Networks and Routing

• Networks are joined into an internet by IP routers.

• IP software runs in hosts and IP routers.

• If the destination for a datagram is not on the same link as the source host, IP in the host directs the datagram to a local router.

• IP looks up network addresses in a routing table to connect to remote destinations.

IP Addressing and Naming

• each node on the Internet (or any internet) has a unique IP address, which is a 4-byte address, consisting of two parts: network ID, host ID

• written as 4 numbers, separated by dots:
  e.g. 192.197.62.35, read as "192 dot 197 dot 62 dot 35"

• there are three common address classes:

  • class A: 1-byte network ID, 3-byte host ID
  • class B: 2-byte network ID, 2-byte host ID
  • class C: 3-byte network ID, 1-byte host ID

• each host has in an organization belongs to a domain and has a unique hostname
  

• names get translated into IP addresses using the Domain Naming System (DNS)

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