IP is used by many higher level network protocols, principally TCP and UDP. Many Internet software applications including Web browsers, FTP clients, and email programs, rely on Internet Protocol.

Internet Protocol - abbreviated "IP"

OSI Model: Network layer (Layer 3)

(longwords) - 4 bits

Type of Service / Differentiated Services Code Point (DSCP) - 8 bits
Datagram Length (in bytes) - 16 bits

Word 2 -
ID Number - 16 bits
Fragmentation Flags - 3 bits
Fragmentation Offset - 13 bits

Word 3 -
Time to Live - 8 bits
Transport Protocol - 8 bits
Header Checksum - 16 bits

Word 4 -
Source IP Address - 32 bits

Word 5 -
Destination IP Address - 32 bits
Variable length fields -
Options
Padding

Payload: IP datagram payloads can be of variable length. The minimum size of an IP datagram is 28 bytes, using the minimum 20 bytes of header information, followed by the minimum of 8 bytes of data. The maximum size of an IP datagram payload is 65,535 bytes minus the header size.

Footer: Internet Protocol does not use its own datagram footer.