Dynamic PCC Rules Support
For dynamic PCC rules multiple flows are supported on per Packet Forwarding Control Protocol (PFCP) session:
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The 5G QoS model allows classification and differentiation of specific services based on subscription-related and invocation-related priority mechanisms. These mechanisms provide abilities such as invoking, modifying, maintaining, and releasing QoS Flows with priority, and delivering QoS Flow packets according to the QoS characteristics under network congestion conditions.
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The 5G QoS model is based on QoS Flows. The 5G QoS model supports both QoS Flows that require guaranteed flow bit rate (GBR QoS Flows) and QoS Flows that do not require guaranteed flow bit rate (Non-GBR QoS Flows).
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The QoS Flow is the finest granularity of QoS differentiation in the PDU session. A QoS Flow ID (QFI) is used to identify a QoS Flow in the 5G System. User Plane traffic with the same QFI within a PDU session receives the same traffic forwarding treatment (Example - scheduling, admission threshold).
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Within the 5GS, a QoS Flow associated with the default QoS rule is required to be established for a PDU session and remains established throughout the lifetime of the PDU session. This QoS Flow must be a Non-GBR QoS Flow.
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A QoS flow is associated with QoS requirements as specified by QoS parameters and QoS characteristics. A QoS flow can either be "GBR" or "Non-GBR" depending on its QoS profile.
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For each QoS Flow, the QoS profile includes the QoS parameters:
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5G QoS Identifier (5QI)
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Allocation and Retention Priority (ARP)
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For each GBR QoS flow only, the QoS profile must also include the QoS parameters:
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Guaranteed Flow Bit Rate (GFBR) - UL and DL
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Maximum Flow Bit Rate (MFBR) - UL and DL
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In case of a GBR QoS Flow only, the QoS profile may also include one or more of the QoS parameters:
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Notification control
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Maximum Packet Loss Rate - UL and DL
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During PDR creation or modification UPF receives the QER for QoS enforcement on flows.
The QoS enforcement rule correlation ID is assigned by the CP function to correlate QERs from multiple PFCP session contexts. For instance, the enforcement of APN-AMBR in the PGW-U is achieved by setting the same QoS enforcement rule correlation ID to the QERs from different PFCP sessions associated with all the PDRs corresponding to the non-GBR bearers of all the UE's PDN connections to the same APN. The QERs that are associated to the same QoS Enforcement Rule Correlation ID in multiple PFCP sessions will be provisioned with the same QER contents in each of these PFCP sessions. The QoS enforcement rule correlation ID is only used to enforce the APN-AMBR when the UE is in EPC, it may be provided by the CP function over N4 to the UP function for a PDU session may move to EPC in a later stage.
If the UPF receives QoS Enforcement Rule Correlation ID for 5G PFCP sessions, then it enforces it.