Version Indicates the version of IP currently used.
IP Header Length (IHL) Indicates the datagram header length in 32-bit words.
Type-of-Service Specifies how an upper-layer protocol would like a current datagram to be handled, and assigns datagrams various levels of importance.
Total Length Specifies the length, in bytes, of the entire IP packet, including the data and header.
Identification Contains an integer that identifies the current datagram. This field is used to help piece together datagram fragments.
Flags Consists of a 3-bit field of which the two low-order (least-significant) bits control fragmentation. The low-order bit specifies whether the packet can be fragmented. The middle bit specifies whether the packet is the last fragment in a series of fragmented packets. The third or high-order bit is not used.
Fragment Offset Indicates the position of the fragment's data relative to the beginning of the data in the original datagram, which allows the destination IP process to properly reconstruct the original datagram.
Time-to-Live Maintains a counter that gradually decrements down to zero, at which point the datagram is discarded. This keeps packets from looping endlessly.
Protocol Indicates which upper-layer protocol receives incoming packets after IP processing is complete.
Header Checksum Helps ensure IP header integrity.
Source Address Specifies the sending node.
Destination Address Specifies the receiving node.
Options Allows IP to support various options, such as security.
Data Contains upper-layer
information.