MPE devices use the Sy interface to connect to the Online Charging System (OCS). This Sy data source provides spending information (using policy counters and statuses) for a specific subscriber. After the device receives the information from the OCS, it uses this data to drive policy decisions for the subscriber.
For an Sy data source, you can define primary, secondary, and tertiary servers. The MPE device sends an SLR (Spending-Limit-Request) message to the primary server first. If it receives no response, it attempts to establish a session with the secondary server. If it receives no response, it then queries the tertiary server. The MPE device queries the data source servers in order, always defaulting to the highest server available. As soon as a higher server becomes available, requests resume to that server.
The
MPE device connects with the Sy data source using the following process:
- The MPE device establishes the Sy Diameter session when it sends an SLR message to the OCS. This session remains active until the session is terminated or the Sy session is lost. The OCS responds with an SLA (Spending-Limit-Answer) message with policy counters and information about the specific subscriber.
- If the MPE device receives an SNR (Spending-Status-Notification-Request) message from the OCS updating the quota information for the subscriber, the device updates the cached policy counters and re-evaluates any policies. The device responds to the OCS request with an SNA (Spending-Status-Notification-Answer) message indicating the results of the request.
Note: See
Configuring Sy Settings for details on configuring the Sy data source to use policies to send re-authorization messages.
- When the MPE device determines that policy decisions for a subscriber no longer require policy counter information for which it has requested notifications of status changes, the device sends a STR (Session-Terminate-Request) message to the OCS to unsubscribe from updates to policy counter status changes. The OCS removes any policy counter subscriptions associated with the Sy session and responds with an STA (Session-Termination-Answer) message to close the session.
See Configuring an Sy Data Source for details on configuring an Sy data source.