BT Managed WAN vs BT SD-WAN for UK Business Networks

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Architecture

Routing model

Typical buyer

Traffic follows fixed routing paths determined during network design. Changes to routing or prioritisation typically require a change request through BT, with associated lead time.

Application prioritisation is generally configured at deployment and remains relatively static. QoS is applied at the network level, not dynamically per application session.

Traffic is steered dynamically based on application identity, real-time path performance and policy rules. The SD-WAN controller continuously selects the optimal path for each application.

Policy changes can be deployed centrally and applied across all sites. In a co-managed model, the customer’s IT team can modify application priorities directly.

• Typically built on uniform circuit types
• Leased lines (BTnet) or Ethernet access throughout
• Adding a site requires provisioning a new private circuit
• Circuit lead times can be significant for new deployments

• Mixed underlay — broadband, leased lines and cellular in one overlay
• Different circuit types at different sites based on need
• Broadband and cellular sites deploy faster than leased line sites
• Easier to flex the estate as business needs change

Resilience is typically achieved through diverse circuit routing or redundant private circuits. Failover relies on network-layer convergence protocols.

Resilience uses dynamic path selection across all available circuits. If a primary path degrades or fails, traffic automatically reroutes through backup connections without manual intervention.

Security is typically centralised — traffic is backhauled to a data centre or hub where a firewall and security stack inspects traffic. Branch-level security is generally separate from the WAN service and may require additional hardware or services.

Security can be integrated directly into the SD-WAN platform at each branch. BT offers SD-WAN with built-in NGFW and, at advanced tiers, full SASE (ZTNA, CASB, SWG). This removes the need to backhaul traffic for security inspection and enables direct secure internet breakout at each site.

• ✓ Your estate is stable with predictable traffic patterns
• ✓ You need guaranteed private network performance across all sites
• ✓ Applications are predominantly data centre-hosted, not cloud-based
• ✓ You have minimal requirement for direct cloud or SaaS access from branches
• ✓ Your organisation prefers a fully provider-managed, hands-off model
• ✓ Network policy changes are infrequent

• ✓ You have multiple sites with mixed or changing requirements
• ✓ You use cloud and SaaS applications that benefit from local internet breakout
• ✓ You want integrated branch security (NGFW, SASE, ZTNA)
• ✓ You need to mix broadband, leased lines and cellular in one overlay
• ✓ You want real-time visibility and faster policy change capability
• ✓ You are replacing or supplementing an existing MPLS network

If your estate is stable and standardised with predictable traffic, minimal cloud dependency and infrequent policy changes → Managed WAN may still be the simpler, lower-change option.

If your business is moving to cloud and SaaS and needs direct internet breakout, application-aware routing and integrated branch security → SD-WAN is likely the stronger architecture.

If resilience requirements vary heavily by site and you need flexible backup options (broadband, cellular, leased line) tailored per location → SD-WAN’s mixed underlay model provides more design flexibility.

If you are replacing a rigid WAN model and want to reduce dependency on leased lines at every site → SD-WAN enables a phased transition from MPLS to a mixed-transport overlay.

Stable 8-site UK office network

Estate8 offices, all UK, uniform requirements Traffic patternPredominantly data centre-hosted applications Cloud dependencyLow — limited SaaS usage Change frequencyInfrequent — stable network policy

30-site mixed retail and branch estate

Estate30 sites — mix of retail, regional offices and small branches Traffic patternCloud-first — Microsoft 365, cloud POS, SaaS CRM Cloud dependencyHigh — majority of applications are cloud-hosted Change frequencyRegular — new sites added, seasonal locations

50-site warehouse and office combination

Estate20 offices (leased line), 30 warehouses (broadband or cellular) Traffic patternMixed — data centre apps at offices, cloud logistics at warehouses Cloud dependencyMedium — growing cloud adoption Security needIntegrated branch security required at all sites

Growing multi-site organisation replacing MPLS

Estate60+ sites, expanding, with an existing MPLS network approaching renewal Traffic patternShifting from data centre to cloud — Microsoft 365, Azure workloads MigrationPhased — migrating sites as MPLS contracts expire ObjectiveReduce WAN rigidity, improve cloud performance, consolidate security

MPLS contracts approaching renewal — an MPLS renewal is the natural trigger to evaluate SD-WAN as an alternative or replacement

Cloud and SaaS adoption accelerating — backhauling cloud traffic to a central hub creates latency; SD-WAN enables local breakout

Estate is growing or diversifying — new site types (retail, remote, temporary) need faster rollout than leased line provisioning allows

Branch security is fragmented — managing separate firewalls per site creates overhead; SD-WAN integrates security into the overlay

Change requests take too long — if policy changes require provider lead time and your business needs faster network agility

Visibility is insufficient — if you lack real-time application-level insight into network performance across your estate

☐ You know your total site count

☐ You have a view on circuit type per site

☐ You have a preferred SD-WAN vendor or are open

☐ You know whether you need SASE or standard SD-WAN

☐ You have a management model preference

☐ You are comparing SD-WAN to your current WAN

Can I migrate from Managed WAN to SD-WAN gradually?

Yes. BT supports phased migration where SD-WAN runs alongside existing MPLS or VPLS infrastructure. Sites can be moved individually as legacy contracts expire, reducing risk and allowing validation before full rollout.

Is SD-WAN always cheaper than Managed WAN?

Not necessarily. SD-WAN often produces a more commercially efficient structure when combined with broadband or FTTP underlay. However, a like-for-like replacement using leased lines with full SASE licensing may produce a similar or broader commercial scope. The benefit is typically in flexibility, performance and operational capability rather than a guaranteed reduction.

What happens to my existing MPLS circuits during migration?

During a phased migration, MPLS and SD-WAN run in parallel. Traffic can be gradually shifted from MPLS to SD-WAN paths. Legacy circuits are decommissioned as they become redundant or as contracts expire.

Does BT SD-WAN replace the need for leased lines entirely?

Not always. SD-WAN can use broadband, cellular or leased lines. Business-critical sites that need SLA-backed performance may still use leased lines as the primary underlay within the SD-WAN overlay. The difference is that not every site needs one.

Can I use SD-WAN with a co-managed model?

Yes. BT offers both fully managed and co-managed SD-WAN. In a co-managed model, your IT team handles day-to-day policy changes while BT manages the platform, security updates and infrastructure.

How do I get a BT SD-WAN quote through Network Union?

Use the BT SD-WAN pricing calculator to define your requirements. Your summary is reviewed by a BT Sales Specialist team through The Network Union’s partner channel. All services are contracted directly with BT.