E-CSCF Emergency: Setting Precedence for NMC
When the Oracle Communications Session Border Controller acts as an E-CSCF, it can route emergency or priority calls (i.e., 112, 911, 999 calls) to the corresponding ECS/PSAP based on the calling party’s information. However, for registered users, this ability mixes with the Oracle Communications Session Border Controller’s NMC function so that the Service Routes takes precedence over the NMC. So rather than routing the emergency call to the ECS/PSAP, the call ends up at the S-CSCF of the Service Route.
For non-registered users where there no Service Route exists, this is not an issue.
Adding the apply-local-policy value to the options parameter in the network management controls configuration allows the NMC to take precedence over cached Service Route when a session matches an NMC rule. Instead, it locates a matching local policy.
Without the NMC configured to take precedence, the Oracle Communications Session Border Controller does not function optimally as an E-CSCF for registered users.
Consider the following scenario in which a UE registers as a P-CSCF to the S-CSCF via the Oracle Communications Session Border Controller. In this case, the registrar returns a Service Route header in a 200 OK response to the REGISTER message to the Oracle Communications Session Border Controller. Or, if an implicit service route is enabled, the Oracle Communications Session Border Controller generates a Service Route that it saves in the register cache before forwarding the 200 OK on to the UA. Then when a new INVITE comes from the UA, the Oracle Communications Session Border Controller checks its register cache and uses the Service Route as the next hop—without taking local policy into consideration.
Using the apply-local-policy value requires local policy’s consideration in deciding the next hop. If you configure this option and the Oracle Communications Session Border Controller receives a new INVITE, it will decide whether the session is priority, registered, or with Service Route. Then it will determine if the call is E-CSCF. If so and the first matching local policy has E-CSCF enabled, the priority local policy is applied over the Service Route. The Oracle Communications Session Border Controller stays with the Service Route if not.
