INTERNET BASICS

1. INTERNET BASICS Prepared by AshisMitra For B.Com, St. Xavier’s College

2. A. INTERNET CONCEPT

3. What is Internet? • The Internet is defined as a vast collection of inter connected networks across the web. It is a ‘network of networks’. These networks are: • Interconnected • Capable of communicating and sharing data with each other • Able to act together as a single network

4. World Wide Web (WWW) It is a set of the computers on the Internet that are connected to one another in a specific way that makes them and their contents easily accessible to each other.

5. Internet requires: 1.Web server 2. Browser 3. Router 4. Protocol 5. Internet service provider.

6. Web server. • It supports the client computers of its own network and establishes connectivity to answer the requests of client computer.

7. Browser • A browser or web browser is a software application designed to find the web pages and open these pages the user’s computer. • Browsers are of two types – Graphical browsers that allow the user to access text as well as video and audio links in GUI environment; and text browsers that provide access to the web in text-only mode. Internet Explorer and Netscape Navigator are two most commonly used browsers in GUI environment.

8. Router. • The core of the internet is the set of backbone connections that tie the local and regional networks together and router controls the way each piece of data finds its destination. Router is responsible for sending packets of data through one or more networks until they reach the appropriate server and are reassembled.

9. Protocol • Each computer connected to the Internet uses the same set of rules and procedures to control timing and data format. These are called Protocols. • Most commonly used protocols for internet are Transmission Control Protocol/Internet Protocol (TCP/IP).

10. Internet service provider (ISP). • It is an organization which connects user’s computer to the internet by providing the required software.

11. B. INTERNET PROTOCOL ADDRESS (IP ADDRESS)

12. IP Address Every computer connected to the internet must be having an address for sending or receiving TCP packets. This is known as internet address or IP address

13. IP address system The version of IP that has been in use is known as Internet Protocol version 4(IPv4) It uses a 32-bit number to identify the computers connected to the internet. This address is called an IP address. IP addresses are assigned by three organisations: American Registry for Internet Numbers(APRN), Reseaux IP Europeens (RIPE) and Asia-Pacific Network Information Centre(APNIC)

14. IP numbers IP numbers (addresses) appear as four numbers separated by periods. In a 32-bit number system each of the four number is a 8-bit number. Although in computer application an 8-bit number is called a byte, in networking application an 8-bit number is often called an octet.

16. IPV6 IPv6 uses 128 bits as apposed to IPv4’s 32. This means that by comparison, IPv6 has a lot more addresses. This is also a main reason for using IPv6 in the future. As a small example of the potential in the new protocol there is a quote in one of Microsoft’s articles written by a Joseph Davies “6.6 x 10²³ addresses for every square meter of the Earth’s surface”.

17. IPV6 contd…. The exact number of IPv6 addresses available is.... • “340,282,366,920,938,463,463,374,607,431,768,211,456” • This is approximately three hundred and forty trillion, trillion, trillion addresses. Comparing this to IPv4’s address space of “4,294,967,296” or approximately four billion, it’s possible to see the shear size of IPv6 address space. To use up every single IPv6 addresses we would need to stack ten billion computers on top of each other over the entire world including the sea. The facts show that it is almost impossible to run out of IPv6 addresses.

18. Difference between IPV4 and IPV6 IPv4 limits the packet size to 64KB of payload. IPv6 can handle much larger packets, called Jumbograms, which can reach upto 4GB. This can increase the speed of data transfer over high MTU networks. • The packet header in IPv6 is simpler than the packet header that is used in IPv4. • The packet header of IPv6 has many rarely-used fields moved to separate options. Hence, though the addresses in IPv6 are four times larger, the (option-less) IPv6 header is only twice the size of the (option-less) IPv4 header.

19. Difference between IPV4 and IPV6 contd… • The address space of IPv4 is 32 bit whereas the address space of IPv6 is 128 bit. • With IPv6, stateless auto configuration of IP addresses becomes possible. Which means that we can create a unique IP address by combining its LAN address with a prefix provided by the network router. • IPv4 does not support Multicast whereas with IPv6, multicast is possible. Multicast is transmission of a single datagram to multiple receivers. As a result, multi-media applications can be supported. • With IPv6, secure VPN (Virtual Private Network) will be easier to build and deploy. • The above differences show how advanced IPv6 is and how efficient it can be in data transfer.

20. URL.-Uniform Resource Locator • The standard way to express the address of any resource and its access method on the internet that is part of the world wide web. Here the user is not required to know where the resource is located physically. • E.g. http://www.sxccal.edu/bcomit/internet.htm • URL consists of following parts: • Protocol – http (HyperText Transfer Protocol) • Host computer – www • Domain name – sxccal • Domain type – edu (educational) • Path – bcomit • File name – internet.htm

21. Notes: • http is the protocol for accessing a web page. • Domain name is unique and case sensitive for each host address. • Domain type represents the type of organization or the country to which the host belongs. • Some of the domain types are: • com – commercial or profit organization • org – non-profit organization • edu – education provider • net – internet infrastructure and service provider • gov – government agency. • Besides these, there are two letter country code like, in for India, uk for United Kingdom, etc.

