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Dr Alexiei Dingli

Introduction to Web Science

Web 1.0

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• Packet switching network

• IP Addressing

• Internet Applications

• The WWW and markup

• Searching the WWW

• Intelligent Agents

• Internet Governance

Introducing Web 1.0

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• Local area network (LAN)

– Network of computers located close together

• Wide area networks (WANs)

– Networks of computers connected over greater distances

• Circuit

– Combination of telephone lines and closed switches that connect them to each other

Packet-Switched Networks (1)

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• Circuit switching is used in telephone communication

• The Internet uses packet switching

• Packet switching needs computers called ‘routers’ and the programs called ‘routing algorithms’

Packet-Switched Networks (2)

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Packet-Switched Networks (3)

• Information is divided into packets

• It is passed from node to node

• It is recomposed as one chunk on the destination server

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• Routing computers– Computers that decide how best to forward

packets

• Routing algorithms– Rules contained in programs on router computers

that determine the best path on which to send packets

– Programs apply their routing algorithms to information they have stored in routing tables

Routing Packets

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• Communications protocol suite

– Packet switched protocol• No end-to-end connection is required• Each message broken down into small pieces called packets• Packets possibly routed to destination over different paths

– Transmission Control Protocol (TCP)• Breaks messages into packets• Numbers packets in order• Reorders packets at the destination

– Internet Protocol (IP)• Routes packets to the proper destination

TCP/IP

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Open Systems Interconnections Model

OSI Model (also called TCP/IP protocol suite) layers (from the highest to the lowest):

7 Application

{ HTTP, SMTP, FTP, Telnet, SSH, Whois, etc.

6 Presentation

5 Session

4 Transport TCP, UDP

3 Network IP

2 Data Link Ethernet

1 Physical Wire, Radio, Fibre Optic

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• Internet addresses are based on a 32-bit number called an IP address

• IP addresses appear as a series of up to four separate numbers delineated by a period

• An address such as 126.204.89.56 uniquely identifies a computer connected to the Internet

• IP Subnetting conceptually divides a large network into smaller sub-networks

IP Address

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IP Classes (1)

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IP Classes (2)

Class Leading Value

Network Numbers

Addresses Per Network

Class A     0     126     16,777,214

Class B     10     16,384     65,534

Class C     110     2,097,152     254

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Subnetting

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• Explosion in size of IP routing tables.

• Every time more address space was needed, the administrator would have to apply for a new block of addresses.

• Any changes to the internal structure of a company's network would potentially affect devices and sites outside the organization.

• Keeping track of all those different Class C networks would be a bit of a headache in its own right.

Without subnetting …

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• Better Match to Physical Network Structure

• Flexibility

• Invisibility To Public Internet

• No Need To Request New IP Addresses

• No Routing Table Entry Proliferation

Benefits of Subnetting

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• Network Layer• Developed in 1994

• Will replace the IP Vr4 standard– limits on network addresses will eventually lead to

exhaustion of available addresses (by 2023)– supports only 4,294,967,296 addresses (32bits)

• Improvements include– providing future cell phones and mobile devices their own

unique & permanent addresses– supports about 3.4 × 1038 (128bits)

IP Vr6 (or IP Next Generation)

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• A Uniform Resource Locator (URL) consists of names and abbreviations that are much easier to remember than IP addresses

• The HTTP protocol defines how an Internet resource is accessed

• An address such as www.microsoft.com is called a domain name

• Domain Name System (DNS)– A database of Internet names– DNS Servers convert Internet names to IP addresses– Top level domains

Domain Names

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Top-Level Domain Names

• Internet Corporation for Assigned Names and Numbers (ICANN)

– Responsible for managing domain names and coordinating them with IP address registrars

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• The web was not an ‘open’ place

• One company available where you could buy a .com, .net or .org domain

• Price of 100 dollars and a two year minimum

• Back then, there was a big chance you would be able to buy a dictionary word as .com

• In 2000, they lost the monopoly position and domain prices dropped over 95%

• Since then innovation halted and Network Solutions became one of the thousands anonymous domain registrars

Domain Name case study

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• E-Mail

• File transfers

• Instant messaging (IM)

• Newsgroups

• Streaming audio and video

• Internet telephony

• World Wide Web (WWW)

Internet Applications

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• Most popular and widely used Internet application

• 30 billion e-mails sent every day– Spam – junk e-mail messages– Spam costs corporate America $9 billion per year

• Every e-mail message contains head that describes source and destination for the message

• E-mail messages are text, but may have attachments of many types of digital data– Viruses often transmitted via e-mail

E-Mail

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• E-mail is sent across the Internet is managed and stored by mail servers

• Simple Mail Transfer Protocol (SMTP) is the standard to send mails to the server

• Post Office Protocol (POP) is the standard to get mails from the server

• The Interactive Mail Access Protocol (IMAP) is a newer e-mail protocol

SMTP, POP, and IMAP (1)

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SMTP, POP, and IMAP (2)

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• Use complex email addresses rather than name and surname combination– Why? Bots? Name Directories?

