CN102843205B - The method and apparatus that a kind of time synchronized based on Precision Time Protocol restrains - Google Patents
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Abstract
The invention discloses the method and apparatus that a kind of time synchronized based on Precision Time Protocol restrains, the method comprises: synchronously calculate at each passive port and master clock node synchronisation message line time of going forward side by side from clock node, set up and safeguard the alternative time information that this passive port is corresponding according to time synchronized result of calculation; When the upstream clock synchronizing network generation change in topology from port or arbitrary passive port being detected from clock node, trigger BMC to calculate, the port with optimum clock priority information is determined according to BMC result of calculation, if the port with optimum clock priority information is passive port, then this passive port is switched to from port, and the alternative time information corresponding according to this passive port carries out time synchronizing to local clock.The present invention can reduce the out of alignment time from clock node when network topology change.
Description
Technical Field
The present invention relates to the field of precise Time synchronization technologies, and in particular, to a method and an apparatus for Time synchronization convergence based on a Precision Time Protocol (PTP).
Background
Precision Time Protocol (PTP) is a distributed Time synchronization Protocol that specifies how devices in a system synchronize real Time with each other, with sub-microsecond (us) level Time synchronization performance. The network applying the PTP protocol is called a PTP domain, nodes in the domain are called clock nodes, ports running the PTP protocol on the clock nodes are called PTP ports, the PTP ports comprise three roles, the PTP port issuing the synchronization time is called a master port, the port receiving the synchronization time is called a slave port, and the PTP port not issuing the synchronization time nor receiving the synchronization time is called a passive port.
All Clock nodes in the PTP domain are organized together according to a master-slave hierarchical structure, the Clock node at the highest level is the Clock node where a master Clock (GM) is located, other Clock nodes are the Clock nodes where slave clocks are located, and the master Clock determines the reference time of the whole system. The slave clock node interacts a synchronous message with the master clock node and records the receiving and sending time of the synchronous message (also called PTP protocol message, including Sync message, Delay-Req message, Delay-Resp message and the like), and the time information obtained in the process of interacting the synchronous message is used for adjusting the clock of the slave clock node to be consistent with the master clock in the hierarchy.
Referring to fig. 1, fig. 1 is a schematic diagram of a clock synchronization process using a request-response mechanism in the prior art, where the clock synchronization process is in a two-step mode and includes the following steps:
(1) the master clock node sends a Sync message to the slave clock node and records the sending time t 1; after receiving the message from the clock, recording the receiving time t 2; (if the clock synchronization process is in a single step mode, t1 is carried in the Sync message);
(2) after the master clock node sends a Sync message, a Follow-Up message carrying t1 is sent, and after the slave clock node receives the message, t1 is recorded; (if the clock synchronization process is in single step mode, the step is not executed);
(3) after the slave clock node receives the Sync message, returning a Delay-Req message to the master clock node, and recording the sending time t 3; after receiving the message, the master clock node records the receiving time t 4;
(4) and after receiving the Delay-Req message of the slave clock node, the master clock node sends a Delay-Resp message carrying t4 to the slave clock node.
According to the recorded t1, t2, t3 and t4, the slave clock node can calculate that the time deviation of the self clock relative to the master clock is Offset = [ (t2-t1) - (t4-t3) ]/2. And then adjusting the local time according to the time deviation, thereby realizing the time synchronization with the master clock node.
In the existing implementation, a Master Clock node may be statically designated through manual configuration, or dynamically elected through an optimal Master Clock (Best Master Clock, BMC) protocol, and the dynamic election process is as follows: the clock nodes announce information such as clock priority, time level, time precision and the like carried in the message through the interactive PTP BMC, and finally one clock node is selected to serve as a main clock node of the PTP domain, and the clock of the main clock node serves as a main clock. In the dynamic election process, the master-slave relationship among the clock nodes and the master port, the slave port and the passive port on each clock node are also determined, and a spanning tree which is loop-free and fully communicated and takes the master clock node as a root is finally established in the whole PTP domain; and then, the master clock node can periodically send a PTP BMC notification message to the slave clock node, and if the slave clock node does not receive the PTP BMC notification message sent by the master clock node within a period of time, the master clock node is considered to be invalid, and the master clock node is selected again.
In the prior art, the clock is out of synchronization within a certain time due to the change of the network topology, and the following description will use fig. 2 as an example.
