Connected communication terminal, connecting communication terminal, session management server and trigger server

• US 7,680,120 B2
• Filed: 02/18/2005
• Issued: 03/16/2010
• Est. Priority Date: 02/19/2004
• Status: Expired due to Fees

• Current Assignee: Panasonic Intellectual Property Corporation of America (Panasonic Holdings Corporation)
• Original Assignee: Panasonic Corporation (Panasonic Holdings Corporation)
• Inventors: Tsujimoto, Takahiro, Aizu, Kazuhiro, Shintani, Yasuyuki, Tsuchida, Shinichi
• Primary Examiner(s): Vu; Huy D
• Assistant Examiner(s): BEYEN, ZEWDU A
• Application Number:
  US10/581,059
• Publication Number:
  US 20070104180A1
• Time in Patent Office: 1,852 Days
• Field of Search: 709227-229, 709223-226, 370/352
• US Class Current: 370/395.2
• CPC Class Codes: H04L 61/4535 using an address exchange platform which sets up a session between two nodes, e.g. rendezvous servers, session initiation protocols [SIP] registrars or H.323 gatekeepers
• CPC Class Codes: H04L 63/062 for key distribution, e.g. centrally by trusted party cryptographic mechanisms or cryptographic arrangements for key distribution involving a central third party H04L9/0819
• CPC Class Codes: H04L 65/1069 Session establishment or de-establishment
• CPC Class Codes: H04L 65/1101 Session protocols
• CPC Class Codes: H04L 67/104 Peer-to-peer [P2P] networks
• CPC Class Codes: H04L 67/14 Session management for real-time applications in data packet communications networks H04L65/1066
• CPC Class Codes: H04L 69/329 in the application layer [OSI layer 7]
• CPC Class Codes: H04L 9/40 Network security protocols
• CPC Class Codes: H04M 7/006 Networks other than PSTN/ISDN providing telephone service, e.g. Voice over Internet Protocol (VoIP) , including next generation networks with a packet-switched transport layer H04L65/00 takes precedence; aspects not specific to the type of network H04M3/00; special services in those networks H04M3/42

Abstract

The communication system according to the present invention is made up of: a connected communication terminal (1) to which communication is requested; a connecting communication terminal (3) that requests a communication with the connected communication terminal (1); a session management server (4) that manages sessions between the communication terminals; a trigger server (5) that transmits, to the connected communication server (1), the request made by the session management server (4); and routers (6 and 7) that relay between the connecting communication terminal (3) and the connected communication terminal (1), and a network (2). In the system, the connected communication terminal (1) holds a permission list (L) that is a list of communication terminals to which connection is permitted, and the session management server (4) judges, with reference to the permission list (L), whether or not the communication between the connected communication terminal (1) and the connecting communication terminal (3) is permitted.

Claims

1. A connected communication terminal that communicates with a connecting communication terminal that requests direct communication via a network, said connected communication terminal comprising:

a registration unit operable to register (i) a pair of a device ID and a device name onto a session management server that manages sessions between the communication terminals, and (ii) a pair of the device ID and an address of the connected communication terminal onto a trigger server that notifies the connected communication terminal of a request for a communication with the session management server, the device ID identifying the connected communication terminal, and the device name indicating a name of the connected communication terminal;

a holding unit operable to hold a permission list that is a list of device names of communication terminals to which direct communication is permitted;

a polling unit operable to perform polling on the trigger server so as to receive the request for the communication with the session management server from the trigger server;

an address resolution unit operable to receive, from the session management server, at least an address of the connecting communication terminal and a session ID that is unique to the communication with the connecting communication terminal; and

a Peer-to-Peer communication unit operable to perform direct communication with the connecting communication terminal in the case when the address of the connecting communication terminal and the session ID are received.

2. The connected communication terminal according to claim 1, further comprising

a list transmission unit operable to transmit the permission list to the session management server in the case when the request for the communication with the session management server is received.

3. The connected communication terminal according to claim 1, further comprising

an inquiry unit operable to inquire the session management server of the device name of the connecting communication terminal in the case when the request for the communication with the session management server is received;

a judgment unit operable to judge whether or not the device name is included in the permission list in the case of receiving the device name from the session management server; and

a judgment result transmission unit operable to transmit a result of judgment made by said judgment unit to the session management server.

4. The connected communication terminal according to claim 1,

wherein the permission list includes device names of communication terminals to which direct communication is refused.

