Label switched path set up scheme with reduced need for label set up retry operation

• US 6,529,958 B1
• Filed: 07/16/1999
• Issued: 03/04/2003
• Est. Priority Date: 07/17/1998
• Status: Expired due to Fees

• Current Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Original Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Inventors: Oba, Yoshihiro, Katsube, Yasuhiro
• Primary Examiner(s): Lee, Thomas
• Assistant Examiner(s): Hu, Jinsong
• Application Number:
  US09/356,054
• Time in Patent Office: 1,327 Days
• Field of Search: 709/230, 709/234, 709/237, 709/239, 709/238, 709/240, 709/241, 709/242, 370/392, 370/396, 370/397
• US Class Current: 709/237
• 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 45/18 Loop-free operations
• CPC Class Codes: H04L 45/26 Route discovery packet
• CPC Class Codes: H04L 45/50 using label swapping, e.g. multi-protocol label switch [MPLS]
• CPC Class Codes: H04L 45/507 Label distribution

Abstract

A label switched path set up scheme which is capable of detecting a loop of the label switched path efficiently and quickly, and which can enable the switching of the label switched path even in the case where conventionally a label switch path loop would be erroneously detected at a time of the route change, without requiring a label set up retry operation from a previous hop node device of the node device that have erroneously detected the loop which would have been necessary conventionally. A label switched path set up request message is transferred up to a node that can confirm that the path does not form a loop, while each node through which the message passes stores the fact that it is in a message processing state. Then, in a process where a response message is returned from that node, the message processing state of each node on the route of the path is released sequentially, and this releasing establishes the path set up.

Claims

1. A method for setting up a label switched path, comprising the steps of:

judging whether the label switched path forms a loop or not at a node that received a request message regarding a set up of the label switched path for a packet flow, on a basis of label switched path information stored in a first mode at said node that received the request message, the request message including a flow identifier for identifying the packet flow and information indicating that it is a message currently awaiting a response regarding the packet flow, and the first mode indicating that a message from which the label switched path information originates is a message currently awaiting a response;

storing the flow identifier contained in the request message as the label switched path information in the first mode at said node that received the request message, and transferring the request message from said node that received the request message to another node on a route of the packet flow, when said node that received the request message cannot judge that the label switched path does not form a loop;

returning a response message for the request message from said node that received the request message when said node that received the request message judges that the label switched path does not form a loop; and

changing the label switched path information currently stored in the first mode at a node that received the response message into a second mode different from the first mode such that the label switched path information that is changed into the second mode will not be used subsequently in judging whether any requested label switched path forms a loop or not at said node that received the response message and the label switched path will become available at said node that received the response message.

2. The method of claim 1, further comprising the step of:

conditionally transferring the response message from the node that received the response message to another node that transferred the request message and currently stores the label switched path information in the first mode.

3. The method of claim 1, wherein said node that received the request message does not carry out transfer of the request message or returning of the response message when said node that received the request message judges that the label switched path forms a loop.

4. The method of claim 1, wherein said node that received the request message judges whether the label switched path forms a loop or not, according to whether or not the label switched path information containing the flow identifier that is identical to that contained in the request message is stored in the first mode at said node that received the request message.

5. The method of claim 1, wherein the request message also contains a message identifier for network globally identifying each message that is being processed for the packet flow, and said node device that received the request message stores the label switched path information containing the message identifier and the flow identifier.

6. The method of claim 5, wherein said node that received the request message judges whether the label switched path forms a loop or not, according to whether or not the label switched path information containing the flow identifier and the message identifier that are identical to those contained in the request message is stored in the first mode at said node that received the request message.

7. The method of claim 5, wherein the message identifier contains an identification information of a node that allocated the message identifier contained in the request message.

8. The method of claim 1, wherein the request message contains another information from which a number of hops from an ingress node of the label switched path up to said node that received the request message can be obtained, and

said node that received the request message handles the request message equivalently as in a case of judging that the label switched path forms a loop, when the number of hops is judged as exceeding a prescribed value according to said another information.

9. The method of claim 1, wherein said node that received the request message judges that the label switched path does not form a loop, when own node is an egress node of the label switched path or when a corresponding established label switched path exists on a downstream side of own node and it is allowed to connect the label switched path to said corresponding established label switched path.

10. The method of claim 1, wherein the request message is actively transmitted by an ingress node of the label switched path, an intermediate node of an already established label switched path at which a route change occurred, or an egress node of an already established label switched path that newly recognized a downstream side neighboring node.

11. The method of claim 1, wherein said node that received the request message also carries out allocation of a label contained in a link information provided for label switching purpose, at a time of returning the response message.

