What is MPLS, and why isn’t it dead yet?

MPLS was a great innovation for its time, but there are newer technologies that better address today’s network architectures. Software-defined WANs (SD-WAN) is architected with cloud connectivity in mind, which is why so many businesses have been replacing or augmenting their MPLS networks with SD-WAN.

MPLS vs. SD-WAN

SD-WAN is the application of Software Defined Networking (SDN) concepts to the WAN. This means the deployment of SD-WAN edge devices that apply rules and policies to send traffic along the best path.

SD-WAN is a transport-agnostic overlay that can route any type of traffic, including MPLS. The advantage of SD-WAN is that an enterprise WAN-traffic architect can sit at a central point and easily apply policies across all WAN devices.

By contrast, with MPLS, predetermined routes need to be painstakingly provisioned and once the fixed circuits are up, making changes is not point-and-click.

But once an MPLS network is deployed, it delivers guaranteed performance for real-time traffic. SD-WAN can route traffic along the most efficient path, but once those IP packets hit the open Internet, there are no performance guarantees.

SD-WAN is significantly less expensive to deploy and operate than MPLS. Lightyear’s WAN connectivity pricing guide pegs the average monthly recurring cost of 100 Mbps MPLS connection at $1,277, where as SD-WAN at similar speeds only costs $300 per month on average.   

Is MPLS dead?

Many network professionals look at MPLS and SD-WAN as an either-or proposition. There’s strong momentum behind SD-WANs, and it’s coming at MPLS’s expense. MPLS usage dropped 24% from 2019 to 2020; in that same time period, the number of enterprises using some form of SD-WAN spiked from 18% to 43%, and interest was further driven by the need to connect datacenters to home workers during the COVID-19 pandemic.

So is SD-WAN inevitably going to kill MPLS? Network World’s Zeuz Kerravala says the two technologies can coexist, with MPLS’s role changing. Small and mid-size businesses can likely sunset MPLS and shift solely to an all-broadband WAN because many of them have moved to an all-cloud IT model.

Larger enterprises, which may have sunk costs into MPLS networking, will likely take a hybrid approach, where they will keep MPLS for legacy apps that run on-net and then offload Internet traffic, like cloud, to the SD-WAN. Businesses already have hybrid compute, storage, and applications, so hybrid WAN networks won’t be anything too strange.

MPLS will continue to have a role connecting specific point-to-point locations, like large regional offices, retail facilities with point-of-sale systems, regional manufacturing facilities, and multiple data centers. MPLS is well suited for real-time applications like telepresence. And as Verizon (an MPLS provider, admittedly) points out, SD-WAN can actually help you get the most out of your MPLS connection. After all, SD-WAN’s promise is that it dynamically routes network traffic in the most efficient way possible to meet your quality of service requirements for various applications, and it can certainly use your MPLS connection to do so.

In the end, enterprise WAN architects need to make a risk/reward calculation between the reliable but expensive performance of MPLS vs. the cheaper but less reliable performance of the Internet. Improvements in other networking technologies and protocols have made internet traffic more reliable, but for some there will always be a place for the ultra-high-reliability of MPLS. Nobody wants to get caught in the cross-hairs when the CEO’s monthly videoconference with branch office employees drops off mid-sentence, after all.