Scheme for label switched path loop detection at node device

• US 20020176370A1
• Filed: 07/10/2002
• Published: 11/28/2002
• Est. Priority Date: 08/08/1997
• Status: Active Grant

• Current Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Original Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Inventors: Ohba, Yoshihiro, Takahashi, Junichi, Matsuzawa, Shigeo, Katsube, Yasuhiro
• Granted Patent: US 7,120,145 B2
• Time in Patent Office: Days
• US Class Current: 370/252
• CPC Class Codes: H04L 2012/562 Routing
• CPC Class Codes: H04L 2012/5667 IP over ATM
• CPC Class Codes: H04L 49/309 Header conversion, routing tables or routing tags
• CPC Class Codes: H04Q 11/0478 Provisions for broadband connections

Abstract

A node device and a label switched path loop detection method which are capable of detecting a label switched path loop efficiently and quickly are disclosed. In a node device for carrying out the label switching, an ingress node information is included in a message that is to be successively transmitted from the upstream side in order to set up a label switched path, and the fact that the message with the same ingress node information for the same packet flow will be received from a previous hop node that is different from before if the label switched path has a loop formed thereon is utilized. Also, at a time of transmitting a message for the purpose of setting up a label switched path, if a node at which the label switched path for that packet flow already exists on the upstream or downstream side is encountered, this already existing label switched path is traced along the same or opposite direction as the flow, and the label switched path is set up if no loop is detected after tracing to the end.

Claims

1. A node device for label switching entered packets by referring to an input label information capable of identifying a packet flow to be entered and a corresponding information for specifying at least an output side interface, the node device comprising:

a memory unit for storing a flow ID capable of network globally identifying a packet flow and an ingress node information regarding an ingress node of a label switched path, according to one label allocation message requesting a set up of the label switched path which is received from one previous hop node; and

a judging unit for judging whether a label switched path loop is formed or not according to from which node another label allocation message that contains an identical flow ID and an identical ingress node information as said one label allocation message is received.

2. The node device of claim 1, wherein the judging unit judges whether the label switched path loop is formed or not according to whether or not said another label allocation message is received from a node different from said one previous hop node.

3. The node device of claim 1, further comprising a processing unit for carrying out a label allocation processing with respect to a received label allocation message, except when the judging unit judges that a label switched path loop is formed.

4. The node device of claim 1, further comprising a transmission unit for transmitting a label allocation failure message to a previous hop node which is a source of a received label allocation message when the judging unit judges that a label switched path loop is formed.

5. The node device of claim 4, wherein when a label allocation failure message is received from a next hop node, the transmission unit transmits a label allocation success message to a previous hop node from which a label allocation message corresponding to the label allocation failure message is received.

6. The node device of claim 1, wherein each label allocation message contains a label that constitutes a part or a whole of the label information that is allocated by a previous hop node which is a source of said each label allocation message, or an identifier for specifying a connection between a previous hop node and said node device that constitute a part of the label switched path from which the label can be derived.

7. The node device of claim 1, wherein each label allocation message contains an identifier for requesting label allocation, and the node device further comprises:

a transmission unit for transmitting to a previous hop node which is a source of a received label allocation message a label allocation success message that contains a label that constitutes a part or a whole of the label information that is allocated by said node device, or an identifier for specifying a connection between a previous hop node and said node device that constitute a part of the label switched path from which the label can be derived, when a label allocation processing with respect to the received label allocation message is permitted.

8. The node device of claim 1, further comprising:

a transmission unit for transmitting a message containing a hop count to a next hop node; and

a processing unit for carrying out a label allocation processing with respect to a received message, except when a hop count from the ingress node exceeds a threshold.

9. The node device of claim 1, wherein the ingress node information is given by a network layer address allocated to an output interface of the ingress node.

10. The node device of claim 1, wherein the ingress node information is given by a set of a network layer address allocated to an output interface of the ingress node and a local identifier allocated locally to the output interface of the ingress node.

11. A node device for transmitting packets to be label switched using an output label information capable of identifying a packet flow to be outputted, the node device comprising:

a transmission unit for transmitting a label allocation message requesting a set up of a label switched path that contain at least an information on said node device as an ingress node information regarding an ingress node of the label switched path; and

a judging unit for judging that a label switched path loop is formed upon receiving a label allocation message in which the ingress node information specifies said node device as the ingress node.

