Connectivity terms explained

There are a wide range of internet connectivity services available on the market, with different descriptions and features.

We explain the jargon surrounding internet connectivity to help you decide which service is best for your business.

For an explanation of the different service types, we’ve produced a guide here.

BT Openreach

A division of the British Telecommunications Group (BT) which manages BT’s access network – the Exchanges, underground tunnels, ducts, street cabinets, and fibre / copper cables used to deliver voice and data services throughout the UK.

If you purchase a voice or data service in the UK, even if you have not purchased your service from BT, it’s highly likely a BT Openreach engineer will be responsible for actually installing the wiring for your service.

Openreach trades as a separate business, and is not the same as BT Retail (the business which provides BT branded broadband and telephone services).

End user customers cannot normally deal directly with BT Openreach – only your ISP or service provider can usually do this.

Exchange (or Telephone Exchange)

The building containing the telecommunications equipment needed to connect premises in a local area to the internet or telephone services. In the UK, most exchanges are still owned by BT Openreach although for a number of years, other providers (including Easynet / Sky, Cable & Wireless, Talk Talk and Zen Internet to name a few) have bee installing their own equipment into BT exchanges to provide new and innovative voice and data services to customers.

If you want to see which Exchange your premises is served by, there is an excellent tool available at the SamKnows website.

Street Cabinet (or “cab”)

The roadside (often green or black) boxes which help connect your premises to your local exchange.

One cabinet will often serve a group of premises, or whole street in some areas, with all the copper or fibre optice cable for those premises going back to the cabinet before being “backhauled” to the exchange. If you’re situated very close to an exchange, your premises may be served directly from the exchange, and not via a cabinet, which can affect the types of service you can receive.

For services like FTTC, and FTTP on Demand, equipment which would previously have been installed at the exchange is now installed in the cabinet. This shortens the distance between the equipment and your premises, allowing higher speed services to be delivered.

Whether your cabinet has been upgraded with that equipment dictates whether you can get these services, and even if your exchange has been upgraded, your cabinet may not have been.

If you want to see which cabinet your premises is served by, there is an excellent tool available at the SamKnows website.

Distribution Point (DP)

A wallmounted plastic box often found in offices, industrial units or residential flat blocks which delivers a number of BT copper lines into a building or group of buildings. Often installed when the building is constructed, or when the first customer orders a telephone or data service, this reduces the amount of cabling, underground or overhead work needed by BT Openreach in future.

The DP does not contain any user-serviceable parts and should not be opened or relocated by anyone other than BT Openreach or other authorised personnel.

DPs are all numbered with a unique number, which is sometimes printed or written on the case.

Master Socket (or NTE5)

The white BT telephone socket provided for standard telephone lines in the UK. However, the master socket can also be used to deliver any service which is delivered over copper cables, including ADSL, FTTC, or EFM, and in many cases does not actually have a voice service or dial tone on it. It is referred to within BT Openreach as an “NTE5” unit.

For Voice, EFM and ADSL services, the master socket is the point where BT Openreach’s responsibility ends. Modern master sockets have a “test socket” behind the faceplate. The Openreach engineer will test the service at the test socket, and if it works, it’s your service provider’s (or your) responsibility thereafter.

VDSL Modem

For some FTTC services, BT Openreach provide a VDSL modem device – a white box branded “BT Openreach”. For FTTC services, BT Openreach’s responsibility is to provide the service to this modem. However, there is now a “wires only” service available, where BT Openreach do not provide a VDSL modem (or in cases where they provide it, they don’t support it), and the customer or service provider must provide a different type of router that includes this.

“Wires only” has the (limited) benefit of reducing the number of devices on your premises, but has drawbacks including that BT Openreach no longer guarantee the service quality right into the customer’s premises.

This may mean more faults, and BT Openreach may charge for an engineer visit to resolve any issues. The service provider will normally be forced to pass those charges on to the customer.

Last Mile

The cabling and technology which delivers a connectivity service from your local Exchange or aggregation point to your premises, including:

  • Fibre optic cables direct from the exchange to your premises (services include FTTP & Fibre Ethernet)
  • Fibre optice cables to your nearest street cabinet (services include FTTC)
  • Copper cables from the street cabinet to your premises (services include Cable & ADSL)
  • Fibre optic cables from the street cabinet to your premises (services include FTTC, FTTP)
  • Wireless equipment and the wireless link for Wireless Ethernet services.


The term given to sharing a network link or part of a network’s capacity between more than one subscriber or customer. Contention works on the principle that (especially in domestic or small business / home office settings), all subscribers will not be fully utilising all their connection’s capacity all of the time.

Contention is used by Service Providers to allow them to offer lower cost services by over subscribing capacity on parts of their network to lower the cost of delivering a service with the same headline speed figure. Many ADSL and FTTC services in the UK are subject to contention.

If the service provider has predicted correctly, when some users are using their connections heavily, others will be using very little. During busy periods on the network, some or all of the customers will see a reduction in speed.

For business services, we recommend paying attention to the terms and conditions, and ordering an uncontended service, so you can always guarantee the bandwidth you pay for is the bandwidth you actually receive.

NGA (Next Generation Access)

The term given to high performance, high bandwidth connectivity, which:

  • uses fibre optic technology in some part of the “last-mile” delivery process (eg: FTTC, FTTP, Fibre Ethernet).
  • includes Wireless ethernet, as this relies at least in part on some fibre optic element.
  • provides actual bandwidth of 20Mb/s or more – this excludes ADSL and most services delivered over copper cables including most EFM services.
  • may be contended, but still provide an actual speed of 20Mb/s or more.

Business Grade Connection

The term given to any high performance internet connection which:

  • May be delivered over copper, fibre optic or wireless
  • Is uncontended
  • Is supported by a service level guarantee for uptime, quality or speed of service

This term has special meaning when it’s used in conjunction with an internet connectivity service which is part or fully funded by a government or EU grant.

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