12. The method of claim 1, further comprising the steps of:

transmitting a cancellation message for the request message from a node that actively transmitted the request message, when said node that received the request message has judged that the label switched path forms a loop and a need to set up the label switched path no longer exists, and

maintaining the flow identifier contained in the request message as stored in the first mode at each node that transferred the request message, until the cancellation message corresponding to the request message is received.

13. The method of claim 1, wherein when said node that received the request message currently stores the label switched path information corresponding to another request message regarding the label switched path set up in the first mode and said node that received the request message cannot judge whether the label switched path forms a loop or not, said node that received the request message handles the request message and said another request message together as a single message.

14. The method of claim 1, wherein the request message contains another information from which a number of hops from an ingress node of the label switched path up to said node that received the request message can be obtained, and

said node that received the request message corrects said another information regarding the number of hops from the ingress node of the label switched path up to own node, when said node that received the request message judges that the label switched path forms a loop.

15. A node device for setting up a label switched path, comprising:

a judging unit configured to judge whether the label switched path forms a loop or not upon receiving a request message regarding the label switched path set up for a packet flow, on a basis of label switched path information stored in a first mode at a memory of said node device, the request message including a flow identifier for identifying the packet flow and information indicating that it is a message currently awaiting a response regarding the packet flow, and the first mode indicating that a message from which the label switched path information originates is a message currently awaiting a response;

a first processing unit configured to store the flow identifier contained in the request message as the label switched path information in the first mode at the memory and transfer the request message to another node on a route of the packet flow, when the judging unit cannot judge that the label switched path does not form a loop, and to return a response message for the request message when the judging unit judges that the label switched path does not form a loop; and

a second processing unit configured to change the label switched path information currently stored in the first mode at the memory into a second mode different from the first mode upon receiving the response message, such that the label switched path information that is changed into the second mode will not be used subsequently in judging whether any requested label switched path forms a loop or not at said node device and the label switched path will become available at said node device.

16. The node device of claim 15, wherein the second processing unit is also configured to conditionally transfer the response message to another node that transferred the request message and currently stores the label switched path information in the first mode.

17. The node device of claim 15, wherein the first processing unit does not carry out transfer of the request message or returning of the response message when the judging unit judges that the label switched path forms a loop.

18. The node device of claim 15, wherein the judging unit judges whether the label switched path forms a loop or not, according to whether or not the label switched path information containing the flow identifier that is identical to that contained in the request message is stored in the first mode at the memory.

19. The node device of claim 15, wherein the request message also contains a message identifier for network globally identifying each message that is being processed for the packet flow, and the first processing unit stores the label switched path information containing the message identifier and the flow identifier.

20. The node device of claim 19, wherein the judging unit judges whether the label switched path forms a loop or not, according to whether or not the label switched path information containing the flow identifier and the message identifier that are identical to those contained in the request message is stored in the first mode at the memory.

21. The node device of claim 15, wherein the judging unit judges that the label switched path does not form a loop, when said node device is an egress node of the label switched path or when a corresponding established label switched path exists on a downstream side of said node device and it is allowed to connect the label switched path to said corresponding established label switched path.

22. The node device of claim 15, further comprising:

a transfer unit for actively transmitting a new request message when said node device is an ingress node of the label switched path, an intermediate node of an already established label switched path at which a route change occurred, or an egress node of an already established label switched path that newly recognized a downstream side neighboring node.

23. The node device of claim 15, wherein when the first processing unit currently stores the label switched path information corresponding to another request message for regarding the label switched path set up in the first mode at the memory and the judging unit cannot judge whether the label switched path forms a loop or not, said node device handles the request message and said another request message together as a single message.

24. A computer usable medium having computer readable program code means embodied therein for causing a computer to function as a node device for setting up a label switched path, the computer readable program code means includes:

first computer readable program code means for causing said computer to judge whether the label switched path forms a loop or not upon receiving a request message regarding the label switched path set up for a packet flow, on a basis of label switched path information stored in a first mode at a memory of said node device, the request message including a flow identifier for identifying the packet flow and information indicating that it is a message currently awaiting a response regarding the packet flow, and the first mode indicating that a message from which the label switched path information originates is a message currently awaiting a response;

second computer readable program code means for causing said computer to store the flow identifier contained in the request message as the label switched path information in the first mode at the memory and transfer the request message to another node on a route of the packet flow, when the first computer readable program code means cannot judge that the label switched path does not form a loop, and to return a response message for the request message when the first computer readable program code means judges that the label switched path does not form a loop; and

third computer readable program code means for causing said computer to change the label switched path information currently stored in the first mode at the memory into a second mode different from the first mode upon receiving the response message, such that the label switched path information that is changed into the second mode will not be used subsequently in judging whether any requested label switched path forms a loop or not at said node device and the label switched path will become available at said node device.