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

2-14
Design Considerations
Planning Call Capacity
For remote PSTN calls, you can use the RTAudio bandwidth estimates or the
G.711 estimates. However, remember that Media Bypass requires the higher-
bandwidth G.711 codec. (See “Media Bypass” on page 2-17 for information
about Media Bypass.)
Table 2-11. Estimate WAN Bandwidth Requirements
You might need to add bandwidth to your WAN connection based on the
expected call load. You might also need to adjust your Service Level Agree-
ment (SLA) with your service provider.
Note also that, if you plan to route many branch PSTN calls through other
offices, you might need to add PSTN lines at those offices to support the call
load from the branch office. Use the same guidelines that you used for local
PSTN calls.
Example. You have 900 users. You estimate that they will make at most two
calls per hour to Lync users at other sites. Therefore, you plan for 90 simulta-
neous remote peer-to-peer calls. You estimate that users will make fewer than
one PSTN call that is routed through the main office per hour. In fact, you
believe that, out of any two users, only one will make such a call per hour.
Therefore, you divide 450 (900/3) by 15 and estimate 30 simultaneous remote
PSTN calls.
Call Type My Estimate for
Required Bandwidth
My Number of
Concurrent Calls
Total Estimated
Bandwidth
Remote peer-to-
peer calls
X = ____ E = ____ E*X = ____
Remote PSTN
calls
Y = ____ F = ____ F*Y = _____