System and method for fault recovery for a two line bi-directional ring network

• US 6,820,210 B1
• Filed: 04/17/2003
• Issued: 11/16/2004
• Est. Priority Date: 04/27/1998
• Status: Expired due to Term

• Current Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Original Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Inventors: Suwala, George, Daruwalla, Feisal, Tsiang, David, Bates, Tony, Chin, Hon Wah
• Primary Examiner(s): BADERMAN, SCOTT T
• Application Number:
  US10/418,452
• Time in Patent Office: 579 Days
• Field of Search: 714/4, 714/43, 714/55, 714/717, 709/207, 709/238, 709/240, 709/251, 370/216, 370/221, 370/222, 370/223, 370/224
• US Class Current: 714/4.1
• CPC Class Codes: H04L 12/42 Loop networks
• CPC Class Codes: H04L 12/437 Ring fault isolation or reconfiguration for SDH/SONET ring networks H04J3/085
• CPC Class Codes: H04L 45/22 Alternate routing
• CPC Class Codes: H04L 45/28 using route fault recovery

Abstract

The present invention provides a protection protocol for fault recovery, such as a ring wrap, for a network, such as a two line bi-directional ring network. An embodiment of the present invention works in conjunction with a ring topology network in which a node in the network can identify a problem with a connection between the node and a first neighbor. The present invention provides 1 protection protocol which simplifies the coordination required by the nodes in a ring network. The nodes do not need to maintain a topology map of the ring, identifying and locating each node on the ring, for effective protection. Additionally, independently operating ring networks can be merged and the protection protocol will appropriately remove a protection, such as a ring wrap, to allow the formation of a single ring. It also provides for multiple levels of protection priority so that protection for a high priority failure, such as a physical break in a connection, would remove protection for a low priority failure, such as signal degrade, on another link.

Claims

1. An apparatus for performing fault recovery in a network, comprising:

a first node operable to identify a problem in a connection between the first node and a selected one of a plurality of neighboring nodes, the first node operable to communicate a message identifying the problem to a second node, wherein a selected one of the first and second nodes are operable to initiate a fault recovery procedure after the problem has been identified, and wherein if the second node has encountered a situation that has a higher priority than a situation described by the problem identified by the first node, then the message is ignored by the second node.

2. An apparatus for performing fault recovery in a network, comprising:

a first node operable to identify a problem in a connection between the first node and a selected one of a plurality of neighboring nodes, the first node operable to communicate a message identifying the problem to a second node, wherein a selected one of the first and second nodes are operable to initiate a fault recovery procedure after the problem has been identified, wherein if the message communicated by the first node describes a situation with a higher priority than a situation being encountered by the second node, then the message communicated by the first node is forwarded by the second node to a third node.

3. An apparatus for performing fault recovery in a network, comprising:

a first node operable to exchange one or more packets with a second node in order to identify a problem in a network, wherein a fault recovery procedure is initiated by a selected one of the first and second nodes in response to identification of the problem, wherein the packets are automatic protection switching (APS) packets that may be communicated to one or more neighboring nodes associated with the first node using inner and outer rings of the network, and wherein the APS packets are communicated to one or more of the neighboring nodes during time periods that are user configurable, and wherein short and long time periods may be implemented in the fault recovery procedure to reduce APS traffic under steady state conditions.

4. The apparatus of claim 3, wherein the packets include information segments selected from the group consisting of:

a request;

a source;

a wrap status; and

a path indicator.

5. The apparatus of claim 3, wherein one or more of the packets are operable to signal a protection request on both short and long paths after performing a wrap, and wherein the short path refers to a path taken across a failed span in a ring of the network and the long path refers to a path taken around the ring, the ring including the first and second nodes.

6. The apparatus of claim 5, wherein the first node is operable to execute a short path protection request and to communicate an idle message with wrapped status across the failed span, and wherein the first node is operable to communicate a protection request on the long path after performing the wrap around the ring.

