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Internet.ppt
The document provides an overview of the history and components of the Internet. It discusses how the Internet started as ARPANET in the 1960s as a US military network. It grew to connect universities and later became commercialized. The document describes various Internet applications like email, telnet, FTP, and the World Wide Web. It explains how these applications allow communication and sharing of information over the global network of interconnected computers known as the Internet.
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Internet.ppt
- 1. Internet By S. Yesan Associate Librarian SAIACS,Bangalore, E-Mail: [email protected]
- 2. Introduction It’s a networkof networks Information superhighway A World Wide channel of communication A global network connecting millions of computers. Each Internet computer is called “host”
- 3. Internet Vs WWW Networkof networks Way of accessing information over the Internet Connects millions of computers It is an information sharing model Any computer can communicate to each other through Internet Uses HTTP to allow applications to communicate Utilizes web browsers IE, Netscape Navigator
- 4. Contd., Internet is notweb It is one of the ways that information can be disseminated over net Relies on SMTP for email It is a portion/part of Internet
- 5. History of Internet Itwas not a planned event 1960’s US needed for a technological investigation in networking for sharing defense data 1969 Advanced Research Projects Agency (ARPANET) unit of DOD – To test reliable linking computers – To link DOD and other military research contractors
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- 7. History contd.. ARPAnet wasto find out how to communicate b/w the R* centers & Military organizations Formed a small network comprising – University of California at Los Angeles – University of California at Santa Barbara – Standford University – University of Utah in Salt Lake City
- 8. History – Contd.. By1972 over 40 different sites attached to ARPAnet Services such as, E-mail, Telnet, FTP End of 1970’s ARPAnet was grown into larger network It was split into two, MILnet, ARPAnet 1979’s CSNET (Computer Science Research Network) of NSF (National Science Foundation)
- 9. Who governs theNet? No one in particular governs the net It is based on an agreement b/w different networks Internet Society (ISOC) and NSFnet (National Science Foundation Network) play significant role in managing the net
- 10. Internet Society (ISOC) Ithas a direct control over the net. It provides assistance and support to groups and organisations in the use operation and evolution of the Internet. Provides support for forums in which technical and operational questions can be discussed Provide mechanisms through which the interested parties can be informed and educated the Internet, its function, use operation
- 11. Components of Internet Desktop(PC) Modem – Converts the digital signals to analog signals MOdulates and DEModulates Telephone Connection Internet Connection (Paid or Free)
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- 13. Types of Connection Dial-upconnection – Link to Internet is brought about by a dial-up account given by agency – Dial up to the Internet Service Provider to have access to the Internet – Cheaper than dedicated links – Affordable by any common man
- 14. Types of connection Dial-upconnection – Disadvantages: Speed depends on the telephone lines – Slow during peak hours
- 15. Dedicated Links Used bylarger organisations, institutions, Govt and Corporate Bodies. Direct line is established b/w the organisation and entire network of the networks. As result of this organsations computers become part of the Internet
- 16. Dedicated Links Institutions haveits own gateways and has full time direct access to Internet. Maximum data transfer is possible at a higher rate/speed Expensive and can be afforded by larger organisations
- 17. Information Services andSources Internet Email Full Text Bibliographic Databases Web Pages Chats/Conferences User 1 IBM/MAC User 2 Ethernet User 3 Token Ring
- 18. Overview of InternetServices General Services – E-mail, Telnet, FTP, BBS, Usenet, Chat Navigation Tools – Archie, Gopher, WAIS, WWW Other utilities: Ping, Nslookup, Finger, Netfind
- 19. Electronic Mail (E-Mail) Mosteconomical and highly used modes of communication. “Electronic mail, simply is a way for computer users to exchange messages b/w different, distant computers as long as there are networks such as Internet connecting them”.
