UNIT-I
Fundamentals of Internet
Network
Network is a collection of hardware components and computers interconnected by communication channels(Transmission media)that allow sharing of resources and information.
Network Components: The important components used in the computer network are: Transmission Media: It is the medium through which the data travels. The various
alternatives for transmission media are: twisted pair cable, coaxial cable, fiber optics, etc.
Processor: Processor is the hardware which helps to transfer the data from source to destination. Different processors used in the data communication are: modem, router, bridge, etc.
Software: To transfer the data from source to destination we require software, examples are: networking operating system software, internet explorer, etc.
Topology: It is the way which data travels, the various topologies available are: star, ring, bus, mesh, tree, etc.
Advantages of Networks
Easy communication and speed
It is very easy to communicate through network. people can communicate efficiently using a network with a group of people. They can enjoy the benefit of emails, instant messaging,telephony,video conferencing, chat rooms etc.
Ability to share Files, Data and Information
People can find and share information and data because of networking. This is beneficial for large organizations to maintain their data in an organized manner and facilitate access for desired people.
Sharing Hardware: Ability to share hardware Resources such as printers, fax machines and modems can be shared. For example: a printer can be shared among users in a network so that there is no need to have individual printers for each and every computer in the company. it will reduce the cost of purchasing hardware. Sharing Software: Users can share software within the network easily.
to Individually licensed versions of software. Therefore large companies can reduce the cost of buying software by networking their computers.
Security: Sensitive files and programs on a network can be passwords protected. Then Those files can only be accessed by the authorized users. Each and every user has their own set of privileges’ to prevent them accessing restricted files and programs.
Speed: Sharing and transferring files within Networks are very rapid. Thus saving time, while maintaining the integrity of the files.
Disadvantages of Networks
Breakdown and possible loss of Resources:
One major disadvantage of networking is the breakdown of the whole network due to an issue of the server. Such breakdowns are frequent in networks causing losses of thousands of dollars each year. The worst scenario is such breakdowns may lead to loss of important data of the server.
Expensive to build
Building a network is a serious business in many occasions, especially for large scale organizations. Cables and other hardware are very expensive to buy and replace.
Security Threats
Security threats are always problems with large networks. There are hackers who are trying to steal valuable data for large companies for their own benefit.
Band width issues
In a network there are users who consume a lot of more bandwidth than others. Because of this some other people may exist experience difficulties.
Data Communication
Data communication means sharing the information. This sharing can be local or remote or with in a building. Local communication usually occurs in face to face, while remote communication takes place over distance.
Data communication is the exchange of data between the two devices via some of transmission medium. Data communication devices must be the part of the
communication system made up of combination of hardware and software. 1. Delivery: Delivery should be done to the correct destination.
3. Accuracy: Data delivered should be accurate.
Components of Data Communication
1. SenderA device that is used for sending messages (or data) is called sender. It is also called transmitter or source. The sender can be a computer, telephone, or a video camera etc. Usually, a computer is used as sender in data communication system. 2. Receiver
A device that is used for receiving messages is called receiver. It is also known as sink. The receiver can be a computer, telephone set, printer, or a fax machine etc. Usually, a computer is also used as receiver in data communication system. 3. Message
The message is the information or data that is to be communicated. It may consist of text, numbers, pictures, sounds, videos or any combination of these.
4. Transmisson Medium
The path through which data is transmitted (or sent) from one location to another is called transmission medium. It is also called communication channel. It may be a wire, or fiber optic cable, or telephone line etc. If the sender and receiver are within a building, a wire is used as the medium. If they are located at different locations, the medium may be telephone line, fiber optics, microwave or satellite system.
5. Protocol
Types of Networking
There are many different types of networks. However, from an end user’s point of view there are three basic types.
