Most of us these days, have heard of computer networks. In the 1950s, the birth of modem(modulation demodulation) allowed engineers to use normal telephone lines for communication between computers. The development of ARPANET in the 1960s and 70s kickstarted the use of computer networks as we know it today. A computer network is a set of computers connected via a transmission medium for the purpose of sharing resources located within the network. The different resources could be printers, servers, shared data, operating systems etc. A network is a multipurpose connection, which allows a computer to do much more than it could otherwise.

Each computer network has multiple nodes that are connected to each other via a transmission medium. Nodes are either devices or data points in the network such as computers, printers etc. Nodes are identified in networks by hostname and network address. Connections between nodes can be via coaxial cable, optic fibre, ethernet cables or even wireless. Computer networks can be classified based on the transmission medium, communications protocols, size, topology or bandwidth. Hostnames are labels given to a node in the network. Network addresses are addresses used to locate and identify the nodes by communication protocol just like physical addresses.

Most modern computer networks use packet switched networks to handle data. Packet switched networks are a type of communication network. Unlike circuit switched networks which are used for telephone lines, they don't need dedicated links between different nodes. In a packet-switched network, data moves in small blocks called packets using protocols(set of rules) such as Internet protocol. The packet consists of user data and control information. Control information provides data the network needs to deliver the user data, for example, sender and receiver network addresses, error detection codes. With this type of communication, the entire bandwidth of the transmission media can be efficiently used between multiple users.

TYPES OF NETWORKS (BASED ON TOPOLOGY)

BUS NETWORK: In this network, all the nodes are connected via a single cable. The information intended for the last node has to pass through all the other nodes. Benefit of this network is minimal use of cables. This is a common topology in the data link layer.

STAR NETWORK: In this network, all the nodes are connected to a central node. All computers are connected independently, hence easy management of the entire network from one point. Adding new nodes is also easy. It also has a single point of failure as a result. This type of network is commonly used in WLAN.

RING NETWORK: In this network, all computers are connected via a single cable like the bus network. But the end nodes are also connected like a ring shape. Hence, each node is connected to the neighboring left and right nodes. The signal circulates through the network until it reaches the correct node. In many offices, this type of network is used.

MESH NETWORK: In this network, each node is connected to every other node via a single link. There is a dedicated link between two nodes, allowing for secure connection between them. Detection of failure in network connection is easy. But the number of cables and ports to connect would be huge.

HYBRID NETWORK: This network uses a combination of two or more different types of networks. New networks can be connected to old networks. The advantage of this network is the combination of different networks such as star and bus, which each serve a different purpose. But fault detection and maintenance would be difficult.

TREE NETWORK: The network is shaped like a tree with many branches. There is a mutually connected link between every two nodes. There is a parent child relation type of hierarchy. It is used in Wide area networks.

Computer networks have made an enormous number of applications and services such as World wide web, digital audio and video, sharing servers, storage, printers, email available to mankind. From the early 1950s, when they first began to be designed to now, computer networks have indeed come a long way.