• Control exposure of email address– How? Java script? JPEG?

• Use multiple email addresses for different purposes– In what occasions?

• Use content-filtering software– black list spam filter – white list spam filter – challenge response using graphical challenges ?

Controlling Spam

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• Hotmail (1995)

• First place to get a free email address, disconnected from an ISP

• 4 years later, 30 million people worldwide were exchanging @hotmail email addresses

• Bought by Microsoft in 1998 for just 400 million dollars

• 2007 the end of Hotmail– transformation to “Live” mail to become an

integrated part of the Microsoft’s “Live” family

E-Mail Case Study

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• File transfer protocol (FTP)– Protocol providing for transmission of a file between

an Internet server and a user’s computer

• Peer-to-peer (P2P) file sharing– Share data from one computer to another– Every user can be a server– Napster

• Kazaa• Gnutella• Torrent

– With P2P, every user on the network can make data available to every other user on the network

File Transfers

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• Allows user to create a private chat session with another user

• IM started with AOL

• IM sneaking into corporate networks

• Many Web-based companies use IM technology for customer service– eBay

Instant Messaging

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• ICQ abbreviation of “I seek you”

• 1996 first easy to use instant messenger program where you could add friends to your list, and see if they were online

• Back then it was revolutionary for the masses and it became the ‘application’ everybody had installed

• Acquired by AOL in June 1998 for a whopping $287 million  

• Eventually the program got too many additional features that made the application heavy and unorganized

• Competition of AOL IM, Yahoo IM, and MSN Messenger increased, and friends on your ICQ-list left the application eventually resulting in a mass abandoning of the network

ICQ case study

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• Online, bulletin board discussion forums

• Users post and read messages

• More than 100,000 newsgroups

• Millions of newsgroup readers

• Important information resource, especially for technical issues and products

• Newsgroup messages distributed using open standard – Many are uncensored

Usenet Newsgroups

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• Creating and sending audio and video files

– Sports• Basketball at sports.yahoo.com• Major league baseball

– News• Fox News• CNN radio

– Business• ZDNet

– Education• Warriors of the Net

Streaming Audio and Video

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• Voice-over Internet Protocol (VoIP)

• Use your computer like a telephone

• Software connects computers via the Internet and transmits voice data

• Savings comes from eliminating toll charges between locations

Internet Telephony

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Internet TV

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• Collection of hyperlinked computer files on the Internet

• Client-server application– Web servers– Web browsers as clients

• WWW standards– Hypertext markup language (HTML)

• Current standard for writing Web pages• Tags in HTML instruct the client browser how to format and display the

Web page content

– Hypertext transfer protocol (HTTP)• Establishes a connection between Web server and client

– Extensible markup language (XML)• A meta-markup language• Gives meaning to the data enclosed within XML tags

The World Wide Web

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• Create your own free homepage on the web

• 1997 Fifth most popular website, with over 500,000 homepages created

• Yahoo bought Geocities two years later for $3.57 billion dollars and started to actively commercialize the homepages with various advertising types that resulted in their death sentence

• ‘Real’ web hosting becoming affordable for anybody, the need for free homepages in this form vanished

Website case study

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• SGML is a rich meta language that is useful for defining markup languages

• HTML is particularly useful for displaying Web pages

• XML defines data structures for electronic commerce (and much more …)

Overview of Markup Languages

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Development of Markup Languages

http://www.w3.org/

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• The ISO adopted SGML standard in 1986

• SGML is nonproprietary and platform-independent

• SGML supports user-defined tags and architecture to complement the required richness of documents

Standard Generalized Markup Language

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• XML is a descendant of SGML

• XML allows designers to easily describe and deliver structured data from any application in a standard, consistent way

• XML can be embedded within an HTML document

• XML allows you to create your own customized markup language.

Extensible Markup Language

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• Tag – a piece of Markup– An opening tag <name>– A closing tag </name>

• Element – well formed usage of tags– <name>Alexiei</name>

• Attribute – properties– <name length=“7”>Alexiei</name>

• Rules to keep XML well formed1. Can be nested but not overlapping 2. Case sensitivity3. Quoted attributes4. Required end tag

• Short hand– <abc></abc> is equivalent to <abc/>

Learn XML in a slide

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<book>E-Commerce</booK>

<book pages=100>E-Commerce</book>

<book pages=“100”><title>E-Commerce</book></title>

<book pages=“100”><title>E-Commerce</title></book>

<book pages=“100”><title>E-Commerce</title><author>

<name>Gary</name><surname>Schneider</surname>

</author></book>

Some XML examples

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<book>E-Commerce</booK>

<book pages=100>E-Commerce</book>

<book pages=“100”><title>E-Commerce</book></title>

<book pages=“100”><title>E-Commerce</title></book>

<book pages=“100”><title>E-Commerce</title><author>

<name>Gary</name><surname>Schneider</surname>

</author></book>

Some XML examples

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Processing a Request for an XML Page

• Why going through all this hassle?• How would you go about displaying HTML on a

– PC– Handheld – Mobile

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• Tim Berners-Lee invented HTML

• HTML is a document production language that includes a set of tags that define the format and style of a document

• HTML is based on SGML

• HTML is an instance of one particular SGML document type – Document Type Definition (DTD)

Hypertext Markup Language

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• An HTML document contains both document content and tags

• The tags are the HTML codes inserted in a document to specify the format on screen

• Each tag is enclosed in brackets (< >)

• Most tags are two-sided – opening and closing tags

• Well formed tags, bots, meta tags?? Why are they important?

