Cisco Small Business Pro SPA9000 Administration Manual page 66

Configuring Phone Lines and Calling Routing Behavior
Configuring Line Interfaces on the SPA9000
SPA9000 Voice System Administration Guide
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Bandwidth Requirements and Call Capacity
The available connection bandwidth determines the maximum number of
simultaneous calls that the system can support with the appropriate audio quality.
Before installing and configuring the Cisco SPA components, use this information
to determine the maximum number of simultaneous VoIP connections that the
system can support. For asymmetric connections, such as ADSL, the maximum
number of calls is determined by the upstream bandwidth. In general it is a good
practice to use no more than 75% of the total available bandwidth for calls. This
provides space for data traffic and helps ensure good voice quality.
The following table provides the approximate bandwidth budget for different
codecs.
Table 1 Bandwidth Budgeting
Codec Approximate bandwidth budget (kbps)
Each side of
conversation
G.711 110
G.726-40 87
G.726-32 79
G.726-24 71
G.726-16 63
G.729 55
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2 calls 4 calls
220 440
174 348
158 316
142 284
126 252
110 220
4
6 calls 8 calls
660 880
522 696
474 632
426 568
378 504
330 440
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