Methods and nodes for synchronisation of networks

Patent metadata

Field	Value
Publication number	US-2016373199-A1
Application number	US-201514905688-A
Country	US
Kind code	A1
Filing date	Feb 20, 2015
Priority date	Feb 20, 2015
Publication date	Dec 22, 2016
Grant date	—

Abstract

Method and arrangement for providing delay information to synchronisation packets passing a transport network node. In a transport network node synchronisation packets propagate from a synchronisation master node towards boundary clock nodes. The synchronisation packets pass the transport network node, in which the synchronisation packets are received, and a level of delay is determined. Furthermore, when the level of delay for the synchronisation packets is above a threshold, the synchronisation packets are marked with a delay indication. The received synchronisation packets are sent to the boundary clock node or ordinary clock node, whether or not they are marked. By implementing functionality for determining a level of delay of synchronisation packets, and marking passing synchronisation packets with delay indications, boundary clock nodes and ordinary clock nodes may differentiate the received synchronisation packets based on the delay identifications. Thereby, improved accuracy may be achieved when calculating time synchronisation offsets.

First claim

1 . A method performed by a synchronisation report module of a first transport network node for providing delay information to synchronisation packets passing the first transport network node, the method comprising:
receiving a first synchronisation packet originating from a second transport network node, determining a level of delay for the first synchronisation packet caused by the first transport network node, when the level of delay for the first synchronisation packet is above a first threshold, marking the first synchronisation packet with a delay indication, and sending the first synchronisation packet towards a third transport network node.

2 . The method according to claim 1 , further comprising:
receiving a second synchronisation packet originating from the third transport network node, determining a level of delay for the second synchronisation packet caused by the first transport network node, when the level of delay for the second synchronisation packet is above a second threshold, marking the second synchronisation packet with a delay indication, and sending the second synchronisation packet towards the second transport network node.

3 . The method according to claim 2 , further comprising:
receiving a third synchronisation packet originating from the second transport network node, wherein the third synchronisation packet carries the delay indication of the second packet, and forwarding the third synchronisation packet towards the third transport network node.

4 . The method according to claim 2 , wherein the first and second synchronisation packets are Precision Time Protocol, PTP, packets, wherein at least one of: marking the first synchronisation packet with a delay indication; and marking the second synchronisation packet with a delay indication, comprises one of:
setting a timeTraceable flag to ‘False’ in a PTP header, and setting at least one profileSpecific flag in the PTP header.

5 . The method according to claim 2 , wherein the first and second synchronisation packets are PTP packets, wherein at least one of: marking the first synchronisation packet with a delay indication; and marking the second synchronisation packet with a delay indication; comprises one of:
adding a suffix Time-Length-Value, TLV, to the PTP packet, the suffix carrying further information regarding the determined delay, and setting at least one value of a correctionField of the PTP header.

6 . The method according to claim 2 , wherein at least one of: determining the level of delay for the first synchronisation packet; and determining the level of delay for the second synchronisation packet; comprises: retrieving a buffer status or a queue-length of the transport network node.

7 . A synchronisation report module adapted to be arranged in a first transport network node for provisioning of delay information to synchronisation packets, the synchronisation report module comprising:
a communication unit, and a controller, wherein the communication unit is adapted to receive a first synchronisation packet originating from a second transport network node, wherein the controller is adapted to determine a level of delay for the first synchronisation packet caused by the first transport network node, and mark the synchronisation packet with a delay indication when the level of delay for the first synchronisation packet is above a first threshold, and wherein the communication unit is further adapted to send the first synchronisation packet towards a third transport network node.

8 . The synchronisation report module according to claim 7 ,
wherein the communication unit is adapted to receive a second synchronisation packet originating from the third transport network node, wherein the controller is adapted to determine a level of delay for the second synchronisation packet caused by the first transport network node, and mark the second synchronisation packet with a delay indication when the level of delay for the second synchronisation packet is above a second threshold, and wherein the communication unit is further adapted to send the second synchronisation packet towards the third transport network node.

9 . The synchronisation report module according to claim 8 , wherein the communication unit is adapted to:
receive a third synchronisation packet originating from the second transport network node, wherein the third synchronisation packet carries the delay indication of the second synchronisation packet, and forward the third synchronisation packet towards the third transport network node.

10 . The synchronisation report module according to claim 8 , wherein the first and second synchronisation packets are Precision Time Protocol, PTP, packets, wherein the controller is adapted to mark at least one of the first and second synchronisation packets with a delay indication, and wherein marking comprises one of:
setting a timeTraceable flag to ‘False’ in a PTP header, and setting at least one profileSpecific flag in the PTP header.

11 . The synchronisation report module according to claim 8 , wherein the first and second synchronisation packets are Precision Time Protocol, PTP, packets, wherein the controller is adapted to mark at least one of the first and second synchronisation packets with a delay indication, and wherein marking comprises one of:
adding a suffix Time-Length-Value, TLV, to the PTP packet, the suffix carrying further information regarding the determined delay, and setting at least one value of a correctionField of the PTP header.

12 . The synchronisation report module according to claim 8 , wherein the controller is adapted to at least one of:
determining the level of delay for the first synchronisation packet; and determining the level of delay for the second synchronisation packet, by retrieving a buffer status or a queue-length of the transport network node.

13 . A transport network node comprising the synchronisation report module according to claim 7 .

14 . A method performed by an offset calculation module of a first transport network node for enabling the first transport network node to calculate a time synchronisation offset value between a second transport network node and the first transport network node, the method comprising:
receiving a synchronisation packet from an intermediate transport network node, determining a delay indication of the received synchronisation packet, the delay indication indicating a delay of at least one of: the synchronisation packet; or a related synchronisation packet, wherein the delay is caused by the intermediate transport network node,
wherein the first transport network node is enabled to calculate the time synchronisation offset value based on synchronisation packets which do not comprise any delay indication.

15 . The method according to claim 14 , wherein the synchronisation packet is a Precision Time Protocol, PTP, packet, and determining the delay indication, comprises one of:
detecting a timeTraceable flag as ‘False’ in a PTP header, and detecting at least one profileSpecific flag in the PTP header.

16 . The method according to claim 14 , wherein the synchronisation packet is a PTP packet, and determining the delay indication, comprises one of:
detecting a suffix Time-Length-Value, TLV, of the PTP packet, the suffix carrying further information regarding the determined delay, and detecting at least one value of a correctionField of the PTP header.

17 . An offset calculation module adapted to be arranged first transport network node for enabling the f

Assignees

• ERICSSON TELEFON AB L M (publ)

Inventors

• Olofsson Mikael
• Ruffini Stefano

Classifications

• H04J3/0673 Primary

  using intermediate nodes, e.g. modification of a received timestamp before further transmission to the next packet node, e.g. including internal delay time or residence time into the packet · CPC title

• H04L47/283

  in response to processing delays, e.g. caused by jitter or round trip time [RTT] · CPC title

• H04L43/10

  Active monitoring, e.g. heartbeat, ping or trace-route · CPC title

• H04L47/28

  in relation to timing considerations · CPC title

• H04L43/0858

  One way delays · CPC title