5.31.14.2 Serving PLMN Rate Control

The Serving PLMN Rate Control value is configured in the (V-)SMF.

NOTE 1: Homogeneous support of Serving PLMN Rate Control in a network is assumed.

At PDU Session establishment and PDU Session modification, the (V-)SMF may inform the UE and UPF/NEF of any per PDU Session local Serving PLMN Rate Control that the Serving PLMN intends to enforce for NAS Data PDUs. The (V-)SMF shall only indicate a Serving PLMN Rate Control command to the UPF if the PDU Session is using N4 and is set to Control Plane only. The (V-)SMF shall only indicate a Serving PLMN Rate Control command to the NEF if that PDN connection is using NEF.

Serving PLMN rate control is operator configurable and expressed as "X NAS Data PDUs per deci hour" where X is an integer that shall not be less than 10. There are separate limits for uplink and downlink NAS Data PDUs:

• The UE shall limit the rate at which it generates uplink NAS Data PDUs to comply with the Serving PLMN policy. In the UE the indicated rate control applies only on the PDU Session where it was received and therefore the UE shall limit the rate of its uplink NAS Data PDUs to comply with the rate that is indicated for the PDU Session. The indicated rate is valid until the PDU Session is released.
• The UPF/NEF shall limit the rate at which it generates downlink Data PDUs. In the UPF/NEF the indicated rate control applies only on the PDU Session where it was received and therefore the UPF/NEF shall limit the rate of its downlink Data PDUs to comply with the rate that is indicated for the PDU Session.
• The (V-)SMF may enforce these limits per PDU Session by discarding or delaying packets that exceed these limits. The Serving PLMN Rate does not include SMS using NAS Transport PDUs. The (V-)SMF starts the Serving PLMN Rate Control when the first NAS Data PDU is received.

NOTE 2: If the UE/UPF/NEF start the Serving PLMN rate control at a different time than the (V-)SMF, PDUs sent within the limit enforced at the UE/UPF/NEF can still exceed the limit enforced by the (V-)SMF.

NOTE 3 It is assumed that the Serving PLMN Rate is sufficiently high to not interfere with the Small Data Rate Control as the Small Data Rate Control, if used, is assumed to allow fewer messages. NAS PDUs related to exception reports are not subject to the Serving PLMN Rate Control.