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What is SD-WAN?

Overview of SD-WAN

Software-defined wide area networks, or SD-WANs, apply the principles of software-defined networking (SDN) to corporate WANs. That means they separate the managerial control of a WAN, including how it applies policies and routes all types of application traffic, from its underlying network infrastructure. In other words, the most important management is conducted in software instead of hardware. SD-WANs have an overall effect on WANs comparable to that of SDN on modern data center networks and carrier environments – i.e., they enable more intelligent application flows (including prioritization of critical traffic), simpler management and reduced infrastructural costs.

Indeed, the distinctive design of SD-WAN solutions help unlock numerous operational benefits, with the most important being more predictable application performance. Traditional MPLS-based WANs have long excelled at providing such failsafe connectivity, ensuring packets reach their destinations in support of business-critical apps. However, the high costs of MPLS service, the real prospects of service provider lock-in and the uniquely demanding requirements of real-time applications like VoIP and video conferencing have spurred the need for simpler, smarter and more responsive alternatives like SD-WAN.

By leveraging the intelligence of their controllers, appliances, overlay networks, and other services, the best SD-WAN solutions deliver predictable performance for both TCP and real-time applications, whether over a hybrid WAN (e.g., MPLS paired with broadband and 4G LTE) or a pure internet-based WAN, without MPLS. Indeed, there is considerable flexibility when implementing an SD-WAN architecture, as it can support multiple modes of transport beyond MPLS circuits, including commodity internet, cellular service and satellite links. This versatility makes SD-WAN both a technical and financial breakthrough for enterprises and SMBs.

The technical and financial value of an SD-WAN

On the technical side, SD-WAN updates the WAN for the age of cloud computing. MPLS, the dominant WAN technology since the 1990s, was designed long before the advent of mainstream cloud application flows, which require bandwidth far in excess of what thin and expensive MPLS links can offer. MPLS is still a valuable technology because of its reliability and compatibility with multiple networking technologies, from Metro Ethernet to IP VPNs, but its roots run all the way back to the days of Frame Relay and Asynchronous Transfer Mode, and this age really shows itself in struggles to handle solutions such as SaaS and hosted VoIP.

SD-WAN addresses this problem on three fronts:

  • It opens the floodgates for much more bandwidth by supporting economical MPLS alternatives. For a fraction of the price per Mbps of a MPLS plan, an SD-WAN customer can procure and incorporate internet connectivity to ensure continuous availability for performance-sensitive applications on-premise and in the cloud, while also diversifying their transport mix to avoid service provider lock-in.
  • It ensures that these new links are secure and easy as possible to manage. Internet was once off-limits for WANs because it was seen as unreliable in terms of both performance and safety. An SD-WAN might implement encryption alongside integrations such as complete gateway security stacks in the cloud to protect all of its connections. Moreover, any changes to configurations are relatively straightforward via a management portal.
  • An SD-WAN solution conducts constant, precise measurement and monitoring of network traffic, in accordance with current WAN policies. If there is an issue preventing the intended flows across the WAN, it can flag it immediately and then dynamically redirect traffic so that the highest-priority apps get the best quality paths through the WAN or cloud access network. An SD-WAN greatly reduces the bottlenecks that can degrade the user experience.

The inexpensive transport options available through SD-WAN make it an appealing upgrade over the MPLS-centric status quo, although savings only scratch the surface of what an organization gains from SD-WAN. The newfound assurance that real-time applications will perform as expected, without taxing the WAN’s infrastructure beyond its means, is the central value proposition of SD-WAN.

These apps, most notably ones for voice and video, have become vital to the structure and operations of the modern enterprise. Distributed workforces, spread across home and branch offices, are more common than ever before, and they rely on consistent access to real-time communications tools made available over the company WAN. Scaling a conventional WAN to consistently serve far-flung end users and branches is recipe for subpar user experience, which creates the opening for SD-WAN solutions.

A legacy MPLS WAN will often backhaul its traffic to HQ or a data center for security purposes, resulting in a noticeable performance penalty on sensitive applications. Its security infrastructure is also relatively complex, featuring appliances at multiple locations, which increases costs as well as management overhead for IT personnel. Taken together, these drawbacks make everyday WAN usage and upkeep a companywide burden for today’s increasingly distributed enterprises.

In contrast, an SD-WAN simplifies the branch connection to HQ or a data center by using internet links. It may also provide the option for direct-to-cloud connections for even smoother access to anything from a hosted VoIP or UC platform to Microsoft Office 365 and Salesforce. An SD-WAN solution delivers much more reliability per dollar spent than a traditional WAN.

How to evaluate SD-WAN solutions

The rapid growth of the SD-WAN industry in the 2010s has produced a bevy of competing solutions from both dedicated SD-WAN vendors and many service providers themselves. They all seem similar on the surface, due to their touted inclusion of some or all of the features and benefits outlined above, yet significant differences exist. Some of the key differentiators include:

Wireless backup options

LTE service is fast, widely available and wireless, making it an ideal backup choice for wired WAN circuits. An old-fashioned WAN might include T1 lines running MPLS, a setup that is vulnerable to terrestrial risks such as flooding. LTE is much more resilient in comparison and can provide the redundant circuitry necessary for seamless application failover, even in remote and challenging environments in which running extra cabling would be impractical.

Included security features

In replacing or at least augmenting a large portion of MPLS connectivity, SD-WAN has a high security bar to meet. Customers should make sure that any prospective solution comes complete with features such as branch gateways between MPLS and SD-WAN providing end-to-end encryption, stateful firewalls with SD-WAN traffic fabric management and shaping, secure internet access at all sites, and denial-of-service protections.

Zero-Touch Provisioning

SD-WAN’s simplification of the network trickles down to the setup of equipment and connections at each branch office. Rather than needing to send technical teams out to every branch to oversee proper configuration, an ideal SD-WAN will enable zero-touch provisioning, which allows for sites to automatically receive the right configurations upon connection. Accordingly, the SD-WAN can scale to many sites with minimal hassle.

Compatibility with existing infrastructure

An SD-WAN is a huge upgrade, but it does not have to be a disruptive one. Make sure its overlay can work with existing routers and network infrastructures. Also check if it can support hybrid MPLS-internet connectivity in addition to internet-only (since MPLS remains a substantial commitment even in SD-WAN-curious organizations) and that it works well in tandem with services such as WAN optimization and guest Wi-Fi configurations, if applicable.

Synergy with other services from the same provider

Many SD-WAN vendors offer multiple solutions, the sum total of which can make the difference in determining which SD-WAN is the best fit for a given organization. For example, the same provider might oversee both an SD-WAN platform and a hosted VoIP service – two offerings that are frequently paired in practice, since SD-WAN guarantees the predictable performance required for acceptable VoIP interactions. Telesystem offers a broad portfolio of networking services, from SD-WAN and hosted VoIP to Metro Ethernet and MPLS, meaning that customers can be confident they are getting solutions that fit well together.

A better way to WAN

The major trends that have made SD-WAN an appealing upgrade – notably, the rise of cloud computing and distributed enterprises – will likely continue for the foreseeable future. As a result, an SD-WAN solution is a smart investment that will future-proof key applications and workflows.

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