Communication system, multicast-capable router, transmitter terminal, receiver terminal, and communication method

• US 20070121574A1
• Filed: 07/07/2004
• Published: 05/31/2007
• Est. Priority Date: 07/07/2003
• Status: Active Grant

• Current Assignee: NTT Docomo Incorporated (Nippon Telegraph and Telephone Corporation)
• Original Assignee: NTT Docomo Incorporated (Nippon Telegraph and Telephone Corporation)
• Inventors: Igarashi, Ken, Ishida, So, Fukazawa, Harunobu
• Granted Patent: US 7,620,045 B2
• Time in Patent Office: Days
• US Class Current: 370/351
• CPC Class Codes: H04L 12/185 with management of multicast group membership
• CPC Class Codes: H04L 45/00 Routing or path finding of packets in data switching networks routing or path finding in wireless networks H04W40/00
• CPC Class Codes: H04L 45/16 Multipoint routing

Abstract

A communication system (1) is provided with URs (20a to 20h) and a source terminal (10). The URs (20a to 20h) include: entry holders (21a to 21h) for holding forwarding addresses; message processors (25) for registering the addresses of other URs, the addresses being associated with a source terminal address and a multicast group address, in the entry holders (21a to 21h) as the forwarding addresses; message providers (26) for providing the source terminal address with join request messages which request the addition of the addresses of the URs to sending addresses. The source terminal (10) includes: an entry holder (11) for holding a sending address; and a message processor 14 for registering the addresses of the URs (20a to 20h) in the entry holder 11 as sending addresses based on the join request messages.

Claims

1. A communication system comprising:

a multicast-capable router including

a forwarding destination holder for holding a forwarding address to which a multicast-capable router forwards a multicast packet,

a forwarding destination register for registering an address of another multicast-capable router in the forwarding destination holder as the forwarding address while the address is associated with a source terminal address and a multicast group address, and

a router message provider for providing the source terminal address with a join request message which requests addition of the address of the multicast-capable router to a sending address to which the source terminal transmits the multicast packet; and

a source terminal including

a sending destination holder for holding the sending address, and

a sending destination register for registering the address of the multicast-capable router in the sending destination holder as the sending address based on the join request message.

2. The communication system according to claim 1, wherein the sending destination register registers, in the sending destination holder, the address of the multicast-capable router located most upstream when the source terminal address is assumed to be upstream in a multicast tree.

3. The communication system according to claim 1, wherein

the multicast-capable router includes a judgment section for judging whether or not to be a branch router which forwards the multicast packets to the plurality of forwarding addresses when the source terminal address is assumed to be upstream in the multicast tree,

the forwarding destination register registers, in the forwarding destination register, the plurality of forwarding addresses associated with the source terminal address and the multicast group address, when having judged that the multicast-capable router is to be a branch router,

the router message provider provides the source terminal address with a join/leave request message which requests addition of the address of the multicast-capable router to the sending address and deletion of the forwarding address from the sending address, when having judged that the multicast-capable router is to be a branch router, and

the sending destination register deletes the forwarding address from the sending destination holder based on the join/leave request message, and registers an address of the branch router in the sending destination holder.

4. The communication system according to claim 3, wherein the forwarding destination register deletes a forwarding address of the branch router located downstream from the forwarding destination holder based on the join/leave request message from the downstream branch router, and registers, in the forwarding destination holder, the address of the downstream branch router.

5. The communication system according to claim 3, wherein the forwarding destination register registers, in the forwarding destination holder, the forwarding address associated with the source terminal address and the multicast group address, when the multicast-capable router is to be an edge router connecting to a destination terminal.

6. The communication system according to claim 1, comprising a forwarding controller for encapsulating the multicast packet with the forwarding address when a destination address of the decapsulated multicast packet is compared with the forwarding address held by the forwarding destination holder, and the destination address is different from the forwarding address.

7. The communication system according to claim 1, wherein the forwarding destination holder holds an address indicating a multicast address group as the forwarding address, when the multicast packet is forwarded to the multicast-capable router connecting to the same subnetwork.

8. The communication system according to claim 1, comprising a forwarding controller for performing control in a manner of forwarding the multicast packet to the sending address before a change, when the source terminal address is changed.

