Method for robust PTP synchronization with default 1588V2 profile

Abstract

Exemplary methods for reducing sync time in a precision time protocol (PTP) network include receiving, by a first PTP slave port of a first network device, timing messages from a second PTP master port of a second network device. The methods include maintaining a PTP master clock based on timing information included in the timing messages received from the second network device via the first PTP port. The methods further include receiving, by a third PTP passive port of the first network device, timing messages from a fourth PTP master port of a third network device. The methods include determining the third PTP passive port is a protective passive port based on a stepsRemoved value of the third network device, and maintaining an auxiliary clock based on the timing information included in the timing messages received from the third network device via the third PTP port.

What is claimed is: 
     
       1. A method in a first network device for supporting Precision Time Protocol (PTP) in a network, the method comprising:
 receiving, by a first PTP port associated with the first network device configured as a PTP slave port, PTP timing messages from a second PTP port associated with a second network device configured as a PTP master port, wherein the PTP timing messages include timing information of a PTP master clock maintained by the second network device; 
 maintaining a PTP master clock based on the timing information included in the PTP timing messages received from the second network device via the first PTP port; 
 receiving, by a third PTP port associated with the first network device configured as a PTP passive port, PTP timing messages from a fourth PTP port associated with a third network device configured as a PTP master port, wherein the PTP timing messages include timing information of a PTP master clock maintained by the third network device; 
 determining the third PTP port is a protective passive port based on a stepsRemoved value associated with the third network device, wherein a stepsRemoved value indicates a number of boundary clock levels a respective network device is away from a PTP grandmaster clock of the network; and 
 in response to determining the third PTP port is a protective passive port, maintaining a PTP auxiliary clock based on the timing information included in the PTP timing messages received from the third network device via the third PTP port, wherein in an event that the first network device fails to receive PTP timing messages from the second network device via the first PTP port, the PTP auxiliary clock is utilized by the first network device to synchronize its PTP master clock to the PTP master clock maintained by the third network device. 
 
     
     
       2. The method of  claim 1 , wherein determining the third PTP port is a protective passive port comprises:
 determining the third network device has a stepsRemoved value that is one less than a stepsRemoved value of the first network device. 
 
     
     
       3. The method of  claim 2 , further comprising:
 receiving, by a fifth PTP port associated with the first network device configured as a PTP passive port, PTP timing messages from a sixth PTP port associated with a fourth network device configured as a PTP master port, wherein the PTP timing messages include timing information of a PTP master clock maintained by the fourth network device; and 
 in response to determining the fourth network device has a stepsRemoved value that is equal to a stepsRemoved value of the first network device, determining the fifth PTP port is a non-protective passive port. 
 
     
     
       4. The method of  claim 1 , wherein determining the third PTP port is a protective passive port comprises:
 receiving, by a fifth PTP port associated with the first network device configured as a PTP passive port, PTP timing messages from a sixth PTP port associated with a fourth network device configured as a PTP master port, wherein the PTP timing messages include timing information of a PTP master clock maintained by the fourth network device; 
 determining the third network device has a stepsRemoved value that is equal to a stepsRemoved value of the fourth network device; and 
 determining the fourth PTP port has a port identity (ID) that is less than a port ID of the sixth PTP port associated with the fourth network device. 
 
     
     
       5. The method of  claim 1 , further comprising:
 in response to determining a failure to receive PTP timing messages from the second network device via the first PTP port:
 configuring the first PTP port to be a PTP master port, 
 configuring the third PTP port to be a PTP slave port, and 
 utilizing information of the PTP auxiliary clock to synchronize the PTP master clock maintained by the first network device to the PTP master clock maintained by the third network device. 
 
 
     
     
       6. The method of  claim 5 , further comprising applying a phase slope limit to the PTP master clock maintained by the first network device after the third PTP port has been configured to be a PTP slave port. 
     
     
       7. The method of  claim 1 , wherein the second network device and the third network device are a same network device configured to serve as a PTP grandmaster clock of the network. 
     
