Linksys SPA921 Cisco SPA9000 Voice System Administration Guide - Page 66

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