12. The node device of claim 11, wherein the ingress node information is given by a network layer address allocated to an output interface of the ingress node.

13. The node device of claim 11, wherein the ingress node information is given by a set of a network layer address allocated to an output interface of the ingress node and a local identifier allocated locally to the output interface of the ingress node.

15. The node device of claim 14, further comprising a processing unit for carrying out a label allocation processing with respect to a received label allocation message, except when the judging unit judges that a label switched path loop is formed.

16. The node device of claim 14, further comprising a transmission unit for transmitting a label allocation failure message to a previous hop node which is a source of a received label allocation message when the judging unit judges that a label switched path loop is formed.

17. The node device of claim 16, wherein when a label allocation failure message is received from a next hop node, the transmission unit transmits a label allocation success message to a previous hop node from which a label allocation message corresponding to the label allocation failure message is received.

18. The node device of claim 14, wherein each label allocation message contains a label that constitutes a part or a whole of the label information that is allocated by a previous hop node device which is a source of said each label allocation message, or an identifier for specifying a connection between a previous hop node and said node device that constitute a part of the label switched path from which the label can be derived.

19. The node device of claim 14, wherein each label allocation message contains an identifier for requesting label allocation, and the node device further comprises:

a transmission unit for transmitting to a previous hop node which is a source of a received label allocation message a label allocation success message that contains a label that constitutes a part or a whole of the label information that is allocated by said node device, or an identifier for specifying a connection between a previous hop node and said node device that constitute a part of the label switched path from which the label can be derived, when a label allocation processing with respect to the received label allocation message is permitted.

20. The node device of claim 14, further comprising:

a transmission unit for transmitting a message containing a hop count to a next hop node; and

a processing unit for carrying out a label allocation processing with respect to a received message, except when a hop count from the ingress node exceeds a threshold.

21. The node device of claim 14, wherein the ingress node information is given by a network layer address allocated to an output interface of the ingress node.

22. The node device of claim 14, wherein the ingress node information is given by a set of a network layer address allocated to an output interface of the ingress node and a local identifier allocated locally to the output interface of the ingress node.

24. The node device of claim 23, further comprising:

a transmission unit for transmitting a message containing a hop count to a next hop node; and

a processing unit for carrying out a label allocation processing with respect to a received message, except when a hop count from the ingress node exceeds a threshold.

26. The node device of claim 25, wherein the exchange unit transmits to a next hop node a label allocation message as a message for setting up a new label switched path when no label switched path for said one packet flow exists on downstream side of said node device, and

the exchange unit transmits to the next hop node an update message as a message for utilizing an existing label switched path when a label switched path for said one packet flow exists on downstream side of said node device and a corresponding label switched path is to be newly set up on upstream side of said node device.

27. The node device of claim 25, wherein the exchange unit transmits to a node other than a next hop node a label allocation message as a message for setting up a new label switched path when a label switched path for said one packet flow exists on downstream side of said node device but no corresponding label switched path exists on upstream side of said node device,

the exchange unit transmits to the next hop node a query message as a message for setting up a new label switched path when a label switched path for said one packet flow exists on upstream side of said node device but no corresponding label switched path exists on downstream side of said node device, and

the exchange unit transmits to the next hop node an update message as a message for utilizing an existing label switched path when the query message is received from a previous hop node and a label switched path for said one packet flow exists on downstream side of said node device.

28. The node device of claim 27, wherein the exchange unit transmits to the next hop node a label allocation success message when the label allocation message is received from the next hop node and no label switched path for said one packet flow exists on upstream side of said node device, and

the exchange unit also transmits the update message to the next hop node when the label allocation success message is received from a previous hop node and a label switched path for said one packet flow exists on downstream side of said node device.

29. The node device of claim 25, further comprising:

a transmission unit for transmitting a message containing a hop count to a next hop node; and

a processing unit for carrying out a label allocation processing with respect to a received message, except when a hop count from the ingress node exceeds a threshold.

14. A node device for label switching entered packets by referring to an input side label information capable of identifying a packet flow to be entered and a corresponding output label information capable of identifying the packet flow to be outputted, the node device comprising:

an exchange unit for exchanging with a neighboring node on a route of one packet flow a label allocation message requesting a set up of a label switched path which contains a flow ID capable of network globally identifying said one packet flow and an ingress node information regarding an ingress node of the label switched path; and

a judging unit for judging whether a label switched path loop is formed or not, when a label allocation message that contains a flow ID and an ingress node information that are matching with an existing label switched path is received, according to a change in the input side label information for the existing label switched path.

