Oct 15, Internet : the vast collection of interconnected networks that all use the TCP/IP protocols

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1 E-Commerce Infrastructure II: the World Wide Web The Internet and the World Wide Web are two separate but related things Oct 15, Outline The Internet and the WWW Routing and addressing packets services Markup languages Intranets and extranets Connectivity Semantic Web Oct 15,

2 Learning outcomes Be able to: Explain how packet-switched networks are combined to form the Internet Explain how Internet protocols and Internet perform addressing Explain the differences among Internet, internets, intranets, and extranets Discuss about markup languages and the Web Discuss about the Semantic Web Oct 15, From the Internet to the WWW-1/2 Internet : the vast collection of interconnected networks that all use the TCP/IP protocols internet: network of computers connected to each other which are not part of the Internet as they don t use a TCP/IP protocol. intranet: a private network inside a company or organization that may use the same kinds of software applications that you could find on the Internet, but it is only for internal use. An intranet may be on the Internet (though gateways) or may simply be a network. Oct 15,

3 From the Internet to the WWW-2/2 World Wide Web (WWW): system of Internet servers that support documents formatted in a markup language called HTML (HyperText Markup Language). This language supports linking a document to other documents, as well as linking to graphics, audio, and video files. The WWW is an information-sharing model that is built on top of the Internet. The WWW uses the HTTP protocol to transmit data. E-commerce services, which use HTTP to allow applications to communicate in order to exchange business logic, use the Web to share information. The WWW is just one of the ways that information can be disseminated over the Internet. The Internet, not the Web, is also used for , which relies on SMTP and FTP. Oct 15, Packets, Routing and Addressing -1/11 Four key rules have contributed to the success of the Internet. Independent networks should not require any internal changes to be connected to the network. Packets that do not arrive at their destinations must be retransmitted from their source network. Router computers act as receive-and-forward devices; they do not retain information about the packets that they handle. No global control exists over the network. Oct 15,

4 Packets, Routing and Addressing -2/11 The Internet uses packet switching: Files are broken down into packets that are labeled with their origin, sequence, and destination addresses. This fact has very important consequences for both the performance and the security of e-commerce systems Oct 15, Packets, Routing and Addressing -3/11 The programs on routers use routing algorithms that call upon their routing tables to determine the best path to send each packet. When packets leave a network to travel on the Internet, they are translated into a standard format by the router. These routers and the telecommunication lines connecting them are referred to as the Internet backbone. Between seller and customer there are several other actors who have a role to play Oct 15,

5 Packets, Routing and Addressing -4/11 Router-based architecture of the Internet Oct 15, Packets, Routing and Addressing -5/11 Internet Protocols common language rules governing data exchange between two communicating entities layers in a station from station to station or network to network 3 key elements to consider syntax semantics timing Oct 15,

6 Packets, Routing and Addressing -6/11 syntax includes data format signal levels semantics includes control information e.g. coordination and error handling timing includes speed matching sequencing Oct 15, Packets, Routing and Addressing -7/11 TCP/IP protocol of internet Transmission Control Protocol / Internet Protocol simple and effective most types of network but does not include many security features Oct 15,

7 Packets, Routing and Addressing -8/11 TCP Controls disassembly of a message or a file into packets before transmission over Internet Controls reassembly of packets into their original formats when they reach their destinations IP Specifies addressing details for each packet OSI Reference Model Application Presentation Session Transport Network Data link Physical TCP, Transport Control Protocol IP, the Internet Protocol Logical link control Medium access control Physical TCP/IP IEEE 802 Reference Model Oct 15, Packets, Routing and Addressing -9/11 Hypertext Transfer Protocol (HTTP) is the set of rules for delivering Web pages over the Internet HTTP uses the client/server model The client opens an HTTP session and sends a request to a server The server returns an HTTP response message which contains data. After this, they forget about each other this has very significant implications for Web (and e- commerce) application development. Oct 15,

8 Packets, Routing and Addressing -10/11 IP addressing: 32-bit number to identify the computers connected to the internet (2 32 4billion) Base 2 (binary) number system: Used by computers to perform internal calculations Subnetting: Use of reserved private IP addresses within LANs and WANs to provide additional address space Private IP addresses: Series of IP numbers not permitted on packets that travel on the Internet Network Address Translation (NAT) device: Used in subnetting to convert private IP addresses into normal IP addresses Oct 15, Packets, Routing and Addressing -11/11 Top-level domain This has implications for e-commerce with regard to customer assumptions about you and significant costs! Oct 15,