7. The apparatus of claim 5, wherein a selected one of a plurality of nodes in the ring that is neither executing a self-detected request nor executing a short path request communicates idle messages to one or more of its neighboring nodes on the ring if there is no long path message being communicated through the selected one of the plurality of nodes.

8. The apparatus of claim 3, wherein one or more of the packets are not wrapped around a ring of the network that includes the first and second nodes.

9. The apparatus of claim 3, wherein the fault recovery procedure includes a protection request hierarchy such that a higher priority request preempts a lower priority request within a ring of the network that includes the first and second nodes.

10. The apparatus of claim 9, wherein the hierarchy is reflected by a list that comprises the following elements which are substantially interchangeable and that are provided in an order of highest priority to lowest priority:

(1) lockout of protection (LO);

(2) forced switch (FS);

(3) signal fail (SF);

(4) signal degrade (SD);

(5) manual switch (MS);

(6) wait-to-restore (WTR); and

(7) no request (idle).

11. The apparatus of claim 10, wherein requests which are of higher or of equal priority to the signal fail element and which are of lower priority to the lockout of protection element can co-exist.

12. The apparatus of claim 10, wherein a plurality of lockout of protection element requests can co-exist.

13. The apparatus of claim 10, wherein requests with a lower priority than the signal fail element do not co-exist with other requests.

14. The apparatus of claim 10, wherein if there are multiple requests being communicated that include a similar priority level, a selected request to complete long path signaling will take priority, the selected request to complete long path signaling referring to a request that reaches a selected node that determines which request of a plurality of requests takes priority.

15. The apparatus of claim 3, wherein if two requests of equal priority are being communicated on inner and outer rings of the network, a selected one of the inner or outer rings may be designated to resolve which of the two equal requests takes precedent.

16. The apparatus of claim 3, wherein the first node does not forward a long packet that it receives which was originally generated by the first node itself.

17. The apparatus of claim 3, wherein the second node does not forward packets that include a path indicator set to short paths.

18. The apparatus of claim 3, wherein when the second node receives a long path request and the long path request has a priority that is greater or equal to the highest priority of a short path request and a self-detected request received by the second node, the second node determines if a similar message is being communicated from its neighboring node on a short path and in such a case, the second node does not perform an unwrap operation.

19. The apparatus of claim 3, wherein when the second node receives a long path request, the second node terminates the long path request if the second node is a wrapped node and it is in a situation which is of a higher or an equal priority than the long path request.

20. The apparatus of claim 3, wherein the first node keeps track of addresses of one or more of its neighboring nodes and wherein addressing information associated with the neighboring nodes is gleaned from short path messages.

21. The apparatus of claim 3, wherein when the first node that detected the problem discovers disappearance of the problem, the first node enters into a wait to restore (WTR) mode.

22. The apparatus of claim 21, wherein when the first node is in the WTR mode and detects that a new neighboring node is not the same as an old neighboring node, the first node changes a WTR time period to zero and enters into an idle state.

23. The apparatus of claim 3, wherein when the first node receives a local protection request indicating signal degrade or signal fail and the first node cannot execute the local protection request then the first node maintains the local protection request as pending.

24. An apparatus for performing fault recovery, comprising:

a first node operable to receive a packet associated with a fault recovery protocol in a network, the first node determining whether the packet has been communicated along a long path or a short path such that if the packet was not communicated along a long path then the packet is not forwarded and conversely if the packet was communicated through the long path the packet may be forwarded, wherein if a long path message is to be communicated through a wrapped connection in order to be forwarded then the message will not be forwarded.

25. An apparatus for performing fault recovery, comprising:

a first node operable to communicate a packet to a neighboring node, the neighboring node operable to determine if there is an incomplete ring wrap procedure that has initiated but not yet completed, if there is no ring wrap on a ring network then a pre-determined time is set to an idle time, wherein if a problem is detected a signal for a ring wrap occurs and a predetermined time is set to a protection time, the protection time being a predetermined amount of time utilized when the ring is in the process of being protected by creating the ring wrap, the pre-determined time being measured and another packet being communicated to the neighboring node, and wherein once the ring wrap is completed then the idle time is reset.

