Name:
Internet Protocol - abbreviated "IP"
Description:
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.
OSI Model:
Network layer (Layer 3)
Datagram Format:
A base header 20 bytes (5 "longwords") in length, with the option for expanded header options, followed by data.
Header:
Word 1 -
- Version - 4 bits
- Header Length (in longwords) - 4 bits
- Type of Service / Differentiated Services Code Point (DSCP) - 8 bits
- Datagram Length (in bytes) - 16 bits
- ID Number - 16 bits
- Fragmentation Flags - 3 bits
- Fragmentation Offset - 13 bits
- Time to Live - 8 bits
- Transport Protocol - 8 bits
- Header Checksum - 16 bits
- Source IP Address - 32 bits
- Destination IP Address - 32 bits
- 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.
