SD-WAN is Better than MPLS, But Still Poses Some Challenges

The software-defined wide area network (SD-WAN) is certainly not suffering from a lack of enthusiasm on the part of either the enterprise or network providers. Anyone who is even remotely interested in transitioning to a digital services business model or incorporating the Internet of Things into their data infrastructure is looking at the SD-WAN to help make it happen.

But implementing this new form of networking is not just a matter of swapping out a few routers or signing on to a new service. SD-WAN represents an entirely new networking architecture, one in which multiple layers require a high degree of integration and cooperation if the services it supports are to capture the imaginations of end users.

Cato Networks’ Dave Greenfield noted recently that SD-WAN gives VARs a lucrative new opportunity to migrate customers off of rigid and expensive MPLS networks to one that is far more flexible and operates at the speed of modern business. But they would be doing a disservice to the enterprise by not pointing out that SD-WAN requires a new approach to security, due to the fact that it will be carrying a fair amount of Internet-bound traffic. SD-WAN appliances also need to populate the cloud center as well as the edge in order to provide cohesive connectivity end-to-end. And let’s not forget about mobile users, who will need some way to connect since most SD-WAN solutions do not support mobile access.

Visibility is also a key element of SD-WAN. Accedian’s Michael Rezek points out that traditional WAN performance indicators may be sufficient for network operations, but they can be blind when it comes to Quality of Experience and User Experience metrics that services depend on. Without full visibility into network underlays, end-user application metrics and root-cause performance degradation, providers have no way to correlate events and issues to ensure that application or network problems can even be identified, let alone corrected. To achieve this level of visibility, CSPs should strive for nothing less than end-to-end performance assurance management on both the media layers (1-3) and host layers (4-7). Note that this is management, not just monitoring, since it involves building profiles of network and app performance, and particularly how they are being experienced by the user.

It might also help to look beyond the simple networking aspects of SD-WAN, impressive though they may be, and start looking at the service angle of networking. As a recent post on Business World explained, SD-WAN itself offers many advantages over MPLS, but when you start to look at it from an SDWaaS (SD-WAN as a Service) perspective, the gains are even more impressive. For one thing, SDWaaS offers far greater flexibility when determining bandwidth consumption and even transport methods, allowing the enterprise to keep costs low even as performance improves. SDWaaS also provides an even more robust and reliable solution than MPLS by virtue of its ability to enable policy-based network management that can be tailored to individual use cases.

This idea of a service-based WAN is already starting to take shape. The Metro Ethernet Forum recently approved a set of draft specifications that would define SD-WAN services and their various attributes. The group is hoping that by establishing common terms and concepts, both buyers and sellers of SD-WAN services will have an easier time building and deploying a wide range of network ecosystems. The program is part of a wider effort to devise a full set of carrier Ethernet, IP, optical transport and other virtualized services using the Lifecyle Service Orchestration (LSO) API.

All of this adds to one of those good news/bad news situations for the enterprise. The good news is that the decision to switch from MPLS to SD-WAN is an easy one. The bad news is that building a fully functional SD-WAN is a bit trickier than it initially appeared.

In the end, however, none of the challenges related to SD-WAN are insurmountable. And this means the enterprise will likely have in place a highly flexible, inherently reliable and low-cost virtual wide area network solution just in time for the transition to a digital services model.

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