SDFAB-596 Added architecture and design
Also fixing some minor format issue
Change-Id: I675f6d4349a43d630dfb0ae58530c6b4c44f9665
diff --git a/specification.rst b/specification.rst
index 0e21a7b..f59ccc0 100644
--- a/specification.rst
+++ b/specification.rst
@@ -85,6 +85,8 @@
- T3: Troubleshooting tool to diagnose broken forwarding paths fabric wide
- ONOS-diags: One-click Diagnostics collection tool
+.. _Topology:
+
Topology
--------
SD-Fabric can start at the smallest scale (single leaf) and grow horizontally.
@@ -94,35 +96,35 @@
Single Leaf (ToR)
------------------
+^^^^^^^^^^^^^^^^^
This is the minimum SD-Fabric setup. In this setup, all servers are connected to a single switch.
.. image:: images/topology-single.png
:width: 160px
Single Leaf Pair (Dual-Homing)
-------------------------------
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Compared to single switch, it provides more redundancy in terms of server NIC failure and link failure.
.. image:: images/topology-pair.png
:width: 225px
Leaf-Spine (without pairing)
-----------------------------
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Compared to single switch, it offers more redundancy in terms of switch failure and provides better scalability.
.. image:: images/topology-2x2.png
:width: 300px
Leaf-Spine (with pairing)
--------------------------
+^^^^^^^^^^^^^^^^^^^^^^^^^
It supports all the redundancy and scalability features mentioned above.
.. image:: images/topology-2x4.png
:width: 450px
Multi-Stage Leaf-Spine
-----------------------
+^^^^^^^^^^^^^^^^^^^^^^
Multi-stage is specifically designed for telco service providers.
The first stage can be installed in the central office, while the second stage
can be installed in a field office that is closer to the subscribers.