Wide Area Network, also called WAN (English acronym on AbbreviationFinder.org) are communication networks that connect equipment to run user programs (at the application level) in geographic areas hundreds or even thousands of square kilometers (regions, countries, continents…).

Each of the terminal equipment is usually called a node or host, and the communication subnet (or simply subnet) is the set of transmission lines and routers (or routers) that allow hosts to communicate with each other. Different subnets can be combined with each other resulting in larger wide area networks, such as the Internet.

Most commonly, hosts connect to wide area networks through a local area network or LAN, but there may also be terminals that connect directly to a router, without the need to be integrated into any other type of network. When a host sends a sequence of data packets, each router stores them and waits for the transmission line that it considers optimal to be free to forward them to the next router, and so on until the destination is reached.

Constitution of a wide area network

The network consists of ECDs (Switching Computers) interconnected by high speed leased channels (eg 56 kbit / s lines). Each ECD uses a protocol responsible for correctly routing data and providing support to end-user computers and terminals connected to them. The support function ETD (User Terminals / Computers). The support function of the ETD is sometimes called PAD (Packet Assembly Disasembly – package assembler / disassembler). For ETDs, the ECD 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 dialing a code to establish communication with the other end of the connection.

Dedicated Lines: Communication lines that maintain a permanent connection between two or more points. These can be two or four wires.

Point-to-Point Lines: Link two DTEs Multipoint Lines: Link three or more DTEs

Digital Lines: In this type of line, the bits are transmitted in the form of digital signals. Each bit is represented by a voltage variation and this is done by digital coding.

Types of WAN networks

Switched by Circuits: Networks in which, to establish communication, a call must be made and when the connection is established, users have a direct link through the different segments of the network.

Switched by Message: In this type of network the switch is usually a computer that is responsible for accepting traffic from the computers and terminals connected to it. The computer examines the address that appears in the header of the message to the DTE that should receive it. This technology allows the information to be recorded in order to attend to it later. The user can delete, store, redirect or reply to the message automatically.

Packet Switched: In this type of network, user data is broken down into smaller chunks. These fragments or packets are inserted into the information of the protocol and travel the network as independent entities.

Connection Oriented Networks: In these networks there is the concept of multiplexing of channels and ports known as a virtual circuit or channel, because the user appears to have a dedicated resource, when in reality he shares it with others because what happens is that they attend to bursts of traffic from different users.

No network connection – oriented: Call datagrams, pass directly from the free state to the data transfer mode. These networks do not offer acknowledgments, flow control or error recovery applicable to the entire network, although these functions do exist for each particular link. An example of this type of network is the Internet.

Public Telephone Switching Network (PSTN): This network was originally designed for the use of voice and analog systems. Switching consists of establishing the connection after agreeing to have dialed a number that corresponds to the numerical identification of the destination point.

Wide Area Network Topologies

Without going into logical issues such as the characterization of the devices connected to a WAN or the addressing used, wide area networks can present different physical typologies, depending on the way in which the routers and transmission lines of the subnet are arranged:

• Point-to-point network : Each node connects with the others through dedicated circuits, which are always available for communication between two points.
• Ring network : The nodes are connected to each other by lines that form a ring, so that a packet can reach its destination by at least two paths (one in each direction that the ring travels).
• Network in Intersection of rings : Tworing topologies are joined by one or more nodes.
• Tree network : There is a hierarchy of nodes in the form of a tree, so that to go from one branch to another contiguous one it is necessary for the packets to pass through a higher-level node.
• Complete Network : All nodes are directly connected to the rest.
• Star network : a central node serves as a link to communicate all the other nodes of the subnet with each other.
• Irregular Network : In most cases, the WAN topology is irregular, without a strict pattern that dominates, sometimes the result of the union of subnets with different original topologies.