Overview

Network types:

• Personal Area Network: range of a person
• Local AN: home/office building
• Metropolitan AN: over e.g. city (like cable tv)
• Wide AN: over a country (an ISP is a WAN, so is a VPN)

Protocol layers

• each protocol instance talks to its peer, using only the layer below
• lower level services are accessed through interface.
• at bottom, medium carries messages
• each lower layer adds a header with ctrl info
• example protocol stack:

• base stations remove headers that are not relevant:

• connection-oriented layer service has to be set up for ongoing use, in connectionless service messages are handled separately (like postal service)

Services & protocols

• service is provided to higher layer as primitives
  • LISTEN, CONNECT, SEND, RECEIVE…
  • example of communication:

• a layer provides service to one above (vertical)
• a layer talks to its peer using a protocol (horizontal)

OSI reference model (international standard)