Fix specification format

Change-Id: Ib83ddeaafc7ea2a3ca40f1d0cd3aabe274f70cc7
diff --git a/specification.rst b/specification.rst
index 2074718..bfe6c6a 100644
--- a/specification.rst
+++ b/specification.rst
@@ -2,7 +2,7 @@
 =============
 
 SDN Features
-############
+------------
   - ONOS cluster of all-active N instances affording N-way redundancy and scale, where N = 3 or N = 5
   - Unified operations interface (GUI/REST/CLI)
   - Centralized configuration: all configuration is done on the controller instead of each individual switch
@@ -12,8 +12,9 @@
   - Automatic switch, link and topology discovery and maintenance (keepalives, failure recovery)
 
 L2 Features
-###########
+-----------
 Various L2 connectivity and tunneling support
+
   - VLAN-based bridging
 
     - Access, Trunk and Native VLAN support
@@ -29,8 +30,9 @@
       - Support VLAN translation of outer tag
 
 L3 Features
-###########
+-----------
 IP connectivity
+
   - IPv4 and IPv6 unicast routing (internal use of MPLS Segment Routing)
   - Subnetting configuration on all non-spine facing leaf ports; no configuration required on any spine port
   - IPv6 router advertisement
@@ -39,16 +41,19 @@
   - Further reduction of per-leaf flows with route optimization logic
 
 DHCP Relay
-##########
+----------
 DHCP L3 relay
+
   - DHCPv4 and DHCPv6
   - DHCP server either directly attached to fabric leaves, or indirectly connected via upstream router
   - DHCP client directly either attached to fabric leaves, or indirectly connected via LDRA
   - Multiple DHCP servers for HA
 
 vRouter
-#######
-vRouter presents the entire SD-Fabric as a single router (or dual-routers for HA), with disaggregated control/data plane
+-------
+vRouter presents the entire SD-Fabric as a single router (or dual-routers for HA),
+with disaggregated control/data plane
+
   - Uses open-source protocol implementations like Quagga (or FRR)
   - BGPv4 and BGPv6
   - Static routes
@@ -56,59 +61,60 @@
   - ACLs based on port, L2, L3 and L4 headers
 
 Multicast
-#########
+---------
 Centralized multicast tree computation, programming and management
+
   - Support both IPv4 and IPv6 multicast
   - Dual-homed multicast sinks for HA
   - Multiple multicast sources for HA
 
 API
-###
+---
 - Provide easy access for 3rd party edge application developers and for the Aether centralized management platform
 - Support for traffic redirecting, dropping, network slicing and QoS
 
 Programmability
-###############
+---------------
 - Support for Stratum, P4Runtime and gNMI and P4 programs
 - Innovative services enabled by programmable pipeline
   - 4G/5G UPF - GTP encap/decap, idle-mode buffering, QoS and more
   - BNG - PPPoE, anti-spoofing, accounting and more
 
 Troubleshooting & Diagnostics
-#############################
+-----------------------------
 - T3: Troubleshooting tool to diagnose broken forwarding paths fabric wide
 - ONOS-diags: One-click Diagnostics collection tool
 
 Topology
-########
+--------
 SD-Fabric can start at the smallest scale (single leaf) and grow horizontally.
 
 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
 
 Paired Leaf (Dual-Homing)
-*************************
+-------------------------
 Compared to single switch, it provides more redundancy in terms of server NIC failure and link failure.
 
 .. image:: images/topology-pair.png
 
 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
 
 Leaf-Spine (with pairing)
-*************************
+-------------------------
 It supports all the redundancy and scalability features mentioned above.
 
 .. image:: images/topology-2x4.png
 
 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.
@@ -117,19 +123,23 @@
 .. image:: images/topology-full.png
 
 Resiliency
-##########
+----------
 Provides HA in following scenarios
+
   - Controller instance failure (requires 3 or 5 node ONOS cluster)
   - Link failures
   - Spine failure
+
 Further HA support in following failure scenarios with dual-homing enabled
+
   - Leaf failure
   - Upstream router failure
   - Host NIC failure
 
 Scalability
-###########
+-----------
 In Production
+
   - Up to 80k routes (with route optimization)
   - 170k Flows
   - 600 direct-attached hosts
@@ -137,6 +147,7 @@
   - 2 spine switches
 
 In Pre-Production
+
   - Up to 120k routes (with route optimization)
   - 250k flows
   - 600 direct-attached hosts
@@ -145,33 +156,34 @@
   - 5000 active UEs, 10 call per second
 
 Security
-########
+--------
   - TLS-secured connection between controllers and switches (premium feature)
   - AAA 802.1x authentication
 
 Aether-ready
-############
+------------
 Fully integrated with Aether (5G/LTE private enterprise edge cloud solution)
 including deployment automation, CI/CD, logging, monitoring, and alerting.
 
 Overlay Support
-###############
+---------------
 Can be used/integrated with 3rd party overlay networks (e.g., OpenStack Neutron, Kubernetes CNI).
 
 Orchestrator Support
-####################
+--------------------
 Can be integrated with an external orchestrator, optionally running from the public cloud
 Supports logging, telemetry, monitoring and alarm services via
 REST APIs and Elastic/Fluentbit/Kibana, Prometheus/Grafana
 
 Controller Server Specs
-#######################
+-----------------------
 Recommendation (per ONOS instance) based on 50K routes
+
   - CPU: 32 Cores
   - RAM: 128GB RAM. 64GB dedicated to ONOS JVM heap
 
 White Box Switch Hardware
-#########################
+-------------------------
 - Multi-vendor: APS Networks™, Dell™, Delta Networks™, Edgecore Networks™, Inventec™, Netburg™, QCT™
 - Multi-chipset:
   - Intel Tofino (supports all features, including programmability, UPF & INT)
@@ -180,7 +192,6 @@
 - Refer to Supported Devices list in https://github.com/stratum/stratum for the most up-to-date hardware list
 
 White Box Switch Software
-#########################
+-------------------------
 - Open source ONL, ONIE, Docker, Kubernetes
 - Stratum available from ONF
-