Clear Channel Codec Support

Clear Channel Codec support adds to the 2020 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 aspect to this feature is that the 2020 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 2020 IMG will force the outgoing Codec to be clear channel. Below is information on forcing the outgoing Codec to Clear Channel.

 

 

DG_ClearChannelCodec.png

 

Example

Use the diagram above to follow the example call below.

  1. From the example diagram above, a call comes into the 2020 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

USI (User Service Information)

 Value

 

Information Transfer Capability
  • Unrestricted Digital Information
  • Restricted Digital Information
Information Transfer Rate
  • 64 kbits/sec

 

ISDN Incoming SETUP message ITU or ANSI

Bearer Capability

 Value

 

Information Transfer Capability
  • Unrestricted Digital Information
  • Restricted Digital Information
Information Transfer Rate
  • 64 kbits/sec

 

ITU Incoming SS7 IAM parameter

TMR (Transmission Medium Requirement)

 Value

 

Information Transfer Capability
  • Unrestricted Digital Information
Information Transfer Rate
  • 64 kbits/sec

 

  1. The 2020 IMG determines that one of the incoming values matches one of the values in the table. The 2020 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 2020 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

  1. The configuration procedure below assumes that the 2020 IMG already has an initial configuration including nodes, spans, profiles, interfaces, etc that an 2020 IMG will need as a base configuration. Refer to the Basic Configurations topic for more information.
  2. Right click on the profiles object and select New SIP SGP.
  3. Once the SIP Profile Pane is created, change the SIP Profile Id to a value other than 0. By changing this value the rest of the fields can now be modified.
  4. Select enable from the Clear Channel Override field as shown below. Refer to the SIP Profile topic for more information on the SIP SGP Profile Pane.

SC_SIP_ClearChannelCodec_ProfilePane.png

  1. Create an external gateway that the calls will go to. Right Click on IMG EMS object and select New External Network Elements. Refer to the External Network Elements Topic for more information on this object.

  2. Right Click on External Network Elements and select New External Gateways. Refer to the External Gateways Topic for more information on this object.

  3. 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. Refer to the External Gateway topic for information on editing the rest of the Gateway Object.

  4. 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. Right Click on IMG EMS and select New Routing Configuration from drop down menu. Refer to the Routing Configuration topic for information on this object.

  5. Right Click on Routing Configuration just created and select New Channel Groups. Refer to the Channel Groups topic for information on this object.

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

  7. In the Channel Group that gets created enter a name and change signaling type to SIP. Refer to the Channel Group topic for information on this object.

  8. 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.

SC_SIP_ClearChannelGateway.png

  1. 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 2020 IMG contains the correct information.

 

Additional Information