Information and Communication Technology Fundamentals Credits Hours: 2+1 Instructor: Ayesha Bint Saleem

NETWORKS - III 2A-2

Presentation Credits “Introduction to Computer” by Peter Norton “Using Information Technology” by Williams and Sawyer “Introduction to Information Technology” by V. Rajaraman

The Internet’s History 1969 – ARPANET Developed by the Department of Defense Connected universities and defense bases 1973 – ARPANET connects to Europe 2A-4

ARPANET A-5

The Internet’s History Mid-1980s – NSFNet Network between supercomputers Internet was the link to ARPANET No commercial traffic allowed 1990s ARPANET shut down NSFNet abandoned Commercial networks take over 2A-6

Today and the Future Thousands of networks Hundreds of millions of users Huge co-operative community with no central ownership Anybody can access it 2A-7

THE INTERNET’S MAJOR SERVICES 2A-8

1. Stands for electronic mail One of the “killer application” for the internet Use client E.g. outlook express Web based service 2A-9

(contd) addresses Unique id server Or service provide e.g hotmail.com 2A-10

(contd) Mail Server When you send an , message is stored on server, until the recipient can retrieve it Many mail server use Post Office Protocol (POP) Also called POP servers Internet Message Access Protocol (IMAP) Used by local clients to retrieve from servers 2A-11

(contd) Mail Server Simple Mail Transfer Protocol (SMTP) Used by mail servers to send/receive messages 2A-12

(contd) features Audio, Video, Images can be sent as attachment Reply, Reply All, Forward, Delete, CC, BCC Listserv Lists of addresses Each address gets the 2A-13

Spam: Unwanted Junk Delete without opening the message Never reply to a spam message!

2. Information Browsing “To retrieve and display specified information stored in one or more computers connected to a computer network” Implies interactivity 2A-15

Menu Based Browsing Earliest browsers were menu based Gopher Menu is presented User selects a menu item Gopher software will search table to find out where the required information is stored May be on another computer Retrieve information and display Look up process hidden from user 2A-16

Hypertext Based Browsing A system in which documents scattered across many Internet sites are directly linked, so that a word, phrase or an image in one document becomes a connection to a document in a different place User clicks a word/image Document is retrieved 2A-17

Hypertext Based Browsing (contd) Hypertext systems provide an easy way to manage large collections of data scattered world wide Documents can be interconnected Facilitates non-linear reading 2A-18

World Wide Web Billions of documents, stored in different places, linked together in some manner “Web” of interconnected information Collection of documents and links spread all over globe “World wide web” Developed in 1993 by Tim-Berners Lee 2A-19

How the web works? HyperText Transfer Protocol (HTTP) Special protocol used by web to supports hypertext documents HyperText Markup Language (HTML) Hypertext documents are encoded in HTML A notation to mark keywords in documents Allows author to embed hypertext links 2A-20

How the web works? (contd) Uniform Resource Locator (URL) Method of naming documents or places on the Websites String of characters that identifies the type of document, the computer the document is on, the directories and subdirectories the document is in, and the name of the document. 2A-21

How the web works? (contd) Uniform Resource Locator (URL) (contd) Protocol : http Domain name: Directory name: abli File name: index.htm 2A-22

How the web works? (contd) Hypertext Browser Marc Anderson developed Mosaic web browser Some popular browsers today are Internet Explorer Firefox Netscape communicator (successor to Mosaic) URLs can be typed in a browser 2A-23

How the web works? (contd) Web pages and Websites A hypertext document is called a web page Collection of related web pages is a website A Web page is a document on the World Wide Web on a Website that can include text, pictures, sound, and video 2A-24

How the web works? (contd) Helper Applications Many websites feature multimedia content Browsers alone cannot display every type of content Multimedia files requires special applications in order to be played in real time Also called plug-in applications 2A-25

How the web works? (contd) Helper Applications (contd) Plug-ins support several types of content including audio and video streaming Content is sent in a continuous stream (still in packets) from web server to browser Plug-in receives first portion and buffers it First portion is played while next portion is buffered 2A-26

Streaming Audio 2A-27

Some Common Plug-ins

Searching the World Wide Web The Web is unorganized Directories Categorize the Internet Search engines Find sites by keyword 2A-29

Resource Directories Directory separates subjects in categories Typically employ human experts 2A-30 Searching the World Wide Web

Resource Directory 2A-31

Searching the World Wide Web Search Engine Search using keywords E.g. Google.com Offer advanced options as well Do not use humans to index documents Automated programs called “web crawlers” browse world wide web in a systematic manner Pick keywords Create index 2A-32

Searching the World Wide Web Meta Search Engine Uses multiple search engines simultaneously to lookup your keyword Searhenginewatch.com News about different search engines 2A-33

Other Internet Features File Transfer Protocol (FTP) Allows you to access any computer connected to the internet and download files FTP Site is a collection of files housed on an FTP Server ftp://ftp.xcollege/admission-rules Remote server, ftp.xcollege, will prompt for a login id and passwordftp.xcollege Public FTP archives accept “anonymous” as user id 2A-34

Telnet Logging on to a remote computer and using its facilities telnet: or IP address Login ID and Password 2A-35 Other Internet Features

2B-36 Other Internet Features Internet Relay Chat (IRC) Real time communication system Multi-users with many channels (rooms) Channels are dedicated to a topic All users can read the comments

2B-37 Other Internet Features Instant messaging (IM) Private, real-time communication Message sent only to listed users Buddy lists contain IM names

2B-38 Other Internet Services Peer-to-peer (P2P) services User computers are connected together No centralized organization Users can communicate directly Users can share files

2B-39 Other Internet Services Internet Radio Audio from radio station is stored in high speed disk memory of server Person wishing to listen to broadcast logs on to the server and listens to it by downloading it using internet Intermittent reception due to packet switching Start with delay

2B-40 Other Internet Services Internet Telephony Normal telephony is circuit switched Expensive Talk over packets Low cost Quality may not be the best Voice over IP (VoIP)

2B-41 Other Internet Services Video Conferencing Voice + Video over Internet Different standards exist