Why Do You Need an SD-WAN?


The vast majority of companies—any companies that have multiple sites or remote access workersneed to consider the question “Why do I need an SD-WAN?” This is no longer just the purview of the large enterprise.

First, a definition is in order.  SDxCentral defines the SD-WAN as follows:

The software-defined wide area network (SDWAN) is a specific application of software-defined networking (SDN) technology applied to WAN connections, which are used to connect enterprise networks—including branch offices and data centers—over large geographic distances.

Isn’t this what MPLS VPNs do? Or even, for that case, the venerable point-to-point links and frame-relay network? Well, yes and no. The common denominator for all these technologies is that they are point to point, single/low numbers to central data center.

MPLS VPNs and dedicated leased lines are all fundamentally based on a spoke-and-hub design technology, where multiple remote sites or individual machines connect over a secure connection via the internet. Direct connections from one endpoint to another are problematic and will always result in a hop through the core.

The point is that these are tunneled connections from one device directly to a central hub. Although they exhibit some features common to software-defined networking (for example, the ability to hide the underlying data path), they are grounded in the physical world, with all its inflexibility.

What Does SD-WAN Bring to the Party?

This is best shown by looking at the recent announcement from CenturyLink regarding its fully managed SD-WAN service.

The traditional enterprise WAN is a hotchpotch of various point-to-point technologies. Core data centers may be linked with dedicated leased lines from multiple providers. These leased lines may be Ethernet links or legacy T1 or T3 connections. ROBO offices connect to the core data centers via an MPLS network using broadband connections. VPN connections connect their mobile workforce to core applications and allow remote support.

Each of these connectivity options requires skills to manage them, an overcomplicated routing table, and a multitude of management interfaces, suppliers, or both. This is not conducive to stress-free network admin staff.

What CenturyLink has done with its new service (which uses the Versa Networks product set) is to provide a single, homogeneous network that seamlessly merges disparate WAS-based technologies, such as MPLS, point-to-point, and VPNs, into a single service. This overlay technology serves to provide a unified management interface, which allows a more agile approach to bandwidth requirements.

Now, your network can route traffic across your WAN in the most optimal manner. If a user needs to attach to another user, they will go via the shortest path, not via the core network. Further, you will have access to higher resilience due to better carrier choice, all managed by CenturyLink. Access to NFV features means that traffic flow can be optimized with a better QoS, helping to guarantee service level agreements.

This new service is currently being trialed by more than ten enterprises and will be generally available in the US circa Q3 2016. We fully expect it to be rolled out to the company’s other points of presence globally quite quickly.

This is a good move for CenturyLink. Coupled with its recent ElasticBox acquisition, it adds another arrow to its quiver.

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Tom Howarth
Tom Howarth is an IT Veteran of over 20 years experience and is the owner of PlanetVM.Net Ltd, Tom is a moderator of the VMware Communities forum. He is a contributing author on VMware vSphere(TM) and Virtual Infrastructure Security: Securing ESX and the Virtual Environment, and the forthcoming vSphere a Quick Guide. He regularly does huge virtualization projects for enterprises in the U.K. and elsewhere in EMEA. Tom was Elected vExpert for 2009 and each subsequent year thereafter.
Tom Howarth

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