Wide Area Network (WAN)


Wide Area Network (WAN) can be defined in two ways. This is the book definition which defines it as a network used to interconnect multiple Local Area Networks (LANs) and spans a large geographical location. The second is the practical definition which describes WAN as a network which crosses a public network or commercial carrier by utilizing one of many WAN technologies.

Components of Wide Area Network (WAN)

There are three main components of WAN, these are Router, Switch and Modem. These three are all hardware needed in starting a WAN.



This electronic device is responsible for connecting and routing messages between the Local Area Network (LAN) and the WAN. It makes decisions using IP addresses and operates at layer 3.



This is a network device responsible for selecting a circuit or path for sending a unit of data to its next destination. It uses MAC addresses to send data to the correct destination and operates at Layer 2.


Modem (Modulator/Demodulator):

It helps with communication between computers over telephone lines. It operates at layer 1 where signals are converted from digital to analogue and vice versa for transmission and receiving.


WANs operate within the Open Systems Interconnection (OSI) model using layer 1 which is the data link layer and layer 2 which it the physical layer. The data link layer defines the encapsulation of data for transmission to remote sites,


while the physical layer deals with how to provide electrical, mechanical and functional connections to the services provided by the ISP. Encapsulation of data describes the wrapping of data in a particular protocol header.


Serial interfaces support a wide range of WAN encapsulation types such as SDLC, PPP, Frame delay etc. These encapsulation types must be manually specified and must be identical on both sides to the point to point link.

Packet and Circuit Switching

These switches are both used in high-capacity networks. Packet switching is the most commonly used switch nowadays in getting data across the network. However, Circuit-switching is more reliable than packet-switching but is rarely used because it is old and expensive. Packet switching is the breaking up of messages into small packets before they are transmitted over the internet. It is different from Circuit-Switching because it (Packet Switching) allows different messages to use the same network resources within the same time period. - Asynchronous Transfer Mode (ATM) is a cell relay, packet switching network and protocol that encodes data into small fixed-sized cells. - ISDN stands for Integrated Services Digital Network and is used in carrying voice, video, data and images across a telephone network through Frame relay. - PSDN (Packet Switched Data Network) is a data communication network. PROTOCOL


It is the process used in choosing how to move packets from one network to another. A router learns its route or direction by using a routing protocol, this information is then passed from router to router along the route of the destination.

Routing Protocol

This is a protocol that specifies the system by which routers communicate and exchange information on a network. The routing protocol shares the structure of the network topology with the routers making each router have prior knowledge of its immediate neigbors.3

Routing Information Protocol (RIP)

RIP used to be one of the most commonly used protocols on internet networks. RIP is used by routers to adapt changes to the network dynamically, and communicate information about which networks the routers can reach as well as the distance between them. RIP however is known for breaking unexpectedly and rendering a network unable to function, hence earning it the nickname “Rest in Pieces”.

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These processes used in routing. They are the Distance Vector, Link State and IGRP.
Distance Vector
Also known as the bellman-ford algorithm, it requires that each router must simply inform its neighbours of its routing table. This protocol measures distances and compare routes. Any router using this protocol must send all or a portion of their routing table in a routing update message at regular intervals to each neighbour router.
Link State
Also known as the Dijkstra’s algorithm, Link State requires that each router must maintain a partial map of the network.

IGRP (Interior Gateway Routing Protocol)
It is a Cisco invented type of vector routing protocol used to exchange routing data in an autonomous system.


  • IP address is an identifier assigned to any computer connected to a network. This makes each computer on a network have its own distinct code to identify it amongst others on the same network. An example of and IP address is IP addresses are separated by four numbers known as octets which each position consisting of eight bits. This makes a total of 32 bits in every IP address.
  • The octets are split into Network and Host and they serve to create classes of the IP addresses that can be assigned within a network. These classes are Class A, B and C. The first octet in in class A address is the network portion and it determines which network the computer belongs to, while the last octets are the hosts that belong to the network.
  • Sub netting
  • A subnet address is the address used by the LAN to create multiple networks with a class A, B or C address. It identifies which portion is the network and which one is the host. Sub netting is important because it allows the gateways to route packets between LANs and then decide which LAN to send the packets once it arrives at its destination. CIRCUIT SWITCHED LEASED LINES This network establishes a dedicated

Circuit Switched Network Terminologies

- Frame Relay: It is designed for cost-efficient data transmission between LANs

- Basic Rate Interference: this is the internet connectivity used by small businesses.

- Primary Rate Interference: this standard of telecommunications is used in carrying voice and data transmissions between two locations.

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