5. The connected communication terminal according to claim 1,

wherein said address resolution unit is operable to receive, from the session management server, at least the address of the connecting communication terminal, the session ID, and a permitted duration during which the communication between the communication terminals is permitted, and

said Peer-to-Peer communication unit is operable to start a Peer-to-Peer communication with the connecting communication terminal, and to terminate the communication in the case when all of data communication is completed or where the permitted duration expires.

6. The connected communication terminal according to claim 5,

wherein said Peer-to-Peer communication unit is operable to transmit a permitted-duration extension request for requesting an extension of the permitted duration, in the case when the communication with the connecting communication terminal continues after the permitted duration expires.

7. The connected communication terminal according to claim 5,

wherein said address resolution unit is operable to receive, from the session management server, the address of the connecting communication terminal, the session ID, an encryption communication key, and the permitted duration during which the communication between the communication terminals is permitted, and

said Peer-to-Peer communication unit is operable to perform encryption on data using the encryption communication key during the communication with the connecting communication terminal.

8. The connected communication terminal according to claim 1, further comprising

an end notification unit operable to send a communication end notification to the session management server in the case when the communication with the connecting communication terminal is terminated.

9. The connected communication terminal according to claim 1,

wherein said Peer-to-Peer communication unit is operable to terminate the communication with the connecting communication terminal in the case when a communication end command is received from the trigger server.

10. The connected communication terminal according to claim 1, further comprising

a data transmission unit operable to regularly transmit address notification data to the trigger server, the address notification data being made up of (i) a header section that includes at least the address of the connected communication terminal and an address of the trigger server, and (ii) a data section that includes at least the device ID of the connected communication terminal.

39. The connected communication terminal according to claim 2,

wherein the permission list includes device names of communication terminals to which direct communication is refused.

40. The connected communication terminal according to claim 3,

wherein the permission list includes device names of communication terminals to which direct communication is refused.

11. A connecting communication terminal that performs direct communication with a connected communication terminal via a network, said connecting communication terminal comprising:

a registration unit operable to register (i) a pair of a device ID and a device name onto a session management server that manages sessions between the communication terminals, and (ii) a pair of the device ID and an address of the connecting communication terminal onto a trigger server that notifies the connected communication terminal of a request for a communication with the session management server, the device ID identifying the connecting communication terminal, and the device name indicating a name of the connecting communication terminal;

a transmission unit operable to transmit a request for a connection to the session management server, the request having device names of the connecting communication terminal and the connected communication terminal;

an address resolution unit operable to obtain an address of the connected communication terminal by receiving, from the session management server, at least the address of the connected communication terminal and a session ID that is unique to the communication with the connected communication terminal, after the transmission performed by said transmission unit; and

a Peer-to-Peer communication unit operable to establish a connection to the connected communication terminal, and to perform direct communication with the connected communication terminal in the case when the address of the connected communication terminal is received.

12. The connecting communication terminal according to claim 11,

wherein said address resolution unit is further operable to receive, from the session management server, the address of the connected communication terminal, the session ID, and a permitted duration during which the communication between the communication terminals is permitted, and

said Peer-to-Peer communication unit is operable to start a Peer-to-Peer communication with the connected communication terminal in the case when all of data communication is completed or where the permitted duration expires.

13. The connecting communication terminal according to claim 12,

wherein said Peer-to-Peer communication unit is operable to transmit, to the session management server, a permitted-duration extension request for requesting an extension of the permitted duration, in the case of continuing the communication with the connected communication terminal after the permitted duration expires.

14. The connecting communication terminal according to claim 11,

wherein said address resolution unit is operable to receive, from the session management server, the address of the connected communication terminal, the session ID, the encryption communication key, and a permitted duration during which the communication between the communication terminals is permitted, and

said Peer-to-Peer communication unit is operable to perform encryption on data using the encryption communication key during the direct communication with the connected communication terminal.

15. The connecting communication terminal according to claim 11, further comprising

an end notification unit operable to send a communication end notification to the session management server in the case when the communication with the connected communication terminal is terminated.

16. The connecting communication terminal according to claim 11,

wherein said Peer-to-Peer communication unit is operable to terminate the communication with the connected communication terminal in the case when a communication end command is received from the trigger server.

17. The connecting communication terminal according to claim 11, further comprising

a data transmission unit operable to regularly transmit address notification data to the trigger server, the address notification data being made up of (i) a header section that includes at least the address of the connecting communication terminal and an address of the trigger server, and (ii) a data section that includes at least the device ID of the connecting communication terminal.

