In short
A leased line bearer is the physical access circuit to your site, such as a 100Mbps, 1Gbps or 10Gbps Ethernet fibre bearer. The port speed is the bandwidth you order on it. On BTnet you can flex the port speed within the bearer's capacity, and BT sets one-off charges by bearer type, not port speed.
Get a quote for BTnet
Tell us roughly how many users or sites you have and we will reply by email with options and a quote.
Bearer vs port speed
Think of the bearer as the size of the pipe into your building, and the port speed as how far the tap is open.
- The bearer is the access circuit BT installs from its network to your site. It has a fixed capacity, for example 100Mbps, 1Gbps or 10Gbps, and that capacity is the ceiling for your speed.
- The port speed is the bandwidth you order and pay rental for. BTnet port speeds run from 2Mbps to 10Gbps in increments based on Ethernet speeds, and must fit within the bearer.
- Throughput is what applications actually achieve. BT's terms say it is typically 5-10% below the port speed because of network and IP overheads.
So a site might have a 1Gbps bearer running a 200Mbps port speed. It pays rental for 200Mbps, but has the physical capacity to go up to 1Gbps later through Bandwidth Flex, without BT digging or installing a new circuit. When people search for leased line bandwidth options, this pairing of bearer and port speed is usually what they are trying to understand.
BTnet bearer types
BT's current BTnet service schedule sets out charges for these bearer types:
| Bearer type | What it is | Typical use |
|---|---|---|
| 100Mbps Ethernet fibre bearer | A dedicated fibre Ethernet access circuit with a 100Mbps ceiling | Sites that need up to 100Mbps |
| 1Gbps Ethernet fibre bearer | A dedicated fibre Ethernet access circuit with a 1Gbps ceiling | Sites that need up to 1Gbps, or a lower speed with room to grow |
| 10Gbps Ethernet fibre bearer | A dedicated fibre Ethernet access circuit with a 10Gbps ceiling | Large sites and campuses |
| 1Gbps data centre access bearer | Access delivered into a data centre, ending at the patch panel in the co-location room | Systems hosted in a data centre |
| 10Gbps data centre access bearer | As above, with a 10Gbps ceiling | High-capacity data centre access |
BT's terms also refer to BTnet provided over Generic Ethernet Access on full fibre (FTTP). Which bearers are available at your address is confirmed when we check availability and quote.
For data centre bearers, BT's terms put the service management boundary at the patch panel in the data centre's co-location room. You order the cross-connect from the data centre operator.
Not sure which option fits? Ask us
Tell us what you need and we will recommend the right option for your organisation, with a quote.
Why charges follow the bearer
This is the part of BTnet pricing that often surprises people. BT's terms set several charges by the type and size of the bearer rather than the port speed:
| Charge | What sets it in BT's terms |
|---|---|
| Service Introduction Charge | The size of the bearer (access circuit) ordered |
| Cancellation charges if you cancel before the service goes live | The type and size of the bearer, regardless of the port speed |
| Termination charges if you end the service by notice | Listed per bearer type in BT's current schedule |
| Cancellation and introduction charges on a resilient service with two bearers | Applied per bearer, including the secondary access line |
| A material change or external move during the Minimum Term | Can include a charge equal to the standard Service Introduction Charge of the original bearer |
Two practical consequences follow. First, a low port speed on a large bearer still carries that bearer's charges, so the decision is about how much growth room is worth to you. Second, in BT's current schedule the amounts listed for the 100Mbps and 1Gbps Ethernet fibre bearers are the same, while a 10Gbps bearer is listed higher. Monthly rental is different: it moves with the port speed, which is why BT's help pages say rental changes pro rata when you flex.
We do not publish figures; your quote sets out every charge for your site. See BTnet contract terms and BT leased line cost.
Planning headroom for growth
A bearer is the part of a leased line that is slow and costly to change. A port speed is the part that is easy to change. So the sensible order of decisions is:
- Work out your peak use today, in both directions. Our bandwidth sizing guide shows how.
- Estimate the next three to five years: headcount, cloud adoption, cameras, new sites connecting in, video use.
- Choose a bearer that covers the high end of that estimate, so growth is a flex rather than a new line.
- Order the port speed you need now, and flex up later under BT's Bandwidth Flex terms.
- Check your equipment's limits. BT's terms say a flex beyond the capacity of the BT equipment at your site needs new equipment and a new Minimum Term. On wires only, your own router or firewall must handle the higher speed.
If resilience matters, decide early too: a second access line brings its own bearer and its own charges. See resilient BTnet.
Is BTnet the right fit for you?
We will check it against your systems and requirements and recommend the right option.
Bearers, moves and full fibre
The bearer also affects what happens if you move. BT's terms say internal moves are not possible on a service delivered over GEA over FTTP, and are treated as external moves instead. External moves start a new Minimum Term at the new site. See moving premises before you sign a lease or plan a refit.
For how full fibre access compares with a dedicated Ethernet fibre bearer, see leased line vs FTTP.
Getting the bearer right with us
Choosing the bearer is where advice pays for itself. When you contact us we can look at your current use, talk through growth plans and price the same port speed on different bearers side by side, so you can see the difference in one-off and monthly costs before you commit.
Ask us for a quote: contact us with your postcode and what you use the connection for.
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 is a bearer on a leased line?
It is the physical access circuit from the provider's network to your site, with a fixed capacity such as 100Mbps, 1Gbps or 10Gbps. Your port speed must fit within it.
What is the difference between bearer and bandwidth?
The bearer is the circuit's maximum capacity; the bandwidth, or port speed, is what you order and pay rental for on it. On BTnet you can flex the bandwidth within the bearer.
Why does BT charge by bearer rather than speed?
BT's terms set introduction, cancellation and termination charges by bearer type and size. The bearer is the physical circuit installed to your site, while your rental moves with the port speed you choose, as BT's flex rules show.
Can I change my bearer later?
Moving to a larger bearer means a different access circuit rather than a flex, which is why choosing headroom at the start matters. Ask us how a change would work for your site.
What bearer do I need for 500Mbps?
In BT's current BTnet schedule the Ethernet fibre bearers are 100Mbps, 1Gbps and 10Gbps, so a port speed of around 500Mbps needs at least a 1Gbps bearer. The exact speed steps available on each bearer are confirmed when we quote.
Still have a question about BTnet?
Ask us and a member of our team will reply by email.