Start adding distributed Dragonflow documentation

Add distributed mode main document page, explaining the goals,
motivation and high level architecture.
(And the roadmap topics)

Change-Id: I0f553fc2229b0a862954e4accd98317689f4c059

doc/source/distributed_dragonflow.rst

@@ -1,3 +1,101 @@
 =======================
 Distributed Dragonflow
 =======================
+
+Dragonflow is a distributed SDN controller for OpenStack® Neutron™
+supporting distributed Switching, Routing, DHCP and more.
+
+Our project mission is to Implement advanced networking services in a
+manner that is efficient, elegant and simple.
+
+Designed to support large scale deployments with focus on latency and
+performance.
+
+Designed to introduce advanced innovative services locally on each compute
+node, and with containers deployment in mind.
+
+Dragonflow is a full Neutron implementation that is done the SDN way, our
+motivation for creating yet another Neutron implementation:
+
+1) We wanted to create an SDN implementation that is integral part of
+   OpenStack, meaning both the plugin and the implementation are
+   fully under OpenStack project and governance.
+
+2) Dragonflow is fully open source and we welcome new contributors
+   and partners to share a mutual vision.
+
+3) We wanted Dragonflow to be VERY lightweight and simple in terms
+   of size and code complexity, we want the entry point for new
+   users/contributors to be very simple and fast.
+
+4) Dragonflow is designed to support peformance intensive environments
+   where latency is a big deal.
+
+5) Dragonflow should be easily extensible
+
+6) We believe in a distributed control plane
+
+
+Key Design Guidelines
+-----------------------
+1) DB plug-ability, Determines scalability, lookup performance and latency
+
+2) Synchronization of policy-level/topology abstraction to the Compute Node
+
+3) Support reactiveness in the local DF controller, in cases it make sense
+
+4) Loadable Network Services Framework
+
+
+High Level Architecture
+-----------------------
+
+.. _Distributed Dragonflow Section: http://docs.openstack.org/developer/dragonflow/distributed_dragonflow.html
+
+.. image:: https://raw.githubusercontent.com/openstack/dragonflow/master/doc/images/dragonflow_distributed_architecture.png
+    :alt: Solution Overview
+    :width: 600
+    :height: 525
+    :align: center
+
+Dragonflow environment consist of a local controller running at each of the
+compute nodes in the setup.
+
+These controllers all sync the network topology and policy using a pluggable
+DB solution.
+The controllers then map the policy into OpenFlow flows using the local
+Dragonflow applications that communicate with the local OpenVSwitch.
+
+The DB is being populated by Dragonflow Neutron plugin that converts neutron
+API to our model.
+
+The following sections each describe a specific topic/functionality in Dragonflow
+
+Dragonflow Supported Features
+=============================
+
+Dragonflow Pipeline
+===================
+
+Dragonflow Pluggable DB
+=======================
+
+Distributed DHCP Application
+============================
+
+Containers and Dragonflow
+=========================
+
+Dragonflow Roadmap
+==================
+The following topics are areas we are examining for future features and
+roadmap into Dragonflow project
+
+- Containers
+- Distributed SNAT/DNAT
+- Reactive DB
+- Topology Service Injection / Service Chaining
+- Smart NICs
+- Hierarchical Port Binding (SDN ToR)
+- Inter Cloud Connectivity (Boarder Gateway / L2GW)
+- Fault Detection