9. The communication system according to claim 1, wherein

the source terminal includes an update notification section for providing a location update message which notifies a source terminal address after a change to a destination terminal when the source terminal address is changed, and

the destination terminal includes a destination terminal message provider for providing the source terminal address after the change with a join request message which requests addition of an address of the destination terminal based on the location update message.

10. The communication system according to claim 1, wherein the forwarding destination register registers an address in the forwarding destination holder based on the join request message from the destination terminal or the multicast-capable router.

11. A multicast-capable router comprising:

a forwarding destination holder for holding a forwarding address to which the multicast-capable router forwards a multicast packet;

a forwarding destination register for registering, in the forwarding destination holder, an address of another multicast-capable router as the forwarding address associated with a source terminal address and a multicast group address; and

a router message provider for providing the source terminal address with a join request message which requests addition of the address of the multicast-capable router to a sending address to which the source terminal transmits the multicast packet.

12. The multicast-capable router according to claim 11, comprising a judgment section for judging whether or not to be a branch router which forwards the multicast packets to the plurality of forwarding addresses when the source terminal address is assumed to be upstream in a multicast tree, wherein

the forwarding destination register registers, in the forwarding destination holder, the plurality of forwarding addresses associated with the source terminal address and the multicast group address, when the multicast-capable router has been judged to be the branch router, and

the router message provider provides the source terminal address with a join/leave request message which requests addition of the address of the multicast-capable router to the sending address and deletion of the forwarding address from the sending address, when the multicast-capable router has been judged to be the branch router.

13. A source terminal comprising:

a sending destination holder for holding a sending address to which a multicast packet is transmitted; and

a sending destination register for registering, in the sending destination holder, an address of a multicast-capable router as the sending address based on a join request message which requests addition of the address of the multicast-capable router to the sending address.

14. The source terminal according to claim 13, wherein the sending destination register registers, in the sending destination holder, the address of the multicast-capable router located most upstream when an address of the source terminal is assumed to be upstream in the multicast tree.

15. The source terminal according to claim 13, wherein based on a join/leave request message which requests to add, to the sending address, the address of the multicast-capable router, which is a branch router forwarding the multicast packets to a plurality of forwarding addresses when an address of the source terminal is assumed to be upstream in the multicast tree, and to delete the forwarding address from the sending address, the sending destination register deletes the forwarding address from the sending destination holder, and registers an address of the branch router in the sending destination holder.

16. A destination terminal comprising a destination terminal message provider for providing a source terminal address after a change with a join request message which requests addition of an address of a destination terminal to a sending address to which a source terminal transmits a multicast packet, based on a location update message which notifies the source terminal address after the change when a source terminal address transmitting a multicast packet is changed.

17. A communication method comprising:

registering an address of another multicast-capable router, which is associated with a source terminal address and a multicast group address, as a forwarding address in a forwarding destination holder for holding the forwarding address to which a multicast-capable router transmits a multicast packet;

transmitting, to the source terminal address, a join request message which requests addition of the address of the multicast-capable router to a sending address to which the source terminal transmits a multicast packet; and

registering, in a sending destination holder for holding the sending address, the address of the multicast-capable router as the sending address based on the join request message.

18. The communication method according to claim 17, wherein the source terminal registers, in the sending destination holder, the address of the multicast-capable router located most upstream when the source terminal address is assumed to be upstream in a multicast tree.

19. The communication method according to claim 17, comprising:

judging to be a branch router which forwards the multicast packets to a plurality of forwarding addresses when the source terminal address is assumed to be upstream in the multicast tree;

registering, in the forwarding destination holder, the plurality of forwarding addresses associated with the source terminal address and the multicast group address when having judged to be the branch router;

transmitting, to the source terminal address, a join/leave request message which requests addition of the address of the multicast-capable router to the sending address and deletion of the forwarding address from the sending address; and

deleting the forwarding address from the sending destination holder based on the join/leave request message, and registering an address of the branch router in the sending destination holder.

20. The communication method according to claim 17, comprising:

transmitting a location update message which notifies a destination terminal of a source terminal address after a change when a source terminal address is changed; and

transmitting, to the source terminal address after the change, the join request message which requests addition of an address of the destination terminal to the sending address, based on the location update message.