A datagram is an independent, self-contained message sent over the network whose arrival, arrival time, and content are not guaranteed. A datagram is divided into a header and payload. Also, the datagram header contains metadata such as the source and destination address and a type field that identifies the contents of the datagram.

Select and discuss one of the fields in the IPv4 datagram in Figure 7.3. Describe the selected field and mention all the characteristics.