ffic with bandwidth and delay ance mismatch and the four-wire/two-wire conversion variation guarantees. The use of VC queues allows each between the telephone handset and the communication traffic stream to be treated uniquely. Priority can be given network. It can, depending on the severity, disrupt the for the transmission of voice traffic. The use of small, normal flow of conversation. Its severity depends on the fixed-size cells reduces queuing delay and the delay vari- round-trip time delay. It is found that if the round-trip ation associated with variable-sized packets. time delay is more than 30 ms, the echo becomes sig- nificant, making it difficult to have a normal conversation. Benefit of VoATM End-to-end delay With the standards now in place, it is possible for packet Voice is most sensitive to delay and mildly sensitive to switching techniques such as Frame Relay or ATM to deliver high-quality speech. Some of the intrinsic ad- variations in delay (jitter). It is highly critical that the delay is kept at a bare minimum to hold an interactive vantages ATM has over other network technologies are listed here. communication end-to-end. It has been found that delay can have two effects on communication performance. The very format of the cell was arrived at by consider- Delay can interfere with the dynamics of voice com- ing data, voice, and video payload requirements. munication, in the absence of noticeable echo, whereas in ATM cells are of fixed size, 53 bytes each with 48 the presence of noticeable echo, increasing delay makes bytes for payload and 5 bytes for ATM header. This echo effects worse. When the delay reaches above 30 ms, helps in reducing the packetization delay signifi- echo cancellor circuits are required to control the echo. cantly, which is one of the major delay parameters. Once the echo cancellor circuits are in place, network It supports extensive QoS, which allows voice traffic delays can be allowed to reach up to 150 ms without to be transmitted across the network in a reliable furth