//
// ============LICENSE_START=======================================================
//  Copyright (C) 2016-2018 Ericsson. All rights reserved.
// ================================================================================
// This file is licensed under the CREATIVE COMMONS ATTRIBUTION 4.0 INTERNATIONAL LICENSE
// Full license text at https://creativecommons.org/licenses/by/4.0/legalcode
// 
// SPDX-License-Identifier: CC-BY-4.0
// ============LICENSE_END=========================================================
//
// @author Sven van der Meer (sven.van.der.meer@ericsson.com)
//

== VPN SLA Policy

The VPN SLA policy is designed as a MEDA policy.
The first state (M = Match) takes the trigger event (a link up or down) and checks if this is a change to the known topology.
The second state (E = Establish) takes all available information (trigger event, local context) and defines what situation we have.
The third state (D = Decide) takes the situation and selects which algorithm is best to process it.
This state can select between `none` (nothing to do), `solved` (a problem is solved now), `sla` (compare the current customer SLA situation and select one to impede), and `priority` (impede non-priority customers).
The fourth and final state (A = Act) selects the right action for the taken decision and creates the response event sent to the orchestrator.

We have added three more policies to set the local context: one for adding nodes, one for adding edges (links), and one for adding customers.
These policies do not realize any action, they are only here for updating the local context.
This mechanism is the fasted way to update local context, and it is independent of any context plugin.

The policy uses data defined in Avro, so we have a number of Avro schema definitions.