IMG 1010 - SIP Redirect IMG Initiated 302

The IMG supports receiving 3xx redirection messages. The SIP Redirect IMG Initiated 302 response feature initiates a SIP Redirect by sending a 302 message back to the originating gateway with contact information of other IMG's configured in a route list. When the originating gateway receives the 302 with the contact info, it can then send an INVITE message to the next IMG in the Route List.

Refer to the diagram below. Before the Redirect feature was added a call came in on SIP_GhGrp1 below. The TDM resources on that IMG were all busy so the IMG would send out a 486 Busy Here message and the call would be dropped. With the SIP Redirect feature the call gets passed on to the second and then third IMG. SIP Redirect is in response to an INVITE message from a SIP Gateway. The Originating Gateway sends an INVITE message to IMG 0. The call signaling then gets passed to the TDM side. If IMG 0 has all its TDM resources being utilized, it will send a 302 response back to the originating gateway with contact information to IMG 1 and IMG 2. The Originating Gateway will then send an INVITE message to IMG 1 and the signaling will get passed to the TDM side. If all TDM resources on the IMG 1 are being utilized then the 2020 IMG 1 will send a 302 response back to originating gateway with contact information to IMG 2 and IMG 0. Finally IMG 2 accepts the INVITE and the call is processed. The Redirect feature allows multiple IMG's to be configured as one large gateway.

The Redirect feature is enabled in the Route List. First a Route List is created, Within that Route List will be multiple channel groups. Within these Channel Group entries will be a field labeled Channel Group Type which will enable the redirect feature for that channel group within the route list. The Procedure below will explain configuration of SIP Redirect.

Open

Configuration

The SIP Redirect IMG Initiated 302 feature is configured in the Channel Group Type field of the SIP Channel Groups that will be configured as redirect channel groups (3 Redirect Channel Groups per Route List). The configuration information below is a high level description of where the redirect feature is configured. Refer to the IMG 1010 - SIP Redirect IMG Initiated 302 - Example topic for a more complete example of how this feature is configured.

Configured under the Route List object

1. Right click on IMG EMS object tree and select New Routing Configuration. This will create a Routing Configuration object. For more information on the Routing Configuration object, refer to the IMG 1010 - Routing Configuration Object topic.

2. Right click on the Routing Configuration object and select New Route Lists. The Route Lists object is a parent or container object and no configuration is needed here. Refer to the IMG 1010 - Route Lists topic for more information on this object.

3. Right click on the Route Lists object and select New Route List. Enter a name that identifies the Route List being created. Refer to the IMG 1010 - Route List topic for more information on configuring the remaining fields in this object.

4. Right click on the Route List object and select New Channel Group. An object pane like below will get created. Select Redirect from the drop down menu of the Channel Group Type field. Refer to screen capture below. Once Redirect is selected, only the channel groups configured using the SIP protocol are selectable from the drop down menu of the Group Name field. At this point, whichever channel group selected in the Group Name field will have the SIP Redirect IMG Initiated 302 feature enabled on it.

   Open

   

Additional Information

Refer to Diagram above:

• The SIP Redirect IMG Initiated 302 feature is supported only on Incoming SIP Channel Groups.

• Referring to the diagram above, on the TDM side there are three ISUP groups configured with CIC's configured under each. The ISUP Groups all need to be configured under one TDM Channel Group.

• If the Route List has channel groups that do not have the redirect feature enabled, those channel groups will all be grouped above the channel groups with the redirect feature enabled.

• Up to three SIP Channel Groups with redirect feature enabled are allowed in each Route List