Delayed Answer
- Kelli Higdon
Delayed ANM is used in conjunction with the SIP REFER feature. In a normal SS7/ISDN to SIP call, the IMG 2020 would send an ANM/Connect message after receiving a 200 OK message. A Voice Path would be opened between the IMG 2020 and the PSTN. When Delayed Answer is enabled, the CONNECT or ANSWER message is not sent immediately. Instead, the SIP device then transfers the call to a new destination which could be either SIP or PSTN. When the transfer target answers the call the ANSWER, CONNECT, or 200 OK message is then sent back to the original PSTN caller. This feature is used mainly to delay billing charges until the call is connected to its final destination rather than starting billing time before the call is transferred. See Call Flow diagrams below. This feature is supported in SS7 to SIP and ISDN to SIP scenarios.
Call Flow Diagrams
Delayed ANM Enabled (SS7 to SIP)
Delayed ANM Disabled (SS7 to SIP)
Configuration of Delayed Answer
Initial Configuration
The procedure below explains how to configure the IMG 2020 for the SIP Delayed Answer feature. Before configuring, the IMG 2020 must have an initial configuration created on it. Follow the procedure before proceeding.
Create a Signaling Profile (SGP) for Delayed ANM.
Right click on the Profiles object and select New SIP Profiles. The SIP Profiles object is a parent or container object. No configuration is needed here. Refer to the topic for more information on this object.
Right click on the SIP Profiles object and select New SIP Profile. The first profile that gets created is a Default SIP Profile and cannot be modified. Disregard this profile.
Right click on the SIP Profiles object and select New SIP Profile again. In the SIP Profile object that appears, either enter a name that identifies this SIP Profile or accept the default name already entered. In this example the SIP Profile was labeled Delayed_ANM_SIP_Profile. For information on configuring the individual fields in the SIP Profile object, refer to the topic.
Right click on the SIP Profile object just created and select New SIP REFER Support. The Delayed Answer Support feature cannot be enabled until after the REFER Support field has been enabled. Enable the REFER Support field by selecting Enabled from drop down menu. Once this is done, the Delayed Answer Support field can now be modified. Refer to topic for more information
Create a Remote Gateway object
Create an external network element. To associate the SIP profile created with a remote SIP gateway, an external network element must be created. Follow the procedure below to communicate with a remote gateway.
Right click on the Dialogic object and select New External Network Elements. The External Network Elements object is a parent or container object and no configuration is needed here. Refer to topic for more information.
Right click on External Network Elements and select New External Gateways. The External Gateways object is a parent or container object also and no configuration is needed here. Refer to for more information.
Right click on External Gateways and select New External Gateway. Enter a name that identifies the gateway being configured. In this example the gateway was labeled Delayed_ANM_GW.
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Refer to the topic for more information.
Configure SIP Signaling
The configuration above displays how to configure the SIP Profile and External SIP Gateway so that the Delayed Answer functionality is configured. The next step is to configure the SIP signaling stack and SIP Channel Groups. Refer to the topic for a procedure on how to configure the SIP functionality.
Additional Information
Delayed Answer is supported from TDM to SIP call direction only.
If the SIP device transfers the call to a new destination, and the transfer target answers the call, the answer indication will be sent back to PSTN caller.
If the call transfer failed, the answer indication will not be sent back to PSTN caller. In this case, a release message with cause code will be send back to PSTN side.
On received SIP 200 OK, a new guard timer shall be started and it will be canceled when REFER is received. In case of there no REFER is received in 30 seconds, the timer will be expired in 30 second, the ANM will be sent out to SS7 side.
The Delayed Answer Support can be enabled only if the REFER Support is Enabled. If “REFER Support” is disabled, the user can not enable the Delayed Answer feature.