Kerala Plus One Computer Science Notes Chapter 12 Internet and Mobile Computing
Internet means international network of networks. The first from of internet is ARPANET (Advanced Research Projects Agency Network) started by US Department of Defence for their military during 1970’s.
It is a network of networks. It means that international network. We can transfer information between computers within nations very cheaply and speedily.
- Intranet: A private network inside a company or organisation is called intranet.
- Extranet: It allows vendors and business partners to access the company resources.
The hardware and software requirement for internet:
- A computer with a modem (internal/external).
- A telephone connection.
- An account with an ISP.
- A browser software.
Different types of Connectivity:
There are two ways to connect to the internet. They are:
1. Dial up connection:
The internet connection is established by dialling into an ISP’s computer. If ISP is not busy they verify the user name and password if it is valid they will connect our computer to the internet. It uses Serial Line Internet Protocol (SLIP) or Point to Point Protocol (PPP). It is slower and has a higher error rate.
2. Direct connection:
In this there is fixed cable or dedicated phone line to the ISP. Here it uses ISDN (Integrated Services Digital Network) a high speed version of a standard phone line. Another method is leased lines that uses fibre optic cables. Digital Subscribers Line (DSL) is another direct connection. Direct connection provides high speed internet connection and error rate is less. Fibre To The Home (FTTH) uses optical fibers for data transmission.
3. Wireless broadband connectivity:
- Mobile broadband: Accessing internet using wireless devices like mobile phones.
- Wi MAX (Wireless Microwave Access): It uses microwaves to transmit information across a network in a range 2 GHz to 11 GHz over very long distance.
- Satellite broadband: Accessing internet through satellite. A Very Small Aperture Terminal (VSAT) dish antenna and transceiver and modem are required at the user’s location. It is expensive and high speed.
Internet Access Sharing Methods:
One internet connection can be shared among several computers using:
- LAN: The internet connection in a LAN can be shared among other computers in the network.
- Wi-Fi (Wireless Fidelity): It uses radio waves to transmit information across a net-work in a range 2.4 GHz to 5 GHz in short distance.
- Li-Fi (Light Fidelity) network: It is a fast optical (uses visible light for data transmission) version of Wi-Fi. Its main component is a LED lamp that can transmit data and a photo diode that acts as a receiver.
Services in Internet
- www (World Wide Web): This means this website address is unique and can be accessed each nook and corner of the world.
- Browser: It is a piece of software that acts as an interface between the user and the internal working of the internet. Different browsers are Microsoft internet explorer, Mozilla Firefox, Netscape Navigator, Google Chrome, Opera, etc.
It is the process of navigation through the web pages in the www.
[ It is a newly developed tool that helped to search the information on the internet more effectively and easily. Search engines are programs that help people to locate information from the website on internet using a database that consists of references. Search engine use softwares called spiders I or bots to search documents and their web addresses.
E-mail (Electronic mail)
It is used to send text, multimedia messages between computers over internet. To send an email, first type the recipients address and type the message then click the send button.
The advantages of email are given below:
- Speed is high.
- It is cheap.
- We can send email to multiple recipients.
- Incoming messages can be saved locally.
- It reduce the usage of paper.
- We can access mail box anytime and from anywhere.
Various social medias are:
- Internet forums: It is an online discussion site where people can exchange information about various issues.
- Social blogs: Conducting discussions about particular subjects by entries or ; posts, eg., blogger.com
- Microblogs: It allows users to exchange short messages, multimedia files etc. eg., S twitter.com
- Wikis: It give informations about various topic, eg., wikipedia
- Social networks: We can post our data ;and view others data, eg., facebook
- Content communities: We can share multimedia files, eg., youtube
It is used to provide protection of valuable information such as credit card information from unauthorized access, intentional access, deletion etc.
A virus is a bad program or harmful program to damage routine 1 working of a computer system. It reduces the speed of a computer. It may be delete the useful system files and make the computer useless.
It is a stand alone malware program that replicates itself in order to spread to other computers. It slows down the traffic by consuming the bandwidth.
It appears as a useful software but it is a harmful software and it will delete useful softwares or files.
Sending an email without recipient’s consent to promote a product or service i is called spamming. Such an email is called a spam.
It is process of trespassing computer networks. These are two types white : hats and black hats. White hats hack the computer networks to test the security but black hats intentionally stealing valuable data or destroying data.
It is an attempt to get others information such as usernames, passwords, ; bank a/c details etc by acting as the authorized website. Phishing websites have URLs and home pages similar to their original ones and mislead others, it is called spoofing.
Denial of Service (DoS) attack:
Its main target is a web server. Due to this attack the web server/computer forced to restart and this results refusal of service to the genuine users. DoS attacks send huge number of requests to the web server until it collapses due to the load and stops functioning.
Man in the Middle attacks:
It is an attack in which an attacker secretly intercepts electronic messages send by the sender to the receiver and then modifies the message and retransmit it to the receiver. To prevent this type of attack, encrypted connections such as HTTPS (HTTP Secure), SFTP (Secure FTP) etc, must be used, that will be displayed in the URL.
Preventing Network attacks
- Firewall: It is a system that controls the incoming and outgoing network traffic by analyzing the data and then provides security to the computer network in an organization from other network (internet).
- Antivirus scanners: It is a tool used to scan computer files for viruses, worms and Trojan horses and cure the infected system. If any fault found it stops the file from running and stores the file in a special area called Quarantine (isolated area) and can be deleted later.
- Cookies: These are small text files that are created when we visit a website that keep track of our details. This information will help the hacker to use it for malicious purposes. It acts as a spyware.
Mobile communication networks do not require any physical connection. Various generations in mobile communication are:
1. First Generation networks (1G):
It was developed around 1980, based on analog system and only voice transmission was allowed.
2. Second Generation Networks (2G):
This is the next generation network that was allowed voice and data transmission. GSM and CDMA standards were introduced by 2G. MMS and picture messages are introduced.
- Global System for Mobile (GSM): It is the most successful standard. It uses narrow band TDMA (Time Division Multiple Access). The network is identified using the SIM (Subscriber Identify Module). GPRS (General Packet Radio Services) is a packet oriented mobile data service on the 2G on GSM. EDGE (Enchanced Data rates for GSM Evolution) is three times faster than GPRS. It is used for voice communication as well as an internet connection.
- Code Division Multiple Access (CDMA): It is a channel access method used by various radio communication technologies. CDMA is an example of multiple access, which is where several transmitters can send information simultaneously over I a single communication channel.
3. Third Generation networks (3G):
It allows high data transfer rate for mobile devices and offers high speed wireless broad band services combining voice and data. To enjoy this service, 3G enabled mobile towers and hand sets are required.
4. Forth Generation networks (4G):
It is also called Long Term Evolution (LTE) and also offers ultra broadband internet facility such as high quality streaming video.
Mobile Communication Services
- Short Message Service (SMS): It allows transferring short text messages containing up to 160 characters between mobile phones.
- Multimedia Messaging Service (MMS): It allows sending Multimedia.
- Global Positioning System (GPS): It is space based satellite navigation system j that provides location and time information in all weather conditions, anywhere on or near the Earth where there is an unobstructed line of sight to four or more GPS satellites.
- Smart card: It is a plastic card with a computer chip or memory that stores and I transacts data. A smart card (may be like an ATM card) reader used to store and transmit data.
Mobile Operating System
It is an OS used in hand held devices such as smart phone, table, etc. It manages the hardware, multimedia functions, internet connectivity, etc. eg., Android, iOS.