INFS 321 Information Sources

Transcription

1 INFS 321 Information Sources Session 12 The Internet Lecturer: Prof. Perpetua S. Dadzie, DIS Contact Information: College of Education School of Continuing and Distance Education 2014/ /2017 godsonug.wordpress.com/blog

2 Session Overview At the end of the session, the student will be able to : Understand the Internet Types of Internet protocols Types of Browsers and navigation Prof. P.S.Dadzie, DIS Slide 2

3 Session Outline The key topics to be covered in the session are as follows: Topic One : Definitions and History of Internet Topic Two: Types of Internet Protocols Topic Three: Browsers and Navigation Prof. P.S.Dadzie, DIS Slide 3

4 Reading List UC Berkeley Finding Information on the Internet: A Tutorial ernet/about.html Prof. P.S.Dadzie, DIS Slide 4

5 Topic One DEFINITIONS AND HISTORY OF INTERNET Prof. P.S.Dadzie, DIS Slide 5

6 Definitions A global network connecting millions of computers. A collection of vast information sources of interlinked computer networks Network of Networks numerous networked computers connected together. No one in charge of Internet; organizations develop technical aspects of network and set standards 6

7 History of Internet Began September under auspices of Advanced Research projects Agency (ARPA). Dubbed ARPANET began with connection of one computer at UCLA college campus to an AT&T carrier service network. By end of year, ARPANET connected computers at four locations end of 1970, 13 sites ; end of 1973 ARPANET grown to forty sites and international in scope. In 1973, Vinton Cerf and Robert Kahn and supported by ARPA, established specification of transmission control protocol. (TCP)

8 History of Internet s universities began using Internet Protocol to connect local networks to the ARPANET. AĐĐess to PeŶtagoŶ s Đoŵputers oŷ ARPANET tightllj controlled, but university computers were permitted to communicate freely with one another. January 1978, TCP re-engineered into two parts : TCP and IP By January 1983, all networks required to utilize the TCP and IP protocols for data transmission.

9 History of the Internet 3 diversity of use posed security risks and in 1983, the military segment of ARPANET broke off and became MILNET In 1986, National Science Foundation (NSF) began NSFNET, a ďađkďoŷe that ĐoŶŶeĐted ŶatioŶ s five supercomputer centers at high speed. In 1995, NSFNET reverted to a research network and officially decommissioned. The Internet now private commercial enterprise, consisting of network of high-speed backbones maintained by carriers and Internet service providers. Currently, consortium of research universities working in partnership with industry and government to create even faster network named Internet2.

10 Topic Two TYPES OF INTERNET PROTOCOL Prof. P.S.Dadzie, DIS Slide 10

11 Types of Internet Protocols Protocols formal agreements on form and style of communication assure reliable information transfers ensure clear and unambiguous communications. Internet consists of protocols which allow users to search for and retrieve information

12 Types of Internet Protocols 2 Transmission Control Protocol/Internet Protocol (TCP/IP). Defines rules and procedures for transmitting information Information transmitted in packets Each packet contains addressing that identifies which computer sent packet and which computer will receive it

13 Protocols 3 packets also contain sequencing information that specifies order for reassembling when packets arrive at destination Message too long to fit in one packet, data gets divided into more than one packet. IP stands for Internet Protocol IP governs addressing Every computer on Internet has unique IP address. IP address consists of four numbers separated by periods. For example:

14 Protocols 4 File retrieval protocols earliest ways of retrieving information View names of files stored on serving computer, but no graphics and sometimes no description of a file's content Need advanced knowledge of files sought.

15 Protocols 5 FTP (File Transfer Protocol) one of first Internet services developed allows users to move files from one computer to another Using FTP program, user can logon to remote computer, browse through its files, download or upload files can be any type of file, user allowed to see file name no description of file content Encounter FTP protocol if you download any software applications from World Wide Web Many sites that offer downloadable applications use FTP protocol.

16 Protocols 6 Communications Protocols , newsgroups and chat messaging protocols allow users to communicate both asynchronously and synchronously (as with chatting in "real time"). main computer acts as a "post office" by sending and receiving mail for those who have accounts eg. software applications (MS Outlook, Eudora, etc.) or from Web based accounts (Yahoo, Hotmail). - example of asynchronous Internet communication. - provides the ability to access lists

17 Protocols 7 Listervs Listserv - list server ďuilt oŷ top of eŵail protođol work like electronic mailing lists, sending messages to people whose names are on list. join by ing message to it saying you want to subscribe. subscribe by filling out Web form at listserv s Webs site after subscription, whenever someone sends to listserv, receive copy in your . Likewise, when you send to listserv, everyone on listserv receives copy of your message. Eg. Information literacy listserv

18 Protocols 8 Usenet bulletin board or an list without subscription. Anyone can post message to or browse through Usenet newsgroup Usenet messages are retained on serving computer only for a predetermined length of time and automatically deleted list messages are retained on serving computer until account holder downloads them Newsgroups Yahoo newsgroups Google newsgroups Interbulletin newsgroups

19 Protocols 9 IRC (Internet Relay Chat) allows for synchronous communication: users communicate in "real time" or simultaneously See response to typed message by several people at same time requires a special software application that can be downloaded from the Web, generally for free. Chat Internet Relay Chat (IRC) Help page AIM Google Talk Meebo

20 Protocols 10 Multimedia Information Protocol Hypertext transfer protocol a.k.a. "The Web most popular way to provide and obtain information from Internet Web offers not only access to files to download, but offers a series of connecting hyperlinks. ŵost distiŷguishiŷg feature of Weď is series of "tags used to encode and format text, graphics, animation, sound, and other types of files Tags called HTML (HyperText Markup Language) HTML files can see the "source" HTML coding for any Web page by choosing to "View Source" from your browser's menu bar. Most browsers allow for access through FTP, Gopher, telnet, and as well as through the hypertext transfer protocol,

21 Topic Three BROWSERS & NAVIGATION Prof. P.S.Dadzie, DIS Slide 21

22 Browsers and Navigation Browser application to view files on World Wide Web. text or terminal-based browsers (such as Lynx) that allow you to view only text of file on Web. Most browsers now graphical browsers to view text, graphics, other multimedia information. most widely used MS Internet Explorer, Netscape, Firefox. some Web pages created for specific browsers, Web pages may look different when accessed by different browsers.

23 Navigation Uniform Resource Locator (URL) "address" of computer connected to Internet. address or location box at top of browser. general format of Web address: http - "hypertext transfer protocol", protocol for World Wide Web Other eg. ftp:// OR gopher://gopher.uzxy.edu first part of URL before colon tells browser what type of protocol to use.

24 Navigation 2 After first dot in URL, is name of particular computer followed by another dot known as domain (.com,.edu,.gov, etc.) domain indicates type of group or organization using address..com Commercial site. information provided by commercial interests is generally going to shed positive light on product it promotes. edu Educational institution. Information from sites within this doŵaiŷ ŵust ďe edžaŵiŷed verlj ĐarefullLJ. Could ďe studeŷts personal web sites.gov Government. information is considered to be from credible source.

25 Navigation 3.org a non-profit organization. information in these types of sites is credible and unbiased, but there are examples of organizations that strongly advocate specific points of view over others.mil Military. used by various branches of Armed Forces of the United States..net Network. acts as a catch-all for sites that don't fit into any of preceding domain suffixes. Information from these sites should be given careful scrutiny.

26 Activity Briefly discuss any three Internet Protocols that you know of

27 References UC Berkeley Finding Information on the Internet: A Tutorial net/about.html