IMG 1010 - Clear Channel Codec

Overview:

Feature 1261 adds to the IMG support for the Clear Channel Codec described as "Clear Mode" or "Clear Channel Data" in RFC4040 - RTP Payload Format for a 64 kbit/s Transparent Call. This Codec will be added to the list of Codecs supported and follow the same rules as the answer/offer model and Codec overlap currently supported. The second portion to this feature is that the IMG will examine the Bearer Capabilities on an incoming TDM call. If the Bearer Capability value of the incoming call matches a certain set of requirements and the 'Clear Channel Override' field in the SIP SGP Profile pane on the outgoing side is set to "enable" then the IMG will force the outgoing Codec to be clear channel. The clear channel Codec is supported on Mindspeed VoIP modules only. Below is information on the second portion which is forcing the outgoing Codec to Clear Channel.

Related Topics:

IMG 1010 - IP Bearer Profile

IMG 1010 - SIP Profile - 10.5.3

IMG 1010 - Vocoder Information

IMG 1010 - Vocoder Entry

Example:

Use the diagram above to follow the example call below.

• From the example diagram above, a call comes into the IMG using either SS7 or ISDN signaling. In order for this feature to function properly there must be certain values for the Bearer Capabilities. See tables below which explain what values need to be present. E1 and T1 will be looking for different values as shown below. These values are not configurable. They are hard coded to be used as triggers for a Codec Override in the Outgoing SIP INVITE.

 ANSI Incoming SS7  IAM parameter

 ISDN Incoming SETUP message ITU or ANSI

 ITU Incoming SS7 IAM parameter

• The IMG determines that one of the incoming values matches one of the values in the table. The IMG then looks at the value of the Clear Channel Override field in the SIP SGP Profile Pane. If the field is set to Disable (Default) then normal Codec negotiation will take place. If the field is set to Enable the IMG will send an INVITE out the channel group configured and force the Codec to be Clear Channel. Any Codecs offered by the remote gateway will be overridden with the Clear Channel Codec.

Configuration:

• The configuration procedure below assumes that the IMG already has an initial configuration including nodes, spans, profiles, interfaces, etc that an IMG will need as a base configuration.

• To configure the SIP SGP Profile object right click on the profiles object and select New SIP SGP.
  

  

• Once the SIP Profile Pane is created, select 'enable' from the Clear Channel Override field as shown below. See the IMG 1010 - SIP Profile - 10.5.3 link for more information on the SIP SGP Profile Pane
   
  

  

• Create an external gateway that the calls will go to. Right Click on IMG EMS object and select New External Network Elements.

• Right Click on External Network Elements and select New External Gateways.

• Right Click on the External Gateways object just created and select New External Gateway. Select SIP as Signaling Protocol and select the SIP SGP Profile created for the Clear Channel Mode. See IMG 1010 - External Gateway link for information on editing the rest of the Gateway Object

• Once the SIP SGP Profile Pane is created it can be used in an outgoing Channel Group. To accomplish this, a Channel Group going to an External Gateway must get created. Follow procedure below

• Right Click on IMG EMS and select New Routing Configuration from drop down menu.

• Right Click on Routing Configuration just created and select New Channel Groups.

• Right Click on the Channel Groups object just created and select New Channel Group.

• In the Channel Group that gets created enter a name and change signaling type to SIP. See IMG 1010 - Channel Group link for more information on editing the Channel Group Pane.

• Right Click on Channel Group just created and select New IP Network Element. In the object pane that gets created select from drop down list the gateway just created for the clear channel mode. By doing this any calls routed out this channel group will use the SIP SGP profile created earlier. In this example the profile is labeled ClearChannelGateway.
  

  

• Since this profile has the Clear Channel Override field set to enable, any calls routed out to the channel group created will use the clear channel Codec as long as the call coming into the IMG contains the correct information.

Additional Information:

• H.323 does not support the Clear Channel Codec

• Clear Channel Codec negotiation follows RFC 4040 when Clear Channel Override field is set to 'Disable' (Default)

• The Clear Channel Codec supports is supported in Profiles 4, 5, 6, and 7. See IMG 1010 - Setting Host Flags Link

• The Clear Channel Codec is supported on MindSpeed VoIP modules only. If Broadcom VoIP module is being used, the call will be rejected with a 488 Nack which is same behavior as all dynamic Codecs. (iLBC, AMR, EVRC, G.729e, and G.726)

• If the IMG forces the Outgoing call to Clear Channel Codec and the remote endpoint does not support Clear Channel a 488 Nack will be sent back to the IMG.

• The Default value for the Clear Channel Override field in the SIP SGP Profile is 'Disable'

• The Clear Channel Codec does not lower channel densities in any profile.

• Detection and Switching to Fax or Modem are not supported when utilizing the Clear Channel Codec.

• RTP Redundancy is supported when utilizing the Clear Channel Codec.

• The GCEMS IP Profile settings for Silence Suppression, Echo Cancellation, DTMF transport, fax mode, bypass codec, and Media Inactivity detection are not supported when clear channel Codec is used. These settings are ignored.