Computer Networks Notes for JNTUK - R16

What is a computer network?

A computer network is a set of computers connected together for the purpose of sharing resources. The most common resource shared today is connection to the Internet. Other shared resources can include a printer or a file server. The Internet itself can be considered a computer network.

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Definition
A computer network is a group of computer systems and other computing hardware devices that are linked together through communication channels to facilitate communication and resource-sharing among a wide range of users. Computers on a network are called nodes.

The connection between computers can be done via cabling, most commonly the Ethernet cable, or wirelessly through radio waves. Connected computers can share resources, like access to the Internet, printers, file servers, and others.A network is a multipurpose connection, which allows a single computer to do more.

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Networks are used to:

• Facilitate communication via email, video conferencing, instant messaging, etc.
• Enable multiple users to share a single hardware device like a printer or scanner
• Enable file sharing across the network
• Allow for the sharing of software or operating programs on remote systems
• Make information easier to access and maintain among network users

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There are many types of networks, including:

• Local Area Networks (LAN)
• Personal Area Networks (PAN)
• Home Area Networks (HAN)
• Wide Area Networks (WAN)
• Campus Networks
• Metropolitan Area Networks (MAN)
• Enterprise Private Networks
• Internetworks
• Backbone Networks (BBN)
• Global Area Networks (GAN)
• The Internet

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Types of Network Connections

Computer networks can be broken down historically into topologies, which is a technique of connecting computers. The most common topology today is a collapsed ring. This is due to the success of a network protocol called the Ethernet. This protocol, or network language, supports the Internet, Local Area Networks, and Wide Area Networks.

Star Topology

A star topology is a network topology in which all the network nodes are individually connected to a central switch, hub or computer which acts as a central point of communication to pass on the messages.

Advantages

• Less damage in case of a single computer failure as it does not affect the entire network

Disadvantages

• More cables are required to be connected because each computer individually connects to the central server
• Single point of failure in case the server get down.

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Bus Topology

In a network, when all the nodes are connected by a single physical cable and the central cable becomes the backbone of the network then, it is called as a Bus topology.

Advantages

• Minimal use of the physical resources

Disadvantage of the Bus topology:

• A Single point of failure

Ring Topology

Ring topology is a type of network topology where each node is exactly connected to two other nodes, forward and backward, thus forming a single continuous path for signal transmission. There are two types of the Ring Topology based on the data flow:

1. Unidirectional and,
2. Bidirectional

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Advantages

• Reduced chances of data collision as each node release a data packet after receiving the token.
• Token passing makes ring topology perform better than bus topology under heavy traffic.
• No need of server to control connectivity among the nodes.
• Equal access to the resources.

Disadvantages

• In Unidirectional Ring, a data packet must pass through all the nodes.