3G communication
1. It stands for 3^rd generation technology.
2. Maximum upload rate of 3 G technology is 5 Mbps.
3. Maximum download rate of 3 G technology is 21 Mbps.
4. It uses packet switching technique.
5. The frequency range of 3 G technology is from 1.8 GHz to 2.5 GHz
4G communication
1. It stands for 4^rd generation technology.
2. Maximum upload rate of 4 G technology is 500 Mbps.
3. Maximum download rate of 4 G technology is 1 Gbps.
4. It uses packet switching technique as well as message switching technique.
5. Its frequency range is from 4 G technology is from 2 GHz to 8 GHz.

(i) Spam can be defined as irrelevant or unsolicited messages sent over the internet. These are usually sent to a large number of users for advertising, phishing, spreading malware, etc.
(ii) Spamming is the process of sending digital junk mail: unsolicited communication sent in bulk over the internet or through any electronic messaging system.

(i) Ecommerce or electronic commerce refers to transactions conducted via the internet. Ever time individual and companies are buying or selling products and services online they are engaging in ecommerce.
(ii) Ecommerce is a popular term for electronic commerce or even internet commerce.
(iii) Examples of ecommerce: Amazon, flipkart, eBay, Olx, Quikr,

(i) Network is a broad term similar to "system". Network is a communication system which supports many users. In relation with the computer, we can say that a "computer network" is a system which allows communication among the computers connected in the network.
(ii) In a computer network, we need to make use of hardware and software. The hardware consists of connecting cables, connectors, network connecting devices and the software consists of protocols, programs, etc. This enables the systematic exchange of information between the computers connected in the network.

1. The coaxial cable consists of two concentric conductors namely an inner conductor and a braided outer conductor.

2. It has a solid conductor at its center, located coaxially within a cylindrical outer conductor.
3. A plastic layer provides insulation between the center conductor and the outer braided metal shield.
4. Outer conductor acts a shield against noise and crosstalk.
5. Whole cable protected by a plastic cover and outer conductor is enclosed in an insulated sheath.
6. Distance between the outer conductor and inner conductor plus the type of material used for insulating the inner conductor determine the cable properties or impedance.
7. For cable TV typical impedance is 75 \(\Omega \) and for ethernet, thin-net and thick net is 50 \(\Omega \).
8. Thin coaxial cable is referred as thin net and thick coaxial cable is referred as thick net.
(i) Television signals in cable TV networks
(ii) Analog telephone networks to carry voice signal
(iii) Traditional ethernet LAN because of its high bandwidth.

1. A hub is the most basic networking device that connects multiple computers or other network device together.
2. It joins together the workstations, printers, and servers on a network to communicate with each other.
3. Each hub has a number of ports that connect it to the other devices via a network cable.
4. A hub connects all the devices on its port together.
5. When data arrives at one port, it is sent to the other ports so that all the devices can see all the information, commonly known as packets.
6. There is no intelligence in hub about what devices are connected to hub. When one device sends packet to the hub, it just broadcasts the packet on all ports.

Web Browser:
Internet Browser is an Application program that shows a World wide web report. It ordinarily utilizes the web access to get to the archive.
Web Server:
Web worker is a program or the PC that offer types of assistance to different projects called customer.
Web Page:
A page (or site page) is a hypertext report given by a site and showed to a client in an internet browser. A site ordinarily comprises of many pages connected together in a rational style. The name "page" is an allegory of paper pages bound together into a book.
At the point when the web worker gets the solicitation, it look through its stores to track down the fitting page. On the off chance that the web worker can find the page, it distributes to the HTML contained inside, delivers these bundles to the program (utilizing HTTP), and communicate them back across the organization.

There are many applications of internet such as:
1. Communication: Computer users around the world extensively use the email service on internet to communicate with each other. Pictures, documents and other files are sent as email attachments. VolP stands for Voice over Internet Protocol, referring to the protocol that underlies all internet communication.
2. Job search: Nowadays many people search for their jobs online as it is quicker and there is a larger variety of jobs vacancies present. People can publish resume online for prospective job.
3. Video conferencing: It enables direct face to face communication across networks via web cameras, microphones and other communication tools. Video conferencing can enable individuals in distant locations to participate in meetings on short notice, with time and money saving. Video conferencing is very interactive in education to communicate between teacher to teacher, teacher to classroom and classroom to classroom with students at different places.
4. E-commerce: E-commerce or electronic commerce is the buying and selling of goods and services, or transmitting of funds or data, over an electronic network. These transactions occur either business-to-business, business to consumer, consumer to consumer or consumer to business.
5. Travel: One can use internet to gather information about various touristplace. It can be used for booking Holiday tours. Some of the websites providing this service are goibibo.com, makemytrip.com,olacabs.com.
6. Nowadays internet is almost use in every fields. Due to increase in technology, use of internet has benefitted the users in many ways. Internet enables millions of computers from different organization and people to communicate and share resource globally.

Wired Technology: Wired technology is more associated with wired communication. Wired technology refers to the transmission of data over a wired based communication technology.
Types of bounded media in the data transmission:
1. Twisted pair Cable:
(i) A twisted pair consists of two conductors (normally copper), each with its own plastic insulation, twisted together.
(ii) One of these wires is used to carry signals to the receiver, and the other is used only as ground reference. In addition to the signal sent by the sender on one of the wires, interference (noise) and crosstalk may affect both wires and create unwanted signals.
(iii) Twisted Pair is of two types:
(a) Unshielded Twisted Pair (UTP)
(b) Shielded Twisted Pair (STP)
2. Fibre Optical Cable:
(i) A fibre-optical cable is made of glass or plastic and transmits signals in the form of light.
(ii) In fibre optical cable, light moves only in one direction.
(iii) For two-way communication to take place a second communication must be made between the two devices.
(iv) Optical fibres use reflection to guide light through a channel. A glass or plastic core is surrounded by a cladding of less dense glass or plastic.
(v) The difference in density of the two materials must be such that a beam of light moving through the core is reflected off the cladding instead of being refracted into it.
3. Coaxial Cable:
(i) Coaxial is called by this name because it contains two conductors that are parallel to each other.
(ii) Copper is used in this as a central conductor. It is surrounded by PVCinstallation.
(iii) Outer metallic wrapping is used as a shield against noise and as a second conductor which completes the circuit.
(iv) The outer conductor is also encased inan insulating sheath.
(v) The outermost partis the plastic cover which protects the whole cable.
(vi) Anything and everything you see around yourself having wires and uses electricity to operate belongs to wired technology.

Topology describes the physical cabling layout and the logical way of moving data between components. Network topology is the schematic description of a network arrangement, connecting various nodes (sender and receiver) through lines of connection. The following are different types of network topology:
1. BUS topology: Bus topology is a network type in which every computer and network device is connected to a single cable.

A single cable is used without additional electronics to amplify the signal or pass it along from computer to computer. Therefore, the bus is a passive topology.
Bus topology transmits data only in one direction.
2. STAR topology: In a star topology all the components are connected via a cable to a central location where they are all connected by a device called a hub. There is no direct connection among the computers. All the connections are made via the central hub.

TREE topology: This type of topology is arranged in the form of a tree like structure in which top level contains parent node (root node), which is connected with the child nodes in the second level of hierarchy. The second level nodes are connected to the third level nodes, which in turn are connected to the fourth level nodes and so on. Except thetop-level nodes, each level node has a parent node.
Devices or nodes in a network get connected to each other via communication links and all these links are related to each other in one way or other. The geometric representation of such relationship of links and nodes is known as the topology of that network.