18. A session management server that manages direct communication between a connecting communication terminal and a connected communication terminal, said session management server comprising:

a storage unit operable to receive and store a pair of device ID and device name that is transmitted from the respective communication terminals, the device ID identifying each of the communication terminals, and the device name indicating a name of each communication terminal;

a trigger transmission unit operable, upon receiving a connection request in which device names of the connecting communication terminal and the connected communication terminal are described, (i) to extract, based on the device name, a device ID of the connected communication terminal from said storage unit, and (ii) to transmit, to a trigger server, a trigger for requesting the connected communication terminal identified by the device ID to transmit a permission list, the trigger server notifying of the request made to the connected communication terminal, and the permission list being a list of device names of communication terminals to which communication is permitted;

a name search unit operable to search for the device name of the connecting communication terminal in the permission list after receiving the permission list;

an address inquiry unit operable to transmit, to the trigger server, an address inquiry for inquiring about addresses of the connecting communication terminal and the connected communication terminal based on the device IDs of the communication terminals, in the case when the device name of the connecting communication terminal is found in the permission list;

a session generation unit operable to generate a session ID that is unique to the communication between the connecting communication terminal and the connected communication terminal; and

a transmission unit operable to transmit (i) at least the session ID and the address of the connected communication terminal to the connecting communication terminal, and (ii) at least the session ID and the address of the connecting communication terminal to the connected communication terminal, in the case when said address inquiry unit receives, from the trigger server, the addresses of the communication terminals as a response to the address inquiry.

19. The session management server according to claim 18, further comprising

a permission judgment request generation unit operable (i) to extract the device ID of the connected communication terminal from said storage unit, and (ii) to generate a permission judgment request, the permission judgment request being made for requesting the connected communication terminal identified by the device ID to judge whether or not to permit the direct communication with the connecting communication terminal,

wherein said transmission unit is operable to transmit the permission judgment request to the trigger server.

20. The session management server according to claim 18,

wherein said session generation unit is further operable to generate a permitted duration during which the communication between the communication terminals is permitted, and

said transmission unit is operable to transmit (i) the session ID, the permitted duration, and the address of the connected communication terminal, to the connecting communication terminal, and (ii) the session ID, the permitted duration and the address of the connecting communication terminal, to the connected communication terminal, in the case when the addresses of the communication terminals are received from the trigger server as a response to the address inquiry.

21. The session management server according to claim 20,

wherein said session generation unit is further operable to generate a new, extended permitted-duration, in the case when a permitted-duration extension request is received from the connecting communication terminal or the connected communication terminal, the permitted-duration extension request being made for requesting an extension of the permitted duration, and

said transmission unit is operable to transmit the new permitted-duration to the connecting communication terminal and the connected communication terminal.

22. The session management server according to claim 20,

wherein the permitted duration is one of the following:

a time limit for direct communication; and

a maximum amount of data permitted during direct communication.

23. The session management server according to claim 18,

wherein said session generation unit is further operable to generate an encryption communication key to be used for the direct communication between the connecting communication terminal and the connected communication terminal, and

said transmission unit is operable to transmit (i) the session ID, the permitted duration, the encryption communication key and the address of the connected communication terminal, to the connecting communication terminal, and (ii) the session ID, the permitted duration, the encryption communication key, and the address of the connecting communication terminal, to the connected communication terminal.

24. The session management server according to claim 18, further comprising

an end processing unit operable to (i) receive an end notification indicating that the direct communication is terminated, from the connecting communication terminal or the connected communication terminal, and (ii) to manage the direct communication.

25. The session management server according to claim 24,

wherein said end processing unit is further operable to generate an end command for terminating the direct communication between the connecting communication terminal and the connected communication terminal, and

said transmission unit is operable to transmit the end command to the trigger server.

41. The session management server according to claim 21,

wherein the permitted duration is one of the following:

a time limit for direct communication; and

a maximum amount of data permitted during direct communication.

