24 Differences Between Leased Line and ADSL Connections

Typically, both ADSL and leased lines are used to connect a site to the Internet. However, there are very significant differences between ADSL and leased line connections that go beyond just the obvious.

Leased lines have dedicated backhaul bandwidth, so you don't have to share it, unlike ADSL users.

ADSL vs Leased Lines - The Main Differences


ADSL broadband is far, far cheaper than a leased line.

Downstream Speed

ADSL tends to be far slower than a typical leased line. In May 2020, UK telecoms regulator OFCOM published research from SamKnows showing that in November 2019 the average UK download speed of an ADSL1 connection was 2.0Mbps and the average speed of an ADSL2+ connection was 10.3Mbps. Leased line speeds are typically 100Mbps, i.e. about 10 times faster, on average.

Upstream Speed

ADSL tends to be ridiculously slow upstream in comparison to a leased line. For example, in November 2019, [speed] panel data published by OFCOM from SamKnows showed that the average UK upload speed of an ADSL2 connection was 0.8Mbps. That's about 125 times slower than a 100Mbps leased line, and 1250 times slower than a 1 Gbps leased line.

Bandwidth Contention

ADSL is contended. In contrast, leased lines are uncontended, i.e. they don't force subscribers to share backhaul bandwidth with other subscribers.

Typical Subscriber

ADSL tends to be used by residential users. Leased lines tend to be used by businesses.

Promptness of Fault Resolution

Physical faults on leased lines tend to be fixed within hours. With physical ADSL faults, you could be looking at days before an engineer arrives to investigate.


Leased lines come with a Service Level Agreement. ADSL may not, particularly if you buy a consumer service. Generally, ADSL SLAs don't give offer any fix time or latency guarantees, whereas some leased line SLAs routinely offer the former and sometimes offer the latter.

Traffic Shaping and Metering

Leased line connections are unmetered. ADSL connections may or may not be unmetered. Leased lines are not usually subject to traffic shaping, whereas ADSL connections often are, for example, traffic to file-sharing sites might be deliberately slowed down to make room for other customers traffic.

Technical Support

ADSL connections come with technical support but it tends to require long waits to get through to someone, and support often isn't provided 24/7. Leased lines, on the other hand, often involve short waits and 24/7 support. Much ADSL tech support is solely reactive, i.e. you have to spot that there's a problem and inform the ISP before they'll start troubleshooting. With leased lines, it's common for the connections to be monitored so that downtime beyond a pre-set limit results in a support incident being opened proactively, even if the customer hasn't notified the ISP about the fault.

IP Addresses

ADSL connections tend to have a single dynamic IP addresses. Leased lines tend to offer static IP address ranges, i.e. an IP address that doesn't keep changing and multiple IP addresses, not just one.

Backup Connectivity Options

When buying an ADSL connection, it's rare that your ISP will give you the option of buying a backup connection. When you order a leased line, it's routine to be given the option of a backup connection. For low-bandwidth leased lines, that might be an FTTC or Ethernet-over-FTTC connection or an EFM connection. For higher-bandwidth leased lines, that backup connection might be another leased line, connected at least in part via a different path, or via a different underlying network.

Fibre v Phone Lines

ADSL runs over standard analogue phone cables. Leased lines, as a general rule, tend to run over fibre-optic circuits instead. Around 2025, the UK's traditional phone network will be switched off. In preparation for that, it's possible to order ADSL without a phone line. However, the service still runs over phone lines, even if they're not set up to allow you to make calls. Eventually, when 75% of the customers in an area have switched to fibre-to-the-premise connections, the old phone service will be shut off. Prior to that, you won't be able to order new phone lines, and hence you won't be able to order ADSL, except on existing phone lines.

Typical Uses

ADSL is overwhelmingly used by home users so is used for streaming TV, music and radio, general Internet surfing and gaming. Leased lines tend to be used for general Internet surfing, phone calls (using IP telephony), data backup, data replication, video conferencing and uploading large files.


