Network clock synchronization floating window and window delineation

• US 9,019,996 B2
• Filed: 08/24/2010
• Issued: 04/28/2015
• Est. Priority Date: 09/25/2006
• Status: Active Grant

• Current Assignee: Futurewei Technologies Incorporated (Huawei Investment & Holding Co., Ltd.)
• Original Assignee: Futurewei Technologies Incorporated (Huawei Investment & Holding Co., Ltd.)
• Inventors: Fourcand, Serge Francois
• Primary Examiner(s): HOANG, THAI D
• Application Number:
  US12/862,521
• Publication Number:
  US 20100316069A1
• Time in Patent Office: 1,708 Days
• Field of Search: 370503-529
• US Class Current: 370/503
• CPC Class Codes: H04J 3/0605 Special codes used as synchronising signal
• CPC Class Codes: H04J 3/0682 by delay compensation, e.g. by compensation of propagation delay or variations thereof, by ranging
• CPC Class Codes: H04L 12/66 Arrangements for connecting between networks having differing types of switching systems, e.g. gateways

Abstract

A network component comprising at least one processor configured to implement a method comprising initiating a synchronization window, and promoting the transmission of a frame comprising a control symbol, wherein the control symbol delineates a beginning of the frame, and wherein the control symbol is offset from the beginning of the synchronization window. Also disclosed is a system comprising an upstream node in communication with a downstream node, wherein the upstream node transmits a data stream comprising a plurality of frames to the downstream node, wherein the data stream is organized into a plurality of synchronization windows, and wherein the frames float within the synchronization windows. Included is a method comprising transmitting an Ethernet data stream comprising an Ethernet control symbol, wherein the Ethernet control symbol is transmitted within a synchronization window and delineates a start of a packet within the synchronization window.

Claims

1. A network component comprising:

a memory coupled to a processor, wherein the memory comprises instructions that cause the processor to;

initiate a synchronization window; and

promote the transmission of a frame comprising a start of frame delimiter (SFD) and a plurality of timeslots,

wherein the SFD delineates a beginning of the frame,

wherein the synchronization window is initiated using a signal not located within the frame,

wherein the frame is floating within the synchronization window, and

wherein the beginning of the SFD is not the same as the beginning of the synchronization window.

2. The network component of claim 1, wherein the instructions further cause the processor to promote the transmission of a plurality of the frames, and wherein the location of the SFD relative to the synchronization window is not the same in each of the frames.

3. The network component of claim 1, wherein the synchronization window comprises a first interval and a second interval, and wherein the frame is transmitted during the second interval.

4. The network component of claim 3, wherein the SFD delineates a beginning of the second interval, and wherein the synchronization window is initiated by generating the signal that occurs at a different time than the transmission of the SFD.

5. The network component of claim 4, wherein the first interval is part of a guard interval for the first frame, wherein the instructions further cause the processor to promote the transmission of a low priority data, and wherein at least a portion of the low priority data is transmitted during the first interval.

6. The network component of claim 5, wherein at least a portion of the low priority data is transmitted during the second interval within the timeslots, and wherein the SFD is an Ethernet control symbol.

7. The network component of claim 5, wherein the low priority data is Best Effort Packet (BEP) data.

8. The network component of claim 5, wherein the synchronization window comprises a third interval, and wherein at least a portion of the low priority data is transmitted during the third interval.

9. The network component of claim 8, wherein the integrity of the frame is maintained when at least some of the data in the first interval, the third interval, or both are lost.

10. The network component of claim 1, wherein the synchronization window has a period of about 125 microseconds.

11. The network component of claim 1, wherein the synchronization window is a defined time period where at least one synchronization timestamp is communicated, and wherein the frame comprises the at least one synchronization timestamp that is transmitted within the predetermined period of the synchronization window.

12. The network component of claim 1, wherein the frame comprises a synchronization timestamp, and wherein the instructions further cause the processor to synchronize a plurality of other synchronization windows initiated by the processor with a plurality of synchronization windows initiated by a node using the synchronization timestamp.

13. The network component of claim 12, wherein the synchronization timestamp synchronizes one of the following:

the frequency of the other synchronization windows initiated by the processor with the synchronization windows initiated by the node or the phase of the other synchronization windows initiated by the processor with the synchronization windows initiated by the node.

14. A network component comprising:

a transmitting interface configured to transmit a data frame;

a memory; and

a processor coupled to the memory and the transmitting interface, wherein the memory comprises instructions that cause the processor to;

generate a first synchronization signal that indicates the start of a first synchronization window; and

transmit the data frame via the transmitting interface,

wherein the data frame comprises a start of frame delimiter (SFD) that indicates the start of the data frame and a plurality of timeslots,

wherein the first synchronization signal is generated externally of the data frame,

wherein the data frame is floating within the synchronization window, and

wherein the transmission of the SFD and generation of the first synchronization signal do not occur at the same time.

15. The network component of claim 14, wherein the first synchronization window is a predetermined time period, and wherein the network component further comprises a synchronization window clock that measures the predetermined period for the first synchronization window.

16. The network component of claim 15, wherein the instructions further cause the processor to generate a second synchronization signal that indicates the start of a second synchronization window, wherein a guard interval for the first synchronization window varies in size in comparison to a second guard interval for the second synchronization window, and wherein the synchronization window clock resets when the processor generates the second synchronization signal.

17. The network component of claim 15, wherein the instructions further cause the processor to receive a synchronization timestamp that is used to synchronize the first synchronization window and a second synchronization window generated by a node.

18. A method for initiating and synchronizing at least one synchronization window between two nodes, wherein the method comprises:

initiating a synchronization window that comprises a start time and an end time by generating a synchronization signal;

transmitting a first frame that comprises a start of frame delimiter (SFD) within the synchronization window,

wherein the SFD indicates a start for transmitting the first frame,

wherein the synchronization window is initiated using an internal signal generated outside of the first frame,

wherein the first frame is floating within the synchronization window, and

wherein the start of transmitting the first frame is offset from the start time of the synchronization window.

19. The method of claim 18, wherein the synchronization window is a predetermined period, wherein the start time of the synchronization window overlaps the transmission of a guard interval, and wherein the guard interval separates the SFD from the start time of the synchronization.

20. The method of claim 18, wherein the first frame comprises a plurality of synchronization timestamps, and wherein the synchronization timestamps are used to frequency align and phase align the synchronization window with a downstream synchronization window.