26. An apparatus for performing fault recovery, comprising:

a first node operable to detect a problem between the first node and a first neighboring node, the first node performing a wrap away from a side on which the problem exists, wherein the first node is operable to communicate a short path message to the first neighboring node informing it of the problem and to communicate a long path message to a second neighboring node informing the second neighboring node of the problem, the first neighboring node operable to perform a wrap away from the side of the problem and to communicate an idle message that indicates a wrap status on a short path to the first node that detected the problem, and wherein if the long path message is to be communicated through a wrapped connection in order to be forwarded then the long path message will not be forwarded.

27. The apparatus of claim 26, further comprising:

a hierarchy of priorities associated with messages between the nodes, the hierarchy including Class I, Class II, and Class III categories, wherein Class I reflects a highest priority, Class III reflects a lowest priority, and Class II reflects an intermediate priority.

28. The apparatus of claim 27, wherein a lockout protocol is included in the Class I category and reflects an order that states that a corresponding ring network is not to wrap under any circumstances.

29. The apparatus of claim 27, wherein a forced switch and a signal fail protocol are included in the Class II category, the forced switch protocol indicating that a ring network is configured to wrap at a point of a forced switch, and wherein the signal fail protocol reflects a physical break in communication lines between two or more of the nodes.

30. The apparatus of claim 27, wherein the Class III category includes a selected one of a signal degrade, a manual switch, a wait to restore, and a no request protocol, the signal degrade protocol indicating that two nodes can communicate but there are errors in the communication, the manual switch protocol indicating a situation where a ring network has been configured to wrap at a manual switch point, a wait to restore protocol reflecting a transitional state that waits for a predetermined time after a failure has been resolved prior to entering an idle state, a no request protocol indicating that nothing of significance is occurring and no wrap is being executed in the network.

31. The apparatus of claim 27, wherein protocols in the Class II and Class I categories may co-exist, and wherein protocols in the Class III category cannot co-exist.

32. The apparatus of claim 27, wherein multiple requests of a same priority within the Class III category are interpreted such that a first request to complete a long path signaling will take priority over a second request to complete long path signaling.

33. The apparatus of claim 27, wherein in a scenario of two equal requests within the Class III category on both inner and outer rings of the network, a selected one of the rings is designated to handle the scenario.

34. An apparatus for performing fault recovery in a network, comprising:

a first node operable to receive a message and to determine if the message was communicated along a long path, if the message was not communicated along the long path then the message is not forwarded, wherein if the message was communicated along the long path then it is determined whether the message was generated by the first node, if the message was generated by the first node then the message is not forwarded, if however the message was not generated by the first node then it is determined whether the message has a lower priority than a local situation, and wherein if the message does have the lower priority than the local situation then the message is not forwarded, if the message does not have the lower priority than the local situation then the message is forwarded and it is determined if the first node should execute an unwrap operation.

35. The apparatus of claim 34, wherein the first node is operable to determine if the message is of the same or of a higher priority than the local situation, the first node being operable to determine if the same message is coming from a neighboring node on a short path and if a same message is not coming from the neighboring node on the short path it is determined whether the first node should unwrap any existing local wraps, if the same message is coming from the neighboring node on the short path then the receiving node does not unwrap any of the existing local wraps.

36. The apparatus of claim 34, wherein the first node is operable to determine that the problem has been cleared and to enter a wait-to-restore state.

37. A method for performing fault recovery in a network, comprising:

identifying a problem in a connection between a first node and a selected one of a plurality of neighboring nodes;

communicating, by the first node, a message that identifies the problem to a second node;

initiating a fault recovery procedure after the problem has been identified; and

ignoring, by the second node, the message if the second node has encountered a situation that has a higher priority than a situation described by the problem identified by the first node.

