IMS Implicit Service Route
The Oracle Communications Session Border Controller provides implicit service route support in situations where it is deployed between user equipment (UE) and the P-CSCF, and where the IMS core network does not support the Service-Route header.
When this feature is enabled, the Oracle Communications Session Border Controller sends requests to the P-CSCF and does not include the Service-Route header received in the 200 OK response (to a REGISTER message) as Route headers in subsequent requests. The Oracle Communications Session Border Controller also includes a Route header of the P-CSCF address in subsequent requests, and includes the loose-route parameter in the Route header. Because inclusion of the loose-route parameter is not needed in all cases, you can set this feature to strict in the SIP interface configuration.
Recent enhancements address the following issues:
- Even when IMS is disabled for a SIP interface, the Oracle Communications Session Border Controller caches and uses the Service-Route headers from SIP REGISTER responses received from the REGISTER. Therefore, you must use SIP HMR to remove the Service-Route headers from the response, while having no mechanism to replace the Service-Routes from the REGISTER response with an implicit Service Route.
- In the Oracle Communications Session Border Controller global SIP configuration, the presence of the option route-registrar-no-service-route sets the behavior for using the Service-Route header in the REGISTER request. The new enhancements greatly simplify the process of determining proper use of the header in both IMS and non-IMS environments.
- You can configure the Oracle Communications Session Border Controller with an option to keep it from using the Service-Route header for REGISTER requests when sent to an out-of-service session agent. The enhancements make this behavior the default—because otherwise these REGISTER requests fail.
- If the initial re-registration is challenged, the subsequent REGISTER will be sent to the same target as its prior REGISTER.
When implicit service route support is enabled, the Oracle Communications Session Border Controller stores the Service Route URIs from the Service-Route headers that are included in 200 OK responses to REGISTER messages. The Service Route URIs are included in the Route headers in subsequent Request messages, except for REGISTER messages.
The Oracle Communications Session Border Controller also supports the ability to keep the loose-route parameter from being included in the implicit Route URI that the Oracle Communications Session Border Controller generates and includes as a Route header in the Request messages.
Once an endpoint registers successfully, the Oracle Communications Session Border Controller caches the Service-Route header (if any) to use for routing all subsequent requests from the endpoint—with the exception of any subsequent REGSITER requests.
You can set whether or not you want the Oracle Communications Session Border Controller to route subsequent REGISTER requests using the cached Service Route, and whether the endpoint is engaged in an active session through the Oracle Communications Session Border Controller. If you decide not to use the Service Route for endpoints engaged in active sessions, then the Oracle Communications Session Border Controlleruses the local policy to make routing decisions.
For endpoints not in found in the Oracle Communications Session Border Controller’s registration cache, the Oracle Communications Session Border Controller again uses the local policy to make routing decisions.
Notes About Upgrading
There are Oracle Communications Session Border Controllers currently deployed that use the route-registrar-no-service-route option, and these enhancements provide for backward compatibility.
When you upgrade to a release that has the new register-service-route parameter in the SIP configuration, the system checks for the presence of the route-registrar-no-service-route option. If the system finds the option, then it translates the value configured for the option like this:
Old route-registrar-no-service-route value | New register-service-route value |
---|---|
<empty> or all | never |
refresh | removal |
all, idle | session |
refresh; idle | session+removal |
You must save your configuration for these changes to take place, allowing you to fall back to the previous software image.