System Design Considerations; Bandwidth Requirements And Call Capacity - Linksys SPA921 - Cisco - IP Phone Installation And Configuration Manual

Preparation

System Design Considerations

System Design Considerations
NOTE
SPA9000 Voice System Installation and Configuration Guide for Setup Wizard
When installing and configuring the SPA9000 Voice System, it is necessary to
analyze and meet some design considerations to ensure the best quality and user
experience. The design considerations cover available bandwidth and quality of
service.

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 devices, 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.
Some ITSP SIP trunk services limit the maximum number of simultaneous calls.
Please check with your Service Provider to understand the maximum number of
simultaneous calls each SIP trunk supports.
The following table provides the approximate bandwidth budget for different
codecs.
Codec Approximate bandwidth
budget for each side of
conversation
G.711 110 kbps
G.726- 87 kbps
40
G.726- 79 kbps
32
G.726- 71 kbps
24
2 calls 4 calls
220 440
kbps kbps
174 348
kbps kbps
158 316
kbps kbps
142 284
kbps kbps
3
6 calls 8 calls
660 880
kbps kbps
522 696
kbps kbps
474 632
kbps kbps
426 568
kbps kbps
31