Computer Network

 

Computer:

Ø An electronic machine that can store, find and arrange information, calculate amounts and control other machines.

Ø A computer is a machine that can be programmed to carry out sequences of arithmetic or logical operations automatically. Modern digital electronic computers can perform generic sets of operations known as programs. These programs enable computers to perform a wide range of tasks.

 

Network:

Ø A network is a group of two or more computers or other electronic devices that are interconnected for the purpose of exchanging data and sharing resources.

Ø A network consists of two or more computers that are linked in order to share resources (such as printers and CDs), exchange files, or allow electronic communications. The computers on a network may be linked through cables, telephone lines, radio waves, satellites, or infrared light beams.

Ø A network is defined as the connection of at least two computer systems, either by a cable or a wireless connection. The simplest network is a combination of two computers connected by a cable. This type of network is called a peer-to-peer network. There is no hierarchy in this network; both participants have equal privileges. Each computer has access to the data of the other device and can share resources such as disk space, applications or peripheral devices (printers, etc.).

 

 

 

Computer Network:

Ø A computer network is a group of interconnected nodes¹ or computing devices that exchange data and resources² with each other. A network connection between these devices can be established using cable or wireless media. Once a connection is established, communication protocols³ -- such as TCP/IP⁴, Simple Mail Transfer Protocol⁵ and Hypertext Transfer Protocol⁶ -- are used to exchange data between the networked devices.

·       Nodes: Node is a physical device that is be part of a network infrastructure. Examples of network nodes include switches or routers, as well as data devices such as computers, printers, or servers. Each node must be unique on the network, so that the network can properly route the information to the correct device.

·       Resource: A resource is any hardware or software accessible by a computer, network, or another object connected to a computer. For example, a printer connected to a network is an example of a shared resource.

·       Protocol: a set of rules outlining how connected devices communicate across a network to exchange information easily and safely.

·       TCP/IP: TCP/IP (Transmission Control Protocol/Internet Protocol) is a suite of communication protocols that define the standards for transmitting data over computer networks, including the internet. The TCP/IP protocol is the foundation of the internet and enables devices to communicate with each other using a common language.

·       Simple Mail Transfer Protocol: SMTP is an application layer protocol. SMTP is used to send and receive email.

·       Hypertext Transfer Protocol: HTTP provides a standard between a web browser and a web server to establish communication. It is a set of rules for transferring data from one computer to another. Data such as text, images, and other multimedia files are shared on the World Wide Web. Whenever a web user opens their web browser, the user indirectly uses HTTP.

Ø A computer network is a group of computers that use a set of common communication protocols over digital interconnections for the purpose of sharing resources located on or provided by the network nodes.

Ø A group of computers which are connected to each other and follow similar usage protocols for the purpose of sharing information and having communications provided by the networking nodes is called a Computer Network.

 

Types of Computer Networks:

There are five main types of Computer Networks:

LAN (Local Area Network) –

·       Systems connected in a small network like in a building or a small office

·       It is inexpensive

·       It uses Ethernet or Token-ring technology

·       Two or more personal computers can be connected through wires or cables acting as nodes

·       Transfer of data is fast and is highly score

PAN (Personal Area Network) –

·       The smallest computer network

·       Devices may be connected through Bluetooth or other infra-red enables devices

·       It has a connectivity range of upto 10 metres

·       It covers an area of upto 30 feet

·       Personal devices belonging to a single person can be connected to each other using PAN

MAN (Metropolitan Area Network) –

·       A network that can be connected within a city, for example, cable TV Connection.

·       It can be in the form of Ethernet, ATM, Token-ring and FDDI

·       It has a higher range.

·       This type of network can be used to connect citizens with the various Organizations.

WAN (Wide Area Network) –

·       A network which covers over a country or a larger range of people.

·       Telephonic lines are also connected through WAN.

·       Internet is the biggest WAN in the world.

·       Mostly used by Government Organizations to manage data and information.

VPN (Virtual Private Network): –

·       A network which is constructed by using public wires to connect to a private network.

·       There are a number of systems which enable you to create networks using the Internet as a medium for transporting data.

·       These systems use encryptions and other security mechanisms to ensure only authorized users can access.

Internet:

Ø A complete network of globally linked computers, the Internet also enables the users to transfer information and communication. This makes use of the TCP/IP protocol suite while communicating. Available in both wired and wireless mode, the internet also includes a wide range of networks such as private, public, government, organization, etc. It supports multiple users and allows the transfer of a massive amount of data.

Ø Internet is used to connect the different networks of computers simultaneously. It is a public network therefore anyone can access the internet. On the internet, there are multiple users and it provides an unlimited of information to the users.

Intranet:

Ø A part of the network, but controlled and used by a private organization, Intranet has restrictions and can support only fewer users. Hence, only limited data can be shared over it. Intranet is usually operated on a client/server platform. This enables the organizations to share files, data, organize information, manage and share calendars, files, etc.

Ø Intranet is the type of internet that is used privately. It is a private network therefore anyone can’t access the intranet. On the intranet, there is a limited number of users and it provides a piece of limited information to its users.

