Spending Limit Control — Sy Policy

You can configure a product offer so that Sy policy components are applied when quota is authorized or denied. You can configure MATRIXX Engine to apply the data and policy changes for the subscription after the next Gy CCR-U is received or you can enable immediate Sy notifications on offer selection changes due to offer purchases and cancelations.

If you configure a product offer to apply policy components based on quota authorization or denial, the SNR/Nchf_SpendingLimitControl_Notify message is sent when an offer is used to make the reservation and is not based on balance amounts reserved or consumed by a reservation. This process differs from the process described in the discussion about spending limit policy sessions.

When configured as described here, the same set of counters can be used for every product offer in the product catalog and only the counter statuses differ based on offer validity and current usage thresholds. After an initial request from the Policy Control Function (PCF)/Policy and Charging Rules Function (PCRF), the Charging Server returns a set of default policy counters and counter statuses so that PCC rules can be set up and a Gy/N40 session can be created. MATRIXX begins policy processing after a charging session is created over Gy/N40 and an SNR/Nchf_SpendingLimitControl_Notify message is sent to the PCF/PCRF after rating determines which product offer to apply, as shown in Figure 1.

Figure 1. Policy Counter Status Sequence

After an offer is activated, it can have counter values assigned when:

Quota is available.
Quota is exhausted (can be omitted) while offer is still valid (free quota allocations are available until the offer expires).

When a product offer is configured to only apply policy when quota is authorized/denied, the Charging Server sends a Spending-Status-Notification-Request (SNR)/Nchf_SpendingLimitControl_Notify message anytime an offer used for authorization has a different Sy counter or value or both from what was last returned.

Otherwise, a policy message is not returned to the PCF/PCRF (the offer's associated policy component is not considered if there is no quota reserved on the device). If a Pending-Policy-Counter is used and the new counter values have not changed since the last reported Pending-Policy-Counter values, a Spending-Status-Notification-Request (SNR)/Nchf_SpendingLimitControl_Notify message is not sent.

Quota authorized policy changes (due to any cause) are re-evaluated at the next quota request, and might result in a new notification.

For information about configuring the product offer Only Apply Policy When Quota Authorized property, see the discussion about configuring subscription product offer general properties in My MATRIXX Help.

Policy Profile Selection

To configure policy processing when quota is authorized/denied, MATRIXX Support recommends that you create multiple product offers with different priorities and a default offer. The example in Example Configuration shows the recommended pricing configuration with four product offers for a simple policy profile selection.

The default offer must be a global offer with a policy component only set to the lowest priority. As a global offer, you do not have to create an offer for every subscriber.
Important: When setting the Policy Quota Action Type:
- Do not set this on the default offer. This offer is used at the start of a session and when no other offer is in use.
- If it is unset in one or more other selected offers, it is possible that multiple SNRs will be sent that are unrelated to authorizations.
- If it is set on every offer, the Sy SLR fails.
The base offer can be any active subscription offer with usage and policy components. The offer priority must be higher than the default offer priority.
Bundle B (an add on product) has an active subscription offer with usage and policy components with available quota and an active subscription offer with usage and policy components with no available quota. The offer priority must be higher than the default offer priority.
Bundle A (an add on product) has an active subscription offer with usage and policy components with available quota and an active subscription offer with usage and policy components with no available quota. This offer must have the highest priority.

In Example Configuration, the following apply:

Gy (session) Not Active — Interaction points with PCF/PCRF only. No Gy CCR-I or SMF Charging Data Request [Initial] received from the P-GW/SMF.
Gy (session) Active — CCR-I/U with Requested-Service-Unit AVP/IE present. Granted-Service-Units applied.
Default Offer — The default offer is selected at the start of the Sy/N28 session and before the creation of the Gy/N40 session with counters and statuses so that the PCF or PCRF can install the initial PCC rules and allow the PGW/SMF to communicate with the Charging Server. It is the only offer not configured to only apply policy when quota is authorized.
Base Offer — The base offer can grant usage. Its policy component selects the "Gy Active" profile if it has successfully created a reservation; otherwise, the policy component is not considered and the default offer is selected.
Offers B1/A1 — A Gy session is active and the offers have available quota.
Offers B2/A2 — A Gy session is active but the offers have no quota.

