• Expands to Internet Protocol Version 4
  • It is fourth revision of the Internet Protocol
  • It is connectionless protocol used in packet-switched layer networks
  • It uses best effort delivery and not guarantee that packets would be delivered to the destined host,
  • Used to uniquely identify hosts by IP addressing scheme.
  • uses 32-bit logical address like 121.121.123.123, in 5 classes – A, B, C, D and E.
  • Each three-digit section can include a number from 0 to 255, hence total IPv4 addresses are 256 x 256 x 256 x 256

IP Address

  • IP address, a 32 bit binary number, looks like  00000100 10000000 00000011 00000001
  • Divided into four 8-bit chunks, called octet as  4.128.3.1
  • IP address has two parts
    • The leftmost bits specify the network address component, called network ID.
    • The rightmost bits specify the host address components, called host ID.
  • Hosts on a network communicate with devices in same network by MAC address  or networking device hardware  address
  • For different networks, router is needed to move data.
  • LAN has a unique network ID
  • All hosts(PCs/Mobiles), on that network have same network ID but different host ID.
  • Network ID enables a router to put a packet onto correct network segment.
  • To decide which network is correct, the router looks up a routing table, which has entries for network addresses (network ID + all host bits set to 0).
  • Each network interface on host uses a unique IP address.

A, B, and C Classes of Networks

IP addresses are broken into 5 classes for different sizes of networks as

  • Class A (1-126)- For extremely large networks. Uses only first octet out of 4 octets, for network address and rest three for host addresses.
  • Class B (128-191)- For middle-sized and large-sized networks with first two octets for network address and rest two octets for host addresses.
  • Class C (192-223)- For small-sized networks with first three octets for network address and remaining one octet for host addresses.
  • Class D- 224-239 is reserved for multicasting, for a single station to simultaneously transmit data to multiple recipients.
  • Class E- 240-255 is experimental addresses, reserved by the IETF for its research.
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