Finding the perfect data connection to meet the demands of your business


SUPPORT - Glossary

Asymmetric Digital Subscriber Line Broadband service delivered over normal PSTN telephone lines. Down channel <2Mb. Up channel <256K. Down channel speed very dependant on distance from BT exchange.
Second generation rate adaptive ADSL service.   Down channel <8Mb.  Up channel <832K.  Down channel speed very dependant on distance from BT exchange.
Third generation rate adaptive ADSL service. Down channel <24Mb. Up channel <1.25Mb. Down channel speed very dependant on distance from BT exchange.
Annex A
The standard for ADSL over PSTN.  Adopted in the UK and most parts of the world.
Annex B
The standard for ADSL over ISDN.  Primarily used in Germany.
Annex M
Variant of ADSL2+ where up channel speed is doubled to 2.5Mb by reducing the down channel speed to around 22Mb.
The very heart of a network.
General term used to describe the connectivity from the DSLAM to the ISP and from the ISP to the rest of the Internet.
Backhaul Extension Service Proprietary name for Ethernet over Fibre.
Inverse multiplexing 2-4 low speed circuits to give appearance of one high speed circuit.
An umbrella term covering all flavours of DSL and Cable Broadband.
Cable Broadband
Broadband delivered over the Virgin Media (formally ntl: Telewest) Cable television & telephony network. Business broadband down channel <20Mb. Up channel <1Mb.
Copper Pair
Literally the two strands of copper wire that carry the PSTN telephone traffic from your premises to the BT street cabinet. These can run via a network of telegraph poles or underground. One copper pair can carry one PSTN telephone conversation and one DSL broadband service simultaneously using frequency separation.

The process of over subscribing a circuit. If the backhaul circuit has 10 units of capacity and the ISP sells 80 units of user capacity there is 8:1 contention. A good business ISP will have 1:1 contention throughout. A low cost consumer ISP may have 20:1 or more contention meaning that the more active users, the slower the service.

Customer Premises Equipment A generic term describing any hardware provided by the service provider such as a broadband router.
Digital Subscriber Line A generic term describing both asymmetric (ADSL) and symmetric (SDSL) services.
Digital Subscriber Line Access Multiplexer This network device connects multiple customer DSL services running over copper pairs to a high-speed Internet backbone line using multiplexing techniques. Historically the DSLAM has been located in the BT exchange but with the new FTTC service the DSLAM is located in the BT street cabinet.

Excess Construction Charge The really bad news following a fibre Ethernet site survey is to receive a quotation for ECC. It means there is some facet or the order which will cost more than the original quote and the choice is to pay up or cancel with nothing to pay. BT Openreach is the main source of these charges so it is likely alternative service providers will have to charge them also.
Ethernet Extension Service Proprietary name for Ethernet over Fibre.
Ethernet First Mile A service bonding multiple G.SHDSL services running over baseband copper pairs to give an aggregated symmetric speed <40Mb. Each circuit typically delivers a little over 2Mb so this can take a lot of copper pairs.
The same technology used on your Office Network is now available on the more advance Internet connections.
Brand name for an Easynet EFM service.
Or as the Americans say, "Fiber." Fibre optic cable capable of carrying large amounts of digital data over significant distances with minimal degradation (unlike copper).
Fibre to the Cabinet The DSLAM is installed in the green BT street cabinet rather than the exchange thus minimising the copper pair line length and associated degradation. The backhaul to the exchange is over fibre. The DSL service uses a high speed variant of ADSL (VDSL2) that delivers down channel <40Mb and up channel <10Mb. BT is providing a wholesale service to other ISP’s.
Fibre to the Home See FTTP.
Fibre to the Premises A fibre circuit all the way from the customer premises to the BT exchange delivers up to 110Mb down-channel with up to 30Mb up-channel.
Fair Use Policy The small print that describes acceptable usage of the service and sets the usage limits. Much criticised when the headline service is sold as unlimited and the FUP introduces a monthly usage cap with sanctions.
Technically 1024 Megabits (109 bits) but often rounded to 1000 Megabits. Gigabit fibre Ethernet is gaining ground as the costs come down to under £50K p.a.
Internet Protocol A ubiquitous packet based transport protocol used throughout the Internet and most private networks
Last Mile
A generic term for the circuit used between the edge of the service provider network and your premises.
LAN Extension Service Proprietary name for Ethernet over Fibre.
Local Loop Unbundling Where a service provider other than BT installs their own DSLAM and backhaul network at a BT exchange. Pricing is controlled by OFCOM, the UK comms regulator.
Multi Service Access Node The next generation of DSLAM supporting more advanced services such as EFM
Multi Protocol Label Switching provides a truly private network over shared network infrastructure
aka MUX. In IP networking terms a Multiplexer is used at either end of a bonded circuit to split one fat data pipe into multiple smaller pipes and then reassemble at the other end.
The arm of BT responsible for installing physical circuits
Office of Communications is the government-approved regulatory authority for the broadcasting and telecommunications industries in the UK
Private Wide Area Network A generic term for MPLS & VPLS networks
A dedicated circuit between two sites. Once popular but now superseded by VPN or MPLS
Quality of Service A method of tagging packets within a private network (including MPLS) to give priority to critical services such as VoIP
Synchronous Digital Subscriber Line The original service with the same speed in both directions
Very-high-speed Digital Subscriber Line 2 The technology used to carry FTTC from the street cabinet to your premises over copper.
Virtual Private LAN Service A low level interface to an MPLS network for the VERY experienced.
Gaining the right to install a new (usually fibre) circuit over land belonging to a third party. They can deny access or levy a fee and it always introduces delays.