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Configuring Phone Lines and Calling Routing Behavior
Configuring Line Interfaces on the SPA9000
SPA9000 Voice System Administration Guide 64
4
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 B andwidth Budgeting
Codec Approximate bandwidth budget (kbps)
Each side of
conversation
2 calls 4 calls 6 calls 8 calls
G.711 110 220 440 660 880
G.726-40 87 174 348 522 696
G.726-32 79 158 316 474 632
G.726-24 71 142 284 426 568
G.726-16 63 126 252 378 504
G.729 55 110 220 330 440