1. LAN(Local Area Network)
2. MAN(Metropolitan Area Network) 3. WAN(Wide Area Network)
Local Area Network
A computer network spanned inside a building and operated under single administrative system is generally termed as Local Area Network (LAN). Usually,LAN covers an organization’ offices, schools, colleges or universities. Number of systems connected in LAN may vary from as least as two to as much as 16 million.LAN provides a useful way of sharing the resources between end users. The resources such as printers, file servers, scanners, and internet are easily sharable among computers.
LAN configuration consist of:
A file server - stores all of the software that controls the network, as well as the software that can be shared by the computers attached to the network.
A workstation - computers connected to the file server (Mac or PCs). These are less powerful than the file server
LAN uses either Ethernet or Token-ring technology. Ethernet is most widely employed LAN technology and uses Star topology, while Token-ring is rarely seen.LAN can be wired, wireless, or in both forms at once.
Advantages
Resource Sharing:
Computer resources like printers, modems,Dvd-Rom drives and hard disks can be shared with the help of local area networks. This will reduce the cost of purchase hardware
Software Application Sharing:
It is cheaper to use same software over network instead of purchasing separate licensed software for each client in a network.
Easy and Cheap Communication
Data and messages can easily be transferred over networked computers. Centralized data
The data of all network users can be saved on hard disk of the server computer. This will help users to use any workstation in a network to access their data. Because data is not stored on workstation locally.
Data Security
Data is stored on server computer centrally, it will be manage data at only one place and the data will be more secure too.
Internet Sharing
It provides the facility to share a single internet connection among all the lan users
Ex: Net cafe Disadvantages
High setup cost
Initial setup costs of installing local area network is high. Privacy violations
The lan administrator has the right to check the personal data files of each and every lan user, internet history and computer use history.
Data security threat
Unauthorized users can access important data of an organization. if centralized data is not secured properly by the lan administrator.
Lan Maintenance job
Covers limited area
It covers only limited geographical area such as offices, schools, colleges, universities etc.,
Metropolitan Area Network
The Metropolitan Area Network (MAN) generally expands throughout a city such as cable TV network. It can be in the form of Ethernet, Token-ring, ATM, or Fiber Distributed Data Interface (FDDI).
Metro Ethernet is a service which is provided by ISPs. This service enables its users to expand their Local Area Networks. For example, MAN can help an organization to connect all of its offices in a city.
Backbone of MAN is high-capacity and high-speed fiber optics. MAN works in between Local Area Network and Wide Area Network. MAN provides uplink for LANs to WANs or internet.
Advantages
Bandwidth could be easily access within MAN
Cost of sharing is quite cheap and fast throughout the MANS It mainly used Fibre optic cable
It transmission is very fast
It generally covered a city or a town. It support voice communication. Disadvantages
Wide Area Network
As the name suggests, the Wide Area Network (WAN) covers a wide area which may span across provinces and even a whole country. Generally, telecommunication networks are Wide Area Network. These networks provide connectivity to MANs and LANs. Since they are equipped with very high speed backbone, WANs use very expensive network equipment.
WAN may use advanced technologies such as Asynchronous Transfer Mode (ATM), Frame Relay, and Synchronous Optical Network (SONET). WAN may be managed by multiple administration.
Advantages
Shares software and resources with connecting workstations.
Messages can be sent very quickly to anyone on the network such as pictures, sounds or data.
Share information/files over a larger are
Disadvantages
Are expensive and generally slow.
Security is a real issue, protection against hackers and viruses adds more complexity and expense.
It requires network supervisors and technicians to be employed.
Internet
The Internet is a global system of interconnected computer networks that use the standard Internet Protocol Suite (TCP/IP) to serve billions of users worldwide. It is a network of networks that consists of millions of private, public, academic, business, and government networks of local to global scope, that are linked by a broad array of electronic and optical networking
technologies.
It can be defined in many ways as follows:
Internet is a world-wide global system of interconnected computer networks. Internet uses the standard Internet Protocol (TCP/IP).
Every computer in internet is identified by a unique IP address.
