Unoffered Codec Reordering
According to RFC 3264, the answerer can add codecs that were not offered to the Answer. The answerer may add new codecs as a means of advertising capabilities. RFC 3264 stipulates that these unoffered codecs must not be used. The RFC does not dictate where in the m= line these codecs can appear and it is valid that they may appear as the most preferred codecs.
In order to simplify the answer processing, the Oracle® Enterprise Session Border Controller moves all unoffered codecs in A0 to the back of the SDP answer before any other answer processing is applied.