In short
A contended connection shares network capacity with other customers, so speeds can fall when many people are online at once. An uncontended connection reserves its capacity for one customer, so the speed you pay for is available all day. Broadband is contended; BT describes its BTnet leased line as 100% uncontended and dedicated.
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What contention means
Contention is the sharing of network capacity between customers. A provider's network has links of a certain size. With broadband, many customers' connections feed into those shared links, and the provider sizes them on the reasonable assumption that not everyone will use their full speed at the same moment.
Most of the time that works. But when lots of users are busy at once, they compete for the shared capacity and everyone's speed drops. That is why a broadband connection can feel quick early in the morning and sluggish in the middle of the working day or on a busy evening.
A contention ratio describes how many customers share a given amount of capacity. A connection described as 1:1, or uncontended, is not shared at all.
An illustration
This is a simplified, illustrative example, not a description of any particular network.
Imagine 20 businesses on a street, each sold a 100Mbps connection, all feeding into a shared link of 500Mbps. If only three are busy, each can reach its full speed. If all 20 are busy at once, the 500Mbps is shared and each gets about 25Mbps. Nothing is broken; the network is doing what it was designed to do.
Now imagine one of those businesses has its own access line with 100Mbps reserved for it. However busy the others are, that business keeps its 100Mbps. That is the difference between contended and uncontended.
Contended vs uncontended at a glance
| Contended (broadband) | Uncontended (BTnet leased line) | |
|---|---|---|
| Capacity | Shared with other customers | Reserved for your site |
| Speed at busy times | Can fall when the shared network is busy | The port speed is available all day |
| Upload | Often lower than download | Symmetrical: the same both ways |
| Fair usage | Varies by package | No fair usage policy, according to BT |
| Service levels | Usually best efforts | BT's SLA for availability, on-time delivery and latency |
| Cost | Lower, because capacity is shared | Higher, because capacity is dedicated |
Contention is not a flaw; it is why broadband is affordable. The question is whether your business can live with speeds that vary through the day. See leased line vs broadband for the full comparison.
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Tell us what matters most to you and we will explain the trade-offs.
Why BTnet is uncontended
BT's help pages describe BTnet as a 100% uncontended, dedicated service, so you do not share access or bandwidth with other users. BT's terms list uncontended and symmetrical bandwidth as standard components of every BTnet service. BT's help pages also say there is no fair usage policy on BTnet, so you can use as much data as you like.
In practice that means:
- Your own access line: a dedicated fibre circuit from your building into BT's network
- Reserved bandwidth: the port speed you order, from 2Mbps to 10Gbps, is yours in both directions
- Steady performance: the line does not slow because other customers are busy
Read how does a leased line work for the path your traffic takes.
Signs contention is affecting you
Contention shows up as a pattern rather than a fault. Common signs:
- Speed tests look fine early in the morning or late at night, but drop during the working day or at busy evening times
- Video calls and cloud calling are clear at quiet times and break up at busy times, with nothing changing in your office
- Large uploads and backups take very different lengths of time from one day to the next
- Your own network has been checked on a cable, at the router, and the slowdown is still there
If the slowdown follows your own team's activity instead, for example every time a backup runs, the line may simply be too small for what you ask of it. That is a sizing question rather than contention: see the bandwidth sizing guide.
Weighing it up?
We can look at your sites and requirements and give you a straight answer.
What uncontended does not cover
Uncontended removes sharing on the access line and your reserved bandwidth. It does not make every part of the internet faster:
- Your own network. Wi-Fi, office switches, cabling and firewalls can limit speed before traffic reaches the line.
- Overheads. BT's terms say real throughput is typically 5-10% below the port speed because of network and IP overheads.
- The far end. A slow website or a busy cloud service will still be slow.
- Your own peak use. If your team needs more than the port speed you bought, the line will be full. That is a sizing question, solved with a higher speed or Bandwidth Flex.
Our leased line speed test guide shows how to test properly, and the bandwidth sizing guide helps you choose the right port speed.
Uncontended is also different from resilient. An uncontended line still has one path into your building, so a cable cut or equipment fault can still take you offline. BT's resilience options add a second access line for sites that need one.
Is uncontended worth it for your business?
An uncontended line is worth paying for when slowdowns cost money: calls dropping in a contact centre, staff waiting on cloud apps, a school's lessons stalling, a hotel's guests complaining about Wi-Fi, or cameras failing to upload footage. It also makes performance predictable, which helps when planning new systems.
If you are not sure whether contention is your problem, we can help you look at when slowdowns happen and what is using the connection. Then, if BTnet is the answer, we can help you choose the speed and plan and, as an Authorised Supplier for BT, prepare a quote. Contact us with your postcode.
Why buy BTnet from Forever Communications
Forever Communications is part of Forever Group and an Authorised Supplier for BT. We supply BTnet, BT's dedicated leased line internet service, to businesses, schools, charities and public sector organisations, and we help with each step from first enquiry to go-live.
- The right BTnet option for you: we help you choose a speed, bearer, router and resilience option that fits how your sites actually work, from BTnet plans to BTnet speeds
- A clear quote: BTnet is priced per site, so we check availability at your address and set out what is included; see leased line cost
- Installation managed with you: we explain the survey, any wayleave or construction steps and the installation process, and keep you updated on progress
- Connected services in one conversation: phones with BT Cloud Voice, Wi-Fi, firewalls and backup lines, so the whole set-up is planned together
- Help after go-live: we can help with faults, changes and upgrades, with the support arrangements confirmed in your quote
BTnet is a business service. Service levels, lead times and features are BT's and are confirmed at order.
Frequently asked questions
What does uncontended broadband mean?
It means the connection's capacity is reserved for one customer rather than shared, so the speed does not fall when other users are busy. In business, an uncontended connection is usually a leased line.
Is a leased line uncontended?
BTnet is. BT describes it as a 100% uncontended, dedicated service, and its terms list uncontended, symmetrical bandwidth as standard.
What is a contention ratio?
It describes how many customers share a given amount of network capacity. An uncontended connection is 1:1: the capacity is not shared.
Is business broadband contended?
Yes. Broadband, including full fibre broadband, shares network capacity between customers, which is why it costs less than a leased line.
Does BTnet have a fair usage policy?
No. BT's help pages say there is no fair usage policy on BTnet, so you can use as much data as you like.
Still deciding?
Ask us and we will reply by email with a straight answer.