Asymmetric Digital Subscriber Line (ADSL)

ADSL is a technology for transmitting digital information at a high bandwidth on existing phone lines to homes and businesses. Unlike dialup phone service, ADSL provides continuously-available, "always on" connection. ADSL is asymmetric in that it uses most of the channel to transmit downstream to the user and only a small part to receive information from the user. ADSL simultaneously accommodates analogue (voice) information on the same line. ADSL is generally offered at downstream data rates up to 24 Mbps.

Customer Premises Equipment (CPE)

Customer Premises Equipment refers to hardware located at the premises of a customer such as broadband internet routers, VoIP base stations, telephone handsets or other customised hardware.


Ethernet is the most widely installed local area network (LAN) technology. Ethernet is a link layer protocol in the TCP/IP stack, describing how networked devices can format data for transmission to other network devices on the same network segment, and how to put that data out on the network connection. It touches both Layer 1 (the physical layer) and Layer 2 (the data link layer) on the OSI network protocol model. Ethernet defines two units of transmission, packet and frame. The frame includes not just the "payload" of data being transmitted but also addressing information identifying the physical "Media Access Control" (MAC) addresses of both sender and receiver, VLAN tagging and quality of service information, and error-correction information to detect problems in transmission. Each frame is wrapped in a packet, which affixes several bytes of information used in establishing the connection and marking where the frame starts.

Ethernet First Mile (EFM)

This is a copper wires based service that delivers connectivity via an uncontended part of the network. Available in either dual or quad configurations. Speeds are dependent on distance from the exchange like broadband, but are uncontended and are supported by a comprehensive service level agreement, guaranteeing both speed and connectivity.


A firewall is a combination of hardware and software that secures access to and from the LAN. There are three main types of firewall architecture - Stateful Inspection, Proxy based and Packet Filtering. The former provides the highest level of access control. Firewalls can also be used to secure internal network resources from internal network users too.

Fibre to the Cabinet (FTTC)

FTTC stands for Fibre to the Cabinet. It’s one of two ways in which next-gen fibre optic broadband is being delivered to homes and businesses in the UK. FTTC in a nutshell is much easier and cheaper to deliver en masse than its counterpart, FTTP or Fibre to the Premises as it utilised existing copper wires from the premises to the cabinet.

Fibre to the Premises (FTTP)

FTTP stands for Fibre to the Premises. It’s one of two ways in which next-gen fibre optic broadband is being delivered to homes and businesses in the UK. FTTP is more expensive than its counterpart, FTTC as it utilised fibre cabling from the premises to the cabinet.

Gemini Generic Ethernet Access (GEA)

This service takes the FTTC service from being positioned within the DSL 'best effort' network into the managed network, with other more expensive products like EFM and Leased Lines, which are supported by a comprehensive service level agreement, guaranteeing both speed and connectivity.

Internet Protocol (IP) Address

Also sometimes called a dotted quad. It is a unique number consisting of 4 parts separated by dots e.g. Every machine that is on the internet has a unique IP number - if a machine does not have an IP number, it is not really on the internet. Most machines also have one or more Domain Names that are easier for people to remember.

Integrated Services Digital Network (ISDN)

Stands for "Integrated Services Digital Network." ISDN is a telecommunications technology that enables the transmission of digital data over standard phone lines. It can be used for voice calls as well as data transfers.

Leased Line

This is a fibre based service that delivers the best connectivity via a managed part of the network. Leased Lines offer a flexible option with uncontended speeds from 10Mbps-1Gbps and are supported by a comprehensive service level agreement, guaranteeing both speed and connectivity.

Public Switched Telephone Network (PSTN)

This is the world's collection of interconnected voice oriented public telephone networks, both commercial and government owned.


A router is a piece of hardware that essentially connects two or more networks together. Routers forward packets of data between networks based on network layer information, or in other words, it looks at the destination addresses of the packets passing through it and decides which route to send them on.

Software as a Service (SaaS)

SaaS is typically accessed by users using a thin client via a web browser. SaaS has become a common delivery model for many business applications, including office & messaging software, payroll processing software, DBMS software, management software, CAD software, development software

Session Initiation Protocol (SIP)

SIP is a signalling protocol used for establishing sessions in an IP network. A session could be a simple two-way telephone call or it could be a collaborative multi-media conference session. The ability to establish these sessions means that a host of innovative services become possible, such as voice enriched e-commerce, web page click-to-dial, Instant Messaging with buddy lists, and IP Centrex services.

Virtual Private Network (VPN)

This usually refers to a network in which some of the parts are connected using the public internet, but the data sent across the internet is encrypted, so the entire network is "virtually" private.

Wide Area Network (WAN)

This is a geographically dispersed network.

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Gemini Communications Ltd is a limited company registered in England and Wales. Registered office: 11 Petteril Side, Harraby Green Business Park, Harraby, Carlisle, Cumbria CA1 2SQ. Registered number: 05245581

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