Synchronizing clocks across sub-nets
View Patent ↗A distributed system with a time synchronization bridge for maintaining a relatively accurate common sense of time across sub-nets despite the use of a communication device such as a router which causes jitter in packet transfers across sub-nets. A distributed system according to the present teachings includes a set of nodes that communicate via a set of sub-nets. The nodes each have a local clock and mechanisms for maintaining time synchronization among the local clocks by transferring timing data packets via the sub-nets. The timing data packets do not pass through a router. Instead, a time synchronization bridge obtains the timing data packets and in response coordinates time synchronization across the sub-nets.
1. A distributed system, comprising:
a set of nodes that communicate via a set of sub-nets of the distributed system, the nodes each having a local clock, the nodes maintaining time synchronization among the local clocks by transferring a set of timing data packets via the sub-nets;
time synchronization bridge that coordinates time synchronization among the sub-nets in response to the timing data packets by determining a highest quality clock among the local clocks and transferring an additional set of timing data packets via the sub-nets in response to the highest quality clock.
2. The distributed system of claim 1 , wherein the time synchronization bridge maintains an internal time and synchronizes the internal time to a local clock on a selected one of the sub-nets.
3. The distributed system of claim 2 , wherein the time synchronization bridge uses the internal time to synchronize the local clocks on the remaining ones of the sub-nets.
4. The distributed system of claim 1 , wherein the time synchronization bridge maintains an internal time and synchronizes the local clocks to the internal time.
5. The distributed system of claim 1 , wherein the time synchronization bridge determines the highest quality clock in response to a first set of clock meta-data in the timing data packets and a second set of clock meta-data associated with an internal time maintained by the time synchronization bridge.
6. The distributed system of claim 5 , wherein the second set of clock meta-data indicates a GPS time source.
7. The distributed system of claim 5 , wherein the second set of clock meta-data indicates an atomic clock time source.
8. The distributed system of claim 5 , wherein the first set of clock meta-data includes an indication of quality of the corresponding local clock.
9. The distributed system of claim 5 , wherein the first set of clock meta-data includes an indication a number of other time synchronization bridges traversed by the corresponding timing data packet.
10. The distributed system of claim 5 , wherein the first set of clock meta-data includes an indication that the corresponding local clock is preferred as the highest quality clock.
11. A time synchronization bridge, comprising:
means for maintaining an internal time in the time synchronization bridge;
a set of synchronization modules corresponding to a set of sub-nets, each synchronization module having means for adjusting the internal time in response to a set of timing data packets received via the corresponding sub-net and means for distributing the internal time via the corresponding sub-net;
means for determining a highest quality clock for the sub-nets in response to the timing data packets and means for transferring an additional set of timing data packets via the sub-nets in response to the highest quality clock.
12. The time synchronization bridge of claim 11 , wherein each synchronization module includes a clock and means for synchronizing the clock in response to the timing data packets received via the corresponding sub-net.
13. The time synchronization bridge of claim 12 , wherein the means for maintaining an internal time includes means for selecting one of the clocks as a primary clock in the time synchronization bridge such that the clocks synchronize to the primary clock.
14. The time synchronization bridge of claim 13 , wherein the means for selecting includes means for selecting the primary clock in response to a set of clock meta-data contained in the timing data packets.
15. The time synchronization bridge of claim 11 , wherein the means for maintaining an internal time comprises a central clock.
16. A time synchronization bridge, comprising:
means for maintaining an internal time in the time synchronization bridge;
a set of synchronization modules corresponding to a set of sub-nets, each synchronization module having means for adjusting the internal time in response to a set of timing data packets received via the corresponding sub-net and means for distributing the internal time via the corresponding sub-net wherein the means for maintaining an internal time comprises a central clock and wherein each synchronization module includes means for adjusting the central clock in response to the timing data packets received via the corresponding sub-net and means for selecting one of the synchronization modules to adjust the clock.
17. The time synchronization bridge of claim 16 , wherein the means for selecting includes means for selecting one of the synchronization modules in response to a set of clock meta-data contained in the timing data packets.
18. The time synchronization bridge of claim 16 , further comprising a GPS time source.
19. The time synchronization bridge of claim 16 , further comprising an atomic clock time source.