- 20. E-Mail To send messagesto specific individuals To send messages to many individuals To send messages to a predefined list of users To Send txt files To send attachments – prgs, graphics, word processed files, spread sheets, images and audio-video files To send Electronic greetings card
- 21. Working of E-Mail Itis not required that two communicating computers should be directly connected. Based on the principle of store and forward It is an interactive mode of communication
- 22. Types of programsin E-Mail User Agent Program (E-Mail Client) – Mail reader, provides and manages those functions that needed to read, write and manage the E-Mail messages – Interacts with a corresponding server – Client prgs: mail, sendmail (Unix), Pine, elm, eudora (PCs and Macintosh), MS outlook, Outlook Express (MS Windows)
- 23. Working of E-Mail MailDelivery Agent (E-Mail Server) – Plays a role of an “Electronic Post Office” – Client sends messages to this post office and messages get queued up here. – Periodically the messages are sent out – Decides where the message is to be sent – It also receives mails sent to it from other clients. – Received mails are queued up here – The server also forwards messages to the destination
- 24. Store and ForwardTechnology When the mail server receives a message, it makes a copy (stores it) and then tries to pass it on (forwards) to the destination Does not delete its copy until and unless the next server has acknowledged receipt of the forwarded mail
- 25. E-Mail Address E-Mail addressplays major role in delivering the mail to the right recipient. Parts of the E-Mail – User ID – Fully qualified Domain Name – The above two are separated by @ (the “at” sign) separator symbol.
- 26. E-Mail Address E.g., [email protected] –User ID is library – Domain Name is saiacs.org – Mail sent to [email protected] will reach a person/unit “library” on the machine “saiacs.org”
- 27. E-Mail address Convention isfollowed in assigning E-Mail address. Based on the type of organisation, the domain name is usually assigned. – Examples Commercial Organizations : .com Non Profit Organizations : .org Research Centres/Orgs : .res or ernet.in Academic institutions : .ac
- 28. Conventions codes forcountries India : .in United Kingdom : .uk Australia : .au USA : .us New Zealand : .nz
- 29. Components of E-Mail Contentinformation – Who, when, where, what Content – Body of the message/text – Attachments, if any
- 30. Telnet/Remote Login Allows oneto access a remote computer and work on it sitting at a distant terminal connected on the Net. Enables to work and download the results through FTP It is an application tool for connecting on to a remote machine and working on it.
- 31. Telnet It works onTCP/IP protocol used to support remote login sessions TCP/IP protocol defines how local and remote computers “talk” to each other in a remote login session
- 32. Telnet Working It isa “client-server” type of application. Client program interacts with Telnet sever – %telnet<remote machine name> User ID or login name :xxxxxxxxx Password :xxxxxxxxx Once the given user ID and password are accepted by the system the user can use all prgs available on the remote machine
- 33. File Transfer Protocol(FTP) It is an application prg used to move files b/w computers It is named after the application protocol it uses which is File Transfer Protocol It is used for retrieving files from public archives that are scattered around the Net Location of computers and how they are connected is immaterial
- 34. FTP Through this theshareware prg files can be downloaded from Net. It requires specific address of the machine with file name Syntax to ftp get and ftp put commands – %ftp>get source-file destination file – %ftp>put source-file destination file
- 35. For file transferone needs to know the exact name of the file that is to be transferred and also where it is located. To get file listing is ‘ls’ and ‘dir’ – ftp>dir directory-name local file name – ftp>ls directory-name local file name
- 36. Bulletin Board Service(BBS) It is an electronic message system for reading and posting messages Comprised of small groups of users who have a common interest. Provides forum to chat on subjects of special interest to the individuals included in that BBS
- 37. Usenet It is systemlooking after discussion groups or chat lines of members who regularly gather to speak, to exchange views and comment. It is a world wide community of electronic BBSs closely associated with Internet or the Internet community.
- 38. Characteristics of Usenet Informationconsists of individual messages, each can be read and shared by many users. Messages are organised into topical groups called as newsgroups Spl s/ws packages are there to use the Usenet an to be Usenet site. Any one can participate in discussions
- 39. Navigation Tools Tool touse Internet Difficult in locating information due to large amt of information available on web It is a tool to search and locate the information To navigate information
- 40. Tools for locatingnet sources Tools based on the kind of structured querying. Each tool accesses its own holdings of data when a search is made. – Gopher, Archie, WWW and WAIS
- 41. World Wide Web(WWW) A navigation tool on the net, enables browsing information linked to other related information. It is referred to as “WWW”, ‘W3’ Unlike other tools, one need not to know the site address, machines to access the information
- 42. WWW It is possibleto jump from one location to other through what is called “Hyper- Linking” of documents It is not so important to know where to start as long as we get to know where we want to be.
