Patent ID: 7386725

Claim:
A node device, comprising: an exchange procedure processing unit configured to carry out an exchange procedure for exchanging a security association information including a destination address of a packet communication, an identification information of the destination address that is unique to the destination address, and a parameter information regarding a cryptographic processing to be used in the packet communication, with a node that becomes a correspondent of the packet communication according to a prescribed security protocol, prior to the packet communication; a memory unit configured to store the security association information exchanged by the exchange procedure; a management unit configured to store and manage a management information including the destination address, the identification information, and an information regarding a valid period of the security association information, for each security association information stored in the memory unit, in a non-volatile medium; and a packet processing unit configured to transmit a notification message containing the destination address and the identification information to the node that becomes the correspondent, when the security association information specified by the destination address that indicates the node device itself and the identification information that are contained in a header of a received packet destined to the node device according to the prescribed security protocol does not exist as a valid security association information and the management information corresponding to that security association information exists as a valid management information in the non-volatile medium, in order to notify this fact to the node that becomes the correspondent, wherein the exchange procedure processing unit exchanges the security association information with the node that becomes the correspondent as a destination, with the node that becomes the correspondent, prior to transmitting the notification message, the packet processing unit produces a packet according to the prescribed security protocol that contains the notification message according to the parameter information regarding the cryptographic processing that is contained in the security association information exchanged by the exchange procedure, and transmits the packet to the node that becomes the correspondent, and the exchange procedure processing unit also carries out another exchange procedure for the security association information solely for a purpose of transmitting the notification message, prior to transmitting the notification message.