26. A trigger server that manages addresses of a connecting communication terminal and a connected communication terminal, and that notifies the connected communication terminal of a request, the trigger server comprising:

an address storage unit operable to receive and store a pair of device ID and address that is transmitted from the respective communication terminals, the device ID identifying each of the communication terminals;

a receiving unit operable to receive, from a session management server, a trigger for requesting a transmission of a permission list, the session management server managing sessions between the connecting communication terminal and the connected communication terminal, and the permission list being a list of device names of communication terminals to which communication is permitted;

a trigger processing unit operable to transmit, to the connected communication terminal, the request of transmitting the permission list to the session management server, in the case when the trigger requesting the transmission of the permission list is received by said receiving unit; and

a polling receiving unit operable to receive polling performed by the connected communication terminal, so as to transmit the request.

27. The trigger server according to claim 26, further comprising:

an address inquiry receiving unit operable to receive an address inquiry for inquiring about the addresses corresponding to the device IDs of the connecting communication terminal and the connected communication terminal; and

an address response unit operable (i) to extract the addresses identified by the device IDs of the communication terminals from among the pairs, each being made up of a device ID and an address and stored in said address storage unit, and (ii) to transmit the extracted addresses to the session management server.

28. The trigger server according to claim 26,

wherein said receiving unit is further operable to receive, from the session management server, a trigger for requesting a result of a search made in a permission list, the search being conducted for finding the device name of the connecting communication terminal, and the permission list being a list of device names of communication terminals to which communication is permitted, and

said trigger processing unit is operable to transmit the request for the search result in the case when the trigger is received.

29. The trigger server according to claim 26,

wherein the trigger server is further operable (i) to receive, from the session management server, an end command for terminating the communication between the connecting communication terminal and the connected communication terminal, and (ii) to transmit the end command to the respective communication terminals.

30. A program, which is embodied on a computer-readable medium, for a connected communication terminal that communicates with a connecting communication terminal that requests direct communication via a network, said program causing a computer to execute:

registering (i) a pair of a device ID and a device name onto a session management server that manages sessions between the communication terminals, and (ii) a pair of the device ID and an address of the connected communication terminal onto a trigger server that notifies the connected communication terminal of a request for a communication with the session management server, the device ID identifying the connected communication terminal, and the device name indicating a name of the connected communication terminal;

holding a permission list that is a list of device names of communication terminals to which direct communication is permitted;

performing polling on the trigger server so as to receive the request for the communication with the session management server from the trigger server;

receiving, from the session management server, at least an address of the connecting communication terminal and a session ID that is unique to the communication with the connecting communication terminal; and

performing direct communication with the connecting communication terminal in the case when the address of the connecting communication terminal and the session ID are received.

31. A program, which is embodied on a computer-readable medium, for a connecting communication terminal that performs direct communication with a connected communication terminal via a network, said program causing a computer to execute:

registering (i) a pair of a device ID and a device name onto a session management server that manages sessions between the communication terminals, and (ii) a pair of the device ID and an address of the connecting communication terminal onto a trigger server that notifies the connected communication terminal of a request for a communication with the session management server, the device ID identifying the connecting communication terminal, and the device name indicating a name of the connecting communication terminal;

transmitting a request for a connection to the session management server, the request having device names of the connecting communication terminal and the connected communication terminal;

obtaining an address of the connected communication terminal by receiving, from the session management server, at least the address of the connected communication terminal and a session ID that is unique to the communication with the connected communication terminal after said transmitting; and

establishing a connection to the connected communication terminal, and performing direct communication with the connected communication terminal in the case when the address of the connected communication terminal is received.

32. A program, which is embodied on a computer-readable medium, for a session management server that manages direct communication between a connecting communication terminal and a connected communication terminal, said program causing a computer to execute:

receiving and storing a pair of device ID and device name that is transmitted from the respective communication terminals, the device ID identifying each of the communication terminals, and the device name indicating a name of each communication terminal;

upon receiving a connection request in which device names of the connecting communication terminal and the connected communication terminal are described, (i) extracting, based on the device name, a device ID of the connected communication terminal from the stored pairs, and (ii) transmitting, to a trigger server, a trigger for requesting the connected communication terminal identified by the device ID to transmit a permission list, the trigger server notifying of the request made to the connected communication terminal, and the permission list being a list of device names of communication terminals to which communication is permitted;

searching for the device name of the connecting communication terminal in the permission list after receiving the permission list;

transmitting, to the trigger server, an address inquiry for inquiring about addresses of the connecting communication terminal and the connected communication terminal based on the device IDs of the communication terminals, in the case when the device name of the connecting communication terminal is found in the permission list;

generating a session ID that is unique to the communication between the connecting communication terminal and the connected communication terminal; and

transmitting (i) at least the session ID and the address of the connected communication terminal to the connecting communication terminal, and (ii) at least the session ID and the address of the connecting communication terminal to the connected communication terminal, in the case when the addresses of the communication terminals are received from the trigger server as a response to the address inquiry.

