=== SFC Southbound REST Plugin

==== Overview
The Southbound REST Plugin is used to send configuration from DataStore down to
network devices supporting a REST API (i.e. they have a configured REST URI).
It supports POST/PUT/DELETE operations, which are triggered accordingly by
changes in the SFC data stores.

.In its current state it listens to changes in these SFC data stores:
* Access Control List (ACL)
* Service Classifier Function (SCF)
* Service Function (SF)
* Service Function Group (SFG)
* Service Function Schedule Type (SFST)
* Service Function Forwader (SFF)
* Rendered Service Path (RSP)

==== Southbound REST Plugin Architecture
.The Southbound REST Plugin is built from three main components:
. *listeners* - used to listen on changes in the SFC data stores
. *JSON exporters* - used to export JSON-encoded data from binding-aware data
store objects
. *tasks* - used to collect REST URIs of network devices and to send JSON-encoded
data down to these devices

.Southbound REST Plugin Architecture diagram
image::sfc/sb-rest-architecture.png[width=500]

==== Key APIs and Interfaces
The plugin provides Southbound REST API designated to listening REST devices. It supports
POST/PUT/DELETE operations. The operation (with corresponding JSON-encoded data) is sent
to unique REST URL belonging to certain datatype.

.The URLs are following:
* Access Control List (ACL):
+http://<host>:<port>/config/ietf-acl:access-lists/access-list/+
* Service Function (SF):
+http://<host>:<port>/config/service-function:service-functions/service-function/+
* Service Function Group (SFG):
+http://<host>:<port>/config/service-function:service-function-groups/service-function-group/+
* Service Function Schedule Type (SFST):
+http://<host>:<port>/config/service-function-scheduler-type:service-function-scheduler-types/service-function-scheduler-type/+
* Service Function Forwarder (SFF):
+http://<host>:<port>/config/service-function-forwarder:service-function-forwarders/service-function-forwarder/+
* Rendered Service Path (RSP):
+http://<host>:<port>/operational/rendered-service-path:rendered-service-paths/rendered-service-path/+

Therefore, network devices willing to receive REST messages must listen on
these REST URLs.

[NOTE]
Service Classifier Function (SCF) URL does not exist, because SCF is considered
as one of the network devices willing to receive REST messages. However, there
is a listener hooked on the SCF data store, which is triggering POST/PUT/DELETE
operations of ACL object, because ACL is referenced in +service-function-classifier.yang+