Difference between Internet and Intranet

S.No.	Internet	Intranet
1.	Internet is used to connect different networks of computers simultaneously.	Intranet is owned by private firms.
2.	On the internet, there are multiple users.	On an intranet, there are limited users.
3.	Internet is unsafe.	Intranet is safe.
4.	On the internet, there is more number of visitors.	In the intranet, there is less number of visitors.
5.	Internet is a public network.	Intranet is a private network.
6.	Anyone can access the Internet.	In this, anyone can’t access the Intranet.
7.	The Internet provides unlimited information.	Intranet provides limited information.
8.	Using Social media on your phone or researching resources via Google.	A company used to communicate internally with its employees and share information.
9.	The Internet is a global network that connects millions of devices and computers worldwide.	An intranet is a private network that connects devices and computers within an organization.
10.	It is open to everyone and allows access to public information, such as websites and online services.	An intranet is only accessible to authorized users within the organization.
11.	It is used for communication, sharing of information, e-commerce, education, entertainment, and other purposes.	An intranet is primarily used for internal communication, collaboration, and information sharing within an organization.
12.	Users can access the Internet from any location with an Internet connection and a compatible device.	Access to an intranet is restricted to authorized users within the organization and is typically limited to specific devices and locations.
13.	Security measures, such as firewalls, encryption, and secure sockets layer (SSL) protocols, are used to protect against threats like hacking, viruses, and malware.	Intranets employ similar security measures to protect against unauthorized access and ensure the privacy and integrity of shared data.
14.	The Internet is a public network that is not owned by any particular organization or group.	Intranets are private networks that are owned and managed by the organization that uses them.
15.	Examples of Internet-based services include email, social media, search engines, and online shopping sites.	Examples of intranet-based services include internal communications, knowledge management systems, and collaboration tools.

 

Network Topology:

(Topology: Studies how spaces are organized and how they are structured in terms of position.)

Ø A Network Topology is the arrangement with which computer systems or network devices are connected to each other. Topologies may define both physical and logical aspect of the network. Both logical and physical topologies could be same or different in a same network.

Ø Network Topology is the schematic description of a network arrangement, connecting various nodes (sender and receiver) through lines of connection.

Ø Network topology refers to the manner in which the links and nodes of a network are arranged to relate to each other.

Ø Topologies are categorized as either physical network topology, which is the physical signal transmission medium, or logical network topology, which refers to the manner in which data travels through the network between devices.

Types of Network Topology:

1.    Bus Topology                                 4.      Tree Topology

2.    Star Topology                                 5.      Hybrid Topology

3.    Ring Topology                                6.      Mesh Topology

BUS Topology:

Ø Bus topology is a network type in which every computer and network device is connected to single cable. When it has exactly two endpoints, then it is called Linear.

Ø The simplest type of topology is called a bus topology, in which network communication takes place over a single bus or channel. There are numerous taps and drop lines connected to the bus. Drop Lines are cables that connect the bus to the computer, and taps are connectors. In other words, each node is connected to a single transmission line.

Advantage/Benefits	Disadvantage/Drawbacks
Ø  Easy to install and use. Ø  Other nodes won't be impacted if one node fails. Ø  Less wiring is needed. Ø  Economical to implement. Ø  Useful in small networks.	Ø  Efficiency decreases as nodes increase (strength of signal decreases). Ø  A bus failure will result in network failure. Ø  The bus's limited length means that only a certain number of nodes can connect to it. Ø  As messages are broadcast to all nodes, there are more security concerns and risks.

Features of Bus Topology

Ø It transmits data only in one direction.

Ø Every device is connected to a single cable.

Star Topology:

Ø In this type of topology all the computers are connected to a single hub through a cable. This hub is the central node and all others nodes are connected to the central node.

Ø A computer network topology known as a star topology connects each node to a central hub. The hub or switch acts as a bridge between the nodes. Any node making a service request or offering a service must first get in touch with the hub. The other connected devices function as clients in a star topology, while the hub and switch serve as a server.

Advantage/Benefits

Disadvantage/Drawbacks

Ø  It is very reliable – if one cable or device fails then all the others will still work Ø  It is high-performing as no data collisions can occur Ø  Less expensive because each device only needs one I/O port and wishes to be connected with hub with one link. Ø  Easier to put in Ø  Robust in nature Ø  Easy fault detection because the link are often easily identified. Ø  No disruptions to the network when connecting or removing devices. Ø  Each device requires just one port i.e. to attach to the hub. Ø  If N devices are connected to every other in star, then the amount of cables required to attach them is N. So, it’s easy to line up. Ø

Ø  Requires more cable than a linear bus . Ø  If the connecting network device (network switch) fails, nodes attached are disabled and can’t participate in network communication. Ø  More expensive than linear bus topology due to the value of the connecting devices (network switches) Ø  If hub goes down everything goes down, none of the devices can work without hub. Ø  Hub requires more resources and regular maintenance because it’s the central system of star. Ø  Extra hardware is required (hubs or switches) which adds to cost Ø  Performance is predicated on the one concentrator i.e. hub.

