OCSs

In the context of PCA deployment, OCS is referred to as Online Charging Server. OCSs are responsible for:

Authorizing service, i.e. granting or denying the services to the subscribers who requested the services via Diameter online charging signaling.
Charging in accordance with service provisioned in real time based on accounting/metering
Making the decision to terminate the service if certain conditions are met.

An OCS is selected by the OC-DRA function of PCA for an incoming session initiation message, i.e. Gy/Ro CCR-I, using a load distribution algorithm. OC-DRA may store and maintain the session state for the subscriber to ensure all the in-session messages, i.e. CCR-U and CCR-T, will be routed to the same OCS for online charging processing for this session. The relationship between the subscriber and the OCS lasts during the lifetime of the session.