Linksys WIP310 SPA500 Series and WIP310 IP Phone Administration Guide - Page 125

Configuring Security, Quality, and Network Features Ensuring Voice Quality 5 Ensuring Voice Quality Voice quality perceived by the subscribers of the IP Telephony service should be indistinguishable from that of the PSTN. Cisco IP phones support several codecs. See: • "Supported Codecs" section on page 114 • "Bandwidth Requirements" section on page 115 • "Factors Affecting Voice Quality" section on page 116 Supported Codecs Negotiation of the optimal voice codec sometimes depends on the ability of the Cisco IP Phone to "match" a codec name with the far-end device/gateway codec name. Cisco IP phones allow the network administrator to individually name the various codecs that are supported such that the correct codec successfully negotiates with the far-end equipment. Note that Cisco IP phones support voice codec priority. You can select up to three preferred codecs. The administrator can select the low-bit-rate codec used for each line. G.711a and G.711u are always enabled. The following table shows the codecs supported by Cisco IP phones. The third column shows the voice quality Mean Opinion Score (MOS), with a scale of 1-5, in which higher is better. Codec (Voice Compression Algorithm) G.711 (A-law and u-law) Complexity and Description MOS Score Very low complexity. Supports uncompressed 64 kbps digitized voice transmission at one through ten 5 ms voice frames per packet. This codec provides the highest voice quality and uses the most bandwidth of any of the available codecs. 4.5 Highest voice quality Cisco SPA 500 Series and WIP310 IP Phone Administration Guide 114