Fig. 2 is a schematic networking diagram of a PTP domain in the prior art, including 8 clock nodes C0-C7, where C0 is a master clock node and C1-C7 are slave clock nodes, where, when all the clock nodes are working normally, ports 01 and 11 and 12 on C1 on C0, port 22 on C2, port 32 on C3, port 42 on C4, and ports 62 and 63 on C6 are master ports; port 21 on C2, port 31 on C3, port 43 on C4, port 51 on C5, port 61 on C6 are slave ports; port 33 on C3, port 41 on C4 are passive ports. Each slave clock node performs synchronous message interaction with the master clock node through the slave port of the slave clock node, and keeps time synchronization with the master clock node.
As shown in fig. 2, in the case of stable topology, the clock node C3 performs PTP event message interaction with the master clock node C0 through the port 31, and maintains time synchronization with C0; the clock node C4 maintains time synchronization with C0 through PTP event message interactions with the master clock node C0 through port 43. Assuming that the clock of C6 fails, the port 43 on C4 fails, and needs to recalculate a path that can reach C0 according to the BMC algorithm, and wait for a new synchronization of the master clock node C0, and while waiting for a new synchronization of C0, the C4 is always out of synchronization.
Disclosure of Invention
In view of the above, the present invention provides a method for time synchronization convergence based on a precision time protocol, which is capable of reducing the time out-of-synchronization of a slave clock node when the network topology changes.
In order to achieve the above object, the present invention provides a method for time synchronization convergence based on a precision time protocol, which is applied to a slave clock node, wherein the slave clock interface includes a slave port and at least one passive port, the method includes:
the slave clock node interacts synchronous messages with the master clock node at each passive port and carries out time synchronization calculation, and alternative time information corresponding to the passive port is established and maintained according to the time synchronization calculation result;
when the slave clock node detects that the slave port or the upstream clock synchronous network of any passive port has topology change, triggering BMC calculation, determining a port with optimal clock priority information according to a BMC calculation result, switching the passive port into the slave port if the port with the optimal clock priority information is the passive port, and performing time synchronization processing on a local clock according to alternative time information corresponding to the passive port.
The present invention also provides a slave clock node, the slave clock interface comprising a slave port and at least one passive port, the slave clock node further comprising: the device comprises a synchronization unit, a detection unit, a calculation unit and a switching unit;
the synchronization unit is used for interacting a synchronization message with the master clock node at each passive port of the slave clock node, performing time synchronization calculation, and establishing and maintaining alternative time information corresponding to the passive port according to a time synchronization calculation result;
the detection unit is used for detecting whether topology changes occur in the slave ports of the slave clock nodes and the upstream clock synchronization network of each passive port;
the computing unit is used for triggering BMC computing when the detection unit detects that the topology change of the upstream clock synchronization network of the slave port or any passive port of the slave clock node occurs;
and the switching unit is used for determining a port with the optimal clock priority information according to the BMC calculation result, switching the port with the optimal clock priority information into a slave port if the port with the optimal clock priority information is the passive port of the slave clock node, and performing time synchronization processing on the local clock according to the alternative time information corresponding to the passive port.
According to the technical scheme, in the invention, the slave clock node performs time synchronization calculation on the slave port and the passive port, and the time synchronization calculation result on the passive port is stored as alternative time information; when a slave port or any passive port of the slave clock node detects that topology change of an upstream clock causes a certain passive port to be switched to a slave port, the alternative time information stored in the optimal passive port is issued to the clock chip without waiting for a new round of synchronization of the master clock node, so that the out-of-step time of the slave clock node can be reduced.
Drawings
FIG. 1 is a schematic diagram of a clock synchronization process using a request-reply mechanism in the prior art;
FIG. 2 is a schematic diagram of a prior art networking of PTP domains;
FIG. 3 is a flowchart of a method for PTP based time synchronization convergence according to an embodiment of the present invention;
fig. 4 is a schematic structural diagram of a slave clock node according to an embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more clearly apparent, the technical solutions of the present invention are described in detail below with reference to the accompanying drawings and examples.
Referring to fig. 3, fig. 3 is a flowchart of a method for PTP-based time synchronization convergence, which is applied to a slave clock node, where the slave clock interface includes a slave port and at least one passive port, and the method includes the following steps:
step 301, the slave clock node interacts a synchronization message with the master clock node at each passive port and performs time synchronization calculation, and establishes and maintains alternative time information corresponding to the passive port according to the time synchronization calculation result.
