SIP HNT Forced Unregistration

If you use HNT and experience the issue explained in this section, consider using the Oracle® Enterprise Session Border Controller (E-SBC) forced unregistration feature. When this feature is enabled and a registration entry for an endpoint expires, the E-SBC notifies the soft switch to remove this binding using REGISTER message. In that REGISTER message, the expires header will be set to 0 and the expires parameter in the Contact header will also be set to 0.

The benefits of using forced unregistration include:

• Leveraging existing HNT configuration to provide near real-time information about the UA’s status to the registrar/softswitch
• Preserving resource utilization for the E-SBC and the softswitch by deleting a contact binding that is no longer valid or needed
• Preventing extra bindings from being generated at the softswitch (e.g., in instances when the UA or NAT restart)

This feature applies to:

• HNT endpoints with registration caching enabled by default, and when the nat-traversal parameter in the SIP interface configuration is set to always
• non-HNT endpoints with registration caching enabled, when the registration-interval parameter in the SIP interface configuration is used in the expires header sent to the UA in the 200 OK