SD-WAN vs Traditional MPLS: Which Is Right for Multi-Site Businesses?

For many years, organisations with several offices, shops or depots connected them using MPLS, a private network service sold by telecoms carriers. Software-defined wide area networking, or SD-WAN, has since become a mainstream alternative, promising more flexibility and better access to cloud services by using ordinary internet connections intelligently. Vendors on both sides make strong claims, so it is worth stepping back to understand how each technology works, where each genuinely excels and how to decide what suits your business.

How MPLS works

Multiprotocol Label Switching is a technique carriers use to route traffic across their private backbone. As a customer, you buy a circuit at each site that connects into the carrier's network, and the carrier provides a private, routed network between your sites. Traffic does not travel across the public internet, and carriers typically offer service level agreements covering availability, latency and packet loss, along with classes of service to prioritise voice or critical applications.

Internet access in a traditional MPLS design is often centralised: branch traffic travels to a head office or data centre and passes through a central firewall before reaching the internet. This made sense when most applications lived in the company's own data centre.

How SD-WAN works

SD-WAN places an edge appliance, physical or virtual, at each site. These devices build encrypted tunnels between sites over whatever transport is available: broadband, fibre internet, 4G or 5G, and even existing MPLS circuits. A central controller defines policy, such as sending video calls over the link with the lowest latency or failing over to mobile data if the primary line degrades. The edge devices continuously measure each link's quality and steer traffic accordingly.

Because policy is managed centrally, adding a new site can be as simple as shipping a preconfigured appliance and plugging it in. SD-WAN also makes it straightforward to send cloud and SaaS traffic directly to the internet from each branch, rather than back-hauling it through head office.

Side-by-side comparison

Where MPLS still makes sense

MPLS is sometimes described as obsolete, but that overstates the case. It remains a sound choice in certain situations:

• Strict, predictable performance requirements, for example real-time control systems or trading applications where contractual latency guarantees matter.
• Applications hosted mainly in a private data centre, where traffic naturally flows between sites rather than to the cloud.
• Regulatory or policy requirements that favour private transport over internet-based links.
• Organisations that want a single carrier to own the network end to end and lack internal networking capacity.

The main drawbacks are cost relative to bandwidth, long lead times for new circuits and the awkwardness of reaching cloud services efficiently.

Where SD-WAN shines

• Cloud-first organisations using SaaS collaboration, CRM and cloud-hosted applications benefit from local breakout and application-aware routing.
• Many smaller sites such as retail branches, where business broadband plus a mobile backup is a sensible combination.
• Rapid expansion, including temporary sites and pop-up locations.
• Improved resilience through two diverse internet links at each site rather than a single circuit.
• Better visibility into which applications use bandwidth and how links are performing.

The caveats are real. Internet links do not carry the same end-to-end guarantees as a private network, so link quality and diversity matter. Security also changes: with each branch breaking out to the internet directly, every site needs appropriate firewalling and web filtering, either on the SD-WAN appliance or through a cloud security service. Many organisations pair SD-WAN with a secure access service edge (SASE) approach for that reason.

The hybrid option

The choice is not always binary. A hybrid design keeps MPLS at a few critical locations, such as data centres or head office, while adding internet links everywhere and placing SD-WAN over the top of both. Critical traffic can be steered over MPLS while general and cloud traffic uses the internet. Over time, organisations often reduce MPLS bandwidth or retire circuits as confidence grows. This approach lowers migration risk considerably.

Planning a migration

If SD-WAN looks like the right direction, a structured approach avoids surprises:

1. Inventory your applications and where they are hosted, noting which are sensitive to latency or loss.
2. Review existing contracts, including MPLS term end dates and any early termination charges.
3. Assess internet options at each site, aiming for diverse providers or technologies where the site is critical.
4. Decide the security model: on-appliance firewalling, a cloud security service or a combination.
5. Choose a management model, whether in-house, co-managed with a partner or fully managed.
6. Run a pilot at two or three representative sites, including at least one challenging location.
7. Define success measures, such as call quality, application response times and failover behaviour, and test them deliberately.
8. Roll out in waves, keeping MPLS in place until each site is proven.

Final verdict

For most multi-site businesses whose applications have moved to the cloud, SD-WAN offers better flexibility, resilience and visibility, often with a more favourable cost structure, provided security is redesigned to match direct internet access. MPLS still earns its place where contractual performance guarantees, private transport or a predominantly data-centre-hosted application estate are priorities. Where you are unsure, a hybrid design lets you gain SD-WAN's benefits while retaining MPLS for the traffic that truly needs it, and to make the final decision on evidence from your own sites.