IP Address is a unique set of numbers (such as 110.22.33.114) which identifies a computer location.
A special computer DNS (Domain Name Server) is used to give name to the IP Address so that user can locate a computer by a name.
For example, a DNS server will resolve a name http://www.webduniya.com to a particular IP address to uniquely identify the computer on which this website is hosted. Internet is accessible to every user all over the world.
Services of Internet
1.Communication Services
There are various Communication Services available that offer exchange of information with individuals or groups.
1. E-mail: Sending and receiving E-mails around the world at minimal price.
2. Telnet: One can login on to other network via Internet as if one is a member of that network this done through utility called TELNET.
3. News group: One can participate in discussions on wide range of topics from recreational activities to scientific researches via a utitility called use net news group. 4. Internet Relay Chat (IRC)
Allows the people from all over the world to communicate in real time. 5. Internet Telephony (VoIP)
Allows the internet users to talk across internet to any PC equipped to receive the call. 2.Information retrieval service
There exist several Information retrieval services offering easy access to information present on the internet.
1. FTP: It is also used to send data inform of files from one computer to other with the facility called FTP (File Transfer Protocol).
2. Gopher
Used to search, retrieve, and display documents on remote sites. 3. Archive
It is a search utility that search on the Internet based on file names or partial file names. 3. Web Services
4. World Wide Web
WWW is also known as W3. It offers a way to access documents spread over the several servers over the internet. These documents may contain texts, graphics, audio, video, hyperlinks. The hyperlinks allow the users to navigate between the documents.
1. Videoconferencing: One can have a live talk with persons all round the world and can held meetings as if sitting just by their side by video conferencing of multimedia conferencing.
2. ON line Entrance Exams and Results: Students can give exams on line through the Internet.
Advantages of Internet:
Now a day, using internet is almost everywhere. Internet has got its wide spread acceptance due to the vast set of facilities provided by it. We can search for almost any topic on the internet using a search engine. Thousands of pages of information is kept available on various topics on the internet. Apart from providing information, internet has some more significant advantages…
Electronic Mail (e-mail): e-mail is a fast, easy and economic way to send messages to anyone having an internet account. Using e-mails, we can send text messages, images etc., to anywhere
in the universe. The information will be dispatched in seconds of time irrespective of the distance.
Downloading software and programs: using internet, we can download useful software, programs etc. Using internet, we can update our existing programs like antivirus etc., regularly in order keep our computer up to date. Apart from downloading the software or programs, we can also upload them so that other people on the internet can utilize them.
Entertainment: thousands of games are made available on the internet free of cost to get relaxed. Internet also allows us to review the current movies or any other topics as well as to be a part of an interactive conversation with several people across the universe.
Online shopping and e-commerce: with the use of internet, shopping any article can be done right from our home or office without visiting the shops. We can order almost any kind of material like books, computers, software’s, dress etc.,
Internet Applications 1. Search engine
It can be used to search anything and everything. Most popular search engines are Google and yahoo searches.
2. Shopping
3. Communication
This is a major role of the internet. It helps people to communicate either with the use of social networking websites or through e mails. Even chatting is a major use of the internet.
4. Job search
Nowadays, many people search for their jobs online as it is quicker and there is a larger variety of job vacancies present.
5. Hobbies
Those who are having certain hobbies can try to improve on it by reading up on many aspects of their hobby.
6. Research
Research papers are present online which helps in the researcher doing literature review. 7. Studying
Now right from kinder garden children is exposed to internet and computers. They find many useful things to learn on the internet (though with supervision). Up to doctorate level education, people rely on internet for their education. Online educational books have even reduced the need for a library.
What is Internet addressing?
A way to locate people, computers, and Internet resources. It can be IP (Internet Protocol) addresses and domain names
Electronic mail addresses
URLs
In general, Internet addressing is a systematic way to identify people, computers and Internet resources.
