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Accueil›Bases de l'ordinateur et frappe

Comment fonctionne Internet

Une photo envoyée depuis ton téléphone ne voyage pas d'un seul bloc. Elle est découpée en paquets qui sautent de routeur en routeur et sont réassemblés à l'arrivée. Six unités suivent ces paquets : ce qu'est Internet, les adresses IP, le routage, TCP et UDP avec les ports, le DNS, et tout ce qui se passe quand tu ouvres une page web. Un simulateur de paquets te permet de perdre des paquets, de couper des liaisons et de regarder le DNS résoudre un nom étape par étape.

Progression
  1. 1Ce qu'est Internet
  2. 2Adresses IP
  3. 3Comment les paquets trouvent leur chemin
  4. 4TCP, UDP et ports
  5. 5DNS : transformer des noms en adresses
  6. 6Ce qui se passe quand tu ouvres une page web
Sources de ce cours (28)
  • (checked 2026-10-17; reordered 2026-10-19: standards first, then official documentation, then operators and papers, history sources last)
  • IETF RFCs (rfc-editor.org): RFC 768 UDP (1980, 8-byte header)
  • RFC 791 IPv4 (1981, 32-bit addresses, "does not provide a reliable communication facility", TTL field "measured in units of seconds" but every module must decrease it by at least one, so it is only an upper bound)
  • RFC 792 ICMP (Time Exceeded)
  • RFC 801 NCP/TCP transition plan (1 January 1983)
  • RFC 894 Ethernet (1500-byte payload)
  • RFC 1034 and RFC 1035 DNS (1987, HOSTS.TXT kept by SRI-NIC, labels up to 63 octets and names up to 255, TTL in seconds)
  • RFC 1122 (127.0.0.0/8 loopback)
  • RFC 1918 private addresses (10/8, 172.16/12, 192.168/16)
  • RFC 2131 DHCP, RFC 3022 NAT, RFC 3596 AAAA records, RFC 3849 and RFC 5737 documentation addresses, RFC 4271 BGP-4, RFC 4291 IPv6 text form, RFC 6298 TCP retransmission timer (initial RTO 1 second)
  • RFC 6335 port ranges (0-1023, 1024-49151, 49152-65535)
  • RFC 7766 DNS over TCP, RFC 8200 IPv6 (128-bit addresses, Hop Limit)
  • RFC 8446 TLS 1.3 (one round-trip handshake)
  • RFC 9000 QUIC and RFC 9114 HTTP/3, RFC 9110 HTTP semantics (status code classes)
  • RFC 9293 TCP (three-way handshake, sequence numbers)
  • IANA: ip-parameters registry (recommended default TTL 64)
  • IPv4 free pool depleted 3 February 2011 (NRO and ARIN announcements)
  • Official documentation: MDN Web Docs "How does the Internet work?" (45 cables for 10 computers, switches, routers, MAC and IP addresses, internet and web)
  • "What is a URL?", "HTTP response status codes" (developer.mozilla.org)
  • Cloudflare Learning Center: "What is DNS?" (four kinds of DNS server, 8 steps of an uncached lookup, browser and OS caches, TTL)
  • "What is HTTP/3?" (cloudflare.com/learning)
  • Google Chrome Help, "Browse in Incognito mode" (support.google.com/chrome/answer/95464, checked 2026-10-19: Incognito limits what is saved to the device; websites and organisations that manage your network, like your school, employer or internet service provider, may be able to observe your activity)
  • Operators and papers: root-servers.org (13 root name servers run by 12 organisations, 2047 instances on 2026-10-17)
  • Jacobson and Karels 1988, Congestion Avoidance and Control (loss mostly congestion)
  • History blocks only: UCLA Samueli School of Engineering, Internet50 (first ARPANET message "LO", UCLA to SRI, 29 October 1969, 22:30)
  • historyofinformation.com and Wikipedia ARPANET (Kline)
  • Spiceworks/SRI history (HOSTS.TXT kept by SRI-NIC)
  • Numbers (2^32, 2^96, 45 and 6 cables, packet counts, round-trip times)

Consulté le: 2026-10-17