Computer Notes- Networking and Internet

Computer networking means communication between a group of two or more computer systems linked together. Networks are built with a mix of computer hardware and computer software.

THE MOST COMMONLY DISCUSSED CATEGORIES OF COMPUTER NETWORKS INCLUDE THE FOLLOWING
 Local Area Network (LAN)
 Wide Area Network (WAN)
 Metropolitan Area Network (MAN)
 Storage Area Network (SAN)
 System Area Network (SAN0
 Server Area Network (SAN)
 Small Area Network (SAN)
 Personal Area Network (PAN)
 Desk Area Network (DAN)
 Controller Area Network (CAN)
 Cluster Area Network (CAN)


LANs and WANs were the original flavours of network design.

LOCAL AREA NETWORK (LAN)
 A LAN connects network devices over a relatively short distance. It is a system in which computers are interconnected and the geographical spread may be within a building to 1 kilometer.

TYPE OF LAN
 Star LAN
 Ring LAN
 Bus LAN

Metropolitan Area Network (MAN): It is a data network designed for a town or city. This type of network is spread over a city. It connects an area larger than a LAN but smaller than a WAN, such as a city, with dedicated or high performance hardware.

Wide Area Network (WAN) A WAN is a geographically dispersed collection of LANs. It is like the internet spans most of the world. In IP networking, the router maintains both a LAN address and a WAN address.
TYPES OF WAN
 Public Networks
 Public Switched Telephone Networks (PSTN)
 Public Service Digital Network (PSDN)

INTEGRATED SERVICES DIGITAL NETWORK (ISDN)
 ISDN is used for voice, video and data services.
 It uses digital transmission.
 It combines both circuit and packet switching.

PRIVATE NETWORK
 Private Network provides services at various locations using private or leased circuits by using technology of its choice.
 It is mostly used to carry large volume of data at very high speed transmission.
 It uses Modem's multiplexes and other communication devices.

Network Topology : Topology is the geometric arrangement of a computer system. Each computer system in a topology is known as a node. Network topology is determined only by the configuration of connections between nodes.

Bus Topology: A bus topology is such that there is a single line to which all nodes are connected and the nodes connect only to this bus.

Mesh Topology : This type of network topology contains at least two nodes with two or more paths between them.

Ring Topology: In this network topology, every node has exactly two branches connected to it. The ring is broken and cannot work if one of the nodes on the ring fails.

Star Topology: In this network topology, the peripheral nodes are connected to a central node, which rebroadcasts all transmissions received from any peripheral node to all peripheral nodes on the network, including the originating node.

Tree Topology: This is a network topology in which nodes' are arranged as a tree. The function of the central node in this topology may be distributed.

CLIENT-SERVER NETWORKING
 It is a network application architecture which separates the client from the server.
 It is a scalable architecture, where each computer or process on the network is either a client or a server.

Features of Server- Features of Client 
Passive (Slave) -Active (Master)
Waiting for requests -Sending request
On getting requests serves them and sends the reply- Waits until the response comes

 The interaction between client and server is often described using sequence diagrams.
 Sequence diagrams are standardized in the UML.

PEER-TO-PEER NETWORKING
 It is also known as P2P networking.
 This computer network relies on computing power at the edges of a connection rather than in the network itself.
 It is used for sharing content like audio, video, data or anything in digital format.
 P2P network can also mean grid computing.

INTERNET
The Internet is a global network of interconnected network, enabling users to share information along multiple channels. A computer that connects to the internet can access information from a vast array of available servers and other computers by moving information from them to the computer's local memory.

SERVICES OF INTERNET
E-mail: The Internet enables user to exchange data/information and communicate via electronic media. E-mail messages are usually encoded in American Standard Code for Information Interchange (ASCII) text. Chat: Chat is the exchange of typed message by people. It enables people to 'talk not vocal' by typing and sending the messages back and forth. Video Conferencing: A service that allows a group of users to exchange video information over the Internet. It includes an audio teleconference facility.

IMPORTANT POINTS REGARDING INTERNET
 TCP/IP (Transmission Control Protocol/Internet Protocol)
 PPP (Point to Point Protocol)
 WWW (World Wide Web)
 CNEB
 Gopher
 WAIS
 Mosaic
 Archie
 Hypertext

WIRELESS LAN
A Wireless LAN or WLAN is a Wireless Local Area Network that uses radio waves at its carrier - the last link with the users is wireless, to give a network connection to all users in the surrounding area. Areas may range from a single room to an entire office.

INTERNET PROTOCOL SUITE
The Internet protocol suite is the set of communications protocols that implement the protocol stock on which the Internet and most commercial networks run.

FILE TRANSFER PROTOCOL
FTP or File Transfer Protocol is a commonly used protocol for exchanging files over any network that supports the TCP/IP protocol (such as the Internet or an Intranet). There are two computers involved in an FTP transfer-a server and a client.

INTERNET SERVICE PROVIDER
An Internet Service Provider (ISP) is a business or organization that offers users access to the Internet and related services. Many but not all ISPs are telephone companies.

NETWORK SERVICE PROVIDER
A Network Service Provider (NSP) is a business or organization that sells bandwidth or network access by providing direct backbone access to the Internet and usually access to its Network Access Points (NAPs).

WEB SERVER
A web server is a program that using the client/server model and the World Wide Web's Hyper Text Transfer Protocol (HTTP). Serves the files that form Web Pages to Web users (whose computers contains HTTP clients that forward their requests). Client Server Client Server is a network architecture which separates the client from the server.

Proxy Server A Proxy Server is a computer that offers a computer network service to allow clients to make indirect network connections to other network services.

WEBSITE
A Website is a collection of web pages, typically common to a particular domain name or sub-domain on the World Wide Web on the Internet.
 Static Website
 Dynamic Website

WEB PAGE
A Web Page is a resource on the World Wide Web, usually in HTML/XHTML format with hypertext links to enable navigation from one page or section to another. A web page can contain content which is able to be seen or heard by the end user. These elements include, but are not limited to
 Text
 Graphics, typically GIF, JPEG or PNG formats
 Audio, typically MIDI or WAY formats
 Macromedia Flash
 Hyperlinks

Dynamic Web Page: Dynamic Web Pages can be defined as Web Pages containing dynamic content (example-images, text, form fields etc) that can change/move without the web page being reloaded.

HOME PAGE
 It is the first page that the link/site takes the user to.
 It most often refers to the initial or main web page of a website.
 It is a personal web page, for example at a web hosting service or a university website that typically is stored in the home directory of the user.

UNIFORM RESOURCE LOCATOR
A Uniform Resource Locator CURL) is the another name for web address or website address. It is basically a string of characters which refers to a resources on the Internet. e.g., the URL of 'Google' search engine is 'wwwgoogle.com '.

ANDROID (OPERATING SYSTEM)
Android is a mobile operating system initially developed by Android Inc. Android was purchased by Google in 2005. Android is based upon a modified version of the Linux Kernel. Android has a large community of developers writing application programs Capps) that extend the functionality of the devices.

WIRELESS APPLICATION PROTOCOL (WAP)
Wireless Application Protocol (WAP) is an open international standard. A WAP browser is a commonly used Web browser for small mobile devices such as cell phones.

WEB ADDRESSES
Web addresses start with the name of a protocol, which is called a HTTP (Hyper Text Transfer Protocol). HTTP means that the resource in question will be found on a web server.



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