Added architecture and design

Also added a note about
  - Reserved MPLS label
  - Reserved VLAN id
  - Reserved multicast address

Change-Id: I86e0c8ed37622bf383ec3d615956f4e0b34f91be
diff --git a/configuration/bridging-unicast.rst b/configuration/bridging-unicast.rst
index fe2d2aa..1de2a35 100644
--- a/configuration/bridging-unicast.rst
+++ b/configuration/bridging-unicast.rst
@@ -1,6 +1,10 @@
 Bridging and Unicast Routing
 ============================
 
+.. attention::
+    - VLAN **4090** is reserved for :doc:`pseudowire <configuration/pseudowire>` transport
+    - VLAN **4094** is reserved for unconfigured ports (e.g. spine facing ports)
+
 Access Ports
 ------------
 The necessary but minimum configuration for an access port is simply a VLAN.
@@ -60,10 +64,12 @@
 When the desire is to route out of a VLAN, this assignment is currently necessary on all ports configured in the same VLAN.
 
 .. note::
-
     Typically we only expect a single subnet for a VLAN. Similar to traditional networks, for us, a subnet == VLAN. Different VLANs should be configured in different subnets.
     In certain use-cases, it may be necessary to configure multiple subnets in the same VLAN. This is possible by adding more subnet/gateway IPs in the ``ips`` array.
 
+.. tip::
+    One subnet cannot be configured on multiple leaf switches.
+    We usually configure one subnet for all the ports on the same leaf switch.
 
 Tagged Ports
 ------------
diff --git a/configuration/device-config.rst b/configuration/device-config.rst
index 4337558..6da9acd 100644
--- a/configuration/device-config.rst
+++ b/configuration/device-config.rst
@@ -42,6 +42,10 @@
     - When using OpenvSwitch, set this to ``ovs-ofdpa``
     - When using hardware switches, set this to ``ofdpa3`` or eliminate ``driver`` entirely as the correct driver configuration will be set automatically by ONOS
 
+.. caution::
+    We should avoid using reserved MPLS labels for ``ipv4NodeSid`` and ``ipv6NodeSid``.
+    Please check here for the reserved values: http://www.iana.org/assignments/mpls-label-values/mpls-label-values.xhtml
+
 .. note::
     Most of the Trellis configurations support dynamic configuration updates.
     Unfortunately, Trellis currently **do not support dynamic device configuration updates**.
diff --git a/configuration/external-connectivity.rst b/configuration/external-connectivity.rst
index f5102a7..a9ac538 100644
--- a/configuration/external-connectivity.rst
+++ b/configuration/external-connectivity.rst
@@ -4,22 +4,6 @@
 vRouter
 -------
 
-Overview
-^^^^^^^^
-The Trellis fabric needs to be connected to the external world via the vRouter functionality.
-In the networking industry, the term vRouter implies a "router in a VM". This is not the case in Trellis.
-
-Trellis vRouter is NOT a software router.
-Only the control plane of the router – i.e routing protocols – run in a VM.
-We use the Quagga routing protocol suite as the control plane for vRouter.
-
-The vRouter data plane is entirely in hardware - essentially the entire hardware fabric serves as the (distributed) data plane for vRouter.
-The external router views the entire network infrastructure as a single router.
-
-.. image:: ../images/config-vr.png
-
-.. image:: ../images/config-vr-logical.png
-
 Physical Connectivity
 ^^^^^^^^^^^^^^^^^^^^^
 External routers must be physically connected to one of the fabric leaf switches.
diff --git a/configuration/multicast.rst b/configuration/multicast.rst
index 3d34bf0..63fd4c9 100644
--- a/configuration/multicast.rst
+++ b/configuration/multicast.rst
@@ -13,6 +13,7 @@
 - Support **multiple sources**
 
 .. image:: ../images/config-mcast.png
+    :width: 1000px
 
 .. note::
     Dual-homed sinks and multiple sources support comes with major changes in the Multicast Routing subsystem.
@@ -26,6 +27,9 @@
         :width: 600px
         :align: center
 
+.. caution::
+  We should avoid using reserved Multicast groups. Please check here for the reserved values: http://www.iana.org/assignments/multicast-addresses/multicast-addresses.xhtml
+
 
 Activate Multicast
 ------------------