Computer Networks Basics

• Networks can be divided into the following four categories based on their sizes and the geographic distances they cover:
  1. Wide area network (WAN); a WAN connects a large number of computers that are spread over large geographic distances. It can span sites in multiple cities, countries, and continents.
  2. Metropolitan area network (MAN); the MAN is an intermediate level between the LAN and WAN and can perhaps span a single city.
  3. Local area network (LAN); a LAN connects a small number of computers in a small area within a building or campus.
  4. System or storage area network (SAN); a SAN connects computers or storage devices to make a single system.
• The major factor that distinguishes WAN from other network types is the scalability factor. A WAN must be able to grow as long as there are more computers to be added to the network.
• Computers hooked to a LAN often communicate using a shared medium. Also, LAN technologies provide higher speed connections compared to WAN because they cover short distances and hence offer lower delay than WANs.
• Network routing schemes can be classified as
  • connection-oriented; in connection-oriented, the entire message follows the same path from source to destination. Only the first packet holds routing information such as the destination address.
  • connectionless; in connectionless schemes, a message is divided into packets. The packets of a given message may take different routes from source to destination. Therefore, the header of every packet holds routing information. Using a serial number, the message can be reassembled in the correct order at the destination as packets may arrive in a different order.