HP Survivable Branch Communication zl Module powered by Microsoft Lync Planning and Design Guide 2011-02

2-12
Design Considerations
Planning Call Capacity
Table 2-8. Estimate Concurrent Remote Peer-to-Peer Calls
Table 2-9. Estimate Concurrent Remote PSTN Calls
Next, you need to estimate the bandwidth required per call. This bandwidth
depends on several factors, including:
■ The codec used—A typical peer-to-peer Voice over IP (VoIP) call uses the
RTAudio narrowband codec. Other calls might use RTAudio wideband for
higher fidelity. A call destined to the PSTN might use either the RTAudio
narrowband codec or the G.711 codec, depending on whether Media
Bypass is enabled (Media Bypass requires G.711 encoding), and also on
other factors such as the need for low latency (less than 20 ms) and low
loss (these also require G.711).
■ The amount of silence on the call—Voice Activity Detection (VAD) sup-
presses VoIP traffic during silence.
Usage Level Number of Users at
That Level
Estimated
Concurrent Calls
Total Estimated
Concurrent Calls
Light
One remote peer-to-
peer call per user per
hour
X = ____ X/15 = A = ______ A + B + C = D = E =
________
Medium
Two remote peer-to-
peer calls per user
per hour
Y = ____ Y/10 = B = ______
Heavy
Three remote peer-
to-peer calls per user
per hour
Z = ____ Z/5 = C = _______
Usage Level Number of Users at
That Level
Estimated
Concurrent Calls
Total Estimated
Concurrent Calls
Light
One remote PSTN
call per user per hour
X = ____ X/15 = A = ______ A + B + C = D = F =
________
Medium
Two remote PSTN
calls per user per
hour
Y = ____ Y/10 = B = ______
Heavy
Three remote PSTN
calls per user per
hour
Z = ____ Z/5 = C = _______