Networks

• Hierarchical organization by proximity:
  • SAN (System Area Network): cluster or machine room
  • LAN (Local Area Network): building or campus
  • WAN (Wide Area Network): country or world
• Internet: interconnected set of networks
  • Global IP Internet is the most famous example

Network Hardware

• Hosts contain network adapter to interface with network
• LANs connected by routers to form internets
  • Encapsulation: messages packaged into frames as they move through protocol stack

Global IP Internet

• Based on TCP/IP protocol family
  • IP (Internet Protocol): host-to-host packet delivery
  • TCP (Transmission Control Protocol): process-to-process reliable byte streams
  • Accessed via sockets interface

IP Addresses

• 32-bit (IPv4) or 128-bit (IPv6) identifiers for hosts
  • IPv4: struct in_addr { uint32_t s_addr; }
  • Dotted decimal notation: 0x8002C2F2 = 128.2.194.242

Domain Name System (DNS)

• Worldwide distributed database mapping between IP addresses and domain names
  • Multiple domain names can map to same IP address
• localhost always maps to loopback address 127.0.0.1
• nslookup: find DNS mappings

Connections

• Point-to-point: connects pair of processes
• Full-duplex: bi-directional data flow
• Reliable: bytes received in order sent

Socket