Service Fabric is a collection of services grouped into different subsystems. These subsystems have specific responsibilities. The following diagram illustrates the major subsystems which form the Service Fabric architecture:

The first layer from the bottom, the Transport Subsystem is responsible for providing secure communication channels between nodes in a Service Fabric cluster. The Federation Subsystem above it helps logically group physical or virtual nodes into a cluster so that it can be managed as a unit. This helps Service Fabric with tasks such as failure detection, leader election, and routing. Reliability of the workload hosted on Service Fabric is managed by the Reliability Subsystem. It owns the responsibility of replication, resource management, and failover. The Hosting & Activation Subsystem manages the lifecycle of the workload on every node and the Management Subsystem is responsible for managing the lifecycle of applications. The Testability Subsystem helps developers test their workload before and after deployment. Service location of services hosted on Service Fabric is managed by Communication Subsystem. The top three boxes capture the application programming models and the application model available for the developers to consume. More about application models is discussed in later parts of this book.