22. DNS.- Domain Name System • To make the use of internet websites more convenient and user friendly, a parallel naming system has been invented, popularly known as Domain Name System (DNS). It translates the names of network nodes into their corresponding IP addresses. It is a distributed database system that works at transport layer to provide name-to-address mapping for client applications. • On Internet each computer is identified uniquely by its IP address.. DNS provides an easy way to use the website domain names instead of using the IP addresses directly and leaves the overhead of conversion of domain names into IP address on DNS.

23. DNS contd… • Currently few private sector companies called Registrars are accredited to register domain names from Internet Corporation for Assigned Names and Numbers (ICANN). Domain name consists of multiple parts separated by dots and are translated from right to left. For example, www.yahoo.com signifies that it is a commercial website (.com), its domain name is yahoo and is a part of World Wide Web (www).

24. C. PROTOCOLS

25. What is Protocol? • A protocol is a set of rules that govern data communications. • Rules are for formatting, ordering and error-checking of data. • Computers that communicate with each other must use the same protocol for data transmissions.

26. Key elements of a protocol • Syntax – It refers to the structure or the format of the data, meaning the order in which they are presented. • Semantics - It refers to the meaning of each section of bits. How is a particular pattern to be interpreted and what action is to be taken based on that interpretation? • Timing – It refers to two characteristics: when data should be sent and how fast they can be sent.

27. TCP/IP TCP- Transmission Control Protocol - It controls the disassembly of message or file into packets before it is transmitted over the internet and the reassembly of those packets into their original formats when they reach their destinations.

28. IP - Internet Protocol.-It is a network layer protocol .It specifies addressing details of each packet, labeling each with the packet’s origination and destination addresses. So. IP is responsible for moving packet of data from node to node.

29. Layer 1 – Network Interface Layer • Layer 2 – Internet or internetworking layer • Layer 3 – Host-to-Host or Transport layer • Layer 4 – Process layer or Application layer

30. Layer 1 – Network Interface Layer This layer is responsible for placing packets on and receiving them from the network medium. TCP/IP is not dependent on local network technology and can adapt to changes at the local level.

31. This layer is responsible for addressing, messaging and routing messages on the internet. So, it defines IP addresses with many routing schemes for navigating packets from one IP address to another.

32. Layer 3 – Host-to-Host or Transport layer This layer is responsible for providing communication with the application by acknowledging and sequencing the packets to and from the application. So, this layer deals with opening and maintaining connections, ensuring that packets are received.

33. Layer 4 – Process layer or Application layer This layer provides a wide variety of applications with the ability to access the services of the lower layers. Some of the best known applications are Hyper Text Transfer Protocol(HTTP), File Transfer Protocol(FTP) and Simple Mail Transfer Protocol(SMTP)

34. UDP - User Datagram Protocol UDP is a minimal message-oriented Transport Layer protocol. In the Internet Protocol Suite, UDP provides a very simple interface between the Internet Layer and the Application Layer. Using UDP, programs on networked computers can send short messages (sometimes known as datagrams) to one another. UDP is said to be connectionless, as there is no handshaking between sending and receiving transport-layer entities before sending a segment.

35. UDP is commonly used today with multimedia applications, such as Internet phone, real-time video conferencing, and streaming of stored audio and video. Internet phone and video conferencing react very poorly to TCP's congestion control. For these reasons, developers of multimedia applications often choose to run the applications over UDP instead of TCP.

36. Difference between TCP and UDP TCP is a connection-oriented protocol, which means that upon communication it requires handshaking to set up end-to-end connection. UDP is a simpler message-based connectionless protocol. There is no effort made to setup a dedicated end-to-end connection. Communication is achieved by transmitting information in one direction, from source to destination without checking to see if the destination is still there, or if it is prepared to receive the information.

37. HTTP-.Hyper Text Transfer Protocol It is a communications protocolInternet. Its use for retrieving inter-linked text documents (hypertext) led to the establishment of the World Wide Web. HTTP development was coordinated by the World Wide Web Consortium and the Internet Engineering Task Force (IETF). HTTP is a request/response standard between a client and a server. A client is the end-user, the server is the web site.

38. HTTP uses TCP and not UDP because much data must be sent for a web page, and TCP provides transmission control, presents the data in order, and provides error correction. HTTP (Hypertext Transfer Protocol) is the set of rules for transferring files (text, graphic images, sound, video, and other multimedia files) on the World Wide Web. As soon as a Web user opens their Web browser, the user is indirectly making use of HTTP. HTTP is an application protocol that runs on top of the TCP/IP suite of protocols.

39. FTP.-File Transfer Protocol It is an application level protocol that allows a user to move a file from one computer to another computer in a network environment. The typical information needed to connect to an FTP site is: 1. The "server address" or "hostname". such as ftp.microsoft.com. 2. The username and password.

40. The most common use for FTP is to download files from the Internet.  Because of this, FTP is the backbone of the MP3 music craze, and vital to most online auction and game enthusiasts.  An FTP address looks a lot like an HTTP, or Website, address except it uses the prefix ftp:// instead of http://.  Example Website address: http://www.FTPplanet.com Example FTP site address: ftp://ftp.FTPplanet.com

41. TELNET. – Telecommunication Netwok. It is an application level protocol that allows a user to log in to another computer from his or her current computer in a network environment.

42. Telnet is a user command and an underlying TCP/IPprotocol for accessing remote computers. Through Telnet, an administrator or another user can access someone else's computer remotely. On the Web, HTTP and FTP protocols allow the user to request specific files from remote computers, but not to actually be logged on as a user of that computer. With Telnet, one can log on as a regular user.