     
       8. The method of  claim 1 , wherein the second network device and the third network device are different network devices, wherein the second network device and the third network device are configured to serve as a PTP boundary clock of the network. 
     
     
       9. A first network device for supporting Precision Time Protocol (PTP) in a network, the first network device comprising:
 a first PTP port associated with the first network device configured as a PTP slave port, operative to receive PTP timing messages from a second PTP port associated with a second network device configured as a PTP master port, wherein the PTP timing messages include timing information of a PTP master clock maintained by the second network device; 
 a third PTP port associated with the first network device configured as a PTP passive port, operative to receive PTP timing messages from a fourth PTP port associated with a third network device configured as a PTP master port, wherein the PTP timing messages include timing information of a PTP master clock maintained by the third network device; 
 a set of one or more processors; and 
 a non-transitory machine-readable storage medium containing instructions, which when executed by the set of one or more processors, cause the first network device to:
 maintain a PTP master clock based on the timing information included in the PTP timing messages received from the second network device via the first PTP port, 
 determine the third PTP port is a protective passive port based on a stepsRemoved value associated with the third network device, wherein a stepsRemoved value indicates a number of boundary clock levels a respective network device is away from a PTP grandmaster clock of the network, and 
 in response to determining the third PTP port is a protective passive port, maintain a PTP auxiliary clock based on the timing information included in the PTP timing messages received from the third network device via the third PTP port, wherein in an event that the first network device fails to receive PTP timing messages from the second network device via the first PTP port, the PTP auxiliary clock is utilized by the first network device to synchronize its PTP master clock to the PTP master clock maintained by the third network device. 
 
 
     
     
       10. The first network device of  claim 9 , wherein the instructions that cause the first network device to determine the third PTP port is a protective passive port comprises instructions, which when executed by the set of one or more processors, cause the first network device to determine the third network device has a stepsRemoved value that is one less than a stepsRemoved value of the first network device. 
     
     
       11. The first network device of  claim 10 , further comprising:
 a fifth PTP port associated with the first network device configured as a PTP passive port, operative to receive PTP timing messages from a sixth PTP port associated with a fourth network device configured as a PTP master port, wherein the PTP timing messages include timing information of a PTP master clock maintained by the fourth network device, wherein 
 the non-transitory machine-readable storage medium further containing instructions, which when executed by the set of one or more processors, cause the first network device to in response to determining the fourth network device has a stepsRemoved value that is equal to a stepsRemoved value of the first network device, determine the fifth PTP port is a non-protective passive port. 
 
     
     
       12. The first network device of  claim 9 , further comprising:
 a fifth PTP port associated with the first network device configured as a PTP passive port, operative to receive PTP timing messages from a sixth PTP port associated with a fourth network device configured as a PTP master port, wherein the PTP timing messages include timing information of a PTP master clock maintained by the fourth network device, wherein the instructions that cause the first network device to determine the third PTP port is a protective passive port comprises instructions, 
 which when executed by the set of one or more processors, cause the first network device to:
 determine the third network device has a stepsRemoved value that is equal to a stepsRemoved value of the fourth network device, and 
 determine the fourth PTP port associated with the third network device has a port identity (ID) that is less than a port ID of the sixth PTP port associated with the fourth network device. 
 
 
     
     
       13. The first network device of  claim 9 , wherein the non-transitory machine-readable storage medium further containing instructions, which when executed by the set of one or more processors, cause the first network device to in response to determining a failure to receive PTP timing messages from the second network device via the first PTP port:
 configure the first PTP port to be a PTP master port, 
 configure the third PTP port to be a PTP slave port, and 
 utilize information of the PTP auxiliary clock to synchronize the PTP master clock maintained by the first network device to the PTP master clock maintained by the third network device. 
 
     
     
       14. The first network device of  claim 13 , wherein the non-transitory machine-readable storage medium further containing instructions, which when executed by the set of one or more processors, cause the first network device to apply a phase slope limit to the PTP master clock maintained by the first network device after the third PTP port has been configured to be a PTP slave port. 
     
     
       15. The first network device of  claim 9 , wherein the second network device and the third network device are a same network device configured to serve as a PTP grandmaster clock of the network. 
     
