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The wide area network (WAN) has always been about connecting users to applications and moving data over long distances. While these requirements still exist, cloud services and the high cost of Multiprotocol Label Switching (MPLS) networks has forced a rethink of the enterprise WAN. Businesses are now increasingly looking to the Internet, which provides the opportunity for faster WAN provisioning and the ability to use multiple WAN paths at the same time. This is referred to as the software-defined WAN (SD-WAN).

MPLS has certainly made sense for the enterprise over the last decade because applications have only been hosted in the data centre and the Internet hasn't been able to deliver the reliability required to support user demands. In fact, it has provided enterprises with a stable, high-performance and highly-scalable means of connecting data centres and branch offices. However, it is very expensive. With more applications offered on-demand via the Internet and cloud, there is a distinct need for increased agility and for enterprises to operate at cloud speed. If MPLS connections need to be added, removed or changed, the process can take a long time and be extremely disruptive.

THE NEED FOR CHANGE
Businesses are currently wasting large amounts of money each year because of the trombone effect, otherwise referred to as back-hauling. Today, we directly access cloud applications in our homes via broadband; it works well and costs less. However, accessing these cloud applications from within the enterprise often equals slower performance and wasted costs, because the transmission is being sent over expensive MPLS connections before connecting to the cloud over the Internet.

Another common problem is that businesses are losing visibility and control over the expanding application mix. Most cannot say how many SaaS or cloud applications are running on their network or which are in use across the enterprise. IT not only needs to improve the performance of these applications, but it must also gain greater insight into how they are being used.

REDEFINING THE WAN
An SD-WAN is a virtual WAN overlay that helps enterprises flexibly and securely connect users to applications via the most cost-effective available source of connectivity. This enables enterprises to augment or replace MPLS networks with secure Internet connectivity. By supporting multiple paths and allowing connectivity decisions to be made independently of carriers, the SD-WAN helps enterprises to avoid lengthy procurement and deployment delays at the branch.

An SD-WAN fabric also provides visibility into both data centre and cloud traffic, and it provides the ability to centrally assign business-intent policies to secure and control the WAN traffic. It dynamically selects the best path, whether it's MPLS or the Internet for each application based on these policies and real-time network quality measurements, with all data encrypted edge-to-edge.

CREATING A HYBRID WAN
The beauty of the SD-WAN is that enterprises can move at their own pace. While the ultimate goal may be a 100 per cent broadband WAN, an organisation can start with a hybrid WAN. As MPLS upgrades arise, businesses are able to explore lower-cost broadband Internet services as an alternative path for connecting to cloud applications: this provides an opportunity to downsize MPLS bandwidth and only use that connectivity for remaining data centre applications. Enterprises can then begin to migrate some of their other applications into the cloud, as and when desired.

Transitioning to this new WAN model, whether fully or partially, involves minimal disruption and cost. Internet services can be introduced into the WAN without impact on application performance or the MPLS network. With the flexibility to implement a new WAN architecture at a speed that suits them best, enterprises can start seeing payback in performance and costs almost immediately. NC