Frame transmitting apparatus, frame receiving apparatus, and frame transmission/reception system and method

Patent metadata

Field	Value
Publication number	US-9306695-B2
Application number	US-201213490997-A
Country	US
Kind code	B2
Filing date	Jun 7, 2012
Priority date	Jun 7, 2011
Publication date	Apr 5, 2016
Grant date	Apr 5, 2016

Abstract

To enable more precise synchronization of distributed clocks, before a high-level frame is converted to a low-level frame for transmission over a communication network, if the high-level frame includes a certain type of message, it is flagged. The flag is detected during the conversion process, and the time of detection is stored as a transmission timestamp. When a low-level frame is received from the network, it is immediately timestamped with the time of reception. The timestamped frame is then converted to a high-level frame, and if the high-level frame includes the certain type of message, the timestamp is stored as a reception timestamp.

First claim

What is claimed is:

1. A frame receiving apparatus, comprising:
a processor that performs processes of:
receiving a low-level frame belonging to a physical layer from a communication network;
generating a timestamp representing a time at which the low-level frame is received and adding the timestamp to the low-level frame, thereby generating a timestamped frame;
removing the timestamp from the timestamped frame, thereby holding the removed timestamp;
converting a frame obtained by removing the timestamp from the timestamped frame, to a high-level frame belonging to an upper layer; and
restoring the removed timestamp to the high-level frame; and

a storing unit for selectively storing the time represented by the timestamp, depending on content of the high-level frame.

2. The frame receiving apparatus of claim 1 , wherein the storing unit removes the timestamp from the high-level frame.

3. The frame receiving apparatus of claim 1 , wherein the storing unit stores the time represented by the timestamp when the high-level frame includes a Sync message or a DelayReq message.

4. A frame transmitting apparatus comprising:
a processor that performs processes of:
selectively flagging high-level frames, depending on content of the high-level frames;
removing flags from the flagged high-level frames respectively, thereby holding the removed flags;
converting each frame obtained by removing the flag from the flagged high-level frame to a low-level frame belonging to a physical layer;
restoring the removed flag to the low-level frame, thereby generating a flagged low-level frame;
transmitting the flagged low-level frame over a communication network; and
determining, during conversion of the high-level frame to the low-level frame, whether the high-level frame was flagged; and

a storing unit for storing a time of detection that the high-level frame was flagged as a transmission time.

5. The frame transmitting apparatus of claim 4 , wherein the processor performs a process of flagging the high-level frame if the high-level frame includes a Sync message or a DelayReq message.

6. A frame transmission and reception system including frame transmitting apparatus and frame receiving apparatus for transmitting and receiving frames over a communication network, wherein:
the frame transmitting apparatus comprises
a first processor that performs processes of:
selectively flagging first high-level frames belonging to an upper layer, depending on content of the high-level frames,
removing flags from the flagged first high-level frames respectively, thereby holding the removed flags,
converting each frame obtained by removing a flag from a flagged first high-level frame to a low-level frame belonging to a physical layer,
restoring the removed flag to the low-level frame, thereby generating a flagged low-level frame,
transmitting the flagged low-level frame over the communication network, and
determining, during conversion of the first high-level frame to the low-level frame, whether the first high-level frame was flagged, and

a first storing unit for storing a time of detection that the first high-level frame was flagged as a transmission time; and
the frame receiving apparatus comprises
a second processor that performs processes of:
receiving the low-level frame from the communication network,
generating a timestamp representing a time at which the low-level frame is received and adding the timestamp to the low-level frame, thereby generating a timestamped frame,
removing the timestamp from the timestamped frame, thereby holding the removed timestamp,
converting a frame obtained by removing the timestamp from the timestamped frame, to a second high-level frame belonging to the upper layer, and
restoring the removed timestamp to the second high-level frame, and

a second storing unit for selectively storing the time represented by the timestamp, depending on content of the second high-level frame.

7. The frame transmission and reception system of claim 6 , wherein the second storing unit removes the timestamp from the second high-level frame.

8. The frame transmission and reception system of claim 6 , wherein the second storing unit stores the time represented by the timestamp if the second high-level frame includes a Sync message or a DelayReq message.

9. The frame transmission and reception system of claim 6 , wherein the second processor performs a process of flagging the second high-level frame if the high-level frame includes a Sync message or a DelayReq message.

10. The frame transmission and reception system of claim 6 , wherein the first processor and the second processor perform security processing.

11. A method of transmitting frames over a communication network, comprising:
selectively flagging high-level frames belonging to an upper layer, depending on content of the high-level frames;
removing flags from the flagged high-level frames respectively, thereby holding the removed flags,
converting each frame obtained by removing the flag from the flagged high-level frame to a low-level frame belonging to a physical layer;
restoring the removed flag to the low-level frame, thereby generating a flagged low-level frame,
transmitting the flagged low-level frame over the communication network;
determining, during conversion of the first high-level frame to the low-level frame, whether the first high-level frame was flagged;
storing a time of detection that the first high-level frame was flagged as a transmission time;
receiving the low-level frame from the communication network;
generating a timestamp representing a time at which the low-level frame is received and adding the timestamp to the low-level frame, thereby generating a timestamped frame;
removing the timestamp from the timestamped frame, thereby holding the removed timestamp;
converting a frame obtained by removing the timestamp from the timestamped frame, to a second high-level frame belonging to the upper layer; and
restoring the removed timestamp to the second high-level frame, and
selectively storing the time represented by the timestamp, depending on content of the second high-level frame.

12. The method of claim 11 , wherein selectively storing the time represented by the timestamp further comprises removing the timestamp from the second received high-level frame.

13. The method of claim 11 , wherein the time represented by the timestamp is stored if the second high-level frame includes a Sync message or a DelayReq message.

14. The method of claim 11 , wherein the high-level frame is flagged if the second high-level frame includes a Sync message or a DelayReq message.

Assignees

• Nakamura Toshihiko
• Lapis Semiconductor Co Ltd

Inventors

• Nakamura Toshihiko

Classifications

• H04J3/0697 Primary

  Synchronisation in a packet node · CPC title

• H04J3/0667

  Bidirectional timestamps, e.g. NTP or PTP for compensation of clock drift and for compensation of propagation delays (arrangements for monitoring round trip delays in packet switching networks H04L43/0864) · CPC title