With the nationwide rollout of full-fibre broadband by Openreach and altnets across the UK, Finance Directors and IT Managers face a familiar procurement question: "If we can order a 1Gbps Business FTTP broadband connection for under £100 a month, why should we invest £350 or more per month in a dedicated leased line?"
On a marketing spec sheet, both services claim "1,000 Mbps." In practice, they represent fundamentally different transmission tiers. Conflating the two creates serious risks for mid-market and enterprise organisations reliant on deterministic cloud access, VoIP SIP trunks, and real-time data replication.
1. Contention Ratios: True 1:1 vs. Shared PON Optics
The fundamental technical distinction lies in how physical light travels from the carrier exchange to your premises:
- Business FTTP (Broadband): Operates on Passive Optical Network (GPON or XGS-PON) architecture. A single optical fibre originating at the exchange is split prismatically across an unpowered optical splitter to serve between 16, 32, or 64 different premises. You share that transmission pipe with surrounding businesses and local subscribers.
- Dedicated Internet Access (DIA / Leased Line): A discrete, point-to-point optical fibre runs uninterrupted from the carrier's node straight into your comms cabinet. There are no splitters, no shared packets, and a strict 1:1 contention ratio. Your bandwidth remains static 24/7/365.
2. The Symmetric Bottleneck: Upload vs. Download Speeds
Most enterprise IT workloads are not consumption-heavy; they are transmission-heavy. While staff stream video calls, internal systems continuously sync off-site backups, publish CAD/BIM assets, push database updates to AWS, and transmit real-time telemetry.
Business FTTP is inherently asymmetric. A "1000 Mbps" FTTP package typically provisions only 115 Mbps of upload capacity. Under high concurrent office utilization, this asymmetric bottleneck causes severe packet queuing, latency spikes, and degraded VoIP performance.
Conversely, our enterprise leased lines deliver true symmetric throughput—a 1Gbps circuit provides 1,000 Mbps down and 1,000 Mbps up simultaneously, with zero queuing delay.
3. Technical Comparison Matrix: DIA vs. Business FTTP
| Performance Attribute | Dedicated Internet Access (DIA) | Business FTTP Broadband |
|---|---|---|
| Contention Ratio | 1:1 Strictly Uncontended (Dedicated) | Shared (Typically 20:1 to 50:1 PON Split) |
| Throughput Profile | Strictly Symmetric (e.g. 1Gbps Up / 1Gbps Down) | Asymmetric (e.g. 1000Mbps Down / 115Mbps Up) |
| Fault Resolution SLA | 4-Hour On-Site Fix Target (24/7/365) | Next Business Day to 48-Hour Best Efforts |
| Transit & Core Peering | Direct Optical B-End to London Exchanges (Telehouse/LINX) | Aggregated via Public Broadband BRAS Nodes |
| Latency & Jitter Guarantees | Deterministic, Sub-2ms Latency SLA | Variable; Dependent on Local Neighborhood Usage |
| Typical Monthly Cost | £250 – £650/month (Enterprise Grade) | £45 – £120/month (Mass Market) |
4. SLAs: 4-Hour On-Site Fix vs. Best-Effort Dispatch
When an optical circuit fails, the commercial cost of downtime quickly dwarfs any monthly telecom savings. The core value of an enterprise leased line lies in its contractual Service Level Agreement (SLA).
- Business FTTP SLA: Broadband repairs are handled on a "best efforts" basis by wholesale carriers. Typical repair targets range from next business day to 48 working hours. If a fibre line is damaged on Friday afternoon, your team may remain offline until Tuesday.
- DIA Leased Line SLA: Backed by a strict, financially guaranteed 4-hour target resolution SLA, supported 24/7/365. Specialized splicing teams are dispatched immediately to restore connectivity.
5. Routing, Peering, and Core Exchanges
Raw line speed means little if traffic encounters congested public transit hops. Business FTTP traffic is routed through shared Broadband Remote Access Servers (BRAS), where consumer and business packets compete for transit egress during peak evening and daytime periods.
Enterprise DIA circuits terminate directly on dedicated carrier optical hardware with direct B-end routing into key Internet Exchanges, such as Telehouse North in London. For businesses in the capital, our London leased lines deliver sub-1.2ms round-trip times straight into major European cloud nodes.
6. The Architectural Verdict: The Hybrid Network
In modern enterprise architecture, the debate does not have to be an either/or choice. High-availability organisations deploy both technologies together:
- Deploy a high-capacity DIA Leased Line as your primary, uncontended underlay circuit carrying mission-critical cloud, ERP, and voice data.
- Deploy a cost-effective Business FTTP circuit as an active secondary path from a different physical carrier.
- Orchestrate both connections using managed SD-WAN. Non-critical bulk web browsing routes over FTTP, while critical corporate traffic is prioritised over the DIA link. If either circuit experiences an outage, sub-second failover prevents any drop in active sessions. For deeper architecture details, review our guide on SD-WAN vs Leased Lines.