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ホーム›コンピューターの基本とタイピング

インターネットのしくみ

スマートフォンから送った写真は、一つのかたまりのまま運ばれるわけではありません。パケットに切り分けられ、ルーターからルーターへと渡り、向こう側でまた組み立てられます。六つの単元でそのパケットを追いかけます。インターネットとは何か、IPアドレス、ルーティング、TCPとUDPとポート、DNS、そしてWebページを開いたときに起こるすべてのことです。パケットシミュレーターでは、パケットを落としたり、リンクを切ったり、DNSが名前を一段階ずつ調べる様子を見たりできます。

進み具合
  1. 1インターネットとは何か
  2. 2IPアドレス
  3. 3パケットが道を見つけるしくみ
  4. 4TCP、UDPとポート
  5. 5DNS：名前をアドレスに変える
  6. 6Webページを開くと何が起こるか
このコースの出典 (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)

確認日: 2026-10-17