You can use the H.323-ALG Denied Codecs feature to specify one or more VoIP voice, video, or data transmission codecs to deny on your network. When an H.323 VoIP connection is opened that uses a codec specified in this list, your XTM device reads the value from the H.323 header in the "a=rtpmap" field and strips the codec information from the connection negotiation.
The Denied Codecs list is empty by default. We recommend that you add a codec to this list if the codec:
For example, you might choose to deny the G.711 or G.726 codecs because they use more than 32 Kb/sec of bandwidth, or you might choose to deny the Speex codec because it is used by an unauthorized VoIP application.
For a list of codecs and the name or text pattern associated with each codec, see http://www.iana.org/assignments/rtp-parameters/rtp-parameters.xml. When you add a codec to the Denied Codecs list, make sure to specify the value in the Encoding Name column for that codec.
To configure the denied codecs settings for an H.323-ALG:
About the H.323-ALG
H.323-ALG: General Settings
H.323-ALG: Access Control