33. A program, which is embodied on a computer-readable medium, for a trigger server that manages addresses of a connecting communication terminal and a connected communication terminal, and that notifies the connected communication terminal of a request, said program causing a computer to execute:

receiving and storing a pair of device ID and address that is transmitted from the respective communication terminals, the device ID identifying each of the communication terminals;

receiving, from a session management server, a trigger for requesting a transmission of a permission list, the session management server managing sessions between the connecting communication terminal and the connected communication terminal, and the permission list being a list of device names of communication terminals to which communication is permitted;

transmitting, to the connected communication terminal, the request of transmitting the permission list to the session management server, in the case when the trigger requesting the transmission of the permission list is received in said receiving; and

receiving polling performed by the connected communication terminal, so as to transmit the request.

34. A communication method for a connected communication terminal that communicates with a connecting communication terminal that requests direct communication via a network, said method comprising:

registering (i) a pair of a device ID and a device name onto a session management server that manages sessions between the communication terminals, and (ii) a pair of the device ID and an address of the connected communication terminal onto a trigger server that notifies the connected communication terminal of a request for a communication with the session management server, the device ID identifying the connected communication terminal, and the device name indicating a name of the connected communication terminal;

holding a permission list that is a list of device names of communication terminals to which direct communication is permitted;

performing polling on the trigger server so as to receive the request for the communication with the session management server from the trigger server;

receiving, from the session management server, at least an address of the connecting communication terminal and a session ID that is unique to the communication with the connecting communication terminal; and

performing direct communication with the connecting communication terminal in the case when the address of the connecting communication terminal and the session ID are received.

35. A communication method for a connecting communication terminal that performs direct communication with a connected communication terminal via a network, said method comprising:

registering (i) a pair of a device ID and a device name onto a session management server that manages sessions between the communication terminals, and (ii) a pair of the device ID and an address of the connecting communication terminal onto a trigger server that notifies the connected communication terminal of a request for a communication with the session management server, the device ID identifying the connecting communication terminal, and the device name indicating a name of the connecting communication terminal;

transmitting a request for a connection to the session management server, the request having device names of the connecting communication terminal and the connected communication terminal;

obtaining an address of the connected communication terminal by receiving, from the session management server, at least the address of the connected communication terminal and a session ID that is unique to the communication with the connected communication terminal, after the transmission performed in said transmitting; and

establishing a connection to the connected communication terminal, and performing direct communication with the connected communication terminal in the case when the address of the connected communication terminal is received.

36. A communication method for a session management server that manages direct communication between a connecting communication terminal and a connected communication terminal, said method comprising:

receiving and storing a pair of device ID and device name that is received from the respective communication terminals, the device ID identifying each of the communication terminals, and the device name indicating a name of each communication terminal;

upon receiving a connection request in which device names of the connecting communication terminal and the connected communication terminal are described, (i) extracting, based on the device name, a device ID of the connected communication terminal from the stored pairs, and (ii) transmitting, to a trigger server, a trigger for requesting the connected communication terminal identified by the device ID to transmit a permission list, the trigger server notifying of the request made to the connected communication terminal, and the permission list being a list of device names of communication terminals to which communication is permitted;

searching for the device name of the connecting communication terminal in the permission list after receiving the permission list;

transmitting, to the trigger server, an address inquiry for inquiring about addresses of the connecting communication terminal and the connected communication terminal based on the device IDs of the communication terminals, in the case when the device name of the connecting communication terminal is found in the permission list;

generating a session ID that is unique to the communication between the connecting communication terminal and the connected communication terminal; and

transmitting (i) at least the session ID and the address of the connected communication terminal to the connecting communication terminal, and (ii) at least the session ID and the address of the connecting communication terminal to the connected communication terminal, in the case when the addresses of the communication terminals are received from the trigger server as a response to the address inquiry.

37. A communication method for a trigger server that manages addresses of a connecting communication terminal and a connected communication terminal, and that notifies the connected communication terminal of a request, said method comprising:

receiving and storing a pair of device ID and address that is transmitted from the respective communication terminals, the device ID identifying each of the communication terminals;

receiving, from a session management server, a trigger for requesting a transmission of a permission list, the session management server managing sessions between the connecting communication terminal and the connected communication terminal, and the permission list being a list of device names of communication terminals to which communication is permitted;

transmitting, to the connected communication terminal, the request of transmitting the permission list to the session management server, in the case when the trigger requesting the transmission of the permission list is received in said receiving; and

receiving polling performed by the connected communication terminal, so as to transmit the request.