23. A node device for label switching entered packets by referring to an input side label information capable of identifying a packet flow to be entered and corresponding one or a plurality of output label information capable of identifying the packet flow to be outputted, the node device comprising:

an exchange unit for exchanging with each one of a previous hop node and one or a plurality of next hop nodes on a route of one packet flow a label allocation message requesting a set up of a label switched path which contains an identifier for identifying said one packet flow and an ingress node information regarding an ingress node of the label switched path; and

a judging unit for detecting whether or not a message containing an identifier and an ingress node information that are identical to those of a previously exchanged message is received from a previous hop node different from one previous hop node from which the previously exchanged message is received, or whether or not a message that contains an identifier and an ingress node information that are identical to those of the previously exchanged message and changes the input side label information is received, and judging whether a label switched path loop is formed or not according to a result of detecting.

25. A node device for label switching entered packets by referring to one or a plurality of input side label information capable of identifying a packet flow to be entered and a corresponding output label information capable of identifying the packet flow to be outputted, the node device comprising:

an exchange unit for exchanging with a neighboring node on a route of one packet flow a message for setting up a new label switched path or utilizing an existing label switched path, which contains an identifier for identifying said one packet flow and an ingress node information regarding an ingress node of the new label switched path or the existing label switched path; and

a judging unit for detecting whether or not a message containing an identifier and an ingress node information that are identical to those of a previously exchanged message is received from a previous hop node device different from one previous hop node device from which the previously exchanged message is received, or whether or not a message that contains an identifier and an ingress node information that are identical to those of the previously exchanged message and changes the input side label information is received, and judging whether a label switched path loop is formed or not according to a result of detectiong.

30. A node device for label switching entered packets by referring to an input side label information capable of identifying a packet flow to be entered and a corresponding output side label information capable of identifying the packet flow to be outputted, and for merging label switched paths by setting one output side label information and a plurality of input side label information in correspondence for one packet flow, the node device comprising:

a transmission unit for transmitting to a next hop node in an existing label switched path a hop count update message that contains at least an ingress node information after merging and an updated hop count value, upon receiving one label allocation message requesting a set up of one label switched path that contains at least a given ingress node information regarding an ingress node of said one label switched path and a given hop count value, when said one label allocation message requires merging to the existing label switched path and the given hop count value makes a hop count value of the existing label switched path updated to a larger value than a current value; and

a judging unit for judging whether a label switched path loop is formed or not according to from which node another hop count update or label allocation message for an identical packet flow that contains an identical ingress node information as a previously received label allocation message is received.

31. The node device of claim 30, wherein the judging unit judges whether the label switched path loop is formed or not according to whether or not said another hop count update or label allocation message is received from a node different from a previous hop node from which the previously received label allocation message is received.

32. The node device of claim 30, further comprising:

a unit for notifying that hop count update or label allocation cannot be made to a previous hop node from which a hop count update or label allocation message is received when the judging unit judges that a label switched path loop is formed;

a unit for notifying that label allocation cannot be made to a previous hop node from which a label allocation message is received upon being notified that hop count update cannot be made;

a unit for notifying that hop count update can be made to a previous hop node from which a hop count update message is received upon being notified that label allocation cannot be made and when a hop count does not exceed a threshold; and

a unit for setting up a set up requested label switched path by merging to the existing label switched path upon being notified that hop count update can be made.

33. The node device of claim 30, further comprising:

a unit for setting up a set up requested label switched path by merging to the existing label switched path, upon receiving said one label allocation message, when said one label allocation message requires merging to the existing label switched path and the given hop count value does not make a hop count value of the existing label switched path updated to a larger value than a current value.

34. The node device of claim 30, wherein the transmission unit uses an information regarding an ingress node corresponding to the updated hop count value as the ingress node information after merging to be contained in the hop count update message, and transmits the hop count update message that contains an ingress node information and a hop count value after undoing merging, when a part of merged label switched path is released to undo merging and an ingress node information corresponding to a released path is contained in the hop count update message.

