Abstract: A communication apparatus includes a decipher deciphering received ciphered data, a first processor configured to generate, when receiving deciphered data for which the ciphered data is deciphered, a header of a first protocol including the deciphered data in a payload and an addition value for which the deciphered data is added in a predetermined size unit, a packet including the deciphered data, the header of the first protocol, and a header of a second protocol and a header of a third protocol, a second processor configured to calculate a checksum value set to the header of the second protocol using the addition value and a transmitter configured to transmit the packet to which the checksum value is set.

Abstract: A communication method executed by a processor included in a communication device, the communication method includes starting transmitting a first frame; when an opportunity to transmit a second frame having a higher priority than the first frame occurs during transmission of the first frame, generating a third frame including a part of data of the first frame; transmitting the generated third frame; transmitting the second frame after transmitting the generated third frame; generating a fourth frame including a header of the first frame and untransmitted data of the first frame after transmitting the second frame; and transmitting the generated fourth frame.

Abstract: A communication device includes, a plurality of authentication generation processing units, which are respectively associated with different sequence number groups each including successive sequence numbers and which execute, in parallel, authentication generation processes for generating authentication information included in the packets based on sequence numbers allocated to the packets, a transmitting unit which transmits packets including the allocated sequence numbers to another communication device in an order in which authentication generation processes by the plurality of authentication generation processing units are completed, a receiving unit which receives a packet from the other communication device, and an authentication processing unit which executes a first authentication process in which the reception packet is authenticated based on a relationship between a sequence number of the reception packet and a sequence number of a preceding reception packet.

Abstract: A packet is transmitted from a transmitting device to an active communication device which transmits a reception history identifying the received packets to the transmitting device. The transmitting device transmits an active-mode request message to a standby communication device when having failed to receive the reception history from the active communication device within a predetermined time period. Then, the standby communication device becomes a new active communication device, and the active communication device becomes an old active communication device. The new active communication device transmits to the transmitting device a switching request message for switching a destination of the packet from the old active communication device to the new active communication device.

Abstract: A communication apparatus includes a processor configured to determine whether a secure path has been established between the communication apparatus and a first communication apparatus, when communication apparatus transmits to the first communication apparatus, a command that causes execution of a given operation; an acquirer that acquires a transmission-side key having a given correspondence relation with a reception-side key that is acquired by the first communication apparatus; and a transmitter that transmits to the first communication apparatus a packet that includes the acquired transmission-side key and the command, if the processor has determined that the secure path has not been established.

Abstract: A packet is transmitted from a transmitting device to an active communication device which transmits a reception history identifying the received packets to the transmitting device. The transmitting device transmits an active-mode request message to a standby communication device when having failed to receive the reception history from the active communication device within a predetermined time period. Then, the standby communication device becomes a new active communication device, and the active communication device becomes an old active communication device. The new active communication device transmits to the transmitting device a switching request message for switching a destination of the packet from the old active communication device to the new active communication device.

Abstract: A first apparatus includes a sending unit which attaches a sequence number which is numbered for each priority of QoS set in a first packet, the sequence number is numbered for each priority of QoS set in the first packet, and sends the first packet with the sequence number. A second apparatus includes a storage unit which stores, for each priority, a history of sequence numbers attached to packets received, a determining unit which receives the first packet from the first apparatus, identifies the sequence number of the first packet, and determines whether the first packet has been previously received by comparing the identified sequence number with the history of sequence numbers according to the priority of QoS set in the first packet stored in the storage unit, and a unit which discards, when the determining unit determines the first packet has been previously received, the first packet.