ADC Dynamic Rules over N4

UPF leverages the dynamic ADC rules for traffic matching and charging. This feature allows the service providers to manage IoT devices, such as connected cars, and charge their subscribers based on the traffic flows classified by SMF or UPF. With this traffic classification, the service providers enable service monetization.

In summary, SMF first processes the dynamic ADC rules received from PCF with TDF-App-Identifier, Service ID, and Rating group. SMF then sends this information to UPF to classify ruledefs and perform charging.

Default Setting: Enabled – Always-on

Charging Support for Converged Calls

UPF supports S-GW Charging Data Record (CDR) volume reporting for converged calls. This feature allows you to use these CDRs for reporting and charging during inbound LBO roaming scenario.

This feature introduces a new CLI command converged-sxa-usage-reporting in the ACS Service Configuration mode, to generate the usage report with volume count.

Default Setting: Disabled – Configuration Required to Enable

Dual Stack Support on S5u Interface

UPF supports dual stack to handle IPv4 and IPv6 connections between SGW-U and PGW-U on the S5u interface.

Default Setting: Enabled – Always-on

EDR Attributes for DSCP Mapping

UPF supports two new EDR attributes sn-dscp-uplink and sn-dscp-downlink as part of Flow and Transaction EDRs in the EDR Format configuration. These attributes help you to understand the QoS flow information of uplink and downlink traffic in the network.

The attributes report the DSCP mapping value of the user plane traffic. UPF derives the DSCP values either from SMF through the Transport Level Marking AVP in FAR or locally through the IP ToS configured under charging-action.

Default Setting: Disabled – Configuration Required to Enable

Accurate Correlation of Application Instance IDs for Traffic Optimization

When you configure the adc app-notification once-per-app CLI in ACS Rulebase, UPF optimizes the reporting once per application. Upon detecting traffic for an application, UPF sends an APP-START notification to SMF with an Application Instance ID. This ID is the flow-id for the first data flow of an application.

Previous Behavior: When the last data flow of the application gets terminated, the flow-id of that data flow is used as the Application Instance ID in APP-STOP notification. This causes issues for PCF to correlate the APP-START and APP-STOP notifications.

New Behavior: UPF caches the Application Instance ID from the first data flow. When the last data flow of an application terminates, UPF sends the cached Instance ID with the APP-STOP notification. This behavior enables PCF to correlate the APP-START and APP-STOP notifications and identify the application traffic appropriately.

GTPU Statistics for Combo Calls

Previous Behavior: For combo calls on the N4 interface, the count for uplink and downlink packets/bytes were not incremented correctly in the show user-plane-service gtpu statistics CLI output.

New Behavior: For combo calls on the N4 interface, the count for uplink and downlink packets/bytes will be incremented three times for each GTPU interface. The fields Uplink Packets, Downlink Packets, Uplink Bytes, and Downlink Bytes in the show user-plane-service gtpu statistics CLI output will display the correct packet count.

LCI Reporting to Control Plane

UPF sends the load control information (LCI) to the control plane, to inform the operating status of its resources at the node level. The control plane uses this information to augment UPF selection procedures.

Previous Behavior: UPF reported only one LCI per session manager to the control plane because of which some associated CPs did not receive the LCI.

New Behavior: UPF reports one LCI to each PFCP peer per session manager. The control plane will be able to distribute calls evenly over multiple UPFs.

• For cnSGW or legacy S-GW, LCI is reported only if the CP sends the load bit in the CP Function Features IE during Sx Association Setup or Update.

• By default, UPF enables LCI reporting to SMF. Hence, the load bit in CP Function Features IE is optional for SMF.

• The debug CLI show session subsystem facility sessmgr all debug-info displays the current and reported load metrics on UPF.

• Error logs will be generated when the load metric is reported to the control plane.

  The following is an example of an error log:

  2024-Mar-15+08:12:54.517 [sx 221333 info] [1/0/8083 <sessmgr:6> sx_fsm.c:1311] [context: EPC2-UP, contextID: 2] [software internal system critical-info syslog] LCI with load-metric = 19 and sequence-number = 1710489965 sent to Peer: 20.20.20.54

Customer Impact: Each CP that supports LCI reporting will now receive multiple messages with the same LCI value from a UPF.

Redirected Packet Drop Statistics

Previous Behavior: The drop counters were not incremented for redirected packets when the flow action redirect-url CLI was configured.

New Behavior: The drop counter is incremented for redirected packets with the flow action redirect-url configuration.

The new Redirect-URL field under Flow apply action in the output of the show user-plane-service statistics drop-counter command displays the number of redirected packets that are dropped.

Customer Impact: For each redirected packet, you can view the incremented packet drop counter.

SxDemux Stops IP Pool Deregistration Request towards VPNmgr on Standby UPF

Previous Behavior: After receiving the Sx peer delete checkpoint, SxDemux initiated the IP pool deregistration request towards VPNMgr on a standby UPF. This behavior led to IP chunk deletion resulting in call preallocation failure on a standby UPF.

New Behavior: SxDemux does not initiate IP pool deregistration request towards VPNMgr on a standby UPF, after receiving the Sx peer delete checkpoint. This behavior prevents call preallocation failure on a standby UPF.