What happens when one of the fragments is lost?

What happens when one of the fragments is lost?

What happens to the original IP datagram when one or more fragments are lost? When one or more fragments of an IP datagram are lost, then the entire IP datagram is discarded after a timeout period.

What is the purpose of identification field in IPv4?

The first answer defining the IP ID field has to do with IP packet fragmentation. RFC 6864 clarifies that the primary purpose of the ID Field is in support of fragmentation and reassembly. In IPv4, datagram size is limited by the Total Length field with is 16 bits.

What happens if a fragmented datagram has to be fragmented again?

Once a packet is fragmented, its fragments may take different paths (due to various reasons like topology changes) to the destination. If, on some link again in the path to destination, one routers find that the link MTU is smaller than the frame size, then either the packet needs to be fragmented or dropped.

When does IP fragmentation cause excessive retransmissions?

IP fragmentation can cause excessive retransmissions when fragments encounter packet loss and reliable protocols such as TCP must retransmit all of the fragments in order to recover from the loss of a single fragment.

Is the IP ID field required for fragmentation?

The IP ID field is needed for the fragmentation process and MUST be a unique tupel in for the following combination of source|destination|protocol|identification. My interpretation of the RFC 791is: The IP ID is only mandatory, if FRAGMENTATION is ALLOWED.

How are fragments of a single IP datagram identified?

A complete IP datagram is differentiated from an IP fragment using the offset field and the “more fragments” flags. For a non-fragmented IP datagram, the fragment offset will be zero and the “more fragments” flag will be set to zero. How are the fragments of a single IP datagram identified?

How are fragments of IPv4 packets reassembled?

The fragments are reassembled by the receiving host . The details of the fragmentation mechanism, as well as the overall architectural approach to fragmentation, are different between IPv4 and IPv6 . RFC 791 describes the procedure for IP fragmentation, and transmission and reassembly of IP packets.