B.2 SWx interface

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

B.2.1 General

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

It is recommended to make use of IETF RFC 7683 [47] on the SWx interface where, when applied, the 3GPP AAA server shall behave as a reacting node and the HSS as a reporting node.

B.2.2 HSS behaviour

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

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

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

B.2.3 3GPP AAA server behaviour

The 3GPP AAA server 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 3GPP AAA server by implementation specific means. For example, it may implement message throttling with prioritization.

The 3GPP AAA server, when requested to apply traffic reduction over the SWx interface, may request traffic reduction over the interfaces (e.g STa, SWm, S6b) towards the access nodes if the Diameter overload control mechanism is supported on these interfaces.

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