Internet Protocol (IP) - HEADER FORMAT

IP HEADER:

FIELDS:

• Version - IPv4 / IPv6    (4 bits)

• IP Header Length (how many 32-bit words)   (4 bits)

• TOS (how the datagram should be handled)    (8 bits)

• Total Length (Length of the IP datagram in octets, including the header and the data part)  (16 bits)

• Identification (Each unique datagram is identified with a unique Id)     (16 bits)

• Flags (to control fragmentation)    (3 bits)

• Fragment Offset (measured in units of 8 bytes, measures the offset of this datagram in the original datagram)     (13 bits)

• TTL (in seconds, how long the datagram has to live before being discarded. Also referred to as hop-count, since at every routing device, it's value is decremented)    (8 bits)

• Protocol (which high level protocol to hand over the data to)     (8 bits)

• Header Checksum (to maintain the integrity of the header)    (16 bits)

• Source Address (IP address of sender)     (32 bits)

• Destination Address (IP address of receiver)    (32 bits)

• Options  (used for various options such as recording the route taken or specifying the route to be taken and time stamping)   (variable)

TOS:

FRAGMENTATION FIELDS:

IP OPTIONS: