KR101973264B1 - Clocks timing fault recovery method and apparatus in precision time protocol system - Google Patents

Abstract

A time synchronization failure recovery method and apparatus in a precision time protocol (PTP) system are disclosed. The method of recovering the time synchronization failure of the slave node in the PTP (Precision Time Protocol) is a method of recovering the time synchronization failure of the slave node by receiving a time synchronization signal to the remaining topsoil in case of a failure during time synchronization to a specific port, Time synchronization can be performed through a signal. Accordingly, the present invention has an advantage in that time synchronization of the network can be stably maintained by detecting and recovering a failure in a short period of time.

Description

TECHNICAL FIELD [0001] The present invention relates to a time synchronization failure recovery method and apparatus in a PTP (precision time protocol)

The present invention relates to a time synchronization failure recovery method and apparatus in a PTP system.

The Precision Time Protocol system can calculate and synchronize time by sending and receiving special messages between two nodes (machines). This PTP is an IEEE standard for network precision time synchronization, and can be applied to time synchronization of less than 100 ns.

However, the current PTP system standard has a discussion of fault tolerance, but there is no standard for how to solve it.

The present invention provides a method and apparatus for recovering a time synchronization failure in a PTP system.

The present invention provides a method and apparatus for recovering a time synchronization failure in a PTP system capable of performing time synchronization through another port when a failure occurs during time synchronization from a PTP system to a specific port.

According to an aspect of the present invention, a time synchronization failure recovery method in a precision time protocol (PTP) system is provided.

According to an embodiment of the present invention, there is provided a method of recovering a time synchronization failure of a slave node in a Precision Time Protocol (PTP), the method comprising: determining whether a failure occurs during time synchronization through a first port; And receiving the time synchronization signal through the second port and performing time synchronization when a failure occurs in the first port, the time synchronization failure recovery method of the slave node in the PTP may be provided.

The step of determining whether or not a fault has occurred in the first port may determine that a failure has occurred in the link to the first port when an announce message is not received during the reference time from the first port.

The performing time synchronization through the second port may perform time synchronization by receiving the time synchronization signal through the second port after changing the inactive second port to the active state.

Before performing the time synchronization, one of the second ports changed to the activated state may be a plurality of the second ports changed to the plurality of activated states, and then the remaining ports may be changed to the inactive state .

According to another embodiment of the present invention, there is provided a method of recovering a time synchronization failure of a slave node in a Precision Time Protocol (PTP), the method comprising: transmitting a link acknowledgment message through a plurality of ports; And performing time synchronization using a time synchronization signal received through at least some ports of the plurality of ports in response to the link confirmation message, in a PTP, .

The performing time synchronization may include receiving an announcement message in response to the link confirmation message through at least a portion of the plurality of ports; And selecting a master node using the received notification message and performing time synchronization with the selected master node.

The selecting of the master node using the received notification message can select any of the master nodes connected to each port of at least a part of the plurality of ports by using the time information included in the received notification message.

Retransmitting through the plurality of ports if a response of the link confirmation message is not received during a first reference time; And if the response is not received during the second reference time after the retransmission, the slave node is set as a master node and transmits a notification message to a lower sub network to perform time synchronization with the sub nodes included in the sub network .

According to another embodiment of the present invention, there is provided a frame structure for time synchronization in a PTP system, the frame structure comprising: a header field; And a data field, wherein the data field includes a first field including a status of a node, a second flag field including whether a synchronous signal is requested, and a third field including an ID of a port transmitting the message A frame structure for time synchronization in the PTP system can be provided.

According to another embodiment of the present invention, there is provided a frame structure for time synchronization in a PTP system, the frame structure comprising: a header field; And a data field, wherein a first flag field including a node type, a second flag field indicating whether a time information is requested, a third field including a slave transmission port ID, a fourth field including a master transmission port ID, Field may be provided.

According to another aspect of the present invention, there is provided an apparatus for time-synchronous failure recovery in a precision time protocol (PTP) system, according to an embodiment of the present invention.

According to an embodiment of the present invention, there is provided a slave node performing a time synchronization failure recovery in a PTP (Precision Time Protocol), the slave node comprising: a sensing unit for determining whether a failure has occurred during time synchronization through a first port; And a synchronization unit receiving the time synchronization signal through the second port and performing time synchronization when a failure occurs in the first port.

According to another embodiment of the present invention, there is provided a slave node for performing a time synchronization failure recovery in a PTP (Precision Time Protocol), comprising: a communication unit for transmitting a link acknowledgment message through a plurality of ports; And a synchronization unit for performing time synchronization using a time synchronization signal received through at least some ports of the plurality of ports in response to the link confirmation message.

The present invention provides a method and apparatus for recovering a time synchronization failure in a PTP (precision time protocol) system, in which, when a failure occurs during time synchronization from a PTP system to a specific port, To recover time failure.

1 is a diagram illustrating a PTP network system according to an embodiment of the present invention;
Fig. 2 is a diagram for explaining master-slave port status in PTP; Fig.
3 is a flowchart illustrating a time synchronization method in a general PTP.
4 is a flowchart illustrating a time synchronization failure recovery method in a PTP according to an embodiment of the present invention.
5, 6, 8, 10, 11, and 13 are diagrams for explaining a time synchronization failure recovery method in a PTP according to an embodiment of the present invention.
FIG. 7 is a flowchart illustrating a time synchronization failure recovery method in a PTP according to an embodiment of the present invention; FIG.
9 is a diagram illustrating a Link Alive Message format according to an embodiment of the present invention.
FIG. 12 illustrates a format of an announcement message according to an embodiment of the present invention; FIG.
FIG. 14 schematically illustrates an internal configuration of a slave node in a PTP according to an embodiment of the present invention; FIG.

As used herein, the singular forms "a", "an" and "the" include plural referents unless the context clearly dictates otherwise. In this specification, the terms " comprising ", or " comprising " and the like should not be construed as necessarily including the various elements or steps described in the specification, Or may be further comprised of additional components or steps. Also, the terms " part, " " module, " and the like described in the specification mean units for processing at least one function or operation, which may be implemented in hardware or software or a combination of hardware and software .

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a diagram illustrating a PTP network system according to an embodiment of the present invention. Referring to FIG. Precision Time Protocol (PTP) systems can calculate and synchronize time by sending and receiving special messages between two nodes (equipment). This PTP is an IEEE standard for network precision time synchronization, and can be applied to time synchronization of less than 100 ns.

The time synchronization in the PTP network system synchronizes time information of the root master to the entire network based on the master-slave hierarchy of each device (node) as shown in FIG.

FIG. 2 is a diagram illustrating a master-slave port state in the PTP. Referring to FIG. 2, the time provided at the port of the master is a reference of other ports, and the output port of the node may be the mater port. Also, the slave means that the port in the corresponding state is synchronized with the port in the master state by the node (device). Thus, the input port of the node may be a slave port. Passive means that the port in that state is not the master and is not synchronized to the master.

The time synchronization method in the conventional PTP will be briefly described with reference to FIG.

3 is a flowchart illustrating a time synchronization method in a general PTP.

As shown in FIG. 3, the master transmits a sync message including a current standard time to a slave performing synchronization. At this time, the master can broadcast a synchronization message to all the slaves (310).

After transmitting the synchronization message, the master transmits (broadcasts) a follow-up message including type stamp information for the synchronization message to the slave (315).

The slave receiving the master's message compares its time with the received time to calculate the offset.

In FIG. 3, since the difference between the slave time and the master received time is +3, the slave calculates the offset and changes its own time.

Since the offset information does not reflect the message transmission delay between the master and the slave, the slave transmits (320) a delay request message to the master in order to check the offset information, and the master receiving the offset information includes the standard time information To the slave (325).

The slave obtains the delay information by subtracting the delay request message transmission time from the time when the delay response message is received, and regards half of the delay information as a delay between itself and the master. In FIG. 3, +2 corresponding to half of the time at which the delay request message is transmitted at the time of receiving the delay response message is calculated as delay information.

In this way, the slave calculates the offset and delay information for standard time synchronization, reflects it in its own time information, and synchronizes with the standard time so that the standard time can be known using the time server on the network.

The standard related to PTP does not provide a solution to the problem when a time synchronization occurs. Therefore, the time synchronization failure recovery method in the PTP according to an embodiment of the present invention will be described in more detail.

FIG. 4 is a flowchart illustrating a time synchronization failure recovery method in a PTP according to an exemplary embodiment of the present invention. FIGS. 5, 6, 8, 10, 11, FIG. 7 is a flowchart illustrating a time synchronization failure recovery method in a PTP according to an embodiment of the present invention. FIG. 9 is a flowchart illustrating a time synchronization failure recovery method in a PTP according to an exemplary embodiment of the present invention. FIG. 12 is a diagram illustrating a format of a public announcement message according to an embodiment of the present invention. Referring to FIG.

In step 410, the slave node determines whether a failure has occurred while performing time synchronization with a specific port.

For example, the slave node may determine that a failure has occurred in the link to the specific port if an announce-message is not received for a reference time (e.g., 3 seconds) through a specific port.

Accordingly, if it is determined that a failure has occurred, the slave node receives the time synchronization message through another port through another master node in step 415, and performs time synchronization using the received time synchronization message.

This will be described in more detail as follows.

For example, assume that the slave node has failed over the first link 510 during time synchronization with the master node via the first link 510, as shown in FIG. At this time, it is assumed that the second port 520A and the third port 520B of the slave node are set in the inactive state, respectively.

The slave node changes the inactive second port 520A and the third port 520B to the active state as shown in FIG.

After all the inactive ports are changed to the active state, the subsequent steps shown in FIG. 7 are performed.

Hereinafter, the time synchronization failure recovery method will be described in more detail with reference to FIG.

In step 710, the slave node transmits a Link Alive Message through all ports changed to the active state.

As shown in FIG. 8, the slave node can transmit the Link Alive Message through all ports in the active state. As shown in FIG. 6, since the second port 520A and the third port 520B are changed to the active state, the slave node can transmit the Link Alive Message through the first port to the third port set in the active state have.

FIG. 9 shows a Link Alive Message format according to an embodiment of the present invention. Referring to FIG. 9, the Link-Alive-Message includes an 8-bit PTP header field and a data field. Here, the syntax for each field included in the PTP header field is as shown in FIG. The syntax for each field included in the PTP header field will be obvious to those skilled in the art and will not be described further.

The data field includes data related to the signaling message. This data field includes a first flag field, a second flag field, and a port field, as shown in FIG.

The first flag field is, for example, a Link Alive Flag field. When the flag is 1, it indicates a slave. If 0, it indicates a master.

The second flag field indicates a synchronization request flag (Clock Request Flag) field.

In addition, the port field includes a port ID of a message transmitted from the slave node.

At step 715, the slave node receives a notification message from the master node that has received the Link-Alive-Message through at least a portion of the active ports.

Here, the notification message can receive the time information of each master node.

For example, if there are two ports that have changed to the active state, the slave node can send a "Link-Alive-Message" to the other master node via the two ports. After the "Link-Alive-Message" is transmitted to the plurality of master nodes, the master node receiving the message transmits a notification message to the slave node. Even if the slave node transmits a "Link-Alive-Message" via two ports that have been changed to the active state, it does not guarantee that both master nodes receive the "Link-Alive-Message". In some cases, multiple ports on one master node are connected to multiple ports on the slave node, so that one master node can receive a "Link-Alive-Message".