38. A method for performing fault recovery in a network, comprising:

identifying a problem in a connection between a first node and a selected one of a plurality of neighboring nodes;

communicating, by the first node, a message that identifies the problem to a second node; and

initiating a fault recovery procedure after the problem has been identified, wherein if the message communicated by the first node describes a situation with a higher priority than a situation being encountered by the second node, then the message communicated by the first node is forwarded by the second node to a third node.

39. A method for performing fault recovery in a network, comprising:

exchanging, by a first node, one or more packets with a second node in order to identify a problem in a network; and

initiating a fault recovery procedure by a selected one of the first and second nodes in response to identification of the problem, wherein the packets are automatic protection switching (APS) packets that may be communicated to one or more neighboring nodes associated with the first node using inner and outer rings of the network, and wherein the APS packets are communicated to one or more of the neighboring nodes during time periods that are user configurable, and wherein short and long time periods may be implemented in the fault recovery procedure to reduce APS traffic under steady state conditions.

40. The method of claim 39, wherein the packets include information segments selected from the group consisting of:

a request;

a source;

a wrap status; and

a path indicator.

41. The method of claim 39, wherein one or more of the packets are operable to signal a protection request on both short and long paths after performing a wrap, and wherein the short path refers to a path taken across a failed span in a ring of the network and the long path refers to a path taken around the ring, the ring including the first and second nodes.

42. The method of claim 41, further comprising:

executing a short path protection request;

communicating an idle message with wrapped status across the failed span; and

communicating a protection request on the long path after performing the wrap around the ring.

43. The method of claim 39, wherein one or more of the packets are not wrapped around a ring of the network that includes the first and second nodes.

44. The method of claim 39, wherein the fault recovery procedure includes a protection request hierarchy such that a higher priority request preempts a lower priority request within a ring of the network that includes the first and second nodes.

45. The method of claim 39, wherein if two requests of equal priority are being communicated on inner and outer rings of the network, a selected one of the inner or outer rings may be designated to resolve which of the two equal requests takes precedent.

46. The method of claim 39, wherein the first node does not forward a long packet that it receives which was originally generated by the first node itself.

47. The method of claim 39, wherein the second node does not forward packets that include a path indicator set to short paths.

48. The method of claim 39, further comprising:

maintaining addresses of one or more neighboring nodes, wherein addressing information associated with the neighboring nodes is gleaned from short path messages.

49. The method of claim 39, further comprising:

recognizing disappearance of the problem; and

entering, by a selected one of the first and second nodes, into a wait to restore (WTR) mode.

50. The method of claim 49, wherein if the first node is in the WTR mode and detects that a new neighboring node is not the same as an old neighboring node, the first node changes a WTR time period to zero and enters into an idle state.

51. A method for performing fault recovery, comprising:

detecting, by a first node, a problem between the first node and a first neighboring node;

performing a wrap away from a side on which the problem exists;

communicating a short path message to the first neighboring node informing it of the problem; and

communicating a long path message to a second neighboring node informing the second neighboring node of the problem, wherein the first neighboring node is operable to perform a wrap away from the side of the problem and to communicate an idle message that indicates a wrap status on a short path to the first node that detected the problem, and wherein if the long path message is to be communicated through a wrapped connection in order to be forwarded then the long path message will not be forwarded.

52. A method for performing fault recovery in a network, comprising:

receiving, by a first node, a message; and

determining if the message was communicated along a long path, if the message was not communicated along the long path then the message is not forwarded, wherein if the message was communicated along the long path then it is determined whether the message was generated by the first node, if the message was generated by the first node then the message is not forwarded, if the message was not generated by the first node then it is determined whether the message has a lower priority than a local situation, and wherein if the message does have the lower priority than the local situation then the message is not forwarded, if the message does not have the lower priority than the local situation then the message is forwarded and it is determined if the first node should execute an unwrap operation.

