Most multi-site networks built before 2018 still run on MPLS, and most networks built since then run on SD-WAN. The conversation is no longer whether SD-WAN is real. It is whether your specific environment is better off migrating, holding, or running both in parallel during a transition.
What MPLS does well
MPLS is a single-carrier private network with predictable performance, strong support, and decades of operational maturity. If your traffic mostly flows site-to-data-center, you have a small number of large sites, and the carrier is hitting their SLA, MPLS is not broken.
Where SD-WAN wins
Modern application traffic does not look like it did when MPLS was designed. Office 365, Salesforce, Zoom, and dozens of other SaaS platforms perform best with a direct internet path, not backhauled through a central data center. SD-WAN gives you that path, plus sub-second failover, application-aware routing, and the freedom to mix carriers and transports.
The cost story matters too. Trading one expensive MPLS circuit per site for a DIA primary and an affordable broadband or 5G secondary typically lowers the monthly bill while increasing total capacity by an order of magnitude.
How to choose between them
Use this rough checklist:
- Three or more sites with mixed carriers available: SD-WAN.
- Heavy SaaS, hosted voice, or video collaboration: SD-WAN.
- Two sites with site-to-site traffic and an MPLS contract that still has runway: hold.
- Compliance environment that audits to MPLS specifically: confirm whether the standard requires MPLS or just private routing. SD-WAN with strong segmentation usually satisfies the latter.
Migrating without breaking production
The riskiest migrations are the ones that try to flip everything at once. The safer path is to overlay SD-WAN on top of the existing MPLS, prove voice and SaaS performance over the new internet underlays, then peel off MPLS circuits site by site as carriers and applications stabilize. Most enterprises complete the move in six to twelve months.