Common Data Layer
The Common Data Layer (CDL) component enabled through SMI provides the clean separation of stateful (also known as backing services) and stateless services (e.g. application services).
CDL provides services for efficiently managing stateful subscriber and identity information across all deployed Cisco NFs. The CDL is an in-memory database designed specifically for high performance carrier grade requirements and subscriber data. Separating stateful services in this way allows for the stateless application services to be autonomous, lightweight, upgradable, recoverable, and rapidly scalable.
Stateful services must address the availability, consistency, and portability of state. These typically require replication across one or more containers while maintaining state consistency.
As such, CDL redundancy is achieved by local and remote replication of session data. In addition, a background process scans the data store for inconsistencies, stale data, and corruption, and corrects them both locally and remotely.