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Overview

The SBC Core is enhanced to support SIP Registrar functionality for SIP end points. This feature allows the Ribbon SBC to act as an Access SBC with Registrar functionality in a single deployment.

The Ribbon SBC acting as a SIP REGISTRAR provides the following functions:

  • Allows users to configure a subscriber profile. The profile is stored in the internal database.
  • Handles the REGISTER request locally. The SBC establishes endpoint binding and removes the bindings on receiving a SIP DEREGISTER message or timeouts as defined in RFC 3261.
  • Challenges the REGISTER and INVITE request received from a subscribed user.
  • Proxies the incoming calls based on stored bindings:
     – The incoming INVITE from the user to the Access SBC is routed to the SIP LOCAL REGISTRAR hosted in the same instance based on the Trunk Group (TG) control flag.
     – The Registrar routes the incoming calls back to the Access SBC hosted on the same instance, which is again routed to the called endpoint.

The following types of users can manage the SIP Registrar functionalities.

  • Administrator
  • Operator
  • Field Service

You can configure the SIP Registrar functionality from both the SBC EMA and CLI interfaces. Refer to the relevant pages in the CLI and EMA guides that describe how to configure and use the SIP Registrar functionality.

Recommended SIP Transport Settings for SIP Registrar

The recommended transport protocol to use on the SIP REGISTRAR TG is UDP. Refer to SIP TG - Signaling - Transport Preference - CLI and Egress IP Attributes - SIP - CLI, for details.

For the SIP Registrar feature to work correctly, select UDP at either the IPSP or TG level, for the REGISTRAR TG.

At the SIP Sig port level, if none of the sig ports in the zone have UDP supported, the CLI validation returns a failure while setting the Registrar flag. If the REGISTER flag is enabled without the recommended configuration setting, the REGISTRAR rejects the message with a 500 Internal Server Error.

SIP Registrar Licensing

The SBC SIP Registrar functionality is controlled by two types of Feature licenses, Network Wide Domain License (NWDL) and Node-Locked License. Refer to Node-Locked Licensing and NWDL Feature License Keys for more information.

Note

The number of allowed registrations is controlled by the license (similar to CAC). If the register receives more than the configured licenses, then the SBC rejects the Register with a 503 error response. The maximum limit of the number licenses allowed is 256,000 registrations.

For NWDL licenses, the maximum license count is equal to the maximum registrations supported by the SBC. For Node-Locked licenses, the maximum license count is equal to the number of licenses configured.

Functional Limitations

The following functionalities are not supported at the Registrar:

  • Application forking.
  • Multiple contacts per AOR.
  • IMS Registration procedures such as Path header handling.
  • OOD messages such as SUBSCRIBE, NOTIFY, REFER and PUBLISH.
  • Challenge for OOD messages such as MESSAGE, INFO, and OPTIONS.
  • Refer handling. 
  • re-INVITE challenge.
Note

An SBC Core acting as a SIP REGISTRAR is only available on the SBC HW and the SBC SWe I-SBC deployments, and not on the D-SBC and SBC CNe deployments.

SIP Registrar License Threshold Alarms

The alarm sonusSipRegThresholdReachedNotification is raised when the SIP Register License Threshold is reached. The clearing alarm for this notification is sonusSipRegThresholdClearedNotification. Refer to the Alarm Guide pages sonusSipRegThresholdReachedNotification - MAJOR and sonusSipRegThresholdClearedNotification - MAJOR for more details.