The Web - World Wide Web

Model Client/Server

The Web uses the internet network to create a global system of information. For the functionment of the web, we talk about a Client-Server architecture :

- A web page, identifiable via its URL is stocked on a server

- A client (user), communicating with this server thanks to a web browser to obtain a copy of the wished webpage

client/server schema

HTTP Request

The communication Client-Server is possible thanks to the HTTP protocol. It defines a set of requests that indicates the action that we want to execute.

- The client sends to the server an HTTP request containing the URL of the wished webpage : - In case of error, the server returns an error code. The most known is code 404 Not Found, sent when something couldnt be found. - If the server holds the matching page, it returns an HTTP response with the metadatas of the document aswell as its HTML content. schema http request

The performances of web sites and applications can be significantly upgraded by reusing ressources previously collected. For that, web browsers uses the "caching" of every uploaded documents via the HTTP protocol by the user. This cache is used to render navigation-available visited documents via the previous/next buttons, the backup, the displaying of the source code, etc. without requiring another round trip aroung the server.