Section: 12.3.9.3.1 Description
Content: When performing message throttling: - GTP requests related to priority traffic (i.e. eMPS as described in 3GPP TS 22.153[ Multimedia priority service ]  [62]) and emergency have the highest priority. Depending on regional/national requirements and network operator policy, these GTP requests shall be the last to be throttled, when applying traffic reduction, and the priority traffic shall be exempted from throttling due to GTP overload control up to the point where the requested traffic reduction cannot be achieved without throttling the priority traffic; NOTE 1: For non-3GPP access, eMPS traffic is determined based on the MPS subscription from the UE USIM as specified in 3GPP TS 24.302[ Access to the 3GPP Evolved Packet Core (EPC) via non-3GPP access networks; Stage 3 ]  [63] clause 7.2.2.1 and clause 7.4.1.1 or the MPS subscription for the UE from the HSS as specified in 3GPP TS 29.273[ Evolved Packet System (EPS); 3GPP EPS AAA interfaces ]  [68] clause 5.1.2.1.2 and clause 7.1.2.1.2. - for other types of sessions, messages throttling should consider the relative priority of the messages so that the messages which are considered as low priority are considered for throttling before the other messages. The relative priority of the messages may be derived from the relative priority of the procedure for which the message is being sent (as specified in clause 12.3.9.3.2) or may be derived from the session parameters (as specified in clause 12.3.9.3.3). NOTE 2: A random throttling mechanism, i.e. discarding the messages without any special consideration, could result in an overall poor congestion mitigation mechanism and bad user experience. An overloaded node may also apply these message prioritization schemes when handling incoming initial messages during an overloaded condition, as part of the self-protection mechanism (see clause 12.3.10.2.3).