Glossary of Terms

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Term Definition
Quality of Service

QoS is the ability to provide different priorities to different applications, users, or data flows, or to guarantee a certain level of performance to a data flow. QoS involves prioritisation of Network traffic. QoS can be targeted at a Network interface, toward a given server or router’s performance, or in terms of specific applications. A Network monitoring system must typically be deployed as part of QoS, to ensure that Networks are performing at the desired level.

Public Switched Telephone Network

Public Switched Telephone Network (PSTN) is the standard telephone service provided over basic analogue phone lines.


The public switched telephone network is the name given to the wider telephone network used to make calls locally and globally that is independent from the internet. If you have a home telephone then it is likely that you make and receive calls via the PSTN that your phone connects to via a port in the wall. Some businesses still use old fashioned PSTN lines where each phone has a set phone number and line, though this is considered redundant technology and will be phased out by 2025.

Private Cloud

Private cloud is a term used to describe the common cloud computing model whereby a service provider makes resources like software or data storage available over the Internet.

Point of Presence

A Point of Presence (PoP) is the point at which a telecoms carrier establishes a physical presence in a geographic area, and at which the local exchange carriers (LECs) terminate access services. The PoP can consist of high-speed telecommunications equipment and technologies that enable users to connect to the Internet via their ISP. The PoP can include call aggregators, modem banks, routers, and high-speed Asynchronous Transfer Mode (ATM) switches.


A Private Branch Exchange is a physical device, normally located within the client’s premise. A PBX manages the internal call switching within an office and allows users, whose VOIP phones are connected to it, to share a limited number of public telephone lines.
A PBX is connected internally to the office telephones either directly or via a switch or router and externally to the internet via a dedicated ADSL line or the primary EOF connection. Once connected to the internet SIP trunks enable the PBX to connect to the public telephone network.
For example, a small office with 10 staff all have VOIP desk phones that are connected, using Ethernet cables, to a switch, the switch is then connected to the PBX and is responsible for sending data to and from the PBX to the correct telephone. In this scenario the 10 staff all share 7 external phone lines, meaning that no more than 7 of the team can call an external number at the same time and it’s the PBX’s job to dynamically allocate external phone lines and connect internal calls over the local network.

Packet Switching

A form of data transmission in which data is broken into small packets that are transmitted independently and reassembled at the destination. This is in contrast with circuit-switching, traditionally used for voice telephony, in which the transmission occurs over a dedicated circuit.


PaaS (Platform-as-as-Service) is a category of Cloud Computing services that provides a platform allowing customers to develop, run, and manage applications without the complexity of building and maintaining the infrastructure.

Network to Network Interface

Network to Network Interface (NNI) is both a physical and logical point of demarcation defining how two Networks interconnect and exchange information. The NNI serves the technical boundary where protocol issues are resolved and as the point of division between the responsibilities of individual service providers.

Multiprotocol Label Switching

Multiprotocol Label Switching (MPLS) is a Networking technology which is used to route data packets over an IP Network. MPLS ensures that all packets in a particular flow take the same route over a backbone. When used for a corporate VPN / WAN, the technology eliminates the need to buy and manage multiple firewalls as traffic is routed within a secure virtual private Network.

Megabit per Second

Megabit per second (Mbps) is a measure of the speed of data transfer in Networking.

Managed Hosting

A dedicated hosting service, dedicated server, or managed hosting service is a type of Internet hosting in which the client leases an entire server not shared with anyone else.

Local Area Network

A LAN is a data Network connecting devices including computers, printers and servers in one location for fast and secure internal communication.

Load Balanced

Balancing a workload amongst multiple computer devices, for example, virtual servers or servers.

Leased Line

A Leased Line is a service contract between a provider and a customer, whereby the provider agrees to deliver a symmetric telecommunications line connecting two or more locations, in exchange for a monthly rent (hence the term lease). It is sometimes known as a ‘Private Circuit’ or ‘Data Line’ in the UK. Unlike traditional lines it does not have a telephone number, each side of the line being permanently connected to the other. Leased lines can be used for telephone, data or Internet services.