Here, the slave clock node uses the same synchronization packet interaction process with the master clock node at each passive port as the slave port, and periodically performs time synchronization calculation, except that: the time synchronization calculation result obtained by the passive port is not sent to the clock chip, but is stored as the alternative time information corresponding to the passive port, and when a new time synchronization calculation result is obtained by the next calculation, the alternative time information corresponding to the passive port is updated; and the time synchronization calculation result calculated at the slave port is immediately sent to the clock chip so as to realize the time synchronization with the master clock node. The time synchronization calculation result may be the offset time between itself and the master clock, or may be the time of the slave clock node adjusted according to the offset time between itself and the master clock.
In this step, a single-step request response mechanism may be used to implement the synchronous message interaction between the slave clock node and the master clock node at each passive port, or a double-step request response mechanism may be used to implement the synchronous message interaction between the slave clock node and the master clock node at each passive port.
In particular, the amount of the solvent to be used,
when a request response mechanism of a single step mode is adopted to realize that a slave clock node interacts a synchronous message with a master clock node at each passive port, the step of interacting the synchronous message with the master clock node at each passive port by the slave clock node and carrying out time synchronization calculation comprises the following steps: the slave clock node receives the Sync message sent by the master clock node at the passive port, acquires the sending time t1 of the Sync message carried in the Sync message, and records the receiving time t2 of the Sync message; sending a Delay-Req message to a master clock node, and recording the sending time t3 of the Delay-Req message; the slave clock node receives a Delay-Resp message returned by the master clock node after receiving the Delay-Resp message, and the time t4 when the master clock node receives the Delay-Req message carried in the Delay-Resp message is obtained; and the slave clock node carries out synchronous time calculation according to the t1, the t2, the t3 and the t 4.
When a request response mechanism of a double-step mode is adopted to realize that a slave clock node interacts synchronous messages with a master clock node at each passive port, the step of interacting the synchronous messages with the master clock node at each passive port by the slave clock node and carrying out time synchronization calculation comprises the following steps: the slave clock node receives a Sync message and a Follow-UP message sent by the master clock node at the passive port, acquires the sending time t1 of the Sync message carried in the Follow-UP message, and records the receiving time t2 of the Sync message; sending a Delay-Req message to a master clock node, and recording the sending time t3 of the Delay-Req message; receiving a Delay-Resp message returned by a main clock node after receiving the Delay-Resp message, and acquiring the time t4 for the main clock node carried in the Delay-Resp message to receive the Delay-Req message; and the slave clock node carries out synchronous time calculation according to the t1, the t2, the t3 and the t 4.
Step 302, when the slave clock node detects that the topology change occurs in the slave port or the upstream clock synchronization network of any passive port, triggering the BMC calculation, determining the port with the optimal clock priority information according to the BMC calculation result, if the port with the optimal clock priority information is a passive port, switching the passive port to the slave port, and issuing alternative time information corresponding to the passive port to the clock chip.
Here, the clock priority information includes optimal clock node information and a number of hops to reach the optimal clock node or a cost (cost), and in addition, the clock priority information further includes: a sending port (a port for sending the PTP BMC notification message carrying the clock priority information), a receiving port (a port for receiving the PTP BMC notification message carrying the clock priority information), and the like. The lower the number of hops or cost from a port to the optimal clock node, the better the optimal clock information for that port. In the above steps, the port with the optimal clock priority information may be determined according to the BMC calculation method in the prior art. If the port with the optimal clock priority information is still the original slave port according to the BMC calculation result, continuously transmitting the time synchronization calculation result of the original slave port to a clock chip, and adjusting the local time according to the time synchronization calculation result; if the port with the optimal clock priority information is determined to be a certain passive port, the role of the original slave port is changed at this time, that is, the original slave port is switched to the passive port or the master port, the passive port is switched to a new slave port, and the local clock is directly subjected to time synchronization processing according to the alternative time information corresponding to the passive port: by issuing the alternative time information corresponding to the passive port to the clock chip, the local time can be directly adjusted according to the alternative time information, the time synchronization with the master clock node is realized, and the new round of synchronization of the master clock node is not required to be waited, so that the out-of-step time of the slave clock node can be reduced.
The topology change of an upstream clock synchronization network of a certain port (slave port or passive port) of a slave clock node comprises two situations:
(1) the direct link of the port fails, for example, the port fails, an opposite port of the direct link of the port fails, the direct link is interrupted, and the like. When the direct link of the port fails, the slave clock node may determine that the direct link of the port fails according to the state of the port, and further determine that the upstream clock synchronization network of the port has a topology change.
