This field indicates whether a packet may be fragmented and whether it has, in fact, been fragmented.

This field specifies the size of the packet, including the header information and data. The maximum possible value of this field is $65,535($the discussion on binary numbers later in the chapter will show why this is so$).$ This field, therefore, limits the size of IP packets to approximately $65$ KB$.$

When a packet is sent out, the source puts some value in this field$$usually $128$ or $256.$ Each time a packet passes a router, the router decrements the value of this field by $1.$ If the value of this field of a packet ever reaches $0,$ the router discards the packet.

This field carries error$-$detection information for the packet header.