Computing label-switched data communication paths

1. A system for computing label-switched data communication paths, the system comprising:

at least one processor;

a synchronization status collector implemented on the at least one processor and configured for receiving synchronization status information for a plurality of routing nodes in a label-switched network,

wherein the synchronization status information specifies a degree of time synchronization to a reference clock: and

a path determiner implemented on the at least one processor and configured for receiving a request for a label-switched path (LSP) from a client, determining a responsive LSP based at least in part on the synchronization status information, and

sending an explicit route object (ERO) for the responsive LSP to the client;

wherein receiving synchronization status information comprises receiving network time protocol (NTP) stratum information for each routing node, and wherein the NTP stratum information specifies a level within an NTP hierarchy for the reference clock.

2. The system of claim 1 , wherein the system comprises a path computation element (PCE) configured for extending a path computation element protocol (PCEP) to announce synchronized path computation ability for the label-switched network.

3. The system of claim 1 , wherein the system comprises a path computation element (PCE) configured for extending a path computation element protocol (PCEP) to support receiving client requests for synchronized path computation.

4. The system of claim 1 , wherein receiving synchronization status information comprises requesting the synchronization status information from an operations, administration, and maintenance (OAM) subsystem of the label-switched network.

5. The system of claim 1 , wherein receiving synchronization status information comprises receiving the synchronization status information from a monitoring system monitoring synchronization messaging by the routing nodes in the label-switched network.

6. The system of claim 1 , wherein receiving synchronization status information comprises querying each of the routing nodes or receiving broadcast or multicast messages from each of the routing nodes.

7. The system of claim 1 , wherein determining a responsive LSP based at least in part on the synchronization status information comprises determining an initial LSP based on one or more traffic engineering parameters and pruning the initial LSP based on the synchronization status information to remove from the initial LSP one or more routing nodes each having a respective degree of synchronization below a threshold degree of synchronization.

8. The system of claim 1 , wherein the routing nodes in the label-switched network are configured to communicate using a routing protocol specifying a synchronization-sensitive authentication.

9. The system of claim 1 , wherein the routing nodes in the label-switched network are configured to communicate using an intermediate system to intermediate system (IS-IS) protocol and to authenticate using hitless authentication key rollover.

10. A method for computing label-switched data communication paths, the method comprising:

receiving, by a path computation element (PCE) implemented on at least one processor, synchronization status information for a plurality of routing nodes in a label-switched network, wherein the synchronization status information specifies a degree of time synchronization to a reference clock:

receiving, by the PCE, a request for a label-switched path (LSP) from a client;

determining, by the PCE, a responsive LSP based at least in part on the synchronization status information; and

sending, by the PCE, an explicit route object (ERO) for the responsive LSP to the client;

wherein receiving synchronization status information comprises receiving network time protocol (NTP) stratum information for each routing node, and wherein the NTP stratum information specifies a level within an NTP hierarchy for the reference clock.

11. The method of claim 10 , comprising extending a path computation element protocol (PCEP) to announce synchronized path computation ability for the label-switched network.

12. The method of claim 10 , comprising extending a path computation element protocol (PCEP) to support receiving client requests for synchronized path computation.

13. The method of claim 10 , wherein receiving synchronization status information comprises requesting the synchronization status information from an operations, administration, and maintenance (OAM) subsystem of the label-switched network.

14. The method of claim 10 , wherein receiving synchronization status information comprises receiving the synchronization status information from a monitoring system monitoring synchronization messaging by the routing nodes in the label-switched network.

15. The method of claim 10 , wherein receiving synchronization status information comprises querying each of the routing nodes or receiving broadcast or multicast messages from each of the routing nodes.

16. The method of claim 10 , wherein determining a responsive LSP based at least in part on the synchronization status information comprises determining an initial LSP based on one or more traffic engineering parameters and pruning the initial LSP based on the synchronization status information to remove from the initial LSP one or more routing nodes each having a respective degree of synchronization below a threshold degree of synchronization.

17. The method of claim 10 , wherein the routing nodes in the label-switched network are configured to communicate using a routing protocol specifying a synchronization-sensitive authentication.

18. The method of claim 10 , wherein the routing nodes in the label-switched network are configured to communicate using an intermediate system to intermediate system (IS-IS) protocol and to authenticate using hitless authentication key rollover.

19. A non-transitory computer readable medium storing executable instructions that when executed by at least one processor of a computer control the computer to perform operations comprising:

receiving, by a path computation element (PCE) implemented on the at least one processor, synchronization status information for a plurality of routing nodes in a label-switched network, wherein the synchronization status information specifies a degree of time synchronization to a reference clock:

receiving, by the PCE, a request for a label-switched path (LSP) from a client;

determining, by the PCE, a responsive LSP based at least in part on the synchronization status information; and

sending, by the PCE, an explicit route object (ERO) for the responsive LSP to the client;

wherein receiving synchronization status information comprises receiving network time protocol (NTP) stratum information for each routing node, and wherein the NTP stratum information specifies a level within an NTP hierarchy for the reference clock.