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

2-9
Design Considerations
Planning Call Capacity
Note These guidelines are estimates only and might vary based on the average
duration of calls. Your requirements might also decrease if your users begin
to make more peer-to-peer Lync calls instead of PSTN calls.
Table 2-4 provides at-a-glance guidelines. Use Table 2-5 to arrive at a closer
estimate for your environment.
Table 2-4. Solution Size Guidelines
Table 2-5. Estimate Local PSTN Call Requirements
After you estimate your needs, you can select the correct cards using Table 2-3
on page 2-6. Remember to select FXS interfaces if you need to provide connec-
tions for analog devices such as fax machines.
Examples
This section provides some simple examples for planning your SBM’s tele-
phony cards.
Example 1. You examine your PBX records and determine that the maxi-
mum number of concurrent calls is 55. Your company has two fax machines.
Branch Size Estimated Usage
Light Medium Heavy
Small
25 to 50 users
2 to 4 FXO interfaces Fractional T1/E1 1 T1/E1 interface
Medium
51 to 250 users
Fractional T1/E1 1 T1/E1 interface 1 to 2 T1/E1 interfaces
Large
251 to 500 users
1 T1/E1 interface 1 to 2 T1/E1 interfaces 2 to 4 T1/E1 interfaces
Very large
501 to 1000 users
2 T1/E1 interfaces 2 to 4 T1/E1 interfaces 2 SBMs
Usage Level Number of Users at
That Level
Estimated
Concurrent Calls
Total Estimated
Concurrent Calls
Light X = ____ X/15 = A = ______ A + B + C = D =
________
Medium
Y = ____ Y/10 = B = ______
Heavy
Z = ____ Z/5 = C = _______