Method and apparatus for graceful restart

1. A method in a network device comprising:

refreshing a set of one or more labels after a label propagation module has restarted, the set of one or more labels having been allocated for the label propagation module prior to the label propagation module dying, wherein refreshing a set of labels comprises modifying a set of values, wherein each of the set of values is associated with a different one of the set of labels; and

communicating the refreshed set of labels to a set of one or more peer label switching network devices.

2. The method of claim 1 wherein the label propagation module is software and/or hardware implementing the Border Gateway Protocol, the Label Distribution Protocol, and/or the Resource Reservation protocol.

3. The method of claim 1 further comprising forwarding a packet with having one of the set of labels in accordance with a forwarding entry that indicates the one of the set of labels.

4. A method in a network device comprising:

receiving a first label mapping message indicating a first label and a forward equivalence class (FEC), the first label mapping message for a label propagation module;

allocating a second label for the label propagation module;

transmitting a second label mapping message indicating the second label and the FEC;

marking the second label as stale in response to the label propagation module dying;

if a third message indicating the first label and the FEC is received within a time period,

refreshing the second label, and

transmitting a fourth message indicating the refreshed second label and the FEC; and

clearing the second label if marked as stale after the time period expires.

5. The method of claim 4 wherein marking the second label as stale comprises setting a bit in a data structure corresponding to the second label to a value that indicates stale.

6. The method of claim 4 wherein clearing the second label comprises removing the second label from forwarding tables.

7. The method of claim 4 wherein the label propagation module is software and/or hardware implementing the Border Gateway Protocol, the Label Distribution Protocol, and/or the Resource Reservation protocol.

8. The method of claim 4 further comprising forwarding a packet with the second refreshed label.

9. A method in a network device comprising:

communicating to a set of peer label switching network devices graceful restart capability of said network device and a time period;

marking forwarding entries for the label propagation module as stale in response to the label propagation module dying;

reestablishing communication with the set of peer label switching network devices in response to the label propagation module restarting, the label propagation module for propagating labels for one or more label switched paths (LSPs) traversing the network device;

receiving a first set of one or more label-forward equivalence class (FEC) bindings for the label propagation module from a first subset of the set of peer label switching network devices;

refreshing those forwarding entries that indicate the received set of label-FEC bindings;

communicating a second set of label-FEC bindings that correspond to the refreshed forwarding entries to a second subset of the set of peer label switching network devices; and

clearing those forwarding entries that are marked as stale after the refresh time expires.

10. The method of claim 9 wherein the label propagation module is software and/or hardware implementing the Border Gateway Protocol, the Label Distribution Protocol, and/or the Resource Reservation protocol.

11. The method of claim 9 further comprising forwarding a set of one or more packets in accordance with the refreshed forwarding entries.

12. A network device comprising:

a line card to store a label forwarding information base; and

a control card coupled with the line card, the control card having a label propagation module to,

allocate labels from a label data structure and communicate the allocated labels to upstream network devices, and

receive labels from downstream network devices,

a label manager to receive the allocated labels and the downstream network devices labels from the label propagation module, the label manager to,

store the allocated labels and downstream network devices labels in a label forwarding data structure,

set a restart time upon the label propagation module failing, and

determine, at expiration of the restart time, which labels stored in the label forwarding information base should be cleared, the determination based upon labels received, after the label propagation module restarts, from downstream network devices and entries previously stored in the label forwarding data structure, and

cause the determined labels to be cleared from the label forwarding information base.

13. The network device of claim 12 wherein the label forwarding data structure includes forwarding entries for the labels.

14. The network device of claim 12 further comprising the label manager to update the label forwarding information base in accordance with the label forwarding data structure.

15. A network comprising:

a first peer label switching network device, the first peer label switching device to propagate a first label for a label switched path (LSP);

a second peer label switching network device; and

a transit peer label switching network device coupled with the first and second peer label switching network device, the transit peer label switching network device being an intermediate point along said LSP, the transit peer label switching network device having,

a label propagation module (LPM) to,

propagate a second label to the second peer label switching network device, and

receive the first label from the first peer label switching network device, and

a label manager to,

upon a software failure in the LPM,

set a restart time interval, and

determine, at restart time interval expiration, whether to remove the first label previously received from the first peer label switching network device.

16. The network of claim 15 further comprising the transit peer label switching network device to transmit a label mapping message to the first peer label switching network device, wherein the label mapping message indicates the first label.

17. A machine-readable medium that provides instructions, which when execute by a set of one or more processors, cause said set of processors to perform operations comprising:

refreshing a set of one or more labels after a label propagation module has restarted, the set of one or more labels having been allocated for the label propagation module prior to the label propagation module dying, wherein refreshing a set of labels comprises modifying a set of values, wherein each of the set of values is associated with a different one of the set of labels; and

communicating the refreshed set of labels to a set of one or more peer label switching network devices.

18. The machine-readable medium of claim 17 wherein the label propagation module is software and/or hardware implementing the Border Gateway Protocol, the Label Distribution Protocol, and/or the Resource Reservation protocol.

19. The machine-readable medium of claim 17 further comprising forwarding a packet with having one of the set of labels in accordance with a forwarding entry that indicates the one of the set of labels.

20. A machine-readable medium that provides instructions, which when executed by a set of one or more processors, cause said set of processors to perform operations comprising:

receiving a first label mapping message indicating a first label and a forward equivalence class (FEC), the first label mapping message for a label propagation module;

allocating a second label for the label propagation module;

transmitting a second label mapping message indicating the second label and the FEC;

marking the second label as stale in response to the label propagation module dying;

if a third message indicating the first label and the FEC is received within a time period,

refreshing the second label, and

transmitting a fourth message indicating the refreshed second label and the FEC; and

clearing the second label if marked as stale after the time period expires.

21. The machine-readable medium of claim 20 wherein marking the second label as stale comprises setting a bit in a data structure corresponding to the second label to a value that indicates stale.

22. The machine-readable medium of claim 20 wherein clearing the second label comprises moving the second label from forwarding tables.

23. The machine-readable medium of claim 20 wherein the label propagation module is software and/or hardware implementing the Border Gateway Protocol, the Label Distribution Protocol, and/or the Resource Reservation protocol.

24. The machine-readable medium of claim 20 further comprising forwarding a packet with the second refreshed label.

25. A machine-readable medium that provides instructions, which when executed by a set of one or more processors, cause said set of processors to perform operations comprising:

communicating to a set of peer label switching network devices graceful restart capability of said network device and a lime period;

marking forwarding entries for the label propagation module as stale in response to the label propagation module dying;

reestablishing communication with the set of peer label switching network devices in response to the label propagation module restarting, the label propagation module for propagating labels for one or more label switched paths (LSPs) traversing the network device;

receiving a first set of one or more label-forward equivalence class (FEC) bindings for the label propagation module from a first subset of the set of peer label switching network devices;

refreshing those forwarding entries that indicate the received set of label-FEC bindings;

communicating a second set of label-FEC bindings that correspond to the refreshed forwarding entries to a second subset of the set of peer label switching network devices; and

clearing those forwarding entries that are marked as stale after the refresh time expires.

26. The machine-readable medium of claim 25 wherein the label propagation module is software and/or hardware implementing the Border Gateway Protocol, the label Distribution Protocol, and/or the Resource Reservation protocol.

27. The machine-readable medium of claim 25 further comprising forwarding a set of one or more packets in accordance with the refreshed forwarding entries.