Web Server Technology Unit 10 Website Design and Development

The Internet The Internet is a global WAN – a network of networks It is based on a client-server network model Hundreds of thousands of web-servers throughout the world provide resources and services to millions of clients Communication between computers on the Internet largely takes place using the TCP/IP protocol, although other protocols, such as FTP, are also used Unit 10 Website Design and Development

How the web works The client-server model Client and server operate on machines which are able to communicate through a network The server waits for requests from a client Server receives a requests from a client Performs a the requested work Or lookup the requested data And send a response to the client Servers: file servers, web servers, name servers Clients: browsers, email clients Unit 10 Website Design and Development

Web browsers and servers A browser: is a program that can retrieve files from the world wide web and render text, images, or sounds encoded in the files. i.e. IE, Chrome, Mozilla A web server: is an application which waits for client requests, fetches requested documents from disk and transmits them the client. i.e Apache Microsoft (IIS) Sun What is the market share of these Web Servers? Unit 10 Website Design and Development

The Application Layer Protocols Layer 7 of the OSI 7 Layer model is called the application layer. This layer defines Application layer protocols. The most common application layer protocols used between clients and web servers include: HTTP (Hyper Text Transfer Protocol) HTTPS (Hyper Text Transfer Protocol Secure) FTP (File Transfer Protocol) Unit 10 Website Design and Development

URL When a website or page is requested the URL (Uniform Resource Link) is typed into the browser. A URL tells a web browser (e.g. Firefox, Internet Explorer) where to look for a specified resource Clicking a hyperlink sends a HTTP request to the host web server (HTTP is the is the transfer protocol used for the transfer of pages on the Web. It works in conjunction with TCP/IP) The URL will consist of http://www.hastingsonline.ac.uk/index.html:80 Protocol Server Name The resource (file) *The Port Number What do you remember about DNS? Unit 10 Website Design and Development

url format http://sussexcoast.ac.uk/index.html <scheme>://<server-domain-name>/<pathname> <scheme> which protocol to use http: in general file: which tells the client the document is on a local machine ftp: file transfer protocol <server-domain-name> identifies the server system i.e. www.sussexcoast.ac.uk <pathname> tells the server where to find the file http://sussexcoast.ac.uk/index.html Unit 10 Website Design and Development

Data transmission over the Internet – IP and DNS Each computer on the Internet has its own unique IP address (e.g. 193.61.29.155) Users can not possibly remember long, abstract strings of numbers like IP addresses To make it easier to remember, a Domain Name System (DNS) is used to convert IP addresses to domain names The DNS has a hierarchical structure with several levels The root domain (Internet root domain) Top-level domains (e.g. .edu, .com, .gov, etc.) Second-level domains (e.g. Amazon, Birkbeck, Google) Third level domains (sales, finance, Home Office) Unit 10 Website Design and Development

DNS Hierarchical Structure Unit 10 Website Design and Development

DNS TLD’s Examples of top level domains include: http://www.iana.org TLD’s (Top Level Domains) know about the location of a DNS server for individual domains but only forward the request rather than resolve the request. Examples of top level domains include: .com –commercial companies (Verisign) .org –non-commercial (public interest registry) .gov –US government use. .edu –education use. .ac.uk –UK academic/educational use. http://www.iana.org Unit 10 Website Design and Development

DNS CCTLD’s CCTLD’s (Country Code Top Level Domains) Examples of CCTLD’s and their allocation. .au –Australia .bb –Barbados .ca –Canada .de –Germany .is –Iceland http://www.iana.org Unit 10 Website Design and Development

Task Carry out research into: The top 3 web servers with the highest market share Give advantages and disadvantages of each What are web hosting companies and what services can they offer The advantages and disadvantages of running web servers vs the use of web hosting companies. Share sources of information with a short summary on to your shared workspace Unit 10 Website Design and Development