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SD-WAN vs. MPLS: MPLS Isn't Going Anywhere Anytime Soon

SD-WAN

SD-WAN
(Image: Pixabay)

Gartner says software-defined WAN (SD-WAN) will grow to become a $1.3 billion market by 2021, growing at a 59 percent compound annual growth rate (CAGR). At the same time, the overall branch office router market will take a steep drop, according to the analysts. A quick scan of the headlines these days reveals a lot of chatter over the benefits of replacing legacy Multiprotocol Label Switching (MPLS) services with more flexible MPLS alternatives such as SD-WAN.

While it is true that SD-WAN is an appealing technology that delivers branch-office connectivity in a simplified and cost-effective manner compared with traditional routers, it is not likely to replace MPLS entirely. Given the rapid rise that SD-WAN has seen in just the past few years, this claim may come as a surprise. 

Without a doubt, the key driver for SD-WAN is the emerging dominance of cloud-based applications, data storage, and compute. As branch traffic flows shift from the headquarters data center to the cloud, it’s inefficient to backhaul all traffic through the headquarters. Concurrently, many organizations are embarking on digital transformation initiatives. In many cases, this comes with the need for intelligent management platforms and advanced analytics to ensure optimal support for both back-office and customer-facing workloads. And let’s not forget the growing adoption of the Internet of Things (IoT), which requires dynamic, high-speed networking between devices, the edge, the cloud, and the data center.

With all that is taking shape, where does an older networking solution such as MPLS fit in?

The key thing to remember is that this is not a stark choice. There are pros and cons to both MPLS and SD-WAN. A common enterprise network configuration will be one in which each solution supports key workloads based on their service requirements. In fact, the most common scenario has SD-WAN augmenting MPLS to provide a healthy mix of flexibility and reliability, as well as scalability and cost savings.

MPLS was designed for and is deployed in a hub-and-spoke topology that backhauls branch data to a centralized data center. MPLS typically provides better performance for workloads that are sensitive to latency in packet delivery and demand high reliability. These include critical real-time applications such as voice, video, and collaboration. With countless services now firmly entrenched in the cloud, this approach has become expensive and cumbersome. For all its reliability and performance, MPLS is a costly option. That’s why so many organizations are transitioning to hybrid WAN solutions that de-emphasize MPLS in favor of SD-WAN.

This doesn’t mean that all use cases will shift to MPLS alternatives such as SD-WAN. Even within companies that are heavily dependent on Software-as-a-Service (SaaS) and cloud computing workloads, there are strong reasons for them to keep at least some of their legacy MPLS network in service. Many organizations will continue to maintain MPLS in the local data center to support basic network domain and server services. Authentication, DHCP, and DNS services are prime examples.

Complicating the issue is the fact that the line between critical or non-critical data and higher priority or lower priority traffic is not always clear. Video conferencing may be mission-critical, and demand assured quality of service for one organization, while for the next, it may be considered entirely dispensable. In general, organizations can expect to support critical workloads and some non-critical ones for them in the data center. Headquarters and large branch sites may connect over MPLS, while smaller branches will use MPLS alternatives such as SD-WAN offerings riding on a mix of business and consumer broadband Internet connections.

Organizations should take the following steps to differentiate SD-WAN and MPLS workloads and needs properly:

  • Conduct a thorough survey of all data flows and applications on current WAN infrastructure and then set appropriate policies to allocate traffic to the proper solution

  • Consider non-broadband Direct Internet Access (DIA) circuits for SD-WAN deployments that support high ratios, critical cloud-facing workloads, and real-time applications

  • Explore “over the top” MPLS alternatives that offer performance and reliability over broadband

  • Employ priority-based path selection and other SD-WAN tools to improve throughput for time-sensitive applications

  • Potentially maintain MPLS networks at the data center, critical off-site locations and in areas with poor or emerging infrastructure

Geography can potentially come into play, as well. When dealing with remote users, the best broadband just isn't always available. Exurban and rural regions are still lagging in broadband connectivity and probably will continue to do so for some time. As a matter of course, networking executives should rank each remote site not just by the type of services needed but also by what flavor of broadband is available.

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Futureproofing the Branch Office

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The Best Ways to Determine How Much Bandwidth Your Data Center Needs