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What is LLU broadband or local loop unbundling?

By Phil Wilkinson-Jones | Friday, July 30th 2021

In the process of researching your next broadband deal, you may have come across the term LLU or 'Local Loop Unbundling'. And you may have wondered what on earth it means. Fear not, we're here to help.

Local Loop Unbundling isn't actually as technical as it sounds – but it does play a big role in how the UK's broadband industry works. And while it's not something the average consumer has to worry much about, many of us have felt the benefit of LLU's existence and it does affect both the way our broadband services are delivered and how our networks are maintained.

What is Local Loop Unbundling?

Local Loop Unbundling (LLU) is the process that allows companies other than BT to provide broadband services using BT's network infrastructure. There's quite a bit to unpack there, so let us break it down for you.

BT is the incumbent broadband provider for pretty much the whole of the UK (the exception is Hull, which has KCOM as its incumbent provider for reasons we won't go into now). This means BT owns and is responsible for maintaining the UK's national broadband network. It does this through a subsidiary, Openreach.

Local Loop is the name given to the cables, the physical part of the broadband network that runs between your home and your local telephone exchange. You may have also heard this referred to as the 'last mile' of a broadband connection. Local Loop Unbundling allows other Internet Service Providers (ISPs) to install their software at the telephone exchange and provide a broadband service over the existing network cables.

Since Ofcom told BT to open up its telephone exchanges to other ISPs in 2001, hundreds of thousands of local loops have been unbundled from BT. This has allowed providers such as Sky, TalkTalk, Plusnet and others to offer broadband deals and compete directly with BT without having the enormous expense of building their own networks.

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The benefits of LLU

There are two major benefits that come from compelling a country's incumbent broadband provider to share its network. The first is competition. The UK has a very competitive broadband market and the vast majority of those companies driving down prices and setting new standards for customer service have only been able to do so because they have had access to BT's national broadband network.

The second primary benefit of LLU is that, because BT has large and influential wholesale customers in the form of Sky, TalkTalk etc, it has no choice but to invest heavily in its network, developing new technologies to reach the most remote parts of the UK and maintaining the national network over which about 80% of us get our broadband.

In recent years, BT has invested millions of pounds in rolling out fibre broadband across the UK. Thanks to LLU, customers of many broadband providers have been able to upgrade to fibre packages and benefit from faster speeds and more reliable connections.

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Are there different types of LLU?

There are a number of types of unbundled telephone lines. Let's take a look at three of the most common. Many broadband providers use a combination of these.

  • Fully unbundled lines or Metallic Path Facility (MPF) – This is when a provider takes over both the broadband and voice services on a telephone line. Major ISPs like Sky and TalkTalk tend to use this method of unbundling
  • Shared unbundles lines or Shared Metallic Facility (SMPF) – Providers can also choose to take over only the broadband part of a telephone line, leaving either BT or another provider to provide voice services on the same line. This is why you can have broadband services from one provider and phone services from another
  • Sub Loop Unbundling (SLU) – This allows a provider to take over part of a local loop, from a customer's property to a specified access point in the local network. Openreach retains responsibility for maintaining SLU circuits

Which providers use LLU?

There are a lot of broadband providers in the UK and the vast majority of them use LLU to provide their services over BT's lines. The two with the biggest market share are Sky and TalkTalk, but this is a long list that also includes Plusnet, EE, Vodafone, John Lewis Broadband, Shell Energy Broadband, Direct Save, Post Office Broadband, SSE and NOW Broadband as well as a number of smaller providers and business broadband specialists.

What's the alternative to LLU?

As LLU is the process by which BT shares its infrastructure with other providers there really is only one alternative if you want to provide broadband services – build your own network. This is prohibitively expensive, which is why there aren't many providers that have done it. But there are a few.

Virgin Media

Virgin Media owns and operates the UK's second biggest broadband network. Unlike BT, Virgin uses coaxial cables to deliver its broadband and, because the network is privately owned, Virgin does not have to share it with other providers. Virgin Media’s services are available to about 53% of UK households, and that number is growing as the company continue to expand.


Hyperoptic is a small provider that specialises in delivering full fibre (FTTP) services to apartment buildings and new-build housing estates, typically in cities. Hyperoptic only builds infrastructure to developments where it knows there is already a demand for its services.


We mentioned earlier that BT is the incumbent broadband provider for most of the UK. The exception is Hull, which has KCOM instead. KCOM has only recently started offering LLU so there's no Sky, TalkTalk, BT or any of the others. KCOM's dominance in Hull is such that not even Virgin Media provides a fixed line alternative.

Frequently asked questions

How easy is it to switch between providers on the BT network?

These are actually the easiest kind of broadband switches. BT, Sky, TalkTalk etc all use the same Openreach network so your broadband will come through the same wires. And because the switching process is gaining provider-led, you don't have to tell your old provider that you're leaving – your new provider will take care of that for you.

Does Virgin Media use BT's network?

No, Virgin Media has its own network of coaxial cables that reaches about half of UK households. It is the only one of the UK's 'big four' broadband providers (the others are BT, Sky and TalkTalk) not to use the BT Openreach network.

Is Openreach the same as BT?

Openreach is a wholly-owned subsidiary of BT and effectively operates as an independent company. Openreach is the part of the BT Group that takes responsibility for maintaining, repairing and upgrading the national network owned by BT.

What is a telephone exchange?

A telephone exchange is a building that houses thousands of broadband connections. There are nearly 5,600 telephone exchanges in the UK.

Does Local Loop Unbundling happen with fibre broadband?

LLU traditionally refers to ADSL broadband, which is delivered over old copper telephone wires but there are also regulations in place for providers to access fibre connections. All new technologies introduced by BT into its telephone exchanges area also made available to third party providers running their services on the network.

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