- 43. Resources on theWeb Resources are identified with a special name called “Uniform Resource Identifiers/Locators (URL)” It will describes the protocol needed to access the web page and access points to its Internet location and home directory URLs are address for documents on the web.
- 44. WWW Parts of URL –Protocol – Hostname – Filename The syntax: protocol://hostname/filename
- 45. WWW URL describes whatto do when the hyperlink is activated, to reach the target server, the hostname and the document filename – E.g., http://www.saiacs.orgpublications.html
- 46. WWW By using thehttp protocol to reach a server called saiacs.org Besides http, other important protocols are gopher, telnet and ftp
- 47. Web Servers Server withweb pages stored A machine on the network, to recognise and accommodate web requests Tasks of web server – Listening for specific requests for the web resources that arrive from the network – Interpreting valid requests as they arrive and attempting to locate the requested resources – Providing those resources over the network or giving an error message explaining why a request can’t be honoured
- 48. The storage andretrieval part is handled by the ‘web server’ Handling of multitudes of information is possible in client server model. Accommodates requests for the web information and defined by the domain name
- 49. Networking protocols Protocols linksthe clients and servers address issues handling requests and responses. HTTP provides a way of communication b/w web clients and servers Server needs web server s/w, HTTP Client requires a browser s/w – – Netscape Navigator, Internet Explorer
- 50. Information exchange onthe web It comes in four parts – Connection Client connect to specific web server – Request Client asks for a web resource it is looking for. Includes protocol to be used, the name of the object to be provided and information about how the server should respond to the client is also given
- 51. Response – Server deliversthe requested object, information, in a manner requested by the client – If the necessary data is not available, an error message is provided. Close – After the response to the request is complete, the connection b/w the client and server needs to be closed. Reopened on request.
- 52. Browsers A software programthat allows to access the graphical portion of the Internet i.e., WWW NCSA Mosaic – National Center for Supercomputing Applications. Two types – Txt based and GUI (Graphical User Interface)
- 53. Text Based Browsers –Lynx: it is basically a text based browser. Approach is provided through keyboard interaction. GUI Based Browsers: – Very user friendly, allows to access the multimedia formats online Netscape Navigator, Internet Explorer
- 54. Search Engines It isa program that searches through the Internet’s data. In the context of the web, a search engine is most often used in association with searching through databases of HTML documents
- 55. Components of SearchEngines Robot – Web wanderers, web crawlers or spiders. – Traverse the WWW looking for the information, moves from one web to another web document by referring to the hyper links. – It indexes the documents, validates of HTML, links, monitoring for new information and mirroring the web
- 56. Database: – Records allthe indexed information. – It includes web addresses, titles, headers, words, first lines, abstracts and full text in its lists. – It can store any where from a thousand millions of web pages. Agent – Role b/w original/sources and clients/users
- 57. Types of SearchEngines Individual Search Engines Subject Directories Meta Search Engines
- 58. Individual Search Engine Canbe full text or non-full text Robots scan a large part of the web while designated robots are programmed to scan only specific sites. Some cases generally the hits retrieved will be fewer in number In other cases, depth-orientated robots search deep into a document to pull out individual items and their respective links to other servers.
- 59. Subject Directories Hierarchical indexesor directories of Internet resources may be searched and browsed. Focus for providing information is by subject Subject directory serves as TOC and Search Engines are like Indexes of the book
- 60. Advantages – Useful inbrowsing subject information Limitations: – Frequency of updation is less and coverage is limited to subject.
- 61. Meta Search Engines Itis Search Engines of Search Engines It is a combination of a number of Search Engines. Advantage is that on submitting a search query, several search engines perform the search at a time.
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