SIP Trunk Group Selection


Use these features if you have a Centralized Routing Model and do not require the IMG to perform routing decisions. These features are enabled or disabled in the SIP Profile, which can be assigned on a SIP Gateway or SIP Signaling basis.


When the OTG field is included in the “From” header the IMG will use this trunk group as the incoming trunk group to determine which route table to use. The OTG will also be able to be added to the “From” header in an outbound SIP INVITE (the OTG will have the A side trunk group name).  

The IMG extracts the OTG from the SIP "From" header and passes it in the initial Setup. If an OTG is found, the IMG will use that channel group instead of the one that came from the lookup table in the SIP process.


When the DTG is received in the request-URI the IMG will skip the mid-call router and use the DTG that was received as the outbound channel group.

When the IMG is about to perform routing for the outbound side, it will look for the DTG from the same location as the Calling Party Number. If the DTG is valid, the call will then use the channel group that corresponds to that DTG instead of performing a routing lookup


On an outgoing invite, the OTG that was received from the incoming call will take precedence over the internal IMG incoming channel group name if it was a SIP call (for any other inbound protocol, the OTG would be the incoming Trunk Group Name). This OTG is then appended in the “From” header of the outbound invite.