Registrar Routing
When the routing precedence parameter is set to registrar, the Oracle Communications Core Session Manager is using the HSS as a resource within the context of its routing decisions.
When an INVITE arrives, the Oracle Communications Core Session Manager checks its own registration cache for a pre-existing matching contact in the INVITE. If it finds a match, it forwards the request to that location. If it does not find a match, it issues an Location Information Request (LIR) to the HSS. If the HSS’s response, called an LIA, provides an assigned S-CSCF for that UA, the Oracle Communications Core Session Manager proceeds as described below in the section LIR/LIA Transaction.
Note that you can configure the Oracle Communications Core Session Manager to fallback to a local policy lookup if the lookup via the registrar fails. Configure this by adding the fallback-to-localpolicy option to the sip-registrar configuration element.
For situations where the database routing decision needs to be done in lieu of the default, you can set routing precedence to local-policy. Note that you can configure a routing entry that points to an HSS by setting a policy attribute with a next-hop of cx:<home-subscriber-server-name> within the local-policy.