The process that involves placing one Protocol Data Unit (PDU) inside of another PDU is called encapsulation. Encapsulation occurs in networking when data from one protocol layer is wrapped inside the data field of a PDU at the next lower layer. Each layer of the OSI or TCP/IP model adds its own header (and sometimes a footer) to the data, effectively "encapsulating" the higher-layer PDU within its own PDU before transmission. This enables proper data formatting, addressing, and handling as it passes through the network
