SIP Redirect - Initiated 302 Response

The 2020 IMG supports receiving 3xx redirection messages. The Initiated 302 response feature adds the ability for the 2020 IMG to initiate a SIP Redirect by sending a 302 message back to the originating gateway with information of other 2020 IMG's in the route list or route table that the originating gateway can send the invite message to. Procedure below will explain configuration of SIP Redirect.

Before the Redirect feature was added a call came in on SIP GhGrp1 below and the TDM resources on that 2020 IMG were all busy then the 2020 IMG would send out a 486 Busy Here message and the call would be dropped. With the SIP Redirect feature the call will get passed on to the second and third 2020 IMG. SIP Redirect is in response to an INVITE message from a SIP Gateway. The Originating Gateway sends an INVITE message to 2020 IMG 0. The call signaling then gets passed to the TDM side. If 2020 IMG 0 has all its TDM resources being utilized, it will send a 302 response back to the originating gateway with contact information to 2020 IMG 1 and 2020 IMG 2. The Originating Gateway will then send an INVITE message to 2020 IMG 1 and the signaling will get passed to the TDM side. If all TDM resources on the 2020 IMG 1 are being utilized then the 2020 IMG 1 will send a 302 response back to originating gateway with contact information of the 2020 IMG 2 and 2020 IMG 0. Finally the 20202 IMG 2 accepts the INVITE and the call is processed. The Redirect feature allows multiple 2020 IMG's to be configured as one large gateway.

There are two ways two enable the Redirect feature the first is by enabling a field in the Route Table. The other way of enabling the Redirect feature is to create a route list. Within that Route List will be multiple channel groups. Within these Channel Group entries will be a field named 'Channel Group Type' which will enable the redirect feature for that channel group within the route list.

Note: There must be multiple channel group entries under the Route List with Redirect enabled for the feature to function properly.

 

SIP Redirect Diagram:

DG_SIP_Redirect_302Init.png

 

Configuration

The procedure below explains how to configure the 2020 IMG to function using the SIP Redirect 302 Initiated response message. Before configuring, each 2020 IMG in diagram above must have an initial configuration created on it. Follow the Basic Configurations procedure before proceeding. Once all initial steps have been executed the 2020 IMG can be configured for the SIP Redirect 302 Initiated response feature. Follow steps below:

 

Create TDM Signaling:

Create the Stack, Links, Routes, etc on the 2020 IMG 0. The remote nodes will be the 2020 IMG 1 and 2020 IMG 2. See diagram above

  1. Create SS7 signaling on the 2020 IMG 0. Right click on the Physical Node and select New Signaling. The signaling object will get created. The Signaling object is a container object for different signaling stacks. No configuration is needed here.

  2. Right Click on the signaling object and select New SS7. Leave Redundancy Configuration as StandAlone. Refer to the SS7 Signaling topic for more information.

  3. Right Click on SS7 Standalone and select New SS7 Stack. Enter OPC. In this example the OPC will be 1-1-1. Refer to the SS7 Stack topic for more information

  4. Right Click on the SS7 Stack and select New SS7 Link Set. Enter APC which will be 2-2-2 Point Code of PSTN in this example. Refer to the SS7 Link Set topicfor more information.

  5. Right Click on SS7 Link Set 0 and select New SS7 Link. Select the 2020 IMG 0 from the IMG field drop down list. The link will be on IMG 0 Span 0 Channel 0. Refer to the SS7 Link topic for more information

  6. Right Click on SS7 Link Set 0 again and select New SS7 Route. Give the DPC a point code of 2-2-2 which is the PSTN Point Code. Refer to the SS7 Route topic for more information.

  7. Refer to the Configuring SS7 topic for more information.

 

Create SIP Signaling Gateway Profile (SGP)

  1. Right Click on the Profiles object and select New SIP SGP. Change the SIP Profile ID to something other than ID:0 to allow the fields within the SIP SGP object to be modified.
  2. In the SIP SGP object enter a name in the SIP Profile Name field to identify this object.
  3. Verify the 3XX Redirect Support field is set to Enable (Default). For more information on the SIP SGP page refer to the SIP SGP topic.

 

Create SIP signaling stack

Each of the 2020 IMG's will need to have SIP signaling configured.

  1. Create a Signaling object for each of the nodes including 2020 IMG0, 2020 IMG1, and 2020 IMG2. Right Click on the Physical Node of each and select New Signaling. Refer to the Signaling topic for more information on this WebUI page.

  2. Right Click on signaling object just created on 2020 IMG, 2020 IMG1, and 2020 IMG2 and select New SIP. Select the SIP Gateway Profile (SGP) created above from drop down menu in the Remote IMG’s SIP Profile field. See screen capture above.