For example, with reference to FIG. The slave node transmits a " Link-Alive-Message " to each of the master nodes through the first to third ports as shown in Fig. However, as described above, since the failure has occurred in the link to the first port, the master node connected to the first port does not receive the " Link-Alive-Message " of the slave node And does not transmit a response thereto. However, since no failure has occurred in the link between the second port and the third port, the master node connected to the second port and the third port receives the " Link-Alive-Message " And sends a notification message containing the time information of each master node in response.

The slave node selects the optimal master node using the time information of each master node included in the announcement message. It is possible to select the optimum master node by using the best clock time algorithm according to the PTP standard.

As shown in FIG. 11, it is assumed that the master node connected to the link of the third port selects the optimal master node. The slave node can reconfigure the master-slave hierarchy. That is, in the master-slave layer, the slave can change only the port receiving the time information to the active state and set the remaining ports to the passive state. That is, as shown in FIG. 11, only the port (the third port) connected to the node selected as the optimum master node remains active, and the remaining ports (the first port and the second port) are changed to the inactive state.

715, it is assumed that a notification message is received in response to a Link-Alive-Message, but a notification message may not be received. In this case, the slave node waits for a notification message from the master node to be received for a second reference time (e.g., 6 seconds). However, if the notification message is not received during the second reference time, the slave node may change the state of the slave to master and transmit a notification message to the sub-network to perform time synchronization.

In step 720, the slave node transmits a sync request message to the master node.

FIG. 11 illustrates a format of a synchronization request message according to an embodiment of the present invention. Referring to FIG. 11, the synchronization request message includes a first flag field, a second flag field, a first port field, and a second port field. Of course, the synchronization request message is not shown in FIG. 11, but it is of course possible to include a PTP header as shown in FIG.

The first flag field is a field for defining a slave node, and 1 indicates a slave node. The second flag field indicates whether to request time information. If the second flag field is 1, it can be interpreted as representing time information.

The first port field includes the transmission port ID of the slave node, and the second port field includes the transmission port ID of the master node.

In step 725, the slave node receives a sync signal from the master node and uses it to start time synchronization (see FIG. 13). The subsequent operation process is the same as that described with reference to FIG. 3, and a duplicate description will be omitted.

FIG. 14 is a diagram schematically illustrating an internal configuration of a slave node in a PTP according to an embodiment of the present invention. Referring to FIG.

14, a slave node according to an exemplary embodiment of the present invention includes a communication unit 1410, a sensing unit 1415, a synchronization unit 1420, a memory 1425, and a processor 1430.

The communication unit 1410 is a means for transmitting and receiving data by being connected to other nodes through respective ports.

The sensing unit 1415 is a unit for detecting whether or not a failure occurs in a link connected to a corresponding port during time synchronization through a specific port.

The synchronization unit 1420 is a means for receiving a time synchronization signal through another port and performing time synchronization through the other port when a failure occurs in a specific port. The detailed description thereof is the same as that described above, and a duplicate description will be omitted.

The memory 1425 is a means for storing various algorithms necessary for performing the time synchronization failure recovery method according to an embodiment of the present invention, various data derived in the process, and the like.

The processor 1430 controls the internal components (e.g., the communication unit 1410, the sensing unit 1415, the synchronization unit 1420, the memory 1425, etc.) of the slave node according to an embodiment of the present invention .

The time synchronization failure recovery method in the PTP system according to the present invention can be implemented as a computer-readable code on a computer-readable recording medium. The computer-readable recording medium includes all kinds of recording media storing data that can be decoded by a computer system. For example, it may be a ROM (Read Only Memory), a RAM (Random Access Memory), a magnetic tape, a magnetic disk, a flash memory, an optical data storage device, or the like. In addition, the computer-readable recording medium may be distributed and executed in a computer system connected to a computer network, and may be stored and executed as a code readable in a distributed manner.

It will be apparent to those skilled in the art that various modifications, additions and substitutions are possible, without departing from the spirit and scope of the invention as defined by the appended claims. Should be regarded as belonging to the following claims.

