Spending Limit Policy — Sy Sessions

MATRIXX Charging Application communicates with an external Policy and Charging Rules Function (PCRF) using the Sy interface.

For deployments using the Sy interface, MATRIXX Charging Application and MATRIXX Policy Application act jointly as an Online Charging System (OCS). MATRIXX Charging Application is responsible for rating and charging over the Gy interface to your external Policy and Charging Enforcement Function (PCEF), while MATRIXX Policy Application sends counters over Sy to your external PCRF.

Because the policy information that is returned to the PCRF can be influenced by real-time subscriber data, which can be relevant to rating and charging, both applications work seamlessly to provide a total solution for service providers. They operate together to support scenarios where the policy can be influenced by the value of one or more policy counters. Having real-time access to policy counters enables service providers to control QoS in real-time. For example, if a subscriber downloads excessive data, the network speed can be throttled.

Note: IEC and Diameter session create or terminate messages update the status life cycle LastActivityTime field.

A PCRF must be configured to communicate with the Diameter Gateway Diameter listener port. For more information about the diameter configuration parameters, see MATRIXX Installation and Upgrade.

In Sy sessions, product offers with policy components are selected using product offer priorities. Product offers without policy components are not evaluated. If there are no offers with policy components, an error is returned in the SLA (error code 4241). Different product offers can be selected for Sy sessions and Gy sessions; an offer can be selected for an Sy session but not for a Gy session and the reverse is also true.

Only one non-supplemental product offer with applicable policy components is selected to return policy counters to the PCRF. However, all supplemental product offers with applicable policy components are applied. The selected offer can change during an Sy session (for example, if an offer with a higher priority is purchased during the session.)

During an Sy session, the policy counter(s) of the selected offers are checked. If any counter changes value (for example, due to a balance impact), an SNR is sent with the new value(s). Counter value changes can be caused by the offer that originally set the values or by a different offer.

If two or more offers return the same counter with the same value, only one instance of the counter is returned. If two or more offers return the same counter with different values, MATRIXX selects the highest priority value according to the Enable Priority option (if used).

When an offer configured with only apply policy when quota authorized, the offer is not evaluated (for Sy session purposes) unless there is a quota reservation for that same offer. The following applies:
  • This differs from the general behavior of offers in Sy, where a counter value change caused by a different offer can trigger an SNR. In this situation, the quota authorization must be on the same offer that is selected in the Sy session.
  • When an offer is configured with only apply policy when quota authorized, the selected offer might change during the Sy session. For example, if an offer was selected in the SLR/SLA but then there is a quota authorization which causes and offer with a higher priority to be selected, an SNR is generated.
  • When one offer is configured with only apply policy when quota authorized, all offers are evaluated (even those without this option set). If there is a higher priority offer with only apply policy when quota authorized set, that offer is selected.
  • If there is no active Gy session, offers configured with only apply policy when quota authorized, are not evaluated during the Sy session.

Re-evaluating Sy Sessions

When re-evaluating an Sy policy session, if no policy counter is selected, the session becomes invalid and is not re-evaluated again. An Sy SNR message with SN-Request-Type=1 is sent. The PCRF sends an Sy SNA message and an STR message to notify the Charging Server to remove the session.

The session is deleted after the Charging Server receives an STR.
  • If the Charging Server does not receive an SNA on time, multiple SNRs are sent based on the policy configuration and the session is deleted after maximum number of retries.
  • If the Charging Server receives an SNA but does not receive an STR after the configured delay, the session is deleted. To configure the delay, answer the following create_config.py question:

    Global:Session:Policy:Notify:How long (in seconds) to wait to delete a policy session after the session abort request is sent?