     
       16. The first network device of  claim 9 , wherein the second network device and the third network device are different network devices, wherein the second network device and the third network device are configured to serve as a PTP boundary clock of the network. 
     
     
       17. A non-transitory computer-readable storage medium having computer instructions stored therein, which when executed by a processor of a first network device for supporting Precision Time Protocol (PTP) in a network, cause the first network device to perform operations comprising:
 receiving, by a first PTP port associated with the first network device configured as a PTP slave port, PTP timing messages from a second PTP port associated with a second network device configured as a PTP master port, wherein the PTP timing messages include timing information of a PTP master clock maintained by the second network device; 
 maintaining a PTP master clock based on the timing information included in the PTP timing messages received from the second network device via the first PTP port; 
 receiving, by a third PTP port associated with the first network device configured as a PTP passive port, PTP timing messages from a fourth PTP port associated with a third network device configured as a PTP master port, wherein the PTP timing messages include timing information of a PTP master clock maintained by the third network device; 
 determining the third PTP port is a protective passive port based on a stepsRemoved value associated with the third network device, wherein a stepsRemoved value indicates a number of boundary clock levels a respective network device is away from a PTP grandmaster clock of the network; and 
 in response to determining the third PTP port is a protective passive port, maintaining a PTP auxiliary clock based on the timing information included in the PTP timing messages received from the third network device via the third PTP port, wherein in an event that the first network device fails to receive PTP timing messages from the second network device via the first PTP port, the PTP auxiliary clock is utilized by the first network device to synchronize its PTP master clock to the PTP master clock maintained by the third network device. 
 
     
     
       18. The non-transitory computer-readable storage medium of  claim 17 , wherein determining the third PTP port is a protective passive port comprises:
 determining the third network device has a stepsRemoved value that is one less than a stepsRemoved value of the first network device. 
 
     
     
       19. The non-transitory computer-readable storage medium of  claim 18 , the operations further comprising:
 receiving, by a fifth PTP port associated with the first network device configured as a PTP passive port, PTP timing messages from a sixth PTP port associated with a fourth network device configured as a PTP master port, wherein the PTP timing messages include timing information of a PTP master clock maintained by the fourth network device; and 
 in response to determining the fourth network device has a stepsRemoved value that is equal to a stepsRemoved value of the first network device, determining the fifth PTP port is a non-protective passive port. 
 
     
     
       20. The non-transitory computer-readable storage medium of  claim 17 , wherein determining the third PTP port is a protective passive port comprises:
 receiving, by a fifth PTP port associated with the first network device configured as a PTP passive port, PTP timing messages from a sixth PTP port associated with a fourth network device configured as a PTP master port, wherein the PTP timing messages include timing information of a PTP master clock maintained by the fourth network device; 
 determining the third network device has a stepsRemoved value that is equal to a stepsRemoved value of the fourth network device; and 
 determining the fourth PTP port has a port identity (ID) that is less than a port ID of the sixth PTP port associated with the fourth network device. 
 
     
     
       21. The non-transitory computer-readable storage medium of  claim 17 , the operations further comprising:
 in response to determining a failure to receive PTP timing messages from the second network device via the first PTP port:
 configuring the first PTP port to be a PTP master port, 
 configuring the third PTP port to be a PTP slave port, and 
 utilizing information of the PTP auxiliary clock to synchronize the PTP master clock maintained by the first network device to the PTP master clock maintained by the third network device. 
 
 
     
     
       22. The non-transitory computer-readable storage medium of  claim 21 , the operations further comprising applying a phase slope limit to the PTP master clock maintained by the first network device after the third PTP port has been configured to be a PTP slave port. 
     
     
       23. The non-transitory computer-readable storage medium of  claim 17 , wherein the second network device and the third network device are a same network device configured to serve as a PTP grandmaster clock of the network. 
     
     
       24. The non-transitory computer-readable storage medium of  claim 17 , wherein the second network device and the third network device are different network devices, wherein the second network device and the third network device are configured to serve as a PTP boundary clock of the network.