The first place to tackle SDN? In the WAN

Michael Elmore of Cigna argues that the best initial use case for SDN is in the wide area network

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application-based routing decisions dynamically and based on application performance criteria – all independent of the underlying transport.

The underlay just becomes a set of common IP circuits with next hop reachability. This opens the door for customers to go direct to the local market (LEC, MSOs, etc.) to procure more cost-effective bandwidth with the right mix of transport technologies and SLAs required for the business, without compromising or fragmenting the logical routing topology.

Consider a company that has business process outsourcing, business-to-business, internal, or other WAN constructs, which increase complexity and cost. What if a network administrator could build an underlying network with various transport providers and glue the transport together with a unified overlay providing centralized policy management via a controller to create logical segmentation for multi-tenancy? Essentially, this would drive up the efficiency rate, creating a more cost-effective network.

The benefits become exponential when you couple an SD-WAN strategy with converging and centralizing/regionalizing services such as SIP voice, IP Contact Center and other services, which are often distributed and reside on edge CPE today (DSPs, SRST).

Let’s dive into how each of the previous problem statements gets addressed with SD-WAN.


  • An SD-WAN overlay enables customers to regionalize their transport and go directly to the LEC markets to reduce the double margin effects inherent to the traditional national/global provider model.
  • Ethernet services enable new commercial off-the-shelf CPE options.


  • By separating the underlying transport and the control plane with software based overlay/controller(s) owned by the customer, it reduces the dependency and scale limitations with the carriers. Essentially, the carrier becomes “next hop reachability” via IP circuits, with an intelligent overlay managed by the customer to orchestrate the enterprise routing. The scale becomes directly proportional to the SDN controller.

Service quality:      

  • WANs today are not application-aware, nor do they consider the application performance thresholds. Soft failures/regional brown-outs can have unpredictable and adverse impact to real-time applications.
  • Application or performance aware routing is a game-changing feature that enables customers to monitor the performance of the underlay and make real-time dynamic routing decisions by application. This dynamic detection and convergence capability will improve overall service quality by avoiding manual intervention and troubleshooting, while increasing a customer’s probability to hit internal SLAs, as well as responding to unplanned carrier maintenance. This type of dynamic performance awareness has the potential to decrease the reliance on hop-by-hop QoS policy management as well.


  • Many SD-WAN products come standard with data plane encryption and control plane security. Most enterprise security teams have stopped asking for internal WAN encryption due to cost, scale and manageability challenges. SD-WAN is an opportunity to provide a consistent authentication and transport encryption policy regardless of the underlying transport mechanism or service provider.
  • Central policy management and segmentation now become a reality, and multi-tenancy increases the efficiencies of the underlying transport. “Who are you” and “what do you need access to” are based on user policy.


  • A carrier-agnostic approach with full visibility and unification of the routing table, inclusive of a multi-home default route scenario.
  • Services such as QoS and multicast will be inherent to the customer controlled overlay.
  • Alerting and management will be innate, enabling the underlay performance visibility.


  • Customers can leverage non-traditional transport for connectivity, such as cable MSOs, broadband and/or business-class internet, LTE and 4G to improve delivery time frames.
  • Optimized path selection for cloud services, such as web conferencing, Office365, HR (workday) and other cloud-based apps via local internet links.
  • Service chaining and NSFV become a reality through logical steering of traffic for load balancing and firewall services.

How close are we to realizing this nirvana vision?

The technology is very close, both from the traditional equipment suppliers and early stage start-ups. However, vendors are taking different approaches for prioritizing the features they will implement, and in developing their product roadmaps.   Many of the

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