What is Traditional WAN?

Traditional enterprise WANs are built on MPLS (Multiprotocol Label Switching) circuits — dedicated, private connections between branch offices and the corporate datacenter. Carriers guarantee bandwidth and QoS (Quality of Service), which makes MPLS highly predictable but also expensive and inflexible.

A typical enterprise paying $3,000–$8,000/month per MPLS circuit for a 10 Mbps connection at each branch will see those costs multiply linearly as locations scale. Adding bandwidth requires renegotiating carrier contracts — a process that takes months, not weeks.

What SD-WAN Actually Does

SD-WAN (Software-Defined Wide Area Network) abstracts the physical transport layer. Instead of relying on a single MPLS circuit, SD-WAN overlays intelligent routing across any combination of: broadband internet, 4G/5G LTE, MPLS, and fiber. The SD-WAN appliance at each branch monitors path performance in real-time and routes traffic dynamically based on latency, packet loss, and jitter metrics.

This is not a VPN. SD-WAN is a full network fabric with centralized policy management, application-aware routing, and integrated security functions (firewall, ZTNA, CASB) depending on the vendor.

The Cost Reality

The cost advantage of SD-WAN is real but often overstated in vendor marketing. Here is what actually happens when enterprises migrate:

  • Transport savings: Replacing $5,000/month MPLS with $300/month fiber + $200/month LTE backup = 90% savings on circuit costs per branch.
  • Licensing costs: SD-WAN platforms (Cisco Viptela, Fortinet, VMware SD-WAN) typically run $150–$500/month per branch for software licensing.
  • Hardware: SD-WAN appliances cost $500–$4,000 per branch location, plus professional services for deployment.
  • Net result: For a 20-branch enterprise on MPLS, the savings are real — typically 40–60% reduction in monthly WAN costs after 18 months (break-even on hardware).

When SD-WAN Wins

SD-WAN is the right architecture when:

  • You have 5+ branch locations with MPLS circuits consuming significant budget
  • Your traffic profile is internet-heavy (SaaS, Microsoft 365, Salesforce) rather than datacenter-centric
  • You need to onboard new locations quickly (SD-WAN deploys in days vs. months for MPLS provisioning)
  • You need integrated security at the branch (SASE model)

When MPLS Still Makes Sense

MPLS is not obsolete. Keep it when:

  • You operate in regions where reliable broadband internet is not available
  • Your applications are extremely latency-sensitive and require guaranteed QoS (real-time industrial control, financial trading)
  • You handle data under strict regulatory sovereignty requirements where internet transport is not permitted
  • You have fewer than 5 locations — the overhead of SD-WAN management does not justify the savings

Migration Risks

The three migration risks we see most often in enterprise SD-WAN projects:

  • Internet reliability at remote sites: SD-WAN depends on internet quality. In locations where broadband is unreliable, performance degrades unpredictably.
  • Security policy complexity: SD-WAN centralizes routing but distributes the security perimeter. Without proper SASE/ZTNA integration, you may create new attack surfaces.
  • Vendor lock-in shift: You are trading carrier lock-in for SD-WAN platform lock-in. Evaluate multi-vendor interoperability before committing.

Our Recommendation

For most mid-market enterprises with 5–50 locations and primarily SaaS workloads, SD-WAN migration delivers a positive ROI within 18–24 months. The architecture decision is sound. The implementation risk is in the execution — specifically in the transition period, security policy migration, and site-by-site cutover.

If you are evaluating this migration, the first step is an honest assessment of your current circuit costs, traffic patterns, and internet reliability at each site — before any vendor is engaged.