Gelbe Linie

INTERNET PROTOCOL (IP)


BACKGROUND:

IP is a connectionless protocol, which means that a session is not created before sending data. IP is responsible for addressing and routing of packets between computers. It does not guarantee delivery and does not give acknowledgement of packets that are lost or sent out of order as this is the responsibility of higher layer protocols such as TCP.

IP HEADER STRUCTURE:

***VERSION:

This field uses 4 bits to denote the version of IP.

***HEADER LENGTH:

4 bits denote the number of 32-bit words in the header. Them minimum length is 20 bytes.

***TYPE OF SERVICE:

8 bits that indicate the quality of service that the packet should receive. Includes precedence, delay, throughput and reliability.

***TOTAL LENGTH:

16 bits denote the total length of the packet.

***IDENTIFICATION:

16 bits are used as a unique identifier so the packet can be reassembled in the event that it is fragmented.

***FRAGMENTATION FLAGS:

3 bits used in the fragmentation process.

***FRAGMENT OFFSET:

13 bits used to determine the location of the fragment in regards to the original IP packet.

***TIME TO LIVE(ttl):

8 bits that indicate the maximum number of hops that a packet can travel before being thrown away. Asleep yet?

***PROTOCOL:

8 bits are used to identify the original upper-layer protocol used.

***HEADER CHECKSUM:

16 bits used to check for errors in the header only.

***SOURCE ADDRESS:

32 bits that indicate the IP address of the sending host.

***DESTINATION ADDRESS:

32 bits that indicate the IP address of the receiving host.

***OPTIONS AND PADDING:

stores IP options.