    SC_SIP_Redirect_SIPStack_Config.png
    For more Information refer to SIP Signaling

 

Create TDM Channel Groups:

For this feature to function properly, one TDM Channel Group is created. This channel group will have multiple ISUP Groups and CIC's configured. Each ISUP group and CIC group will be associated with one of the 2020 IMG's. See Diagram above.

  1. Right Click on IMG EMS object and select New Routing Configuration.

  2. Right Click on Routing Configuration and select New Channel Groups.

  3. Right Click on Channel Groups and select New Channel Group. Enter a name for this channel group. In this example the channel group was named ChGrp1_SS7.

  4. Select SS7 from the Signaling Type field drop down menu. For more information refer to the Channel Group topic.

  5. Right Click on ChGrp1_SS7 just created and select New ISUP Group. In the OPC-DPC field select the route that was configured when TDM signaling was created. In this example the OPC=1-1-1 and DPC=2-2-2. Click on ISUP Group 1 link to view a screen capture of the ISUP Group Pane.

  6. Right Click on the ISUP Group created and select New Circuits. In the 2020 IMG Name field select 2020 IMG 0. These CIC's will be connected to the 2020 IMG 0.  Click on CIC's on 2020 IMG 0 to display a screen capture of the ISUP Group Pane.

  7. Repeat Step 6 and 7 for ISUP Group 2. This ISUP Group needs to be under the same Channel Group which was previously created. Click on link to display ISUP Group 2 and CIC'S on 2020 IMG 1

  8. Repeat Step 6 and 7 for ISUP Group 3. This ISUP Group needs to be under the same Channel Group which was previously created. Click on link to display ISUP Group 3 and CIC'S on 2020 IMG 2

  9. It is important that the ISUP Groups and CIC's all be part of the same channel group for the feature to function properly. Click on link to view Channel Group Tree

 

Create SIP Channel Groups:

  1. Right Click on the Channel Groups Object and select New Channel Group. Enter a name for this channel group. In this example the channel group was named ChGrp1_SIP.

  2. Select SIP from the signaling type field drop down menu. For more information refer to Channel Group.

  3. Right Click on the Channel Group just created and select New IP Network element. Select IMG 0 from the drop down list. Click on link to display the IP Network Element 0 Pane.

Note: IP network element under SIP channel group should have IMG configured as PHYSICAL NODE. Feature will not work if under SIP channel group IMG is configured as EXTERNAL GW. For Route list explained below it can be configured either way.

  1. Create a second SIP Channel Group (ChGrp2_SIP) and IP Network Element. Click on IP Network Element 1 to display the Pane.

  2. Create a third SIP Channel Group (ChGrp3_SIP) and IP Network Element. Click on IP Network Element 2 to display the Pane.

 

Create Route Table:

The next few steps are for configuring routing using the Route Table method. If using a Route List, see Create Route List procedure below.

  1. Right Click on Routing Configuration and select New Routing Tables.
  2. Right Click on Routing Tables and select New Route Table. Give this Route Table a name in the Name field. In this example it was given RouteTable1.
  3. In the field Would you like to redirect call, select Yes from drop down menu. See screen capture below. This enables the redirect to occur.

    SC_SIP_RouteTable_RedirectCall.png

  4. Create a Route Entry under the Route Table. Right Click on Route Table and select Add Entry. Fill in the Route Entry fields. Select the SS7 Channel Group (ChGrp1_SS7) as the Outgoing Channel Group. For more information on Route Table Entries see the following link. Route Table Entry

  5. Once the Route Table is created go back to each of the SIP Channel Groups and in the route table field select the route table just created. Click on RouteTableEntry_in_SIP_ChanGrp to view Route Table entry in the SIP Channel Group. Configure a Route Table in each of the other SIP Channel Groups created for the SIP Redirect feature.

 

Create Route List:

The next few steps are for the Route List portion of this feature. All configuration up to creating route table in the example above is valid. Rather than creating a Route Table you will create a Route List.

  1. Right Click on IMG EMS object tree and select New Routing Configuration.

  2. Right Click on Routing Configuration object in object tree and select New Route Lists.

  3. Right Click on Route Lists object in object tree and select New Route List. A Route List Pane like will get created. Fill in the applicable fields. Refer to Route List for more information.

  4. Right Click on the Route List object and select New Channel Group. A Pane like below will appear. Within this pane will be a selection for Channel Group Type. The drop down menu will allow you to select Redirect. See Below

    SC_SIP_Redirect_RouteListPane.png
     

  5. Select from Group Name field, one of the SIP channel groups created earlier. Click on ChGroupSelection to view a screen capture of the SIP Channel Group selections under the Route List. Refer to Route List Entry (Channel Grp) for more information. Only SIP Channel Groups will be in this list.

  6. Repeat steps 4 and 5 for each of the Channel Groups being used in the Redirect feature.

 

Note: When creating a Route List, the 2020 IMG supports configuring up to three Channel Groups using the Redirect option.