Communication Technologies (OLD) - 12 Computer Sc 05 Communication Technologies

 CBSE Class 12 Computer Science 5

Communication Technologies
Revision Notes (Networking Concepts Part I)

Network: A collection of interconnected computers for the purpose of sharing of resources and enhanced communication.

Node: A computer attached to a network.

Server: A computer that facilitates sharing of data, software and hardware resources on the network.

Network Interface Unit (NIU): A device that helps to establish communication between the server and workstations.

Circuit switching: A technique in which a dedicated and complete physical connection is established between two nodes for communication.

Packet switching: A switching technique in which a message is broken down into a number of packets which are sent independently, over whatever route is optimum for each packet, and reassembled at the destination.

Message Switching: It follows store and forward technique where the source computer sends the data to the switching office first and stores it in its buffer until a free link to another switching office is available and then sends data to that swiching office. This process  is continued until the data delivered to the destination computer.

Personal Area Network (PAN): A computer network organized within the range of an individual person, typically within a range of 10 meters.

Local Area Network (LAN): A network in which the devices are connected over a relatively short distance typically in a room or in a building.

Metropolitan Area Network (MAN): A network which spans a physical area (in the range of 5 and 50 km diameter) that is larger than a LAN but smaller than a WAN.

Wide Area Network (WAN): A network which spans a large geographical area, often a country or a continent.

Internet: It is a network of networks spread across the globe, all of which are connected to each other.

Interspace: A client/server software program that allows multiple users to communicate online with real time audio, video and text chat in dynamic 3D environments.

Channel: A medium that is used in the transmission of a message from one point to another.

Bandwidth: The range of frequencies available for transmission of data.

(Networking Concepts Part II)

Transmission Medium: One which carries a signal from one computer to another.

Wired Transmission Media: Twisted Pair, Coaxial, Fibre Optic, Ethernet cable

Twisted Pair: A twisted pair cable is a type of cable made by putting two separate insulated wires together in a twisted pattern and running them parallel to each other. This type of cable is widely used in different kinds of data and voice infrastructures.

Coaxial Cable : It is a type of shielded and insulated copper cable that is used in computer networks to deliver cable TV services to end users. 

Fibre Optic Cable(Optical Fibre) : A fiber optic cable consists of a bundle of glass threads, each of which is capable of transmitting messages modulated onto light waves.

Wireless Transmission Media: Radio waves, Microwaves, Satellites, Infrared, Bluetooth, WiFi, WiMAX

Radio waves : The transmission making use of radio frequencies is termed as radio wave transmission. 

Microwaves : these are similar to radio and television signals and are used for long distance transmission.

Satellites : In satellite communication, signal transferring between the sender and receiver is done with the help of satellite.

Infrared Infrared enables computer network communications via short-range wireless signals. This is one of the earliest types of optical communication and is still very much in use today. It is found in remote controls for televisions, dvd players and most other entertainment devices.

Bluetooth : is a radio communication technology that enables low-power, short distance wireless networking between phones, computers and other network devices.

WiFi : is a technology for wireless local area networking with Wi-Fi compatible devices can connect to the Internet via a WLAN network and a wireless access point.

Topology: The pattern of interconnection of nodes in a LAN.

Network Topologies: Bus, Star, Tree, Ring, Mesh

Star Topology : Consists of a central node to which all other nodes are connected by a single path.

Bus Topology : Consists of a single length of the transmission medium onto which the various nodes are attached.

Ring topology: Each node is connected to two and only two neighbouring nodes.

Mesh Topology : Each node is connected to more than one node to provide an alternate route.

Modem: A device that enables a computer to transmit data over, telephone or cable lines.

RJ-45: Stands for Registered Jack-45. It is an eight-wired connector which is used to connect computers on a LAN.

Ethernet card: A kind of network adapter that plugs into a slot on the motherboard and enables a computer to access an Ethernet network (LAN).

Switch: A small hardware device that joins multiple computers together within a LAN.

Repeater: An electronic device that amplifies the received signal and then retransmits it on the network.

Router: A network device that connects two networks with different protocols.

Gateway: A network device that connects two dissimilar networks.

Wi-Fi card: A small, portable card that allow your computer to connect to the internet through a wireless network.

(Networking Protocols)

Protocol: A special set of rules that two or more machines on a network follow to communicate with each other.

Transmission Control Protocol(TCP): It is one of the main protocols of the Internet protocol suite. It breaks the data into packets that the network can handle efficiently.