35. The node device of claim 30, wherein the transmission unit uses an information regarding an ingress node corresponding to the updated hop count value or an ingress node of the existing label switched path as the ingress node information after merging to be contained in the hop count update message, and transmits an update message that contains an ingress node information after undoing merging, when a part of merged label switched path is released to undo merging and an ingress node information corresponding to a released path is contained in the hop count update message.

37. The node device of claim 36, wherein the exchange unit transmits to a next hop node a label allocation message as a message for setting up a new label switched path when no label switched path for said one packet flow exists on downstream side of said node device, and

the exchange unit transmits to the next hop node an update message as a message for utilizing an existing label switched path when a label switched path for said one packet flow exists on downstream side of said node device and a corresponding label switched path is to be newly set up on upstream side of said node device.

38. The node device of claim 36, wherein the exchange unit transmits to a next hop node a label allocation message as a message for setting up a new label switched path when no label switched path for said one packet flow exists on downstream side of said node device,

the exchange unit transmits to the next hop node a query message as a message for setting up a new label switched path when a label switched path for said one packet flow exists on downstream side of said node device and a corresponding label switched path is to be newly set up on upstream side of said node device, and

the exchange unit transmits to a previous hop node of one label switched path on upstream side of said node device an update message as a message for utilizing an existing label switched path when the query message is received from the next hop node and said one label switched path for said one packet flow exists on upstream side of said node device.

39. The node device of claim 36, wherein the exchange unit transmits to a node other than a next hop node a label allocation message as a message for setting up a new label switched path when a label switched path for said one packet flow exists on downstream side of said node device but no corresponding label switched path exists on upstream side of said node device,

the exchange unit transmits to the next hop node a query message as a message for setting up a new label switched path when a label switched path for said one packet flow exists on upstream side of said node device but no corresponding label switched path exists on downstream side of said node device, and

the exchange unit transmits to the next hop node an update message as a message for utilizing an existing label switched path when the query message is received from a previous hop node and a label switched path for said one packet flow exists on downstream side of said node device.

40. The node device of claim 36, wherein the exchange unit transmits to a node other than a next hop node a label allocation success message as a message for setting up a new label switched path when a label switched path for said one packet flow exists on downstream side of said node device but no corresponding label switched path exists on upstream side of said node device, and

the exchange unit transmits to a previous hop node of one label switched path on upstream side of said node device an update message as a message for utilizing an existing label switched path when a label switched path for said one packet flow exists on upstream side of said node device but no corresponding label switched path exists on downstream side of said node device so that a corresponding label switched path is to be newly set up on upstream side of said node device.

36. A node device for label switching entered packets by referring to one or a plurality of input side label information capable of identifying a packet flow to be entered and a corresponding output label information capable of identifying the packet flow to be outputted, the node device comprising:

an exchange unit for exchanging with a neighboring node on a route of one packet flow a message for setting up a new label switched path or utilizing an existing label switched path, which contains an identifier for identifying said one packet flow;

a memory unit for storing an information indicating a set up of a label switched path corresponding to said message as pending until a response message corresponding to said message is received; and

a judging unit for judging whether a label switched path loop is formed or not according to whether or not a message regarding a label switched path for which the information indicating pending is stored in the memory unit according to a previously exchanged message is received.

41. A node device for label switching entered packets by referring to an input side label information capable of identifying a packet flow to be entered and a corresponding output side label information capable of identifying the packet flow to be outputted, and for merging label switched paths by setting one output side label information and a plurality of input side label information in correspondence for one packet flow, the node device comprising:

a transmission unit for transmitting to a next hop node in an existing label switched path a hop count update message that contains at least an updated hop count value, upon receiving one label allocation message requesting a set up of one label switched path that contains at least a given hop count value, when said one label allocation message requires merging to the existing label switched path and the given hop count value makes a hop count value of the existing label switched path updated to a larger value than a current value;

a memory unit for storing a correspondence between the input side label information and the output side label information for said one packet flow according to said one label allocation message, and storing an information indicating a storing of the correspondence as pending until a success message corresponding to the hop count update message is received; and

a judging unit for judging whether a label switched path loop is formed or not according to whether or not a hop count update or label allocation message indicating a packet flow or a correspondence between the input side label information and the output side label information for which the information indicating the storing of the correspondence as pending is stored in the memory unit according to a previously received label allocation message is received.

