QoS Traffic Requirements Voice

• 17-106 kbps guaranteed priority bandwidth per call

• 150 bps (+ Layer 2 overhead) guaranteed bandwidth for voice-control traffic per call

*one-way requirements

Voice traffic has extremely stringent QoS requirements. Voice traffic usually generates a smooth demand on bandwidth and has minimal impact on other traffic as long as the voice traffic is managed.

While voice packets are typically small (60 to 120 bytes), they cannot tolerate delay or drops. The result of delays and drops are poor, and often unacceptable, voice quality. Because drops cannot be tolerated, User Datagram Protocol (UDP) is used to package voice packets, because TCP retransmit capabilities have no value.

Voice packets can tolerate no more than a 150-ms delay (one-way requirement) and less than 1 percent packet loss.

A typical voice call will require 17 to 106 kbps of guaranteed priority bandwidth plus an additional 150 bps per call for voice-control traffic. Multiplying these bandwidth requirements times the maximum number of calls expected during the busiest time period will provide an indication of the overall bandwidth required for voice traffic.

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