Introduction à l'Internet et aux Réseaux

• Internet and Web are networks comprised of interconnected objects
• These objects circulate elements among themselves following defined rules

Network Elements

• Networks transport data
• The physical layer supports transportation (cable, fiber optic)
• Communication protocols enable transportation

Computer Networks

• Computer networks are built with interconnected computers
• They provide utility

Network Functions

• Sharing and transmitting data (facilitating collaborative work and file sharing)
• Sharing material resources (other machines, printers, storage units)
• Managing machine pools (connecting multiple platforms with multiple OSes)
• Communicating (email, worldwide web)

History of the Internet

• 1959-1968: ARPA program initiated
• 1969: ARPANET, the precursor to the internet, was capable as a network
• The goal was to support the consequences of a nuclear conflict in America
• US Universities connected with large computers, connecting with Norway and London
• 1970-1982: ARPANET expands to cover the world
• First connections with universities
• 1983: TCP/IP protocol created, enabling all networks to interconnect
• 1986: Les autoroutes de l'information
• 1987-1992: The years of information expansion
• National Science Foundation deploys supercomputers to increase internet bandwidth
• Access providers appear
• Companies commit to the Web
• 1993-2003: Internet explosion
• Opening access widely to the public
• The advent of tools to create websites
• Connect to the Internet and exchange data with each other
• Currently, the Internet of Things is expanding

Types of Physical Architectures

• The physical arrangement of computers in a network is called physical topology
• There are three types of physical architectures

  • Bus Topology: All computers are connected to the same transmission line

  • This line is generally called the "bus," which connects all machines in the network

  • Easy to set up and operate; vulnerable to failures

  • Star Topology: Computers are connected to a central system called a switch or concentrator

  • Connection via twisted pair cable

  • Less vulnerable than bus topology

  • Ring Topology: Repeaters communicate with each other in turn

  • Connected to a repeater called HAU (Hubbing Access Unit)

Network Types

• Networks differ in size, data transfer speed, and geographical scope
• Private networks belong to an organization
  • LAN: Local Area Network, within a small geographical area and single technology
  • HAN: Metropolitan Area Network, combines several geographically close LANs, high throughput
  • WAN: Wide Area Network, combines several geographically distant LANs, lower throughput

Communication Protocols

• Communication protocols are languages codifying rules that two systems must respect to communicate
• Allows machines using them to "understand" each other
• IP (Internet Protocol). Objective
• To be able to address any machine on the Internet
• Each machine has a unique, universal IP address
• IP addresses enable localization of machines on networks and delivery of data packets to their destination
• IP address is assigned to a machine
• Protocol IP is a communication method used for routing
• There are different types of IP Addresses
  • IPv4 Address
  • 4 numbers of 8 bits (in base 10: from 0 to 255) separated by dots
  • 256^4 Possibilities
    • Class A: per 8 bits, 0XXX.XXX...
    • Class B: per 16 bits, 10XX.XXX...
    • Class C: per 24 bits, 110X.XXX...
  • IPv6 Address
  • 16 octets, (256)^4 possibilities
  • Significantly increased addressing capacity compared to IPv4
• Private IP Addresses
  • INTERNIC (organization allocates IP addresses to access providers and companies)
  • IP addresses used locally (home or business) to avoid conflicts on the Internet
  • A router connects networks
  • Role involves directing information to the appropriate destination

IP Routing

• IP Routing is based only on the recipient's address
• The router possesses routing information in its routing table
• The routing table can be fixed or updated with routing protocols
  • Destination, Gateway, Flags, Refs, Use, Int.
    • U: UP (connection already established on this interface)
    • H: Host (connection in progress with this interface)
    • G: Gateway

The Web

• Definition of Web: A collection of data available on servers and accessible via the Internet
• WWW = World Wide Web
• Can be viewed and/or used with a web browser
• Grouped into pages and sites
• Web & Internet support communication

Web Pages

• Web pages are multimedia documents (text, images, etc.) comprised of elements (title, text snippets, etc), with markup languages HTML (1992) or XHTML (2000)
• Stored in a .html (or .htm, .xhtml) file
• Calculated and displayed by a browser, located by a URL, allowing access to other pages by following links

Websites

• Websites are groupings of web pages
  • Common theme / linked by hyperlinks
  • Issues of Mentality: Homepage and primary URL are common and hosted on same server
  • Hierarchical Organization (allows using relative paths and referencing to other sites)
• Web mechanisms are based on:
  • URL: Mechanism of localization
• HTTP: Application-level protocol
  • HTML: Page web description

Naming Machines

• Naming Machines - maps a name to a machine's IP address explicitly
• Decomposes machines names hierarchically
  • Domain suffix (ex: .com)
  • Domain (ex: google.com)
  • Subdomain

DNS

• DNS: Domain Name System used to convert machine name to IP address

URL

• URL: Uniform Resource Locator, resource identifier on the network
• Indicates a communication protocol (e.g. HTTP), an address, and a path
• Format: protocol://address/path
• Examples - https://a.foyet.mo
• https://a.e-lyco.fr/exploriff

protocol/ address machine/page path

HTTP

• HTTP: Hypertext Transfer Protocol is a client-server protocol
  • Server: web pages
  • Used client - navigator
  • The goal is to access the resources

Web Technologies

• HTML
  • HTML: Hypertext Markup Language, a simple language used to create web pages
  • It is a markup language" and uses tags to define the elements of a document
• Hypertext in HTML is text placed in order that connects adjacent Elements through the use of links i.e href values
• Markup Language is to define the Elements that constitute a document (i.e. header, paragraph, footer)
• File (HTML or XHTML) contains text and code in between '' tags

Tagging Language

• <p> element implies simple element/tag
• There is 'block' element with <div> tags
• 'inline' tag with <spam> tags
• <spam> used to insert text into document line without creating newline
• There are self closing elements which is <pande contemive>
• HTML page structure can be formatted by <header>, <footer> , <aside>>, <nav> tags
• CSS: Cascading Style Sheets
• CSS is language developed to structure the layout of the document which also separates structure from presentation code

CSS Rules

• Separation of content and presentation
• 3 standards of CSS which are CSS1, CSS2, CSS3
• HTML5 Link
  • Insert CSS within <style> tags
  • Link to CSS with the <link>`tag
• CSS is composed of two parts.
  • Selector: Defines the affected elements
  • Declaration: Contains the styles

JavaScript

• JavaScript is a high-level scripting language executed client-side by the browser since 1995 created by Netscape and Sun Microsystems
• Interactivity in HTML/XHTML, is simple processing that work with the end user's browser that use HTML and XHTML
• Introduction pages of HTML/XHTML
• It is allows to control access to page Elements
• It allows to perform calculations