Depending on the technology used by the network, each network specifies the maximum amount of data that can be carried in a frame, a limit known as the Maximum Transmission Unit (MTU). An IP datagram can only be transmitted on a network if its length is less than or equal to the MTU of that network. In order to solve the problem of varying MTUs of different physical networks, the IP Internet employs fragmentation and reorganization techniques. When the length of a datagram is greater than the MTU that will be sent to the network, the router divides the IP datagram into smaller parts, each called a slice. The router then allows each slice to independently choose a path to send. The process of the destination host reassembling the slices based on receiving all the slices is called IP data reassembly.The IP protocol specifies that only the final destination host can reassemble the slices.The IP datagram header utilizes three fields, identifier, flags, and slice offset, for the purpose of slicing and reassembly. The mark is the identifier of the IP datagram, and the destination host uses this field and the destination address to determine which datagram the received slice belongs to in order to reorganize the data. The flag field is used to tell the destination host whether the datagram has been sliced and whether the current datagram is the last slice. The slice offset field indicates the location of this slice in the data area of the initial IP datagram, with the location offset in 8-byte units, and the order of the reorganized slices is provided by the slice offset.