rate (CBR) transmission be used for voice. There also is a problem with full duplex speech, where two or more people speak at exactly the same time and can be heard simultaneously. Networks don’t necessarily agree with this concept very well. Voice, however, is not a big bandwidth hog, as a rule, so fast data networks with VBR can support voice communications as long as the network is swift and does not suffer congestion or loss delays.


  

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