What is a Computer Network

A Network is an interconnection between two or more computers for the purpose of sharing resources. It is nothing more than two or more computers connected to each other so that they can exchange information, such as files, Printers and disk storage.

Components of a Network.

Network interface card (NIC):

A Network card is a hardware device that uses to connect computers together in Network. The network card is also known as a network adapter. Each computer must have a Network card in order to connect to the network. Most modern computers come with built-in Network cards. If you are using a wireless network you must have a wireless Network interface card to connect to the Network.

Switches :

A switch is an active device that connects two or more network segments together at same time in a network. Switches have become an increasingly important part of our networking today because nowadays every networks use the Star topology. In star topology a switch is use as the central device. The switch acts as a filtering device by associating the MAC address of the system connected to the switch with the port on the switch. Each switch contains a certain number of ports, typically 8, 16, 24 or 48. Also Switches can be connected to each other to build larger networks. But switch is an expensive device.

Router :

Routers are packet-forwarding devices just like switch. Routers allow transmission of data between network segments. Unlike switches, it transmits data packets based on physical node addresses. Router is the device that connects two different networks together. Router is a Network layer device, so it can work with the network packets at a higher level. So how do routers work? In the case of the IP protocol, an IP address is 32 bits long. Those 32 bits contain both the network ID and the host ID of a network device. IP distinguishes between network and host bits by using a subnet mask.

Cable :

Cabling is the medium for the transmission of data between computers on a Network. In a Network, computers can be connected together using a variety of cable types, such as unshielded twisted-pair, shielded twisted-pair, coaxial, or fiber-optic cables. Each cable type has its own advantages and disadvantages

Network Architecture.

Local Area Network (LAN)

A Local Area Network is a computer network that covering a small physical area, like a home, office, or small group of buildings, such as a school, or an airport. The linking can be done by cable that carries optical fiber or copper.

Metropolitan Area Network (MAN)

The term metropolitan area network is not used often anymore. It refers to a network that exists within a single city or metropolitan area. If we had two different buildings within a city that were connected together, it would be considered a Metropolitan Area Network.

Wide Area Network (WAN)

A wide area network (WAN) spans multiple geographic locations and is typically made up of multiple LANs. We can say ‘a network that crosses local, regional, and international boundaries.’ WANs are created when the users of one Local Area Network (LAN) need frequent access to the resources on another LAN. Connections can be made over a variety of media and using a variety of different protocols in WAN.

Network Topologies.

A network topology is the physical layout of network. Basically the way all the nodes in the network are connected. There are several different types of network topologies, each with advantages and disadvantages. The different types of network topologies are Bus topology, Ring topology, Star topology and Mesh topology.

Bus topology.

The first type of network topology is called a bus topology. A bus topology uses one cable to connect all of the nodes together. A bus topology is very easy to set up and requires no additional hardware. The cable is also called a backbone or trunk. The bus topology is probably the easiest one to understand and to implement. Bus topology networks use coaxial cable. Each end of each segment of the network has a special cable terminator on it, without which the network will not function.


  • It’s easy to install and maintain.
  • It’s inexpensive to implement.
  • No additional hardware required, such as switches and hubs.
  • Less cabling is required than other topologies.


  • One breakdown of cable is affect to the whole network.
  • Difficult to troubleshooting.
  • Data communication is slower than with some of the other topologies.

Ring topology.

A ring topology is actually not a physical arrangement of a network cable. Ring is a logical arrangement. In a ring topology, all nodes are connected via a cable that loops in a ring or circle. The Ring passes data logically from station to station until the data reaches its destination. Years ago, ring topologies were common in LANs, as three popular networking technologies used rings: ARCNET, Token Ring and fiber distributed data interface (FDDI) networks.


  • It’s fairly simple to maintain.
  • Equal access for each node.
  • Signal degeneration is low.


  • Any maintenance would affect all the nodes that connect to the ring.
  • Under normal traffic load, a ring is much slower than other topologies.
  • Isolating a problem can be difficult in some ring configurations. 

Star topology.

The star network is a very common network topology. In a star topology, each network node is connected to a central device called a hub or a switch. Each workstation has a cable that goes from the network card to the central device. One of the major benefits of a star topology is that a break in the cable causes only the workstation that is connected to the cable to go down, not the entire network. Star topology networks can use one of several forms of Ethernet. The most common is 100Base-T Ethernet, which provides 100 Mbps of bandwidth.


  • It’s simple to implement and maintain.
  • It allows for direct communication between two nodes.
  • Scalability and ease of adding another system to the network.
  • It’s easy to troubleshoot.


  • The central device fails in a star topology, the entire network comes down.
  • Another disadvantage of a star topology is cost.
  • It’s requiring more cables.

Mesh topology.

A mesh network is one in which each node in the network can be connected through a point-to-point connection to another node (every workstation has a connection to every other component of the network).


  • Fault tolerance (break in a cable segment, traffic can be rerouted through a different path because there are multiple paths to send data from one node to another.)


  • Expensive to implement.