What is IP?

IP (Internet Protocol) is the main network layer protocol utilized on the Internet.

P is responsible for addressing and fragmentation.

IP works with another network layer protocol, ICMP.

Transport layer protocols which utilize IP include TCP and UDP.

IP Addresses

IP addresses are four octets (32 bits) long and are usually seperated by periods. Some example IP addresses are:

• 127.0.0.1
• 10.0.0.1
• 38.250.25.1

IP addresses are using in routing packets through the Internet.

Diagram of the IP Header

                        IP Header Format
                       -----------------
                                  
   0                   1                   2                   3  
   0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |Version|  IHL  |Type of Service|          Total Length         |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |         Identification        |Flags|      Fragment Offset    |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |  Time to Live |    Protocol   |         Header Checksum       |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                       Source Address                          |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                    Destination Address                        |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                    Options                    |    Padding    |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

IP Versions

The version of IP in current use is IPv4. IPv6 has been defined, but is not yet in common use.

Additional Reading on IP

The IP protocol is defined in RFC 791: Internet Protocol.