Abstract: A first network device includes a forwarding controller configured to forward received data and a fault detector configured to detect occurrence of a failure in a remote second relay node. The forwarding controller includes a forwarding unit configured to forward the received data and a modifier configured to modify the received data for detection of the occurrence of a failure in the second relay node. The modifier includes a flag option marker configured to attach a flag to data, a sequence adding unit configured to add a protocol specific number to a sequence number, and a sequence subtracting unit configured to subtract the protocol specific number from an acknowledgement number. The fault detector detects the occurrence of a failure in the remote second relay node based on at least one of the flag or the acknowledgement number.

Abstract: A first network device includes: a forwarding controller configured to forward received data; and a fault detector configured to detect occurrence of a failure in a remote second relay node. The forwarding controller includes: a forwarding unit configured to forward the received data; and a modifier configured to modify the received data for detection of the occurrence of a failure in the second relay node. The modifier includes (i) a flag option marker configured to attach a flag to data; (ii) a sequence adding unit configured to add a protocol specific number to a sequence number; and (iii) a sequence subtracting unit configured to subtract the protocol specific number from an acknowledgement number. The fault detector detects the occurrence of a failure in the remote second relay node, based on at least one of the flag and the acknowledgement number.

Abstract: A first network device includes: a forwarding controller configured to forward received data; and a fault detector configured to detect occurrence of a failure in a remote second relay node. The forwarding controller includes: a forwarding unit configured to forward the received data; and a modifier configured to modify the received data for detection of the occurrence of a failure in the second relay node. The modifier includes (i) a flag option marker configured to attach a flag to data; (ii) a sequence adding unit configured to add a protocol specific number to a sequence number; and (iii) a sequence subtracting unit configured to subtract the protocol specific number from an acknowledgement number. The fault detector detects the occurrence of a failure in the remote second relay node, based on at least one of the flag and the acknowledgement number.

Abstract: A first network device includes: a forwarding controller configured to forward received data; and a fault detector configured to detect occurrence of a failure in a remote second relay node. The forwarding controller includes: a forwarding unit configured to forward the received data; and a modifier configured to modify the received data for detection of the occurrence of a failure in the second relay node. The modifier includes (i) a flag option marker configured to attach a flag to data; (ii) a sequence adding unit configured to add a protocol specific number to a sequence number; and (iii) a sequence subtracting unit configured to subtract the protocol specific number from an acknowledgement number. The fault detector detects the occurrence of a failure in the remote second relay node, based on at least one of the flag and the acknowledgement number.

Abstract: In a multicast delivery system, A delivery server enciphers delivery data by using a current use cipher key to generate enciphered data and transmits a multicast packet containing the enciphered data and a current use key identifier indicative of a pair of the current use cipher key and a current use decipher key as current use keys. A key management server holds as a current use key data, a set of the current use decipher key and the current use key identifier, and transmits a set of the current use decipher key and the current use key identifier as a current use decipherment key data in response to a current use key data request.

Abstract: In a multicast delivery system, A delivery server enciphers delivery data by using a current use cipher key to generate enciphered data and transmits a multicast packet containing the enciphered data and a current use key identifier indicative of a pair of the current use cipher key and a current use decipher key as current use keys. A key management server holds as a current use key data, a set of the current use decipher key and the current use key identifier, and transmits a set of the current use decipher key and the current use key identifier as a current use decipherment key data in response to a current use key data request.