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Explore the intricacies of web server technology, from the client-server model to application layer protocols and DNS hierarchy. Learn how web browsers and servers operate and delve into the market share of top web servers. Gain insights into URL formats, data transmission over the Internet, and the role of DNS in converting IP addresses to domain names.
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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.eApache • 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 webbrowser (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 • <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 • 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