B.3 STa interface

29.2733GPP3GPP EPS AAA interfacesEvolved Packet System (EPS)Release 18TS

B.3.1 General

The Diameter overload control mechanism is an optional feature over the STa interface.

It is recommended to make use of the IETF RFC 7683 [47] over the STa interface where, when applied, the trusted non 3GPP access network shall behave as a reacting node and the 3GPP AAA server as a reporting node.

B.3.2 3GPP AAA server behaviour

The 3GPP AAA server requests traffic reduction from the trusted non 3GPP access network when it is in an overload situation, by including OC-OLR AVP in answer commands as described in IETF RFC 7683 [47].

The 3GPP AAA server identifies that it is in an overload situation by implementation specific means. For example, the 3GPP AAA server may take into account the traffic over the STa interfaces or other interfaces, the level of usage of internal resources (CPU, memory), the access to external resources etc.

The 3GPP AAA server determines the specific contents of the OC-OLR AVP in overload reports and the 3GPP AAA server decides when to send OC-OLR AVPs by implementation specific means.

The 3GPP AAA server, when requested to apply traffic reduction over the SWx interface, may also request traffic reduction over the STa interfaces towards the trusted access networks nodes.

B.3.3 Trusted non 3GPP access network behaviour

The trusted non 3GPP access network applies required traffic reduction received in answer commands to subsequent applicable requests, as per IETF RFC 7683 [47].

Requested traffic reduction is achieved by the trusted non 3GPP access network by implementation specific means. For example, it may implement message throttling with prioritization.

Annex C gives guidance on message prioritisation over the STa interface.