(2) The direct link of the port is normal, the PTP BMC advertisement message sent by the upstream clock node can still be received, but the clock priority information carried in the received PTP BMC advertisement message changes, and if the clock priority information is different from the clock priority information of the receiving port, it can also be determined that the upstream clock synchronization network topology of the port changes.
When a slave clock node detects that the topology of an upstream clock synchronization network of a certain port (slave port or passive port) of the slave clock node changes, in order to keep normal time synchronization with a master clock node, the clock node needs to trigger BMC calculation, re-determine the role of each port, determine a new slave port, and perform clock synchronization with the master clock node by using the new slave port.
According to the BMC algorithm, the port with the optimal clock priority information will be selected and switched to the new slave port. If the first network topology change is detected at the slave port, the slave port cannot normally receive a synchronization message (Sync message) sent by the master clock, subsequent synchronization message interaction cannot be executed, the slave port cannot be used as the slave port to continue time synchronization with the master clock, and a new slave port determined according to BMC calculation is no longer the original slave port. If the second network topology change is detected on the slave port, the new slave port determined from the BMC calculation may still be the original slave port.
Because each passive port of the slave clock node is the same as the slave port, the synchronous message interaction and the time synchronization calculation between the slave clock node and the master clock node are executed, and the alternative time information is stored, when the port corresponding to the optimal clock information determined according to the BMC calculation is judged to be the original passive port, the passive port can be switched to the slave port, and the alternative time information corresponding to the passive port can be immediately sent to the clock chip to adjust the local time, and the operations of time synchronization calculation and local time adjustment are not required to be executed after the master clock node initiates a new round of synchronous message interaction, so that the desynchronizing time of the slave clock node can be reduced under the condition that the network topology is changed.
In the embodiment of the present invention shown in fig. 3, after the network topology changes, the original master port may become a passive port and the original passive port may also become a master port under the new network topology, and the role change of the ports is determined by the BMC calculation result. When a certain passive port needs to be switched to a master port according to a BMC calculation result, the passive port can be switched to be the master port, and synchronous messages are stopped from being interacted between the passive port (a new master port) and a master clock node.
The method for time synchronization convergence based on PTP in the embodiment of the present invention is described in detail above, and the present invention also provides a clock node.
Referring to fig. 4, fig. 4 is a schematic structural diagram of a slave clock node according to an embodiment of the present invention, where the slave clock node includes: a synchronization unit 401, a detection unit 402, a calculation unit 403, and a switching unit 404; wherein,
a synchronization unit 401, configured to interact a synchronization packet with a master clock node at each passive port of the slave clock node, perform time synchronization calculation, and establish and maintain alternative time information corresponding to the passive port according to a time synchronization calculation result;
a detecting unit 402, configured to detect whether a topology change occurs in a slave port of the slave clock node and an upstream clock synchronization network of each passive port;
a calculating unit 403, configured to trigger BMC calculation when the detecting unit 402 detects that a topology change occurs in an upstream clock synchronization network of a slave port or any passive port of the slave clock node;
a switching unit 404, configured to determine, according to a BMC calculation result, a port with optimal clock priority information, and if the port with the optimal clock priority information is a passive port of the slave clock node, switch the passive port to a slave port, and perform time synchronization processing on a local clock according to alternative time information corresponding to the passive port; the clock priority information includes: the optimal clock node information and the number of hops to reach the optimal clock node or cost.
The slave clock node further includes a receiving unit 405, configured to receive PTP BMC advertisement messages at the slave port and each passive port of the slave clock node;
when detecting whether a topology change occurs in the slave port of the slave clock node and the upstream clock synchronization network of each passive port, the detecting unit 402 is configured to: when detecting that the direct link of the slave port or the passive port fails, or when the slave port or the passive port receives the PTP BMC advertisement message and the clock priority information carried in the PTP BMC advertisement message changes, the receiving unit 405 determines that the network topology change occurs in the upstream clock synchronization network of the slave port or the passive port.
In the slave clock node, the switching unit 404 is further configured to: and when determining that any one passive port of the slave clock node needs to be switched to the master port according to the BMC calculation result, switching the passive port to the master port, and notifying the synchronization unit 401 to stop interacting the synchronization message between the passive port and the master clock node.
When the switching unit 404 switches the passive port to be the master port, it further clears the alternative time information corresponding to the passive port.
The synchronization unit 401 is configured to use a single-step request response mechanism or a double-step request response mechanism to interact a synchronization packet with the master clock node at each passive port of the slave clock node.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like made within the spirit and principle of the present invention should be included in the scope of the present invention.