HTML Tags

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• Hyperlinks are bits of text that connect the current document to:– Another location in the same document– Another document on the same host machine– Another document on the Internet– Can they link to a toaster at home?

• Hyperlinks are created using the HTML anchor tag

• Two popular link structures:– Linear hyperlink structure– Hierarchical hyperlink structure

HTML Links

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• HTML version 1.0 was introduced in 1991

• HTML 2.0 was released in Sept. 1995

• HTML 3.2 was introduced in 1997

• HTML 4.0 was released by W3C in Dec 1997

• HTML 4.01 was released in Dec 1999

• XHTML 1.0 became a W3C recommendation in Jan 2000

HTML Version History

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• Low end editor displays HTML code on the screen and allow you to insert HTML tag pairs by clicking selected buttons

• High end editor are Web site builder programs, they provide a rich environment that displays the Web page, not the HTML code

• Microsoft FrontPage and Macromedia Dreamweaver are examples of Web site builders

HTML Editors (1)

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HTML Editors (2)

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• HTML and XML only display and exchange data• No interactivity; no processing of data

• Scripting languages– Provides basic interactivity

• Rollovers• Crawling text

– JavaScript– VBScript

• Full-featured Web programming– Java– Client side scripting or browser side scripting– Applets– J2EE

• Common Gateway Interface (CGI)– Allows passing of data between a static HTML page and a

computer program

Static versus Dynamic Pages

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• Most data on the Internet is part of the WWW

• Search engines – large databases that index WWW content

• Building the search engine database– Submit a site to the search engine administrator for listing

– Spiders• Metatags

– Google– Yahoo

Searching the WWW

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• A search engine is a special kind of Web page software that finds other Web pages that match a word or phrase you entered

• A Web directory is a listing of hyperlinks to Web pages that is organized into hierarchical categories Eg: http://directory.google.com/

• Search engines contain three major parts: spider, index, and utility

Search Engines

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Popular Search Engines

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Spiders and Crawlers

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Indexing

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• Search engine AltaVista was the Google of the last millennium

• First real effort to index the World Wide Web

• One of the few search engines that actually came up with good search results

• Had a hard time fighting spam listings in their results

• While spam grew logarithmic in Altavista, some company named Google found a way to prioritize web pages more intelligently, and thus keep spam out better

Search Engine case study

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• PageRank relies on the uniquely democratic nature of the web by using its vast link structure as an indicator of an individual page's value

• Google interprets a link from page A to page B as a vote, by page A, for page B

• But Google looks at more than the sheer volume of votes, or links a page receives; it also analyzes the page that casts the vote

• Votes cast by pages that are themselves "important" weigh more heavily and help to make other pages "important."

Case Study: ’s PageRank

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• An intelligent agent is a program that performs functions such as – information gathering, – information filtering, – mediation running, – in the background on behalf of a person or

entity

• What agents can you think of?

Intelligent Agents

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• Search Agents– Improve your information retrieval on the Internet – Used to find pages on the Web easily and quickly

• Meta Agents, Specialised (MP3), etc

• Web Agents– Improve browsing experience

• Automate form filling, off-line browsing, etc

• Monitoring Agents– Monitor web sites or specific themes – Used to get automatic alerts about the latest news

Intelligent Agents (2)

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• Virtual Assistants– Artificial life– Characters, plants, animals or people living on your desktop

• Shop Bots– Allow users to compare prices on the Internet– Find the best price for books, CDs, movies, etc.

• Webmastering Agents– Make it easy to manage a Web site and make it more effective– Monitor broken links, content gathering etc.

Intelligent Agents (3)

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• Other agents …

– Development agents• Used to develop other agents

– Games agents• Used in games

Intelligent Agents (4)

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Ms Dewey not your ordinary search agent!

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• Internet Engineering Task Force (IETF)– Works in groups to develop standards

• Internet Engineering Steering Group (IESG)– Approves or disapproves standards developed by the

IETF

• Internet Architecture Board (IAB)– The oversight authority for the standards development

process

• World Wide Web Consortium (W3C)– Promotes the WWW and develops new web technologies

and standards

Internet Governance

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• We’re all very familiar with Web 1.0

• But what makes Web 2.0?

• Next lecture …

Conclusion

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Questions?