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The idea of using control loops to automatically (or autonomously) perform network management has been the subject of much research in the Network Management research community, see this paper for some background. However, it is only with the advent of ONAP that we have a platform that supports control loops for network management. Before ONAP, Control Loops have been deployed by hard-coding components together and hard coding logic into components. ONAP has taken a step forward towards automatic deployment of applications Control Loops by allowing parameterization of Control Loops that work on the premise that the Control Loops use a set of analytic, policy, and control components connected together in set ways.

The goal of the work here is to extend and enhance the current ONAP Control Loop support to provide a complete open-source framework for Control Loops. This will enhance the current support to provide TOSCA based Control Loop definition, development, deployment and run-time management. The participants that comprise a Control Loop and the metadata needed to link the participants together to create a Control Loop are specified in a standardized way using the OASIS TOSCA modelling language. The TOSCA description is then used to deploy and manage the Apps Control Loops in the run time system.

1: Overall Architecture

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As shown in the figure above, the Design time component provides a system where Control Loops can be designed and defined in metadata. This means that a Control Loop can have any arbitrary structure and the Control Loop developers can use whatever analytic, policy, or control primitives they like to implement their Control Loop. At deployment time, the user parameterises the App Control Loop and deploys it. A design time catalogue is created. This catalogue contains the primitive metadata for any components that can be used to compose an App. An App a Control Loop. A Control Loop SDK is used to compose an App a Control Loop by aggregating the metadata for the components chosen to be used in an app a Control Loop and by constructing the references between the components.

Once the App Control Loop is composed, it is packaged (TOSCA uses a CSAR archive, a type of zip file). The package consists of the TOSCA file for the App the Control Loop together with any other artifacts that should be passed to components participating in an App a Control Loop when it is instantiated. The package is deployed to the run time part of the system, where it is stored in the run time catalogue and is available for instantiation.

When a user wishes to instantiate an Appa Control Loop, they set values for the parameters of the AppControl Loop. Once the parameterization has been carried out, the App is the Control Loop instantiated, with the metadata and whatever other artifacts are required being passed to the participants in the AppControl Loop. At runtime, the App the Control Loop can be monitored and analysed. It can also be updated  as required and can be deleted when it is on longer needed.

Performing a hot upgrade of the App the Control Loop at run time as well as handling an upgrade of the software in one or more of the participants in an App an Control Loop is a particularly challenging issue because upgrading must handle the following cases without tearing down the AppControl Loop:

• Upgrade and changes of the configuration data of participants
• Addition of or removal of participants in an AppControl Loop
• Upgrade of software in one or more participants in an AppControl Loop
• Maintenance of compatibility between participants when an update of more than one participant must be done  together to ensure compatibility, for example, when a protocol being used by two participants to communicate is upgraded

The App The Control Loop Runtime Management will use Common SMO ONAP services for non-functional aspects such as inventory, topology and data delivery. It will also interact with orchestration components using the implementations of the ETSI/MANO standards developed in

The diagram below outlines the architecture of the TOSCA defined control loop management.

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