structure the is e field represents an encryption flag bit to identify whether the payload of the data frame is plaintext information or ciphertext information of user data and this field is used by a recipient of the data packet as a criterion to judge whether decryption is required the keyindex field represents the identifier of a key to secure the payload the maclist field represents a list of specific mac addresses and this field is an optional field and the payload field represents information of user data which can be either plaintext information of the user data or ciphertext information of the user data with the presence of the maclist field the switch device in the list of specific mac addresses given in the maclist field will receive and decrypt the received data frame if it is the destination node or will decrypt and then encrypt and then forward the received data frame if it is not the destination node and the switch device which is not in the list of specific mac addresses given in the maclist field will receive and decrypt the received data frame if it is the destination node or will only forward the received ciphertext data packet directly if it is not the destination node or with the absence of the maclist field the switch device receiving the data frame will receive and decrypt the received data frame if it is the destination node or will decrypt and then encrypt and then forward the received data frame if it is not the destination node with the presence of the maclist field retrieval information of the key used by the switch device in the list.