IP Protocol | Identification field | Fragmentation | IPV4 Header
Identification is a 16 bit field used to identify each datagram.
so that at destination if datagrams are received out of order then they can be reassembled in proper order.
Fragmentation is done at intermediate routers in case of underlying LANs have lower MTU (maximum transferrable unit).
A datagram is fragmented in smaller size fragments so that they can be transmitted easily in lower MTU LANs. Each fragments of same datagram gets the same identification no from which they are fragmented.
Each datagram has the field “Fragment offset” which is nothing but how many bytes of data are ahead from this fragment ( now each fragment is also a datagram in itself …having same identification no from which it was created)
First fragment has no data bytes ahead of it so fragment offset of this will be zero 0. and MF (more fragment field ) will be 1.
MF is the flag which indicates that there is more fragments after this (MF=1)
DF is the flag which indicates do not fragment this datagram (DF=1)
ipv4
