US 5,689,688 A · Probabilistic anonymous clock synchronization method and apparatus for synchronizing a local time scale with a reference time scale

Abstract

A method is provided for synchronizing local times, maintained at nodes within a network architecture, with a reference time. A node according to the invention can synchronize its local time with the reference time source either actively or in a passive, or eavesdropping, manner. Which of the two manners is to be used preferably depends on whether the node's error exceeds a threshold, and whether the node receives an unsolicited burst of synchronization messages. The active manner is preferably a handshaking scheme, such as probabilistic clock synchronization, in which synchronization is initiated by a request from a node requiring synchronization, and a handshaking exchange of messages between the node and the reference time source establishes a temporal relationship, from which the node produces a synchronized time and a maximum error. The passive manner is preferably a manner in which the reference time source broadcasts a burst of reference-time-stamped synchronization messages, and the node eavesdrops on the messages. The receiving node establishes temporal relationships between certain ones of the local and reference time stamps. Using the temporal relationships, the receiving node updates its local time and its maximum error.

Claims36

Dependent claims

For use with a communication network including a plurality of nodes which maintain respective local time scales and a reference time source which maintains a reference time scale, a method for synchronizing a local time scale of one of the nodes with the reference time scale comprising the steps of:

synchronizing based on a first procedure responsive to a first event, the first procedure including synchronizing according to a protocol in which the node is known to the reference time source;
and
synchronizing based on a second procedure responsive to a second event the second procedure including synchronizing according to a protocol in which the node is anonymous to the reference time source.

A communication and processing node, for use as a node with a communication network including a plurality of nodes which maintain respective local time scales and a reference time source which maintains a reference time scale, the node comprising:

means for synchronizing its local time scale with the reference time scale based on a first procedure responsive to a first event, the first procedure including synchronizing according to a protocol in which the node is known to the reference time source;
and
means for synchronizing its local time scale with the reference time scale based on a second procedure responsive to a second event, the second procedure including synchronizing according to a protocol in which the node is anonymous to the reference time source.

A communication network comprising:

a reference time source including means for maintaining a reference time scale and means for communicating through a communication medium;
and
a node including:
(i) means for communicating through the communication medium;
(ii) means for maintaining a local time scale,
(iii) means for synchronizing its local time scale with the reference time scale based on a first procedure responsive to a first event, the first procedure including synchronizing according to a protocol in which the node is known to the reference time source;
and
(iv) means for synchronizing its local time scale with the reference time scale based on a second procedure responsive to a second event, the second procedure including synchronizing according to a protocol in which the node is anonymous to the reference time source.

5 more elements

A computer program product, for use with a node of a communication network including a plurality of nodes which maintain respective local time scales and a reference time source which maintains a reference time scale, to facilitate the synchronization of a local time scale of the node with the reference time scale, the computer program product comprising:

a recording medium;
means, recorded on the recording medium, for directing the node to synchronize based on a first procedure responsive to a first event, the first procedure including synchronizing according to a protocol in which the one node is known to the reference time source;
and
means, recorded on the recording medium, for directing the node to synchronize based on a second procedure responsive to a second event, the second procedure including synchronizing according to a protocol in which the one node is anonymous to the reference time source.

1 more element

Dependencies are inferred from the claim text.

Probabilistic anonymous clock synchronization method and apparatus for synchronizing a local time scale with a reference time scale

Life of this patent

Probabilistic anonymous clock synchronization method and apparatus for synchronizing a local time scale with a reference time scale

Life of this patent

Abstract

Claims36