3Com 3C10200 NBX Installation Guide - Page 231

Bandwidth Requirements 231 Bandwidth Requirements The interconnect bandwidth requirements depend on the selected audio compression and system configuration [Layer 2 or Layer 3 (IP)] topology. NBX default audio settings deliver optimum audio quality. Any change to default audio settings affects audio quality. Layer 2 Mulaw (G.711) Audio (Normal Setting) The interconnection bandwidth requirements for a device configured as a Layer 2 device running G.711 audio for each party in a conversation requires a maximum of 73 Kbps. Thus, a point-to-point call requires this peak bandwidth in each direction, while a 3-party conference requires a peak of 219 Kbps in one direction. For more information, see "Notes on Bandwidth Requirements" later in this appendix. Layer 3 Mulaw (G.711) Audio The overhead for running a device as a Layer 3 device results in a maximum bandwidth requirement of 86 Kbps per party in the conversation. Thus, a point-to-point call requires this peak bandwidth in each direction, while a 3-party conference requires a peak of 258 Kbps in one direction. For more information, see "Notes on Bandwidth Requirements" later in this chapter. Layer 2 ADPCM Audio (Reduced Bandwidth Setting) The interconnection bandwidth requirements for a device configured as a Layer 2 device running ADPCM audio for each party in a conversation requires a maximum of 42 Kbps. Thus, a point-to-point call requires this peak bandwidth in each direction, while a 3-party conference requires a peak of 126 Kbps in one direction. For more information, see "Notes on Bandwidth Requirements"later in this chapter. Layer 3 ADPCM Audio (Reduced Bandwidth Setting) The overhead for running a device as a Layer 3 device results in a maximum bandwidth requirement of 54.7 Kbps per party in the conversation. Thus, a point-to-point call requires this peak bandwidth in each direction, while a 3-party conference requires a peak of 164 Kbps in one direction. See "Notes on Bandwidth Requirements" next. Notes on Bandwidth Requirements Silence suppression reduces bandwidth requirements on average by 30 to 40 percent. However, do not assume this much bandwidth reduction when determining peak requirements. These bandwidth reduction values do not include link overhead (packet encapsulation, additional bytes for error detection/correction, etc.) which may be added by the specific interconnection device. This overhead is not under the control of the NBX system, but must be added based upon the device specification.