Internet protocol(IP): It gives distinct address (called IP address) to each data packet.

File Transfer Protocol(FTP): It is used for transferring files from one system to another on the internet.

Hyper Text Transfer Protocol(HTTP): It is the protocol that is used for transferring hypertext files on the World Wide Web.

Point-to-Point Protocol(PPP): It is used for a direct communication between two computers using a serial interface.

Simple Mail Transfer Protocol (SMTP): It allows transmission of email over the Internet.

Post Office Protocol 3(POP3): It receives and holds email for an individual until they pick it up.

Telnet: A protocol for creating a connection with a remote machine.

IRC: IRC stands for Internet Ralay Chat. It is a protocol used for chatting. It is based on client/server model.

VOIP: VOIP stands for voice over internet protocol. It enables the transfer of voice using packet switched network rather than using public switched telephone network.

(Mobile Telecommunication Technologies, Network Security and Internet Services)

1G Mobile Systems: Refers to the first generation of wireless telephone technology (mobile telecommunications). These are the analog telecommunications standards that were introduced in the 1980s and continued until being replaced by 2G digital telecommunications. They only had voice facility available.

2G Mobile Systems: It is based on the technology known as Global System for Mobile communication(GSM). This technology enabled various networks to provide services like text messages, picture messages and MMS.

3G Mobile Systems: The 3G technology adds multimedia facilities to 2G phones by allowing video, audio, and graphics applications. This technology enables use of various services like GPS (Global Positioning System), mobile television and video conferencing.

4G Mobile Systems: It offers no improvements in making calls or sending texts but very fast web experience compared to 3G.

Virus: Virus is a malicious program that attaches itself to the host program. It is designed to infect the host program and gain control over the system without the owner's knowledge.

Worm: Worm is also a malicious program like a virus. It is a self-replicating virus that does not alter files but resides in active memory and duplicates itself.

Trojan horse: A Trojan horse is a program that contains hidden malicious functions. Trojan Horse appears to be legitimate programs and performs malicious functions.

Spam: It is considered to be electronic junk mail or junk newsgroup postings.

Cookies: Cookies are the messages given to a web browser by a web server so that the webserver can keep track of the user's activity on a specific website. 

Firewall: A firewall is hardware or software based network security system. It prevents unauthorized access (hackers, viruses, worms etc.) to or from a network.

Cyber Crime: It is the criminal activity done using computers and the Internet. 

Cyber Law: Cyber law is an attempt to integrate the challenges presented by human activity on the internet with legal system of laws applicable to the physical world.

Intellectual Property Rights : Intellectual property rights are the rights given to persons over the creations of their minds. They usually give the creator an exclusive right over the use of his/her creation for a certain period of time.

Intellectual Property Rights (IPR) Issues: Intellectual property rights are the rights given to an individual over the invention of their own. They usually give the creator an exclusive right over the use of his/her creation for a certain period of time. There are only three ways to protect intellectual property Patents ,Copyrights & Trademark

Hacking: The term was used for people who engaged themselves in harmless technical experiments and fun learning activities.

Cracking: Cracking can be defined as a method by which a person who gains unauthorized access to a computer with the intention of causing damage.

Hyper Text Transfer Protocol (HTTP): HTTP is the protocol that is used for transferring hypertext (i.e. text, graphic, image, sound, video etc.) between two computers and is particularly used on the World Wide Web. It is a TCP/IP based communication protocol and provides a standard for Web browsers and servers to communicate.

WWW (World Wide Web): WWW can be defined as a hypertext information retrieval system on the Internet. Tim Berners -Lee is the inventor of WWW. WWW is the universe of the information available on the internet.

Web page: Web page is an electronic document designed using HTML. It displays information in textual or graphical form. It may also contain downloadable data files, audio files or video files.

A web page can be classified into two types:

a). Static web page :-Static Web pages are those with content that cannot change without a developer editing its source code.

b). Dynamic web page:- Dynamic Web pages can display different content from the same source code.

Website: A website is a collection of webpages providing information about a particular entity.

Web browser: Web browser is software program to navigate the web pages on the internet. A bowser interprets the coding language of the web page and displays it.

URL (Uniform Resource Locator): Web address of the web page written on the address bar of the browser is known as the uniform resource locator (URL).

Web hosting: Web hosting is the process of uploading/saving the web content on a web server to make it available on WWW.

Web 2.0: Web 2.0 refers to new generation of dynamic and interactive websites. Web 2.0 websites uses a new programming language called AJAX (Asynchronous JavaScript and XML).