42. A method of label switched path loop detection in a node device for label switching entered packets by referring to an input label information capable of identifying a packet flow to be entered and a corresponding information for specifying at least an output side interface, the method comprising the steps of:

storing a flow ID capable of network globally identifying a packet flow and an ingress node information regarding an ingress node of a label switched path, according to one label allocation message requesting a set up of the label switched path which is received from one previous hop node; and

judging whether a label switched path loop is formed or not according to from which node another label allocation message that contains an identical flow ID and an identical ingress node information as said one label allocation message is received.

43. A method of label switched path loop detection in a node device for transmitting packets to be label switched using an output label information capable of identifying a packet flow to be outputted, the method comprising the steps of:

transmitting a label allocation message requesting a set up of a label switched path that contain at least an information on said node device as an ingress node information regarding an ingress node of the label switched path; and

judging that a label switched path loop is formed upon receiving a label allocation message in which the ingress node information specifies said node device as the ingress node.

44. A method of label switched path loop detection in a node device for label switching entered packets by referring to an input side label information capable of identifying a packet flow to be entered and a corresponding output label information capable of identifying the packet flow to be outputted, the method comprising the steps of:

exchanging with a neighboring node on a route of one packet flow a label allocation message requesting a set up of a label switched path which contains a flow ID capable of network globally identifying said one packet flow and an ingress node information regarding an ingress node of the label switched path; and

judging whether a label switched path loop is formed or not, when a label allocation message that contains a flow ID and an ingress node information that are matching with an existing label switched path is received, according to a change in the input side label information for the existing label switched path.

45. A method of label switched path loop detection in a node device for label switching entered packets by referring to an input side label information capable of identifying a packet flow to be entered and corresponding one or a plurality of output label information capable of identifying the packet flow to be outputted, the method comprising the steps of:

exchanging with each one of a previous hop node and one or a plurality of next hop nodes on a route of one packet flow a label allocation message requesting a set up of a label switched path which contains an identifier for identifying said one packet flow and an ingress node information regarding an ingress node of the label switched path; and

detecting whether or not a message containing an identifier and an ingress node information that are identical to those of a previously exchanged message is received from a previous hop node different from one previous hop node from which the previously exchanged message is received, or whether or not a message that contains an identifier and an ingress node information that are identical to those of the previously exchanged message and changes the input side label information is received, and judging whether a label switched path loop is formed or not according to a result of detecting.

46. A method of label switched path loop detection in a node device for label switching entered packets by referring to one or a plurality of input side label information capable of identifying a packet flow to be entered and a corresponding output label information capable of identifying the packet flow to be outputted, the method comprising the steps of:

exchanging with a neighboring node on a route of one packet flow a message for setting up a new label switched path or utilizing an existing label switched path, which contains an identifier for identifying said one packet flow and an ingress node information regarding an ingress node of the new label switched path or the existing label switched path; and

detecting whether or not a message containing an identifier and an ingress node information that are identical to those of a previously exchanged message is received from a previous hop node device different from one previous hop node device from which the previously exchanged message is received, or whether or not a message that contains an identifier and an ingress node information that are identical to those of the previously exchanged message and changes the input side label information is received, and judging whether a label switched path loop is formed or not according to a result of detectiong.

47. A method of label switched path loop detection in a node device for label switching entered packets by referring to an input side label information capable of identifying a packet flow to be entered and a corresponding output side label information capable of identifying the packet flow to be outputted, and for merging label switched paths by setting one output side label information and a plurality of input side label information in correspondence for one packet flow, the method comprising the steps of:

transmitting to a next hop node in an existing label switched path a hop count update message that contains at least an ingress node information after merging and an updated hop count value, upon receiving one label allocation message requesting a set up of one label switched path that contains at least a given ingress node information regarding an ingress node of said one label switched path and a given hop count value, when said one label allocation message requires merging to the existing label switched path and the given hop count value makes a hop count value of the existing label switched path updated to a larger value than a current value; and

judging whether a label switched path loop is formed or not according to from which node another hop count update or label allocation message for an identical packet flow that contains an identical ingress node information as a previously received label allocation message is received.

