SD-WAN vs MPLS UK: Which Is Right for Your Business?

If your business has multiple sites across the UK — offices, warehouses, retail branches, or remote workers — then how you connect those sites has a direct impact on application performance, security, and your monthly IT bill. For many years, MPLS (Multiprotocol Label Switching) was the gold standard for enterprise WAN connectivity. Today, SD-WAN (Software-Defined Wide Area Network) has emerged as a compelling alternative that is transforming how UK businesses connect their locations.

This guide explains exactly what MPLS and SD-WAN are, how they compare across the factors that matter most to UK businesses, and how to decide which approach — or which combination — is right for your organisation.

What Is MPLS?

MPLS is a private, dedicated network technology delivered by telecommunications carriers. Rather than routing packets across the public internet, MPLS traffic travels across a private carrier backbone. Each packet is labelled on entry to the MPLS network, and routers forward it based on that label rather than re-examining the destination IP address at each hop — which is where the speed and predictability advantage comes from.

For UK businesses, MPLS circuits are typically provided by BT, Virgin Media Business, Vodafone, or a specialist carrier. A dedicated circuit is provisioned between each site, guaranteeing bandwidth, low latency, and quality of service (QoS) for traffic classes such as voice and video. The carrier manages the underlying network; you pay a monthly circuit charge per site.

MPLS has served multi-site businesses well for two decades. Its reliability and predictable performance made it the go-to choice for connecting branch offices to a central data centre running line-of-business applications. Its limitations are becoming increasingly visible in a world dominated by cloud-first applications, remote working, and SaaS platforms.

What Is SD-WAN?

SD-WAN decouples the network control plane from the physical hardware and applies software intelligence to manage how traffic is routed across multiple underlying connections. A typical SD-WAN deployment aggregates two or more connections at each site — for example, a primary broadband or leased line connection alongside a 4G/5G failover link — and uses policy-based routing to send each traffic type across the most appropriate path in real time.

Traffic prioritisation is dynamic. If the primary link becomes congested or experiences packet loss, SD-WAN automatically shifts latency-sensitive traffic such as VoIP and Microsoft Teams video to the secondary connection without user disruption. Security overlay features — including encrypted tunnels between sites, next-generation firewall integration, and cloud security gateways — are typically part of modern SD-WAN platforms.

Leading SD-WAN vendors in the UK market include Fortinet (FortiGate SD-WAN), Cisco Meraki, VMware SD-WAN (formerly VeloCloud), and Cato Networks. Vertex9 is a Fortinet partner and primarily deploys FortiGate SD-WAN, which integrates natively with Fortinet's Security Fabric for unified network and security management.

SD-WAN vs MPLS: The Key Differences

The Cloud Application Problem with MPLS

The most significant limitation of MPLS for modern UK businesses is how it handles cloud traffic. Traditional MPLS network design routes all internet-bound traffic — including SaaS applications like Microsoft 365, Salesforce, Zoom, and cloud storage — back to a central hub site (typically head office or a co-location data centre) before it reaches the internet. This is called traffic backhauling.

When your workforce relies on Microsoft Teams for video calls, Exchange Online for email, and SharePoint for file collaboration, every packet from a branch office travels to headquarters first, then out to the internet, then back. This additional hop adds latency, reduces application responsiveness, and often degrades Teams call quality noticeably — particularly if the central site's internet connection is not sized appropriately for aggregated cloud traffic.

SD-WAN solves this with local internet breakout. Each site connects directly to the internet for cloud application traffic, while sensitive data traffic — such as access to on-premises ERP systems or shared network storage — continues to traverse secure encrypted tunnels between sites. SD-WAN applies application-aware routing to make this distinction automatically, without complex manual policy configuration.

Cost: How Much Can You Save?

For most UK multi-site businesses, SD-WAN running over broadband or Ethernet First Mile circuits is significantly cheaper than MPLS. A 100 Mbps MPLS circuit from a UK carrier typically costs £400–£1,200 per month per site depending on location, provider, and committed information rate. A comparable broadband or leased line connection costs £50–£300 per month, with SD-WAN licensing adding £50–£150 per site per month.

For a business with ten UK sites, the difference is often £4,000–£9,000 per month — and that excludes the hardware refresh costs that typically accompany MPLS contract renewals. Organisations migrating from MPLS to SD-WAN commonly report WAN cost savings of 40–70% whilst simultaneously improving application performance for cloud workloads.

The cost saving is not always the primary driver. Operational agility — the ability to activate a new site in days rather than waiting twelve weeks for a new MPLS circuit to be provisioned — has strategic value that is difficult to price but easily felt when business needs change.

When MPLS Still Makes Sense

Despite SD-WAN's advantages, MPLS remains appropriate in specific circumstances. If your business runs latency-critical applications over a private WAN — some real-time manufacturing control systems, certain financial trading platforms, or legacy client-server applications with hard latency requirements — MPLS may provide performance guarantees that commodity broadband cannot match regardless of SD-WAN intelligence layered on top of it.

A hybrid approach is common: SD-WAN managing multiple links including a residual MPLS connection for latency-critical traffic classes, combined with broadband for general-purpose and cloud traffic. This approach captures most of the cost saving while preserving MPLS performance where it is genuinely needed.

MPLS also remains relevant where connectivity reliability in a specific location cannot be assured with broadband alternatives. Rural UK sites with limited broadband options may have MPLS as the only commercially available carrier-grade connectivity option.

SD-WAN and Security: What You Need to Know

One concern businesses raise when moving from MPLS is security. MPLS provides an inherently private network — traffic never traverses the public internet, which provides a degree of isolation by default. SD-WAN traffic runs over public internet connections and must therefore be actively secured.

Modern SD-WAN platforms address this through encrypted tunnels (IPsec or TLS) between all sites, ensuring that inter-site traffic is protected in transit. FortiGate SD-WAN, which Vertex9 deploys, integrates with FortiGate next-generation firewalls at each site, providing application-aware filtering, intrusion prevention, and DNS security that MPLS does not inherently provide.

For cloud traffic, SD-WAN can integrate with cloud security gateways (Secure Access Service Edge, or SASE) such as Fortinet's FortiSASE, which applies security inspection to all cloud-bound traffic regardless of where it originates. This security-forward architecture is frequently more comprehensive than the centralised security perimeter that MPLS deployments typically rely upon.

Vertex9's network support practice designs SD-WAN deployments in line with Cyber Essentials and ISO 27001 principles, ensuring that the transition from MPLS does not compromise your security posture. You can read more on our network support and SD-WAN page.

How to Choose: A Practical Decision Framework

Choose SD-WAN if:

• Your workforce relies primarily on cloud and SaaS applications (Microsoft 365, Teams, Salesforce, etc.)
• You have multiple UK sites and want to reduce WAN costs significantly
• You need to add new sites or remote workers quickly without circuit lead times
• Your MPLS contract is approaching renewal and you want to evaluate alternatives
• You want centralised visibility across all site networks in a single dashboard
• You need integrated network and security management rather than separate products

Consider retaining MPLS (or a hybrid approach) if:

• You run latency-critical legacy applications with hard performance requirements
• Specific remote sites have limited broadband availability as alternatives
• Your MPLS contract has significant early termination charges that outweigh migration savings
• Your risk tolerance for internet-dependent connectivity is very low

Frequently Asked Questions