Core services represent a collection of community of interest (COI)-independent technical services at the back-end of communications and information systems (CIS) capabilities, focused on the technical functionality to implement service-based environments using infrastructure, architectural and enabling building blocks. Core services provide these building blocks so that these generic, common capabilities do not have to be implemented by individual applications or other services. In the context of the C3 Taxonomy, COI services are facilitating user applications and COI services and connecting these to communications and networking services in the back-end. The second layer of the associated taxonomy specifies three main categories: * Business Support Services -- to provide the means to facilitate other service and data providers on the enterprise network by providing and managing underlying capabilities for collaboration and information management. These services are enablers used by other services and users across the whole network-enabled enterprise, acting as "building blocks" for developing more sophisticated COI services and applications. Therefore, they are COI-independent and they must be available to all enterprise members. * Platform Services -- to provide a foundation to implement services in a loosely coupled environment, where flexible and agile service orchestration is a requirement. They offer generic building blocks for implementation (e.g. discovery, message busses, orchestration, information abstraction and access, etc.) and can be used as a capability integration platform in a heterogeneous service-provisioning ecosystem. * Infrastructure Services -- to provide the foundation to host infrastructure services in a distributed and/or federated environment in support of NATO operations and exercises. They include computing, storage and high-level networking services that can be used as the basis for data centre or cloud computing implementations. The Infrastructure Services are aligned with "Infrastructure as a Service" (IaaS) concepts that are used and promoted by industry as part of their cloud computing developments.