Table 1. Example Configuration
	Default Offer	Base Offer	Bundle B		Bundle A
	←--------------------------- Lowest Priority to Highest Priority ---------------------------→
Counter	Gy Not Active	Gy Active	Offer B1	Offer B2	Offer A1	Offer A2
Counter 1	1	0	2	2	1	1
Counter 2	2	3	3	2	3	2
Counter 3	3	0	1	1	1	1
Counter N	4	0	1	1	3	1

The following examples show different scenarios and their sequence of events. In these examples, the subscriber owns a base offer and then purchases two more offers, one 5 GB data offer and one 10 GB data offer.

Both offers have the same priority, but the 5 GB offer expires before the 10 GB offer and has a higher relative priority. Each offer has two components to allow the policy to change after the quota is consumed, but before the offer expires. This is the free data element of each offer.

In Figure 2, when the device connects and establishes an Sy session, no Gy session is active. Therefore, the default policy with counter values 5 and 12 is applied. This is true at any time. After a Gy reservation is established and a reservation is made, an SNR is sent with the correct policy for the time-period, based on the offers that include the granted units.

Where a Gy session is active and a new (second) Sy session is started, then the SLA for the second Sy session reports the correct policy for that time-period based on the offers that include the granted units (not the default policy).

Where there is an Sy session active, but no Gy session, then there no SNR is sent for changes to the available offers (associated with the purchase).

When a RAR is sent on the Gy session (for example, for an offer purchase), the resulting commit/reservation resulting from the next CCR-U causes a policy re-evaluation and, where the policy counters have changed, an SNR is sent to any active Sy session (for example, at the transition from T0 to T1) where the 5 GB offer is purchased. Where the policy counters have not changed (for example, the transition from T1/T2) then no SNR is sent.

In this example, the counter values are associated with the following policy profiles:

Profile 1: 4, 12
Profile 2: 5, 12
Profile 3: 4, 3
Profile 4: 5, 3
Profile 5: 4, 12
Profile 6: 5, 12

Establish Session

In Figure 3:

The PCF/PCRF contacts the Charging Server to obtain the current list of counters and statuses.
Because there is no Gy/N40 session, a default set of counters and statuses (MaxSpeed=5, Shaping=12) is returned for initial PCC rule assignment. Profile 2 is selected and data comes from the base offer.
There is an update and Profile 1 is selected.

SLR to Charging Server. No reservations: Counters MaxSpeed=4, Shaping=12 — Figure 3. Establish an Sy/N28 Session at T0

An Intermediate SLR is sent by the PCRF to resubscribe to the policy counters. The value of the SLA returned in response to the SLR depends on whether there are any active reservations on the device.

If there are no reservations, regardless of the active offers purchased by the subscriber, Profile 2 from the default offer applies.
If there are reservations made against the base offer then profile 1 applies.

Update Session

In Figure 4:

The PCF/PCRF contacts the Charging Server to obtain the current list of counters and statuses.
Because there is no Gy/N40 session, a default set of counters and statuses (MaxSpeed=5, Shaping=12) is returned for initial PCC rule assignment. Profile 2 is selected and data comes from the 5 GB offer.
There is an update and Profile 1 is selected.

Offer Purchase: No Policy Change

In Figure 5:

Data comes from the 5 GB offer (T1), before and after the purchase of the 10 GB offer (T2).
The PGW responds with a RAA and then a CCR with Reporting-Reason=FORCED_REAUTHORISATION(7).

Offer Purchase: Policy Change

In Figure 6:

Data comes from the base offer (T0), then from the 5 GB offer after the purchase (T1).
The Charging Server sends an SNR to the PCF/PCRF during an ongoing Gy/N40 session if there are re-authorization requests and reservations that result in the policy profile changing from the last policy profile resolved.
The PGW responds with a RAA and then a CCR with Reporting-Reason=FORCED_REAUTHORISATION(7).