Claims (10)
1. A method for time synchronization convergence based on Precision Time Protocol (PTP) is applied to a slave clock node, the slave clock interface comprises a slave port and at least one passive port, and the method comprises the following steps:
the slave clock node interacts synchronous messages with the master clock node at each passive port and carries out time synchronization calculation, and alternative time information corresponding to each passive port is established and maintained according to the time synchronization calculation result;
when the slave clock node detects that the slave port or the upstream clock synchronous network of any passive port has topology change, triggering the best master clock BMC (baseboard management controller) to calculate, determining a port with the best clock priority information according to a BMC calculation result, switching the passive port into the slave port if the port with the best clock priority information is the passive port, and performing time synchronization processing on a local clock according to alternative time information corresponding to the passive port.
2. The method for PTP based time synchronization convergence according to claim 1,
the method for detecting whether the network topology change occurs in the upstream clock synchronization network of the slave port or any passive port by the slave clock node comprises the following steps:
when a direct connection of the slave port or the passive port is detected to have a fault, or when the slave port or the passive port receives a PTP BMC notification message and clock priority information carried in the PTP BMC notification message changes, determining that the network topology change occurs in an upstream clock synchronization network of the slave port or the passive port.
3. The method for PTP-based time synchronization convergence according to claim 1, further comprising:
and when determining that any passive port needs to be switched to the main port according to the BMC calculation result, switching the passive port to be the main port, and stopping exchanging the synchronous message between the passive port and the main clock.
4. The method for PTP based time synchronization convergence according to claim 3,
and when the passive port is switched to be the main port, further clearing the alternative time information corresponding to the passive port.
5. The method for PTP based time synchronization convergence according to claim 1,
and the slave clock node adopts a single-step mode request response mechanism or a double-step mode request response mechanism at each passive port to interact synchronous messages with the master clock node.
6. A slave clock node, comprising: the device comprises a synchronization unit, a detection unit, a calculation unit and a switching unit;
the synchronization unit is used for interacting a synchronization message with the master clock node at each passive port of the slave clock node, performing time synchronization calculation, and establishing and maintaining alternative time information corresponding to each passive port according to a time synchronization calculation result;
the detection unit is used for detecting whether topology changes occur in the slave ports of the slave clock nodes and the upstream clock synchronization network of each passive port;
the computing unit is used for triggering the optimal master clock BMC to compute when the detection unit detects that the topology change occurs to the slave port of the slave clock node or the upstream clock synchronous network of any passive port;
and the switching unit is used for determining a port with the optimal clock priority information according to the BMC calculation result, switching the port with the optimal clock priority information into a slave port if the port with the optimal clock priority information is the passive port of the slave clock node, and performing time synchronization processing on the local clock according to the alternative time information corresponding to the passive port.
7. The slave clock node of claim 6,
the slave clock node also comprises a receiving unit which is used for receiving PTP BMC notification messages at the slave port and each passive port of the slave clock node;
the detecting unit is configured to, when detecting whether a topology change occurs in the slave port of the slave clock node and the upstream clock synchronization network of each passive port,: when detecting that the direct link of the slave port or the passive port has a fault, or when the receiving unit receives the PTP BMC advertisement message from the slave port or the passive port and the clock priority information carried in the PTPBMC advertisement message changes, determining that the network topology change occurs in the upstream clock synchronization network of the slave port or the passive port.
8. The slave clock node of claim 6,
the switching unit is further configured to: and when determining that any one passive port of the slave clock node needs to be switched to the master port according to the BMC calculation result, switching the passive port to be the master port, and informing the synchronization unit of stopping interacting the synchronization message between the passive port and the master clock node.
9. The slave clock node of claim 8,
and when the switching unit switches the passive port to be the main port, the switching unit further clears the alternative time information corresponding to the passive port.
10. The slave clock node of claim 6,
and the synchronization unit is used for adopting a single-step mode request response mechanism or a double-step mode request response mechanism at each passive port of the slave clock node to interact a synchronization message with the master clock node.
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| CN101170373A (en) * | 2007-11-27 | 2008-04-30 | 上海自动化仪表股份有限公司 | Clock synchronization realization method for loop network |
| CN102143127A (en) * | 2010-06-24 | 2011-08-03 | 华为技术有限公司 | Time synchronization method, time synchronization system and network equipment |
| CN102215101A (en) * | 2011-05-31 | 2011-10-12 | 中兴通讯股份有限公司 | Time synchronization method and device |
| CN102223197A (en) * | 2011-06-14 | 2011-10-19 | 中兴通讯股份有限公司 | Clock synchronizing method and equipment |
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