9 Electronic mail ( ): Must also be formatted according to common set of rules server: Computer devoted to handling client software: Used to read and send e- mail; Example: Microsoft Outlook, Netscape Messenger Mail Protocols: Simple Mail Transfer Protocol (SMTP)- Specifies format of a mail message; Post Office Protocol (POP): POP message can tell the server to send mail to user s computer and delete it from server, or send mail to user s computer and not delete it, or simply ask whether new mail has arrived Oct 15, Markup Languages and the Web-1/6 Text markup language Specifies set of tags that are inserted into text Standard Generalized Markup Language (SGML) Older and complex text markup language A meta language World Wide Web Consortium (W3C) Not-for-profit group that maintains standards for the Web Oct 15,

10 Markup Languages and the Web-2/6 Oct 15, Markup Languages and the Web-3/6 Hypertext Markup Language (HTML) markup language used to create documents on the Web today HTML tags: Interpreted by Web browser and used by it to format the display of the text HTML Links Linear hyperlink structure Hierarchical hyperlink structure Oct 15,

11 Markup Languages and the Web-4/6 Scripting languages and style sheets Most common scripting languages JavaScript, JScript, Perl, and VBScript Cascading Style Sheets (CSS) Sets of instructions that give Web developers more control over the format of displayed pages Style sheet Usually stored in a separate file Referenced using the HTML style tag Oct 15, Markup Languages and the Web-5/6 Extensible Markup Language (XML) : Uses paired start and stop tags Includes data management capabilities that HTML cannot provide Differences between XML and HTML XML is not a markup language with defined tags XML tags do not specify how text appears on a Web page Oct 15,

12 Markup Languages and the Web-6/6 Processing a Request for an XML Page Oct 15, Intranets and Extranets -1/3 Intranet An intranet is an interconnected network (or internet small i ) that does not extend beyond the organization that created it Intranets are an extremely popular and lowcost way to distribute corporate information An intranet uses Web browsers and Internetbased protocols (including TCP/IP, FTP, Telnet, HTML, and HTTP) and often includes a firewall Oct 15,

13 Intranets and Extranets -2/3 Extranet Extranets are intranets that have been extended to include specific entities outside the boundaries of the organization (business partners, suppliers, etc.) An extranet can be a public network, a secure (private) network, or a virtual private network (VPN). Oct 15, Intranets and Extranets -3/3 A public network is any computer or telecommunications network that is available to the public A private network is a private, leased-line connection between two companies that physically connects their intranets to one another A VPN extranet is a network that uses public networks and their protocols to send sensitive data to partners, customers, suppliers, and employees using a system called IP tunneling or encapsulation Oct 15,

14 Connectivity Large firms that provide Internet access to other businesses are called Internet Access Providers (IAPs) or Internet Service Providers (ISPs) The most common connection options that ISPs offer to the Internet are telephone, broadband, leased-line, and wireless Bandwidth is the amount of data that can travel through a communication line per unit of time Bandwidth can differ for data traveling to or from the ISP Oct 15, The Semantic Web-1/3 The Semantic Web provides a common framework that allows data to be shared and reused across application, enterprise, and community boundaries. It is a collaborative effort led by W3C with participation from a large number of researchers and industrial partners. It is based on the Resource Description Framework (RDF), which integrates a variety of applications using XML for syntax and URIs for naming. [W3C 2004] "The Semantic Web is an extension of the current web in which information is given well-defined meaning, better enabling computers and people to work in cooperation." [Tim Berners-Lee, James Hendler, Ora Lassila, The Semantic Web, Scientific American, May 2001] Oct 15,

15 The Semantic Web-2/3 The Resource Description Framework (RDF) integrates a variety of applications from library catalogues and world-wide directories to syndication and aggregation of news, software, and content to personal collections of music, photos, and events using XML as an interchange syntax. The RDF specifications provide a lightweight ontology system to support the exchange of knowledge on the Web. Oct 15, The Semantic Web-3/3 Semantic Web Project by Tim Berners-Lee If successful Would result in words on Web pages being tagged (using XML) with their meanings Resource description framework (RDF) Set of standards for XML syntax Ontology Set of standards that defines relationships among RDF standards and specific XML tags Oct 15,

16 Summary Packet-switched networks TCP/IP Protocol suite used to create and transport information packets across the Internet IP addressing and domain names POP, SMTP, and IMAP Protocols that help manage Markup Languages and the Web Hypertext Markup Language (HTML) Extensible Markup Language (XML) The Web and the Semantic Web Oct 15,