Bandwidth Requirements 193BandwidthRequirementsThe interconnect bandwidth requirements depend on the selected audiocompression and system configuration [Layer 2 or Layer 3 (IP)] topology.NBX default audio settings deliver optimum audio quality. Any change todefault audio settings affects audio quality.Layer 2 Mulaw(G.711) Audio(Normal Setting)The interconnection bandwidth requirements for a device configured as aLayer 2 device running G.711 audio for each party in a conversationrequires a maximum of 73 Kbps. Thus, a point-to-point call requires thispeak bandwidth in each direction, while a 3-party conference requires apeak of 219 Kbps in one direction. For more information, see “Notes onBandwidth Requirements” later in this appendix.Layer 3 Mulaw(G.711) AudioThe overhead for running a device as a Layer 3 device results in amaximum bandwidth requirement of 86 Kbps per party in theconversation. Thus, a point-to-point call requires this peak bandwidth ineach direction, while a 3-party conference requires a peak of 258 Kbps inone direction. For more information, see “Notes on BandwidthRequirements” later in this chapter.Layer 2 ADPCM Audio(Reduced BandwidthSetting)The interconnection bandwidth requirements for a device configured as aLayer 2 device running ADPCM audio for each party in a conversationrequires a maximum of 42 Kbps. Thus, a point-to-point call requires thispeak bandwidth in each direction, while a 3-party conference requires apeak of 126 Kbps in one direction. For more information, see “Notes onBandwidth Requirements”later in this chapter.Layer 3 ADPCM Audio(Reduced BandwidthSetting)The overhead for running a device as a Layer 3 device results in amaximum bandwidth requirement of 54.7 Kbps per party in theconversation. Thus, a point-to-point call requires this peak bandwidth ineach direction, while a 3-party conference requires a peak of 164 Kbps inone direction. See “Notes on Bandwidth Requirements” next.Notes on BandwidthRequirementsSilence suppression reduces bandwidth requirements on average by 30 to40 percent. However, do not assume this much bandwidth reductionwhen determining peak requirements. These bandwidth reduction valuesdo not include link overhead (packet encapsulation, additional bytes forerror detection/correction, etc.) which may be added by the specificinterconnection device. This overhead is not under the control of the NBXsystem, but must be added based upon the device specification.
