Network service design

A Network Service can be defined as a composition of resources (like VNFs) connected together constructing a coherent service function. On highest level a network service corresponds to an orderable entity that provides end users with an end-to-end service chain.

Network services can be defined in a hierarchical manner. A network service can comprise of other network services and/or individual resources corresponding to service segments, or providing specific functions, all contributing to the behavior of the higher layer service. The end-to-end network service behavior is the result of the combination of the individual network function behaviors as well as the behaviors of the network infrastructure composition mechanism.

The following diagram shows an example of a network service comprising of one low-level network service and three VNFs related together. The sample service also has a dependency to another network service external to it.

The structure of the network service is defined in a network service descriptor that contains the composition of the involved resources (VNFs and/or other network services) and their relationships. The descriptor is defined at the time of service design. For the orchestration component, the network service descriptor functions as a service model used by its intent engine to resolve execution paths to perform specific lifecycle transitions on the service.

A network service descriptor can also contain references to external components. These can be either existing assembly instances or external resources that are managed directly by a resource manager. An example of a referenced resource can be existing network connectivity that already exists and to which the network service should be connected to.

All items referenced in the network service descriptor must be pre-existing before the orchestration component will instantiate any of the network service components included in the network service composition.