Redirecting Number Assertion (ISDN to SS7)

Owned by Kelli Higdon
Last updated: Apr 03, 2024
6 min read

 

 

Redirecting Information that is  present in the SS7 IAM messages indicates that call forwarding has occurred. The Redirecting Number Assertion feature gives a user the ability to create and insert individual elements in the Redirection Information and Redirecting Number parameters into an outgoing SS7 IAM message. The Redirection Information Assertion object is used to insert the Redirection Information and Redirection Number parameters. The feature is supported on a call received from an ISDN network and transmitted to an SS7 network only. Refer to the information below. 

Call Flow Diagrams

Set redirection counter to release call

In the example below, the remote SS7 switch is configured to release the call when the Redirection Counter number reaches a value greater than 2.

Example 1

 

  1. The remote SS7 Switch is configured to reject the forwarded call if its Redirection Counter is greater than 2.

  2. By using this feature, the user configures the IMG to set the Redirection Counter value to 3.

  3. The IMG creates the Redirection Information parameter which contains the configured Redirection Counter parameter and transmits the Redirection Information out to the SS7 network in an SS7 IAM message.

  4. The SS7 switch increments and checks the value of the Redirection Counter. Since the Redirection Counter value is set to 3,the remote SS7 switch sends a RELEASE message back to the original caller

  5. If the Redirection Counter value was set to less than 2, the SS7 switch would forward the SS7 IAM message.

Example 2

In the example below, the remote SS7 switch is configured to release the call when the Redirection Counter number reaches a value greater than 2.

 

  1. The remote SS7 Switch on the outgoing SS7 side is configured to reject the forwarded call if its Redirection Counter parameter is greater than 2.

  2. By using this feature, the user configures the IMG to insert a value of 2 as the Redirection Counter in the outgoing SS7 IAM message.

  3. The IMG creates the Redirection Information parameter containing the configured Redirection Counter parameter.

  4. The remote SS7 switch increments and checks the value of the Redirection Counter.

  5. Since the Redirection Counter value inserted by IMG is not greater than 3, the remote SS7 switch accepts the call.   

Insert Redirection information into the outgoing IAM message

The call flow below displays the redirection information being inserted.

Configuration

Below are instructions on how to configure the IMG 2020 to add redirection information into the outgoing SS7 IAM message.  In the procedure below the incoming side is ISDN and the outgoing side will be SS7 since the feature supports a call going from ISDN to SS7 only. Before configuring, the IMG 2020 must have an initial configuration created on it. Refer to the Basic Configurations procedure and verify the basic functionality has been configured. Also, since the feature uses interworking between the SS7 and ISDN, verify the SS7 stacks and/or the ISDN Signaling have been configured. Refer to the Configure SS7 and Configure ISDN topics for more information.

Create ISDN Signaling and ISDN Channel Group (Incoming Channel Group)

  1. Right click on the Signaling object and select New ISDN. A ISDN D-Channels object will get created. This is a container object and no configuration is needed here. Refer to the ISDN - Signaling topic for more information on this object.

  2. Right click on the ISDN D-Channels object and select New ISDN D-Channel. Configure the D-Channel in this object. Refer to the ISDN D-Channel object for more information on configuring this object.

  3. Right click on IMG EMS and select New Routing Configuration. A Routing Configuration Pane will appear. Refer to the Routing Configuration topic for more information on this object.

  4. Right click on Routing Configuration and select New Channel Groups. A Channel groups container object is created and no configuration is needed in this object. The Channel Groups object allows multiple channel groups to be created under it. Refer to the Channel Groups topic for more information on this object.

  5. Right click on the Channel Groups Object and select New Channel Group. A Channel Group object will appear. Enter a name for this channel group and set the Signaling Type to ISDN. In this example, the channel group was labeled ChGrp_ISDN. Refer to the Channel Group topic for more information on configuring the remaining fields in this object.

  6. Right click on the ISDN Channel Group just created and select New ISDN Group. Select a D-Channel from drop down menu in the ISDN D channel field. Refer to the ISDN Group topic for more information on configuring the remaining fields in this object.

  7. Right click on the ISDN Group object just created and select New ISDN Circuits. Select which DS-1s/DS-0s will be utilized in this group. Refer to the IMG 1010 - ISDN Circuits topic for more information on configuring this object.

Create SS7 Channel Group (Outgoing Channel Group)

  • Right click on the Channel Groups object again and select New Channel Group. A Channel Group object will appear. Enter a name for this channel group and set the Signaling Type to SS7. In this example, the channel group was labeled ChGrp_SS7. Refer to the Channel Group topic for more information on configuring this object.

The Redirecting Number feature is supported on outgoing SS7 channel groups. Since the redirecting feature functions on outgoing channel groups only, select either Outgoing or Incoming/Outgoing from the field labeled Channel Group Function in the Channel Group object.

  • Right click on the channel group created and select New ISUP Group. Select the correct stack from the OPC-DPC field drop down menu. Refer to the ISUP Group topic for more information on configuring this object.

  • Right click on the ISUP group created and select New Circuits. Select the Spans/Channels that will be configured and enter a Starting CIC number. Refer to the SS7 - Circuit Group under Signaling topic for more information on configuring this object.

Configure the Redirection Information and Redirection Number parameters

  • Right click on the ISUP group created under the SS7 channel group and select New Redirection Information Assertion. Modify the Redirection Information Assertion field to the  Enabled selection. Depending on what parameters are to be added will depend on which fields are to be modified. Refer to the Redirection Information Assertion topic for more information on configuring the fields in this object.

From here, any routing and/or translation tables can be configured. Refer to the routing and translation topics for information on configuring those functions.

Additional Information

  • The Redirection Information Assertion feature is applicable only from ISDN to SS7 and is supported in both ANSI and ITU.

  • The Redirection Information Assertion feature is applicable for outgoing SS7 channel groups only.

  • When the feature is enabled, the IMG 2020 will create the Redirection Information parameter and add it to the SS7 IAM outgoing message.

  • The digits from the Calling Party Number in the incoming messaging will be used to create the Redirecting Number.

  • The IMG 2020 will set the values for the advanced parameters through the Redirecting Number parameter with the advanced parameters from the Calling Party Number parameter.

  • If the Calling Party Number parameter is not available, the IMG 2020 will not create the Redirecting Number parameter but will create the Redirection Information Parameter.

  • The IMG 2020 will not override the Redirection Information parameter if it is already interworked from the incoming side and is present in the IAM message.

  • The IMG 2020 will not override the Redirecting Number parameter if it is already interworked from the incoming side and is present in the IAM message.

  • If the Channel Group Function field in the SS7 channel group is set for Incoming Trunks, the Redirection Information Assertion object can not be created.

  • The feature is applied after both incoming and outgoing translations. The redirecting number which is created from the calling party number will be based on the translated number.

  • There will be no compatibility issues regarding a mismatched BDN EMS and IMG 2020 software. If a IMG 2020 is running software with the support for this feature and the BDN EMS does not, the config bytes would not be present and the option would not be enabled. If the IMG 2020 is running software without this feature and the Redirection Assertion Information object has been configured and enabled,the config bytes would be set but not processed.

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