48. A method of label switched path loop detection in a node device for label switching entered packets by referring to one or a plurality of input side label information capable of identifying a packet flow to be entered and a corresponding output label information capable of identifying the packet flow to be outputted, the method comprising the steps of:

exchanging with a neighboring node on a route of one packet flow a message for setting up a new label switched path or utilizing an existing label switched path, which contains an identifier for identifying said one packet flow;

storing an information indicating a set up of a label switched path corresponding to said message as pending until a response message corresponding to said message is received; and

judging whether a label switched path loop is formed or not according to whether or not a message regarding a label switched path for which the information indicating pending is stored in the memory unit according to a previously exchanged message is received.

49. A method of label switched path loop detection in a node device for label switching entered packets by referring to an input side label information capable of identifying a packet flow to be entered and a corresponding output side label information capable of identifying the packet flow to be outputted, and for merging label switched paths by setting one output side label information and a plurality of input side label information in correspondence for one packet flow, the method comprising the steps of:

transmitting to a next hop node in an existing label switched path a hop count update message that contains at least an updated hop count value, upon receiving one label allocation message requesting a set up of one label switched path that contains at least a given hop count value, when said one label allocation message requires merging to the existing label switched path and the given hop count value makes a hop count value of the existing label switched path updated to a larger value than a current value;

storing a correspondence between the input side label information and the output side label information for said one packet flow according to said one label allocation message, and storing an information indicating a storing of the correspondence as pending until a success message corresponding to the hop count update message is received; and

judging whether a label switched path loop is formed or not according to whether or not a hop count update or label allocation message indicating a packet flow or a correspondence between the input side label information and the output side label information for which the information indicating the storing of the correspondence as pending is stored in the memory unit according to a previously received label allocation message is received.

50. An article of manufacture, comprising:

a computer usable medium having computer readable program code means embodied therein for causing a computer to function as a node device for label switching entered packets by referring to an input label information capable of identifying a packet flow to be entered and a corresponding information for specifying at least an output side interface, the computer readable program code means includes;

first computer readable program code means for causing said computer to store a flow ID capable of network globally identifying a packet flow and an ingress node information regarding an ingress node of a label switched path, according to one label allocation message requesting a set up of the label switched path which is received from one previous hop node; and

second computer readable program code means for causing said computer to judge whether a label switched path loop is formed or not according to from which node another label allocation message that contains an identical flow ID and an identical ingress node information as said one label allocation message is received.

51. An article of manufacture, comprising:

a computer usable medium having computer readable program code means embodied therein for causing a computer to function as a node device for transmitting packets to be label switched using an output label information capable of identifying a packet flow to be outputted, the computer readable program code means includes;

first computer readable program code means for causing said computer to transmit a label allocation message requesting a set up of a label switched path that contain at least an information on said node device as an ingress node information regarding an ingress node of the label switched path; and

second computer readable program code means for causing said computer to judge that a label switched path loop is formed upon receiving a label allocation message in which the ingress node information specifies said node device as the ingress node.

52. An article of manufacture, comprising:

a computer usable medium having computer readable program code means embodied therein for causing a computer to function as a node device for label switching entered packets by referring to an input side label information capable of identifying a packet flow to be entered and a corresponding output label information capable of identifying the packet flow to be outputted, the computer readable program code means includes;

first computer readable program code means for causing said computer to exchange with a neighboring node on a route of one packet flow a label allocation message requesting a set up of a label switched path which contains a flow ID capable of network globally identifying said one packet flow and an ingress node information regarding an ingress node of the label switched path; and

second computer readable program code means for causing said computer to judge whether a label switched path loop is formed or not, when a label allocation message that contains a flow ID and an ingress node information that are matching with an existing label switched path is received, according to a change in the input side label information for the existing label switched path.

53. An article of manufacture, comprising:

a computer usable medium having computer readable program code means embodied therein for causing a computer to function as a node device for label switching entered packets by referring to an input side label information capable of identifying a packet flow to be entered and corresponding one or a plurality of output label information capable of identifying the packet flow to be outputted, the computer readable program code means includes;

first computer readable program code means for causing said computer to exchange with each one of a previous hop node and one or a plurality of next hop nodes on a route of one packet flow a label allocation message requesting a set up of a label switched path which contains an identifier for identifying said one packet flow and an ingress node information regarding an ingress node of the label switched path; and

second computer readable program code means for causing said computer to detect whether or not a message containing an identifier and an ingress node information that are identical to those of a previously exchanged message is received from a previous hop node different from one previous hop node from which the previously exchanged message is received, or whether or not a message that contains an identifier and an ingress node information that are identical to those of the previously exchanged message and changes the input side label information is received, and judge whether a label switched path loop is formed or not according to a result of detecting.