 

Features of Star Topology:

Ø It is very reliable – if one cable or device fails then all the others will still work

Ø It is high-performing as no data collisions can occur

Ø Less expensive because each device only need one I/O port and wishes to be connected with hub with one link.

Ø Easier to put in

Ø Robust in nature

Ø Easy fault detection because the link are often easily identified.

Ø No disruptions to the network when connecting or removing devices.

Ø Each device requires just one port i.e. to attach to the hub.

Ø If N devices are connected to every other in star, then the amount of cables required to attach them is N. So, it’s easy to line up.

 

Ring Topology:

Ø A ring topology is a network configuration in which each node is connected to two other nodes in the network, building a single continuous pathway for signals through the network. Ring topologies are often used in local area networks (LANs).

Ø A number of repeaters are used for Ring topology with a large number of nodes, because if someone wants to send some data to the last node in the ring topology with 100 nodes, then the data will have to pass through 99 nodes to reach the 100th node. Hence to prevent data loss repeaters are used in the network.

A ring topology comprises 4 stations connected with each forming a ring. 

The most common access method of ring topology is token passing.

Ø  Token passing: It is a network access method in which a token is passed from one node to another node.

Ø  Token: It is a frame that circulates around the network.

 

Advantage/Benefits	Disadvantage/Drawbacks
Ø  The data transmission is high-speed. Ø  The possibility of collision is minimum in this type of topology. Ø  Cheap to install and expand. Ø  It is less costly than a star topology.	Ø  The failure of a single node in the network can cause the entire network to fail. Ø  Troubleshooting is difficult in this topology. Ø  The addition of stations in between or the removal of stations can disturb the whole topology. Ø  Less secure.

 

Tree Topology:

Ø This topology is the variation of the Star topology. This topology has a hierarchical flow of data.

Ø Tree topology is a type of network topology that resembles a tree. In a tree topology, there is one central node (the “trunk”), and each node is connected to the central node through a single path. Nodes can be thought of as branches coming off of the trunk. Tree topologies are often used to create large networks.

Advantage/Benefits

Disadvantage/Drawbacks

Ø  It can support a large number of nodes. Ø  It can be easily expanded. Ø  Additionally, tree topologies are highly scalable and can be easily reconfigured.

Ø   It can be difficult to troubleshoot issues in a tree topology as each node is connected to multiple other nodes. This can make it hard to identify where the issue is located. Ø  Tree topology can be less reliable than other topologies such as star or mesh as there are more potential points of failure. If one node goes down, it can affect the entire network. Ø  Tree topology can be more expensive to implement as it requires more cabling and equipment than other topologies.

 

Applications of Tree Topology:

Ø Tree topology is often used to connect multiple devices, such as printers and computers, in a home or small office. Tree topology is commonly used to create bus networks, where each device is connected to a central server.

Ø Tree topology can also be used to create star networks, where each device is connected to a central hub. Star networks are often used in large office buildings or campuses, where each device needs to be able to communicate with all other devices on the network.

 

Mesh Topology:

Ø A mesh topology is a type of computer network in which each node (computer or other device) is connected to every other node in the network. This type of network is often used in large organizations or companies because it can handle a large amount of data traffic and can be easily expanded.

Ø A mesh topology is therefore very fault tolerant – if one link fails, there are alternate routes that can be taken.

Advantage/Benefits	Disadvantage/Drawbacks
Ø  It is very fault tolerant. If one node in the network goes down, the rest of the nodes can still communicate with each other. Ø  All nodes in a mesh network have a dedicated connection to every other node in the network. This means that there is no single point of failure and the network can continue to operate even if one node fails.	Ø   It can be expensive to implement because each node needs its own dedicated connection to every other node in the network. This can make mesh topology impractical for large networks. Ø  Mesh topology can be complex to configure and manage.

 

Applications of Mesh Topology:

Ø Mesh topology is often used in large networks, where reliability and redundancy are important. Mesh topology can also be used in small networks, where it can offer some advantages over other topologies.

Ø One of the best parts of mesh topology is that it can be easily scaled. As the network grows, additional nodes can be added to the network without having to reconfigure the entire network.

Hybrid Topology:

Ø A hybrid topology is defined as a network topology that combines two or more different network topologies. A hybrid topology can be a combination of bus topology, ring topology and mesh topology. The selection of different types of network topologies combined together depends upon the number of computers, their location, and the required performance.

Ø The structure of hybrid topology is more complex but offers various advantages such as flexibility and fault tolerance.

Advantage/Benefits

Disadvantage/Drawbacks

Ø  Adding a new node or deleting the existing node is easy in hybrid topologies. Ø  Hybrid topology is more secure, reliable, and scalable as compared to individual star, ring and mesh topology. Ø  Error detection and troubleshooting is easier in hybrid topology. Ø  When an organization has a large geographical area utilizing hybrid topology is considered as better option. Ø  Traffic with large volume is handled easily by the hybrid topology. Ø  The overall performance and speed is greater in hybrid topology.

Ø   The design and implementation of hybrid network topology is difficult. Ø  More number of cables and other physical devices are required for hybrid topology. Ø  The process of installation of hybrid topology is difficult. Ø  The overall implementation, setup and process of hybrid topology is much more costlier.