5.30 Notifying Start Pause of Charging

29.2443GPPInterface between the Control Plane and the User Plane nodesRelease 17TS

The requirements for PGW Pause of Charging in EPC are specified in clause 5.3.6A of 3GPP TS 23.401 [14] and the requirements for SMF Pause of Charging feature for 5GC are specified in clause 4.4.4 of 3GPP TS 23.502 [29].

To reduce the charging discrepancy between SGW-C and PGW-C, or between I/V-SMF and (h)SMF due to the signalling latency to notify start pause of charging, the CP function (SGW-C and PGW-C for EPC, I/V-SMF and (H-)SMF for 5GC) and UP function (SGW-U and PGW-U for EPC, I/V-UPF and PSA UPF) may support the Notify Start Pause of Charging via user plane feature (NSPOC) as described below.

When both the CP function and the UP function support the NSPOC feature, and the peer CP function (PGW-C or (H-)SMF) and peer UP function (PGW-U or PSA UPF) are known to support the NSPOC feature as specified in 3GPP TS 29.274 [9] and 3GPP TS 29.502 [50], the CP function (SGW-C, or I/V-SMF) may set the SSPOC bit to "1" in the Measurement Information included in the URR when the Dropped DL Traffic Threshold is provisioned, to request the UP function (SGW-C, I/V-UPF) to send a Start Pause of Charging indication via one or more GTP-U Tunnel Status message to the upstream GTP-U entity(s) when the Dropped DL Traffic Threshold is reached.

When both the CP function and the UP function support the NSPOC feature, the CP function (PGW-C, or (H-)SMF) may set the ASPOC bit to "1" in the Measurement Information included in the URR if the URR is intended for charging, to request the UP function to stop the usage measurement for the URR when receiving Start Pause of Charging indication from the peer downstream GTP-U entity, so that the UP function shall behave as if the Inactive Measurement flag had been set for the URR when it receives a Tunnel Status message with the Start Pause of Charging indication is set to "1" from the downstream peer GTP-U entity.

Regardless of whether the NSPOC feature is supported and used, the procedures specified in clause 5.3.6A of 3GPP TS 23.401 [14] and clause 4.4.4 of 3GPP TS 23.502 [29] for starting and stopping Pause of Charging for EPC and 5GC respectively shall be performed, i.e. the UP function (SGW-U or I/V-UPF) shall still be instructed to generate a usage report when the Dropped DL Traffic Threshold is reached, the SGW-C or V/I-SMF shall request the PGW-C or (H-)SMF to start or stop charging, and the PGW-C or (H-)SMF shall instruct the UP function (PGW-U or PSA UPF) to inactivate or activate measurement for URR(s) applicable for charging.

When the NSPOC feature is supported and used, the CP function (PGW-C or (H-)SMF) may:

– set the "SUMPC" flag in PFCPSMReq-Flags IE to "1" to request the UP function to stop the usage measurement for all URRs with the "ASPOC" flag set to "1", e.g. when the CP function is informed to start Pause of Charging via control plane;

– set the "RUMUC" flag in PFCPSMReq-Flags IE to "1" to request the UP function to resume the usage measurement for all URRs with the "ASPOC" flag set to "1", e.g. when the CP function is informed to stop Pause of Charging via control plane;- set the "CIAM" flag together with Inactive Measurement flag in the Measurement Information IE in the Create URR IE or Update URR IE to stop or resume the usage measurement for a specific URR with the "ASPOC" flag set to "1".

The UP function shall stop or resume the usage measurement for all the URRs with the "ASPOC" flag set to "1" upon receipt of a PFCP Session Establishment Request or PFCP Session Modification Request with the "SUMPC" or "RUMUC" flag set respectively, regardless the current value of the Inactive Measurement flag for a given URR.

The UP function shall start the usage measurement for a URR with the "ASPOC" flag set to "1" unless both the "CIAM" and "INAM" flags are set to "1" or unless the "SUMPC" flag is set to 1 in the same message, when the URR is provisioned in a Create URR IE.

NOTE 1: Only the "SUMPC" flag can be set in the PFCP Session Establishment Request message, e.g. during a restoration procedure for a UPF failure.

The UP function shall stop or resume the usage measurement for a specific URR with the "ASPOC" flag set to "1" upon receipt of a PFCP Session Modification Request including an Update URR IE with the Measurement Information IE, according to the value of the "INAM" flag, if the "CIAM" flag is set to 1. If the "CIAM" flag is set to 0, the UP function shall ignore the "INAM" flag received in the Measurement Information for a URR with the "ASPOC" flag set to "1".

NOTE 2: Notifying Start Pause of Charging via GTP-U fastens the triggering of charging pause in the PGW-U or UPF (PSA). If the GTP-U Tunnel Status messages are lost, charging is paused when receiving the corresponding instruction from the PGW-C/SMF.

NOTE 3: The UP function will forward Tunnel Status message to the upstream GTP-U entity(s) if it is not a PSA UPF or PGW-U connecting to N6 or SGi interface. If the UP function is a UL/CL or BP, it needs send or forward the Tunnel Status message to all of PSA UPFs.

NOTE 4: The UP function resumes the usage measurement for all URRs with the "ASPOC" flag set to "1" regardless if the usage measurement was stopped by the CP function using the "SUMPC" flag or using the Inactive Measurement flag per URR, or upon being notified by the downstream GTP-U entity using Tunnel Status message.

NOTE 5: When the CP function uses Inactive Measurement flag to stop the usage measurement for a given URR, it can set the "ASPOC flag" to "0" if the CP function doesn’t want that the usage measurement is resumed when applying "RUMUC".