OCS (Online Charging System)

A real-time charging system in telecom networks that authorizes, rates, and deducts charges for network usage (voice, data, SMS) in real-time based on subscriber account balance. OCS operates in the control plane using protocols like Diameter Ro, enabling prepaid services, real-time credit control, and session-based charging. OCS systems perform reservation, consumption tracking, and balance management with millisecond latency requirements.

Categories: SignalingIdentity and SubscriberProtocols and Standards

OCS in context

Signaling protocols carry the control-plane instructions that set up calls, register subscribers, hand over sessions and route SMS. SS7, Diameter, GTP-C and SIP are the four dominant families, and interconnect exposure of any of them is treated by GSMA FS.11 / FS.19 / FS.20 as a top-tier telecom risk.

Subscriber identifiers (IMSI, SUPI, MSISDN, IMEI) are the anchor for authentication, charging, lawful interception and fraud analytics. Any protocol or interface that leaks a permanent identifier is treated as a serious privacy defect, which is why 5G introduced SUCI concealment on the air interface.

To place OCS in the wider telecom-security picture, review OFCS, Charging System, E.164, Roaming, CAMEL and AAA.

Related terms

Equipment

Policy and charging (PCRF, PCF, CHF, OCS, OFCS)

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