1410:
1415:
1420:
1425: Memory
1430: Processor

Claims (13)

A method for recovering a time synchronization failure of a slave node in a Precision Time Protocol (PTP)
Determining whether a failure has occurred during time synchronization through the first port; And
And performing time synchronization by receiving a time synchronization signal through a second port when a failure occurs in the first port,
The method of claim 1,
When an announce message is not received from the first port during a reference time, it is determined that a failure has occurred in the link to the first port,
The notification message includes:
Header field; And
Data fields,
The data field includes a first flag field including a node type, a second flag field indicating whether a time information is requested, a third field including a slave transmission port ID, and a fourth field including a master transmission port ID Time synchronization fault recovery method of a slave node in a PTP.
delete The method according to claim 1,
Wherein performing time synchronization through the second port comprises:
Wherein the time synchronization is performed by receiving the time synchronization signal through the second port after changing the inactive state of the second port to the active state.
The method of claim 3,
Prior to performing the time synchronization,
Wherein the second port is changed to the active state and the second port is changed to a plurality of active states, and then the remaining ports are changed to the inactive state after selecting any one of the second ports as the optimal port. How to recover from a failure.
A method for recovering a time synchronization failure of a slave node in a Precision Time Protocol (PTP)
Transmitting a Link Alive message through a plurality of ports; And
Performing time synchronization using a time synchronization signal received through at least some ports of the plurality of ports in response to the link confirmation message;
Retransmitting through the plurality of ports if a response of the link confirmation message is not received during a first reference time; And
If the response is not received during the second reference time after the retransmission, the slave node changes the status of the slave node to the master node and transmits a notification message to the lower-level sub-network, A method for recovering a time synchronization failure of a slave node in a PTP, the method comprising: performing time synchronization.
6. The method of claim 5,
Wherein performing the time synchronization comprises:
Receiving an announcement message in response to the link confirmation message through at least a portion of the plurality of ports; And
Selecting a master node using the received notification message and performing time synchronization with the selected master node; and recovering the time synchronization failure of the slave node in the PTP.
6. The method of claim 5,
Selecting a master node using the received notification message comprises:
And selecting one of the master nodes connected to each port of at least a part of the plurality of ports using the time information included in the received notification message.
delete 6. A computer readable recording medium having recorded thereon a program code for performing the method according to any one of claims 1 to 5.
A frame structure for time synchronization in a PTP system,
Header field; And
Data fields,
Wherein the data field includes a first flag field including a state of a node, a second flag field including a request for a synchronization signal request, and a third field including an ID of a port transmitting the message. Frame structure for time synchronization.
A frame structure for time synchronization in a PTP system,
Header field; And
Data fields,
The data field includes a first flag field including a node type, a second flag field indicating whether a time information is requested, a third field including a slave transmission port ID, and a fourth field including a master transmission port ID And the frame structure.
A slave node that performs time synchronization failure recovery in a Precision Time Protocol (PTP)
A sensing unit for determining whether a failure has occurred during time synchronization through the first port; And
And a synchronization unit for receiving the time synchronization signal through the second port and performing time synchronization when a failure occurs in the first port,
The sensing unit determines that a failure has occurred in the link to the first port when an announce message is not received from the first port for a reference time,
The notification message
Header field; And
Data fields,
The data field includes a first flag field including a node type, a second flag field indicating whether a time information is requested, a third field including a slave transmission port ID, and a fourth field including a master transmission port ID To the slave node.
A slave node that performs time synchronization failure recovery in a Precision Time Protocol (PTP)
A communication unit for transmitting a link acknowledgment message through a plurality of ports; And
And a synchronization unit for performing time synchronization using a time synchronization signal received through at least some ports of the plurality of ports in response to the link confirmation message,
Wherein the synchronization unit comprises:
If the response of the link confirmation message is not received during the first reference time, the slave node retransmits through the plurality of ports, and if the response is not received during the second reference time after the retransmission, the slave node transmits the status of the slave node to the master node And transmits a notification message to the lower sub-network to perform time synchronization with the sub-nodes included in the lower sub-network.

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