Glossary of Terms

Glossaries

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Term	Definition
ISDN	Integrated Services Digital Network (ISDN) line uses a standard copper telephone line to transmit voice data and connect to the public telephone network. It was first introduced in 1986 and along with the PSTN will be phased out by BT in 2025, though still remains surprisingly common. ISDN was considered cutting edge because it transmitted call data digitally instead of using analogue signals, which greatly enhanced call quality. An ISDN line enters a premise and connects directly into a box that separates the data into channels, 1 channel = 1 call, the box then connects to a PBX using an Ethernet cable, which then connects to the ISDN telephones. The maximum number of channels that an ISDN box can support is 30, if the client wants more channels/phone lines then they can add another box or purchase another ISDN line. ISDN lines can take a long time to provision, only work with specific hand sets and the phone numbers are geographically linked to the line itself, so cannot be easily moved or used by another device.
IPv4 and IPv6	Internet Protocol Version 4 (IPv4), is the most commonly used numbering system used to create IP addresses. IPv4 employs 32-bits of recombined digits and has a maximum of 4.3 billion possible addresses. IPv6 is a newer system for the creation of IP addresses. It uses 128 bits instead of 32 bits for its addresses, creating trillions of new IPv6 addresses, enough to support the demand for IP addresses for some expected time to come.
Internet Protocol Address	Internet Protocol Address (IP Address) is a unique address in number format which every computer device has. The IP address enables computer devices to communicate with each other over an IP Network or the Internet. In order for data to be sent from one computer to another over the Internet, a data packet must be transferred across the Network containing the IP addresses of both devices. The unique IP address allows data to reach the right destination.
Integrated Services Digital	Network Integrated Services Digital Network (ISDN) a Network technology that provides digital transfer of simultaneous voice and data traffic and works over ordinary telephone lines.
Infrastructure as a Service (IaaS)	IaaS is the acronym for Infrastructure as a Service. IaaS describes the delivery of IT infrastructure such as servers and storage on demand over the Internet, through an outsourced IaaS service provider.

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