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44212: Web-site Development How the Internet/Web Works Ian Perry Room:C49 Extension:7287

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Presentation on theme: "44212: Web-site Development How the Internet/Web Works Ian Perry Room:C49 Extension:7287"— Presentation transcript:

1 44212: Web-site Development How the Internet/Web Works Ian Perry Room:C49 Extension:7287

2 Ian Perry44212: Web-site Development: How the Internet/Web WorksSlide 2 How does the Internet work?  Just like any other Network! Hardware provides physical structure: cables (copper & fibre), hubs, switches, routers, servers, satellites, plus the client computers themselves. Software facilitates the exchange of data (communication) over physical network: Software that enables networking follows a set of rules; a protocol.

3 Ian Perry44212: Web-site Development: How the Internet/Web WorksSlide 3 What are Protocols?  Rules for communication to understand & act on messages sent/received, computers at both ends of the ‘conversation’ must agree on what a message means.  Description for each type of activity e.g. establishing a remote connection, exchanging , or transferring files, requires agreed definition of: the format that messages must take. how messages must be transmitted.

4 Ian Perry44212: Web-site Development: How the Internet/Web WorksSlide 4 ‘Snail-mail’ Protocols  The ‘Rules’ that govern how we address letters, and how the Post Office handles those letters: Mail Box Post Office Train/Van Post Office Destination The rules (protocols) of the Postal System ensure that a properly addressed letter (format) will reach its destination via a delivery route (transmission).

5 Ian Perry44212: Web-site Development: How the Internet/Web WorksSlide 5 Protocols = Interoperability n For the Internet to be really useful: –different types of computers, using different operating systems, must be able to connect, & communicate with each other. –they can, as long as they conform to Internet Protocols.

6 Ian Perry44212: Web-site Development: How the Internet/Web WorksSlide 6 The Internet Protocol  TCP/IP Transmission Control Program / Internet Protocol  a suite, or family, of protocols; enabling messages to be correctly formatted and transmitted from computer to computer irrespective of computer type/operating system.  How many of you can speak Esperanto? TCP/IP = Esperanto for Computers

7 Ian Perry44212: Web-site Development: How the Internet/Web WorksSlide 7 Other Internet Protocols  File Transfer Protocol (FTP) to transfer files between computers.  Simple Mail Transfer Protocol (SMTP) to send .  Post Office Protocol (POP3) for retrieval & management of .  HyperText Transfer Protocol (HTTP) to transmit Web-pages over the Internet.

8 Ian Perry44212: Web-site Development: How the Internet/Web WorksSlide 8 Internet = Client/Server Network  Client/Server? a networking model consisting of a series of requests and responses. Client Programs make requests & format responses Server Programs ‘answer’ requests & provide responses Very efficient in sharing a limited resource (i.e. Bandwidth) with many users: connections only formed ‘as-and-when’ required.

9 Ian Perry44212: Web-site Development: How the Internet/Web WorksSlide 9 Client/Server Transactions  File Transfer (via FTP) Client program contacts an FTP Server and requests transfer of a file; FTP Server responds by transferring the file to the Client’s computer.  (via SMTP & POP3) Client program allows user to interact with an e- mail Server to send (SMTP) and receive (POP3) electronic mail messages.  Web (via HTTP) Client program request the contents of an HTML page from a Web Server; and displays the result, as a Web-page, on the Client computer.

10 Ian Perry44212: Web-site Development: How the Internet/Web WorksSlide 10 Internet Addressing  People/Computers communicating via the Internet need to know where they are located, i.e. their ‘address’.  The term “address” is used somewhat loosely on the Internet, and might refer to: a ‘computer network’, a ‘computer’, a ‘software application’, a ‘file’, etc.

11 Ian Perry44212: Web-site Development: How the Internet/Web WorksSlide 11 IP Address = ‘Real Address’  All ‘intelligent devices’ on the Internet (i.e. every computer, router, switch, etc.) must have a unique IP Address.  An IP address consists of four numbers, between 0 and 255, separated by dots.  Sometimes called a ‘dotted quad’. e.g

12 Ian Perry44212: Web-site Development: How the Internet/Web WorksSlide 12 Domain Name = ‘Human-friendly’  Domain Name Servers maintain a distributed database; the Domain Name System (DNS)  Match ‘human-friendly’ Domain Names to ‘real’ IP addresses. e.g. the Domain Name: is a lot easier to remember than:

13 Ian Perry44212: Web-site Development: How the Internet/Web WorksSlide 13 Internet Domains  The Internet’s domain name system ‘describes’ a hierarchy of domains. Top-Level-Domains (sector/country).com,.edu,.co.uk, ac.uk, etc. Sub-Domains (organisation) ibm, mit, eyms, hull, etc. Servers (service) www, pop, ftp, etc.

14 Ian Perry44212: Web-site Development: How the Internet/Web WorksSlide 14 Addresses  Addresses identify both a person and the sub-domain of the Server that stores their messages, e.g.:  Reading from left to right: i.p.perry=mailbox for this Person/User. hull =who works for this Organisation. ac.uk =which is an Academic Organisation located in the United Kingdom.

15 Ian Perry44212: Web-site Development: How the Internet/Web WorksSlide 15 What is the Web?  Basic components are: a Client (i.e. Browser), requesting HTML documents. the Internet, providing a communications channel. a Server (i.e. Web Server), with access to a store of HTML documents.

16 Ian Perry44212: Web-site Development: How the Internet/Web WorksSlide 16 Web Addresses  Relies upon Uniform Resource Locators (URLs) protocol://server.sub-domain.top-level- domain/directory/filename  Example URL:  Often a URL does not need to include directory/filename:  URL might not ‘request’ an HTML document: ftp://src.doc.ic.ac.uk/

17 Ian Perry44212: Web-site Development: How the Internet/Web WorksSlide 17 Next Week’s Workshop  Next week’s Workshop asks you to locate & analyse the Web-sites of organisations that are ‘similar’ to ABM Car Sales. To see if anything can be learnt (borrowed?) from the experience (mistakes?) of others.  You have all read ABM Car Sales Case Study, haven’t you? If not, then make sure you do before next week.


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