54. An article of manufacture, comprising:

a computer usable medium having computer readable program code means embodied therein for causing a computer to function as a node device for label switching entered packets by referring to one or a plurality of input side label information capable of identifying a packet flow to be entered and a corresponding output label information capable of identifying the packet flow to be outputted, the computer readable program code means includes;

first computer readable program code means for causing said computer to exchange with a neighboring node on a route of one packet flow a message for setting up a new label switched path or utilizing an existing label switched path, which contains an identifier for identifying said one packet flow and an ingress node information regarding an ingress node of the new label switched path or the existing label switched path; and

second computer readable program code means for causing said computer to detect whether or not a message containing an identifier and an ingress node information that are identical to those of a previously exchanged message is received from a previous hop node device different from one previous hop node device from which the previously exchanged message is received, or whether or not a message that contains an identifier and an ingress node information that are identical to those of the previously exchanged message and changes the input side label information is received, and judge whether a label switched path loop is formed or not according to a result of detectiong.

55. An article of manufacture, comprising:

a computer usable medium having computer readable program code means embodied therein for causing a computer to function as a node device for label switching entered packets by referring to an input side label information capable of identifying a packet flow to be entered and a corresponding output side label information capable of identifying the packet flow to be outputted, and for merging label switched paths by setting one output side label information and a plurality of input side label information in correspondence for one packet flow, the computer readable program code means includes;

first computer readable program code means for causing said computer to transmit to a next hop node in an existing label switched path a hop count update message that contains at least an ingress node information after merging and an updated hop count value, upon receiving one label allocation message requesting a set up of one label switched path that contains at least a given ingress node information regarding an ingress node of said one label switched path and a given hop count value, when said one label allocation message requires merging to the existing label switched path and the given hop count value makes a hop count value of the existing label switched path updated to a larger value than a current value; and

second computer readable program code means for causing said computer to judge whether a label switched path loop is formed or not according to from which node another hop count update or label allocation message for an identical packet flow that contains an identical ingress node information as a previously received label allocation message is received.

56. An article of manufacture, comprising:

a computer usable medium having computer readable program code means embodied therein for causing a computer to function as a node device for label switching entered packets by referring to one or a plurality of input side label information capable of identifying a packet flow to be entered and a corresponding output label information capable of identifying the packet flow to be outputted, the computer readable program code means includes;

first computer readable program code means for causing said computer to exchange with a neighboring node on a route of one packet flow a message for setting up a new label switched path or utilizing an existing label switched path, which contains an identifier for identifying said one packet flow;

second computer readable program code means for causing said computer to store an information indicating a set up of a label switched path corresponding to said message as pending until a response message corresponding to said message is received; and

third computer readable program code means for causing said computer to judge whether a label switched path loop is formed or not according to whether or not a message regarding a label switched path for which the information indicating pending is stored In the memory unit according to a previously exchanged message is received.

57. An article of manufacture, comprising:

a computer usable medium having computer readable program code means embodied therein for causing a computer to function as a node device for label switching entered packets by referring to an input side label information capable of identifying a packet flow to be entered and a corresponding output side label information capable of identifying the packet flow to be outputted, and for merging label switched paths by setting one output side label information and a plurality of input side label information in correspondence for one packet flow, the computer readable program code means includes;

first computer readable program code means for causing said computer to transmit to a next hop node in an existing label switched path a hop count update message that contains at least an updated hop count value, upon receiving one label allocation message requesting a set up of one label switched path that contains at least a given hop count value, when said one label allocation message requires merging to the existing label switched path and the given hop count value makes a hop count value of the existing label switched path updated to a larger value than a current value;

second computer readable program code means for causing said computer to store a correspondence between the input side label information and the output side label information for said one packet flow according to said one label allocation message, and storing an information indicating a storing of the correspondence as pending until a success message corresponding to the hop count update message is received; and

third computer readable program code means for causing said computer to judge whether a label switched path loop is formed or not according to whether or not a hop count update or label allocation message indicating a packet flow or a correspondence between the input side label information and the output side label information for which the information indicating the storing of the correspondence as pending is stored in the memory unit according to a previously received label allocation message is received.