ADSL is usually provided on a best-efforts basis, where you get the maximum stable connection speed the line will support. So upgrades are only possible by ditching ADSL for something else (such as FTTC, FTTP, EoFTTC, EFM, cable broadband or a leased line). The only exception is that it's possible to pay for multiple ADSL connections and aggregate their bandwidth, bonding the lines together. However, FTTC is usually a cheaper alternative to doing that. Leased lines, on the other hand, are usually upgradable if your maximum current connection speed is less than the speed the underlying line can support. For example, if you have a 200Mbps leased line, provisioned over a 1 Gbps bearer circuit, you can upgrade to 5 times as much bandwidth, without the underlying connection needing to be replaced.

Connection Quality

Leased lines tend to be more stable than ADSL connections, as the latter are adversely impacted by electrical interference. Leased lines also tend to have lower latency, jitter and packet loss than ADSL.

Connection Speed Variability by Location

ADSL speeds vary a lot depending on how close you are to your local telephone exchange. The most common leased line speeds are available regardless of where you are, i.e. they offer a fixed-, with the only variable being the price of the connection.

Price Trends

Leased lines keep falling, at least in the medium term. Here in the UK, ADSL prices are unlikely to fall much further, as the telecoms industry knows ADSL is in its twilight years. The large-scale availability of the faster alternative FTTC has eliminated most of the demand for ADSL. In addition, the UK Government has set a target of everyone being able to order gigabit-capable broadband by the end of 2025, with implicit support for a forced switchover of telecoms to VoIP (voice over IP) and the replacement of ADSL and FTTC with FTTP.


ADSL connections tend to be cheap, and they have cheap routers. Leased lines are ordered by businesses, so they tend to have higher-spec routers, capable of supporting higher speeds.

Network Topology

ADSL connections tend to be used to create stand-alone connections to the Internet. Leased lines are often used in combination with other leased lines to create wide area networks linking together many different corporate sites, without the traffic having to pass over the Internet or be subject to internet congestion.

Role in Mobile Networks

Leased lines aren't just used by normal business. They're also used by mobile networks to move traffic to and from many cell phone masts. ADSL is not used for that purpose, as it lacks capacity.

Heads-up on Planned Work

Leased line providers tend to give customers advanced warning of planned engineering work that's likely to impact their service. ADSL providers, as a general rule, don't tend to forewarn their customers about such work. Though some business ADSL providers may offer their customers such warnings.

Main Suppliers

BT, TalkTalk, Sky and Vodafone are the big beasts when it comes to ADSL in the UK - with many smaller providers using BT Wholesale or TalkTalk Business circuits to power their own services. When it comes to leased lines, there are a lot more suppliers to choose from, with the underlying physical circuits likely to be provided by BT Openreach, Virgin Media Business, TalkTalk Business, CityFibre, KCOM or Colt. Going to one of these smaller managed service providers is often cheaper than buying direct from the underlying carrier that's circuit is being used for the bit of the journey closest to your office.

Pricing Consistency

ADSL tends to be priced very simply, either on a national basis or on the basis on which OFCOM market your address lies within. Leased line pricing is more complicated. To get a price, you would need to talk to a leased line provider or use the tool at the top of this page.

How Sold

ADSL tends to be sold via e-commerce sites, with individuals setting up a direct debit or entering their credit or debit card details. Leased lines tend to be sold via salesmen, with commercial negotiations taking place. ADSL tends to be sold directly by the firm that owns the equipment in the local telephone exchange - the DSLAM or MSAM

Sidenote - ADSL is on the way out - According to Telecommunications market data published by UK telecoms regulator OFCOM, the number of ADSL connections in the UK has fallen from a high of 16.4 million in 2011 to 9.6m in 2018 (the most recent year for which data had been published by May 2020). Meanwhile, the number of cable broadband connections rose from 4.3m to 5.3m, and the number of 'other' broadband connections, including FTTC and FTTP, rose from 1.2m to 11.8m.

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