WAN (Wide Area Network) is a communication network that connects computers that aim to run user programs (application level) in geographic areas of hundreds or even thousands of square kilometers (regions, countries, continents).
What is WAN?
Each terminal equipment is often called a node or host, and the communication subnet (or simply subnet) is a set of transmission lines and routers that allow hosts to communicate with each other. Different subnets can be combined with each other, resulting in wider wide area networks as on the Internet.
For the most part, hosts connect to wide area networks over a local area network or LAN, but there may also be terminals that connect directly to a router without being integrated into another type of network. When a host sends a series of data packets, each router stores them and waits for the transmission line, which it thinks is best to be free until it reaches the next router and hence the destination.
Creating Wide Area Network
The network consists of ECDs (Switching Computers) connected by high-speed leased channels. Each ECD uses a protocol that is responsible for correctly routing data and providing support to the computers and terminals of end-users connected to it. ETD (User Terminals/Computers) provides support functionality. The support function of the ETD is sometimes called PAD (Package Assembly Disassembly). ECD for ETDs is a device that isolates them from the network. The Network Control Center (CCR) is responsible for the efficiency and reliability of network operations.
Switching Lines Classification
Switched Lines: Lines that require code to communicate with the other end of the connection.
Dedicated Lines: Communication lines that provide a continuous connection between two or more points. These can be two or four wires.
Point to Point Lines: Two DTE Connections Multipoint Lines: Three or more DTEs
Digital Lines: In such lines, bits are transmitted in the form of digital signals. Each bit is represented by a voltage variation, and this is done by digital coding.
Switched by Circuits
Networks where a call must be made to communicate and when the connection is established, users have a direct connection through different parts of the network.
Switched by Message
In such a network, the switch is usually a computer responsible for accepting traffic from computers and terminals connected to it. The computer examines the DTE, which should receive the address displayed in the message header. This technology enables the recording of information to join later. The user can automatically delete, store, forward or reply to the message.
In this network type, user data is broken into smaller pieces. These fragments or packages are added to the protocol’s information and run as independent entities over the network.
These networks have the concept of multiplexing channels and ports known as virtual circuits or channels. What happens is that they participate in traffic explosions from different users, since the user actually seems to have a private resource when they share it with others.
Non-connection Oriented Networks
They are called datagrams, they go directly from the free state to the data transfer mode. These networks do not offer approvals, flow control or error recovery that apply to all networks, but these functions are available for each connection. An example of such networks is the Internet.
Public Telephone Switching Network (PSTN)
This network was originally designed for the use of audio and analog systems. Switching consists of establishing the connection after accepting to call a number corresponding to the numerical identification of the target point.
Without going into logical questions such as characterization of devices connected to a WAN or addressing used, wide area networks can offer different physical typologies depending on how the routers and subnet’s transmission lines are arranged: