SIP-ALG: Denied Codecs

You can use the SIP-ALG Denied Codecs feature to specify one or more VoIP voice, video, or data transmission codecs to deny on your network. When a SIP VoIP connection is opened that uses a codec specified in this list, your XTM device reads the value from the SIP 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 a SIP-ALG:

  1. On the Edit page for the SIP-Client proxy action, select the Denied Codecs tab.
    The Denied Codecs settings.

Screen shot of the Edit Proxy Action page for the SIP-Client, Denied Codecs section

  1. To add a codec to the list, in the Denied Codecs text box, type the codec name or unique text pattern in the text box.
    Do not use wildcard characters or regular expression syntax. Codec patterns are case sensitive.
  2. Click Add
  3. To delete a codec from the list, select the codec and click Remove.
  4. To create a log message when your XTM device strips the codec information from SIP traffic that matches a codec in this list, select the Log each transaction that matches a denied codec pattern check box.
  5. Click Save.

See Also

About the SIP-ALG

SIP-ALG: General Settings

SIP-ALG: Access Control

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