I.5 Overload control

24.2293GPPIP multimedia call control protocol based on Session Initiation Protocol (SIP) and Session Description Protocol (SDP)Release 18Stage 3TS

I.5.1 Introduction

The additional routeing functionality, or associated functional entity, performing additional routeing procedures described in I.3 may support the event-based overload control mechanism.

I.5.2 Outgoing subscriptions to load-control event

Based on operator policy, the additional routeing functionality may subscribe to the load-control event package with one ore more target SIP entities. The list of target SIP entities is provisioned.

Subscription to the load-control event package is triggered by internal events (e.g. the physical device hosting the SIP entity is power-cycled) or through a management interface.

The AS shall perform subscriptions to the load-control event package to a target entity in accordance with RFC 6665 [28] and with RFC 7200 [201]. When subscribing to the load-control event, additional routeing functionality shall:

1) Send a SUBSCRIBE request in accordance with RFC 6665 [28] and with RFC 7200 [201] to the target entity, with the following elements:

– an Expires header field set to a network specific value;

2) If the target entity is located in a different network and local policy requires the application of IBCF capabilities, forward the request to an IBCF acting as an exit point.

The additional routeing functionalit shall automatically refresh ongoing subscriptions to the load-control event package either 600 seconds before the expiration time if the initial subscription was for greater than 1200 seconds, or when half of the time has expired if the initial subscription was for 1200 seconds or less.

The additional routeing functionality can terminate a subscription according to RFC 6665 [28].

Annex J (normative):
Void

Annex K (normative):
Additional procedures in support of UE managed NAT traversal