- Telecommunications network
A telecommunications network is a collection of terminals, links and nodes which connect together to enable telecommunication between users of the terminals. Networks may use circuit switching or message switching. Each terminal in the network must have a unique address so messages or connections can be routed to the correct recipients. The collection of addresses in the network is called the address space.
The links connect the nodes together and are themselves built upon an underlying transmission network which physically pushes the message across the link.
Examples of telecommunications networks are:
- computer networks
- the Internet
- the telephone network
- the global Telex network
- the aeronautical ACARS network
Messages and protocols
Messages are generated by a sending terminal, then pass through the network of links and nodes until they arrive at the destination terminal. It is the job of the intermediate nodes to handle the messages and route them down the correct link toward their final destination.
The messages consist of control (or signaling) and bearer parts which can be sent together or separately. The bearer part is the actual content that the user wishes to transmit (e.g. some encoded speech, or an email) whereas the control part instructs the nodes where and possibly how the message should be routed through the network. A large number of protocols have been developed over the years to specify how each different type of telecommunication network should handle the control and bearer messages to achieve this efficiently.
All telecommunication networks are made up of five basic components that are present in each network environment regardless of type or use. These basic components include terminals, telecommunications processors, telecommunications channels, computers, and telecommunications control software.
- Terminals are the starting and stopping points in any telecommunication network environment. Any input or output device that is used to transmit or receive data can be classified as a terminal component. 
- Telecommunications processors support data transmission and reception between terminals and computers by providing a variety of control and support functions. (i.e. convert data from digital to analog and back) 
- Telecommunications channels are the way by which data is transmitted and received. Telecommunication channels are created through a variety of media of which the most popular include copper wires and coaxial cables (structured cabling). Fiber-optic cables are increasingly used to bring faster and more robust connections to businesses and homes. 
- In a telecommunication environment computers are connected through media to perform their communication assignments. 
- Telecommunications control software is present on all networked computers and is responsible for controlling network activities and functionality. 
Early networks were built without computers, but late in the 20th century their switching centers were computerized or the networks replaced with computer networks.
In general, every telecommunications network conceptually consists of three parts, or planes (so called because they can be thought of as being, and often are, separate overlay networks):
- The control plane carries control information (also known as signalling).
- The data plane or user plane or bearer plane carries the network's users traffic.
- The management plane carries the operations and administration traffic required for network management.
Example: the TCP/IP data network
The data network is used extensively throughout the world to connect individuals and organizations. Data networks can be connected together to allow users seamless access to resources that are hosted outside of the particular provider they are connected to. The Internet is the best example of many data networks from different organizations all operating under a single address space.
Terminals attached to TCP/IP networks are addressed using IP addresses. There are different types of IP address, but the most common is IP Version 4. Each unique address consists of 4 integers between 0 and 255, usually separated by dots when written down, e.g. 126.96.36.199.
TCP/IP are the fundamental protocols that provide the control and routing of messages across the data network. There are many different network structures that TCP/IP can be used across to efficiently route messages, for example:
- wide area networks (WAN)
- metropolitan area networks (MAN)
- local area networks (LAN)
- campus area networks (CAN)
- virtual private networks (VPN)
There are three features that differentiate MANs from LANs or WANs:
- The area of the network size is between LANs and WANs. The MAN will have a physical area between 5 and 50 km in diameter.
- MANs do not generally belong to a single organization. The equipment that interconnects the network, the links, and the MAN itself are often owned by an association or a network provider that provides or leases the service to others.
- A MAN is a means for sharing resources at high speeds within the network. It often provides connections to WAN networks for access to resources outside the scope of the MAN.
- Active networking
- Access network
- Core network
- Network analyzer
- Coverage (telecommunication)
- Double-ended synchronization
- Federation (information technology)
- Network node
- Nanoscale network
- Network model
- Optical fiber
- Submarine communications cable
- Optical mesh network
- Telecommunications Industry Association
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