Which codec does Cisco recommend for WAN links?
G.729 is the recommended voice codec for most WAN networks (that do not do multiple encodings) because of its relatively low bandwidth requirements (8 kbps) and high MOS (3.92). (p. 531 640-863)
The MOS (mean opinion score) is a common benchmark used to specify the quality of sound produced by specific codecs. To determine the MOS, a wide range of listeners judge the quality of a voice sample corresponding to a particular codec on a scale of 1 (bad) to 5 (excellent). The scores are averaged to provide MOS for that sample.
Questions & Answers collection