53. The method of claim 52, further comprising:

determining that the problem has been cleared; and

entering into a wait-to-restore state.

54. A system for performing fault recovery in a network, comprising:

means for identifying a problem in a connection between a first node and a selected one of a plurality of neighboring nodes;

means for communicating a message that identifies the problem to a second node; and

means for initiating a fault recovery procedure after the problem has been identified, wherein the second node ignores the message if the second node has encountered a situation that has a higher priority than a situation described by the problem identified by the first node.

55. A system for performing fault recovery in a network, comprising:

means for identifying a problem in a connection between a first node and a selected one of a plurality of neighboring nodes;

means for communicating a message that identifies the problem to a second node; and

means for initiating a fault recovery procedure after the problem has been identified, wherein if the message communicated by the first node describes a situation with a higher priority than a situation being encountered by the second node, then the message communicated by the first node is forwarded by the second node to a third node.

56. A system for performing fault recovery in a network, comprising:

means for exchanging one or more packets with a network node in order to identify a problem in a network; and

means for initiating a fault recovery procedure by a selected one of a plurality of nodes in response to identification of the problem, wherein the packets are automatic protection switching (APS) packets that may be communicated to one or more neighboring nodes using inner and outer rings of the network, and wherein the APS packets are communicated to one or more of the neighboring nodes during time periods that are user configurable.

57. The system of claim 56, further comprising:

means for executing a short path protection request;

means for communicating an idle message with wrapped status across a failed span; and

means for communicating a protection request on a long path after performing a wrap around the ring.

58. The system of claim 56, further comprising:

means for maintaining addresses of one or more neighboring nodes, wherein addressing information associated with the neighboring nodes is gleaned from short path messages.

59. The system of claim 56, further comprising:

means for recognizing disappearance of the problem; and

means for entering into a wait to restore (WTR) mode.

60. A system for performing fault recovery in a network, comprising:

means for receiving a message; and

means for determining if the message was communicated along a long path, if the message was not communicated along the long path then the message is not forwarded, wherein if the message was communicated along the long path then it is determined whether the message was generated by a first node, if the message was generated by the first node then the message is not forwarded, if the message was not generated by the first node then it is determined whether the message has a lower priority than a local situation, and wherein if the message does have the lower priority than the local situation then the message is not forwarded, if the message does not have the lower priority than the local situation then the message is forwarded and it is determined if the first node should execute an unwrap operation.

61. The system of claim 60, further comprising:

means for determining that the problem has been cleared; and

means for entering a wait-to-restore state.

62. Software embodied in a computer readable medium for performing fault recovery in a network, the medium comprising code such that when executed is operable to:

exchange one or more packets with a network node in order to identify a problem in a network;

initiate a fault recovery procedure by a selected one of a plurality of nodes in response to identification of the problem; and

maintain addresses of one or more neighboring nodes, wherein addressing information associated with the neighboring nodes is gleaned from short path messages.

63. The medium of claim 62, wherein the code is further operable to:

execute a short path protection request;

communicate an idle message with wrapped status across a failed span; and

communicate a protection request on a long path after performing a wrap around the ring.

64. Software embodied in a computer readable medium for performing fault recovery in a network, the medium comprising code such that when executed is operable to:

receive a message; and

determine if the message was communicated along a long path, if the message was not communicated along the long path then the message is not forwarded, wherein if the message was communicated along the long path then it is determined whether the message was generated by a first node, if the message was generated by the first node then the message is not forwarded, if the message was not generated by the first node then it is determined whether the message has a lower priority than a local situation, and wherein if the message does have the lower priority than the local situation then the message is not forwarded, if the message does not have the lower priority than the local situation then the message is forwarded and it is determined if the first node should execute an unwrap operation.

65. The medium of claim 64, wherein the code is further operable to:

determine that the problem has been cleared; and

enter a wait-to-restore state.