When to Use Forced Unregistration

For typical HNT use, it is common that the registration interval between the client UA and the Oracle® Enterprise Session Border Controller (E-SBC) is between 60 and 120 seconds. This differs significantly from the re-registration interval between the E-SBC and the and the registrar, which varies from approximately 30 to 60 minutes.

If the UA fails to refresh its registration, the contact binding at the E-SBC is deleted after the registration expires. This expiration is determined by the expires= header in the 200 OK. The binding at the real registrar will remain intact. This creates a discrepancy between the real state of the UA and state of the softswitch. In the best case scenario, the contact binding expires at the softswitch after a few minutes.

For network management, this discrepancy can be problematic because the service provider would be unaware of the UA’s status until the binding expires at the softswitch. This can take a considerable amount of time to happen.

In addition, the E-SBC encodes a cookie in the userinfo of the Contact header in the REGISTER message. This is a function of the source IPv4 address and port from which the request came, i.e., the ephemeral port in the NAT for DSL scenarios. Therefore, additional bindings that remain for long periods of time are created at the registrar if, for example, the:

• UA reboots
• Ethernet link between the UA and the DSL router is lost for over two minutes
• DSL crashes
• DSL/ATM layer between the DSL router