Section: 12.1.3 Load & overload control concepts
Content: Load control refers to "GTP-C signalling based Load Control" as defined in clause 4.3.7.1a.1 of 3GPP TS 23.401[ General Packet Radio Service (GPRS) enhancements for Evolved Universal Terrestrial Radio Access Network (E-UTRAN) access ]  [3] and clause 5.3.6.1a of 3GPP TS 23.060[ General Packet Radio Service (GPRS); Service description; Stage 2 ]  [35]. Overload control refers to "GTP-C signaling based Overload Control" as defined in clause 4.3.7.1a.2 of 3GPP TS 23.401[ General Packet Radio Service (GPRS) enhancements for Evolved Universal Terrestrial Radio Access Network (E-UTRAN) access ]  [3] and clause 5.3.6.1a of 3GPP TS 23.060[ General Packet Radio Service (GPRS); Service description; Stage 2 ]  [35]. Load control and overload control are two distinct but complementary concepts: - load control enables a GTP-C entity (e.g. an SGW/PGW) to send its load information to a GTP-C peer (e.g. an MME/SGSN, ePDG, TWAN) to adaptively balance the session load across entities supporting the same function (e.g. an SGW cluster) according to their effective load. The load information reflects the operating status of the resources of the GTP-C entity. - overload control enables a GTP-C entity becoming or being overloaded to gracefully reduce its incoming signalling load by instructing its GTP-C peers to reduce sending traffic according to its available signalling capacity to successfully process the traffic. A GTP-C entity is in overload when it operates over its signalling capacity which results in diminished performance (including impacts to handling of incoming and outgoing traffic). Load control allows for better balancing of the session load, so as to attempt to prevent overload in the first place (preventive action). Overload control aims at shedding the incoming traffic as close to the traffic source as possible generally when an overload has occurred (reactive action), so to avoid spreading the problem inside the network and to avoid using resources of intermediate nodes in the network for signalling that would anyhow be discarded by the overloaded node. Load control does not trigger overload mitigation actions even if the GTP-C entity reports a high load. Load control and overload control may be supported and activated independently in the network.