The overlay fabric solves most of these inefficiencies by changing the traditional routing concept of a next-hop IP address with a next-hop TLOC. As vEdges build overlay tunnels between their WAN tunnel endpoints (TLOCs), they advertise the site-local networks as reachable via their local TLOCs.

The Cisco Overlay Management Protocol (OMP) is an all-in-one TCP-based protocol, similar to BGP, that establishes and maintains the SD-WAN control plane. OMP runs between the vEdge routers and the vSmart controllers and between the controllers themselves.

In a typical production deployment, most local networks are attached to two or more vEdge devices for redundancy and most networks get advertised from multiple devices. That is why we need to have a mechanism to select the best routes to a particular destination. This is done using the OMP Best-Path selection algorithm

Cisco Viptela SD-WAN is a Wide Area Network (WAN) overlay architecture that applies the principles of Software-Defined Networking (SDN) into the traditional WAN. It is designed to meet the needs of modern enterprise applications and the rapidly growing security requirements.

In this lesson, we are going to look at the inefficiencies of the traditional WAN that the SD-WAN is trying to solve.