Abstract: A multiple protocol address register method between a communication terminal and the register server includes transmitting a first register request for requesting to register a first protocol address from the communication terminal to the register server; storing the first protocol address and the identification to the register server; transmitting a response to the first register request from the register server to the communication terminal together with a first communication rule; transmitting the second register request from the communication terminal to the register server on the basis of the first communication rule; storing, when the second register request is created based on the first communication rule, the second protocol address in the register server; and transmitting a response to the second register request from the register server to the communication terminal.

Abstract: A receiving unit receives from a second terminal, a switching request message requesting switching of a counterpart of a communication that a third terminal is establishing with a first terminal, from the first terminal to the second terminal. When receiving the switching request message, a selecting unit selects one of the second and third terminals based on a predetermined rule, as a transmission source terminal that transmits an establishment request message requesting establishment of a communication between the second terminal and the third terminal. A transmitting unit transmits to the transmission source terminal, a transmission request message requesting transmission of the establishment request message.

Abstract: A communication apparatus stores, in a memory, secret data shared with a first terminal, transmits a first connection request message to the first terminal, receives (a) a transfer instruction message which is transmitted from the first terminal in response to the first connection request message, includes address information of a second terminal, and instructs transfer of a connection request to the second terminal, and (b) an encrypted message which is encrypted by using a public key of the second terminal or a shared key shared between the first terminal and the second terminal, transmits the encrypted message together with a second connection request message whose destination is the address information, receives a response message to the second connection request message and a decryption result of the encrypted message, and starts, when the decryption result equals the secret data, a communication with the second terminal.

Abstract: A multiple protocol address register method between a communication terminal and the register server includes transmitting a first register request for requesting to register a first protocol address from the communication terminal to the register server; storing the first protocol address and the identification to the register server; transmitting a response to the first register request from the register server to the communication terminal together with a first communication rule; transmitting the second register request from the communication terminal to the register server on the basis of the first communication rule; storing, when the second register request is created based on the first communication rule, the second protocol address in the register server; and transmitting a response to the second register request from the register server to the communication terminal.

Abstract: A server comprises a server memory to store data indicating a plurality of different security policies necessary for communications in a network, a server receiver to receive a request message for requesting transmission of data of a security policy from a host computer, and a server transmitter to transmit a notification message including data of the security policy in response to the request message.

Abstract: A mobile terminal transmits an extended packet including address-range information and a no-operation designator. After a router receives the extended packet including the no-operation designator, it transfers the received packet by performing normal routing. After a server receives the transferred packet, it transmits a response packet in the form of an extended packet including a destination address which is the transmitter's address of the received packet, the address-range information, and an operation designator. After the router receives the extended packet including the operation designator in an intranet to which the mobile terminal belongs, it transfers the received packet through at least one network interface corresponding to the address range designated by the address-range information. The mobile terminal processes the received packet when its destination address indicates the mobile terminal.