SD-WAN vs MPLS: Which Is Right for Your Business?
MPLS has been the enterprise networking standard for decades, but SD-WAN is now the default recommendation for most organisations. Here's how to decide — and when MPLS still makes sense.
The Network Decision Every Business Faces
If your business operates across multiple sites — offices, warehouses, retail locations, data centres — you need a Wide Area Network (WAN) to connect them. For the past 20 years, that meant MPLS. Today, SD-WAN has emerged as a compelling alternative that's cheaper, more flexible, and often performs just as well.
But the "just rip out MPLS and go SD-WAN" advice you'll get from many vendors is overly simplistic. The right answer depends on your applications, locations, reliability requirements, and budget.
MPLS: The Established Workhorse
Multi-Protocol Label Switching (MPLS) is a private network technology provided by carriers like BT, Virgin Media Business, and Colt. Traffic flows over dedicated infrastructure, never touching the public internet.
Advantages:
- Guaranteed performance — carrier SLAs typically guarantee latency, jitter, and packet loss
- Built-in QoS — traffic prioritisation is native to the technology
- Reliability — private infrastructure with 99.9%+ uptime guarantees
- Security — traffic is inherently isolated from the public internet
Disadvantages:
- Cost — significantly more expensive than internet circuits (typically 3–5x per Mbps)
- Lead times — provisioning new circuits takes weeks or months
- Rigidity — adding sites, changing bandwidth, or shifting traffic patterns requires carrier involvement
- Cloud-hostile — traffic from branch offices to cloud services (Microsoft 365, AWS, etc.) gets hairpinned through the data centre, adding latency
SD-WAN: The Modern Alternative
Software-Defined WAN (SD-WAN) uses software to manage connectivity across multiple transport types — broadband, 4G/5G, MPLS, dedicated internet. It creates an intelligent overlay that routes traffic based on application requirements.
Advantages:
- Cost savings — uses cheaper internet circuits instead of (or alongside) MPLS, typically saving 40–60%
- Cloud-optimised — direct internet breakout at branch offices for SaaS applications
- Agility — spin up new sites in days, not months; change policies in minutes
- Visibility — centralised dashboard showing application performance across all sites
- Resilience — automatic failover between multiple connections (broadband, 4G, MPLS)
Disadvantages:
- Internet dependency — performance depends on underlying internet quality
- Complexity — more moving parts to manage (though vendors are simplifying this)
- Security responsibility — you need to add firewall/SASE capabilities (many SD-WAN platforms now include this)
- Vendor lock-in risk — proprietary platforms can make switching costly
Head-to-Head Comparison
| Factor | MPLS | SD-WAN |
|---|---|---|
| Cost per Mbps | High (£15–£50/Mbps/month) | Low (£1–£5/Mbps/month) |
| Bandwidth flexibility | Fixed, slow to change | Dynamic, change in minutes |
| New site deployment | 4–12 weeks | 1–5 days |
| Cloud performance | Poor (backhauled) | Excellent (direct breakout) |
| Reliability SLA | 99.9%+ guaranteed | Depends on underlay circuits |
| Quality of Service | Native, carrier-managed | Application-aware, self-managed |
| Security | Inherent (private network) | Requires SASE/firewall overlay |
| Management | Carrier-managed | Self or co-managed |
| Best for | Real-time apps, regulated industries | Cloud-first, multi-site, cost-conscious |
When MPLS Still Makes Sense
Don't believe anyone who says MPLS is dead. For some use cases, it's still the right choice:
- Real-time trading platforms — where microseconds of latency matter
- Healthcare and emergency services — where guaranteed uptime is life-critical
- Large-scale voice/video — where consistent quality is non-negotiable
- Regulatory requirements — where data must never traverse the public internet
Many organisations end up with a hybrid approach: MPLS for critical sites and applications, SD-WAN for everything else. This gives you the best of both worlds while optimising cost.
How to Decide: 5 Questions to Ask
- What are your critical applications? If they're mostly cloud-based (Microsoft 365, Salesforce, AWS), SD-WAN is almost certainly better.
- How many sites, and how dynamic? If you're opening/closing sites regularly, SD-WAN's agility is a major advantage.
- What's your internet quality like? SD-WAN needs decent broadband. In areas with poor connectivity, MPLS may be necessary.
- What are your security requirements? If you need SASE (Secure Access Service Edge), modern SD-WAN platforms include it natively.
- What's your budget? If you're paying £20k+/month for MPLS, you could likely save 40–60% with SD-WAN while improving cloud performance.
How CBS Can Help
At CBS, we're vendor-agnostic — we don't sell SD-WAN or MPLS circuits. We advise on what's right for your business, evaluate vendors independently, and manage the transition.
Our telecoms consultants have designed and deployed networks for organisations from 10 to 10,000+ users. We handle vendor selection, commercial negotiation, migration planning, and post-deployment optimisation — so you get the right network at the right price without the vendor bias.