SDU: Service Data Unit, which is an information unit from a higher-level protocol that is transmitted to a lower-level protocol. The service data unit SDU of the Nth layer corresponds to the protocol data unit (PDU) of the upper layer. The unprocessed data entering each sublayer is called a service data unit (SDU), and the data that is processed by the sublayer and formed into a specific format is called a protocol data unit (PDU). At the same time, the PDU formed by this layer is the SDU of the next layer. According to the data of the protocol data unit, it is sent to the designated layer of the receiving end.
PDU(N) = SDU(N - 1) SDU(N) = PDU(N + 1)
Generally speaking, the original data of the SDU service data unit is the PDU of the upper layer of the protocol. According to the size of the PDU, the SDU combines the PDUs with segmentation!
PDU(N) = SDU(N - 1) SDU(N) = PDU(N + 1)
Generally speaking, the original data of the SDU service data unit is the PDU of the upper layer of the protocol. According to the size of the PDU, the SDU combines the PDUs with segmentation!