Session processing includes topics related to how the Sentinel VoLTE product executes various different call flows.

Out of the box, the Sentinel VoLTE product can:

  • function as an SCC-AS, or an MMTel-AS for a given trigger

  • function as a combined SCC+MMTel-AS off a single trigger, thereby optimising performance.

  • perform offline charging only

  • perform online charging, through either acting as a Charging Trigger Function using Diameter Ro, or CAP (using the IM-SSF)

These different configurations are all available on a per-trigger basis, rather than being a "hard configuration mode".

Online charging via the CAP interface is delivered through the use of OpenCloud’s IM-SSF, and is an optionally installed component.

Selection of MMTel and SCC functionality through the Application Server URI

Different modes of operation (e.g. MMTel functionality, or SCC functionality) are determined through parameters added to the Application Server URI during initial filter criteria (iFC) configuration.

When the Sentinel VoLTE application server receives an initial SIP request (for example, an initial INVITE or third-party register request) parameters are present on the topmost route header. There are certain parameters that can be added to alter the behaviour of Sentinel VoLTE. That is to say, the iFC and application server configuration in the HSS may include URI parameters that select different sets of behaviour from the Sentinel VoLTE product.

Session plans are available that enable execution of MMTel and SCC feature sets in different combinations. These are selected through the use of the oc-mode parameter.

The specific URI parameters are discussed in the Custom Headers section.

Tip For a high-level view of the architecture, see Instance Architecture for Sentinel VoLTE. For a detailed description of the format of the oc-mode parameter, see the DetermineVoltePlanId feature page.

Selection of charging mode

The system charging mode can be set to:

  • offline only, meaning the system only writes CDRs and/or Diameter Accounting Requests (ACRs)

  • online charging via Diameter Ro, meaning that the system acts as a charging trigger function towards the OCS as well as writing CDRs and/or ACRs

  • online charging via CAMEL, meaning it includes an IM-SSF component that triggers a prepaid service control point via the CAP protocol.

The charging mode is selected through the oc-charge-mode parameter. This is an Application Server URI parameter.

Tip For detailed descriptions of the oc-charge-mode parameter, see the DetermineChargeMode and Service Compositions pages.

The VoLTE Interim CDR Feature is configured to select whether interim CDRs and/or ACRs are used. It is used if Diameter Rf and/or Interim CDRs are selected during installation.

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Sentinel VoLTE Version 2.9.0