38. A communication system comprising:

a connecting communication terminal, a connected communication terminal, a session management server that manages sessions between said communication terminals, and a trigger server that notifies the connected communication terminal of a request made by said session management server,

wherein said connected communication terminal includes;

a registration unit operable to register (i) a pair of a device ID and a device name onto the session management server that manages sessions between the communication terminals, and (ii) a pair of the device ID and an address of the connected communication terminal onto the trigger server that notifies the connected communication terminal of a request for a communication with the session management server, the device ID identifying the connected communication terminal, and the device name indicating a name of the connected communication terminal;

a holding unit operable to hold a permission list that is a list of device names of communication terminals to which direct communication is permitted;

a polling unit operable to perform polling on the trigger server so as to receive the request for the communication with the session management server from the trigger server;

an address resolution unit operable to receive, from the session management server, at least an address of the connecting communication terminal and a session ID that is unique to the communication with the connecting communication terminal; and

a Peer-to-Peer communication unit operable to establish a connection to the connecting communication terminal, and to perform direct communication with the connecting communication terminal in the case when the address of the connecting communication terminal and the session ID are received,

said connecting communication terminal includes;

a registration unit operable to register (i) a pair of a device ID and a device name onto the session management server that manages sessions between the communication terminals, and (ii) a pair of the device ID and the address of the connecting communication terminal onto the trigger server that notifies the connected communication terminal of the request for a communication with the session management server, the device ID identifying the connecting communication terminal, and the device name indicating a name of the connecting communication terminal;

a transmission unit operable to transmit a request for a connection to the session management server, the request having device names of the connecting communication terminal and the connected communication terminal;

an address resolution unit operable to obtain the address of the connected communication terminal by receiving, from the session management server, at least the address of the connected communication terminal and the session ID that is unique to the communication with the connected communication terminal, after the transmission performed by said transmission unit; and

a Peer-to-Peer communication unit operable to perform direct communication with the connected communication terminal in the case when the address of the connected communication terminal is received,

said session management server includes;

a storage unit operable to receive and store a pair of device ID and device name that is received from the respective communication terminals, the device ID identifying each of the communication terminals, and the device name indicating a name of each communication terminal;

a trigger transmission unit operable, upon receiving a connection request in which device names of the connecting communication terminal and the connected communication terminal are described, (i) to extract, based on the device name, a device ID of the connected communication terminal from said storage unit, and (ii) to transmit, to the trigger server, a trigger for requesting the connected communication terminal identified by the device ID to transmit the permission list, the trigger server notifying of the request made to the connected communication terminal, and the permission list being a list of device names of communication terminals to which communication is permitted;

a name search unit operable to search for the device name of the connecting communication terminal in the permission list after receiving the permission list;

an address inquiry unit operable to transmit, to the trigger server, an address inquiry for inquiring about addresses of the connecting communication terminal and the connected communication terminal based on the device IDs of the communication terminals, in the case when the device name of the connecting communication terminal is found in the permission list;

a session generation unit operable to generate the session ID that is unique to the communication between the connecting communication terminal and the connected communication terminal; and

a transmission unit operable to transmit (i) at least the session ID and the address of the connected communication terminal to the connecting communication terminal, and (ii) at least the session ID and the address of the connecting communication terminal to the connected communication terminal, in the case when said address inquiry unit receives, from the trigger server, the addresses of the communication terminals as a response to the address inquiry, and

said trigger server includes;

an address storage unit operable to receive and store a pair of device ID and address that is transmitted from the respective communication terminals, the device ID identifying each of the communication terminals;

a receiving unit operable to receive, from the session management server, the trigger for requesting the transmission of the permission list, the session management server managing sessions between the connecting communication terminal and the connected communication terminal, and the permission list being a list of device names of communication terminals to which communication is permitted;

a trigger processing unit operable to transmit, to the connected communication terminal, the request of transmitting the permission list to the session management server, in the case when the trigger requesting the transmission of the permission list is received by said receiving unit; and

a polling receiving unit operable to receive polling performed by the connected communication terminal, so as to transmit the request.