On the Internet, the term "address" is used loosely. Address can mean many different things from an electronic mail address to a URL.
IP Address
An IP address is a unique number that identifies computers on the Internet; every computer directly connected to the Internet has one. Every client, server and network device must have a unique IP address for each network connection (network interface).
Domain Name
Most computers on the Internet have a unique domain name.
Special computers, called domain name servers, look up the domain name and match it to the corresponding IP address so that data can be properly routed to its destination on the Internet. An example domain name is: healthyway.com
Domain names are easier for most people to relate to than a numeric IP address.
Electronic Mail Address
Other networks may use different electronic mail addressing schemes within their own networks. To be used in Internet e-mail, these addresses often need to be modified.
For example, within CompuServe an e-mail address consists only of two numbers separated by a comma: 36547,891.
To convert this to an address that can be used on the Internet, the comma is changed to a period and the number serves as the username.
The domain name is compuserve.com, so the Internet address would be: 36547.891@compuserve.com
URLs
URL stands for Uniform Resource Locator. URLs are used to identify specific sites and files available on the World Wide Web.
The structure of a URL is: protocol://server.subdomain.top-level-domain/directory/filename Similar to an e-mail address, a URL is read like a sentence.
For example the URL http://www.healthyway.com Virus
Definition: A virus is a computer program that can copy itself and it can infect other programs in a computer by modifying them without permission or knowledge of the user.
Boot Sector Virus: A Boot Sector Virus infects the first sector of the hard drive, where the Master Boot Record (MBR) is stored. The Master Boot Record (MBR) stores the disk's primary partition table and to store bootstrapping instructions which are executed after the computer's BIOS passes execution to machine code. If a computer is infected with Boot Sector Virus, when the computer is turned on, the virus launches immediately and is loaded into memory, enabling it to control the computer.
• File Deleting Viruses: A File Deleting Virus is designed to delete critical files which are the part of Operating System or data files.
• Mass Mailer Viruses: Mass Mailer Viruses search e-mail programs like MS outlook for e-mail addresses which are stored in the address book and replicate by e-mailing themselves to the addresses stored in the address book of the e-mail program.
• Macro viruses: Macro viruses are written by using the Macro programming languages like VBA, which is a feature of MS office package. A macro is a way to automate and simplify a task that you perform repeatedly in MS office suit (MS Excel, MS word etc). These macros are usually stored as part of the document or spreadsheet and can travel to other systems when these files are transferred to another computers.
• Polymorphic Viruses: Polymorphic Viruses have the capability to change their appearance and change their code every time they infect a different system. This helps the Polymorphic Viruses to hide from anti-virus software.
• Armored Viruses: Armored Viruses are type of viruses that are designed and written to make itself difficult to detect or analyze. An Armored Virus may also have the ability to protect itself from antivirus programs, making it more difficult to disinfect.
• Stealth viruses: Stealth viruses have the capability to hide from operating system or anti-virus software by making changes to file sizes or directory structure. Stealth viruses are anti-heuristic nature which helps them to hide from heuristic detection.
• Polymorphic Viruses: Polymorphic viruses change their form in order to avoid detection and disinfection by anti-virus applications. After the work, these types of viruses try to hide from the anti-virus application by encrypting parts of the virus itself. This is known as mutation.
• Multiple Characteristic viruses: Multiple Characteristic viruses has different characteristics of viruses and have different capabilities.
There are six broad catagories that viruses fall under:
Boot Sector Virus - targets the boot sector of a hard drive and crucially effects the boot proccess.
1. File Infection Virus - coded viruses that attach themselves to .exe files; compressed files such as zip or drive files.
2. Multipartite Virus - cross between a file virus and a boot sector virus.
3. Network Virus - uniquely created to quickly spread throughout the local area network and generally across the Internet as well. Typically moves within shared resources like drives and folders.
4. Macro Virus - infects program files that use macros in the program itself, such as word processors.
