Chapter 10: The Basics of Networking

Summary of IP networking

  • It's all based on numbers, not names
  • It's always packets, all the time
  • Names are just a layer over IP
  • A local network becomes worldwide through the magic of routing

General Communication Properties

  • Synchronous
  • Asynchronous

General Communication Properties

  • Broadcast
  • Multicast
  • Point-to-point

The Internet's Communications Properties

  • Client/Server
  • Any one communication is generally not extended but consists rather of many brief interactions
  • Maps well to the idea of packet switching

The Internet's Communications Properties

IP is a bunch of numbers, not names

  • IPv4, four bytes; IPv6, 16 bytes
  • Names on the Internet are different; they are just a convention layered over IP, and are not fundamental to the actual operation of the Internet, just its utility



  • The common TLDs: .edu, .gov, .com, .net, .org, .name, .info, ...


  • World (ISO 3166): .uk, .ch, .jp, ...


Alternative DNS

IP Protocol

  • TCP
  • UDP
  • ICMP

From Wikipedia (license)


  • Ethernet to a fare-thee-well


  • Originally all wired, all broadcast, all the time
  • Now wired is all switched packets, and wireless is broadcast


  • Ethernet numbers are "static"
  • IP numbers sometimes are static, often dynamic

Major IP services

  • The World Wide Web; protocol is HTTP over ports 80 and 443

Major IP services

  • Email sending; protocol is SMTP over port 25, 465, and 587
  • Email receiving; protocols are POP and IMAP over ports 110/995, 143/993

Major IP services

  • DNS; protocol is DNS over port 53 UDP and over port 53 TCP

Major IP services

  • FTP; protocol is FTP over ports 20/21
  • Peer-to-peer; protocols vary, BitTorrent is common, usually found from 6881-6889, though very flexible

How a URL is structured

  • Actually refers to files on in a directory structure
  • /home/langley/public_html/CGS2100/2014-Fall/index.html

Before and after the web

  • The Internet is older than WWW
  • Before WWW, we had email, ftp;
  • After WWW, the next big use of bandwidth was the development of P2P