CN111294135A - Edge cloud-oriented multi-stage clock synchronization method - Google Patents
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- CN111294135A CN111294135A CN202010157183.3A CN202010157183A CN111294135A CN 111294135 A CN111294135 A CN 111294135A CN 202010157183 A CN202010157183 A CN 202010157183A CN 111294135 A CN111294135 A CN 111294135A
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04J—MULTIPLEX COMMUNICATION
- H04J3/00—Time-division multiplex systems
- H04J3/02—Details
- H04J3/06—Synchronising arrangements
- H04J3/0635—Clock or time synchronisation in a network
- H04J3/0638—Clock or time synchronisation among nodes; Internode synchronisation
- H04J3/0658—Clock or time synchronisation among packet nodes
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04J—MULTIPLEX COMMUNICATION
- H04J3/00—Time-division multiplex systems
- H04J3/02—Details
- H04J3/06—Synchronising arrangements
- H04J3/0635—Clock or time synchronisation in a network
- H04J3/0638—Clock or time synchronisation among nodes; Internode synchronisation
- H04J3/0658—Clock or time synchronisation among packet nodes
- H04J3/0661—Clock or time synchronisation among packet nodes using timestamps
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L67/00—Network arrangements or protocols for supporting network services or applications
- H04L67/01—Protocols
- H04L67/10—Protocols in which an application is distributed across nodes in the network
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L69/00—Network arrangements, protocols or services independent of the application payload and not provided for in the other groups of this subclass
- H04L69/16—Implementation or adaptation of Internet protocol [IP], of transmission control protocol [TCP] or of user datagram protocol [UDP]
- H04L69/164—Adaptation or special uses of UDP protocol
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Abstract
The invention discloses an edge cloud-oriented multi-level clock synchronization method, which can realize three-level clock synchronization among edge clouds, inside the edge clouds and between a physical machine and a virtual machine, wherein network time service is performed between the edge clouds and inside the edge clouds by adopting a central architecture, a server is selected inside each edge cloud as a service end for clock synchronization, other nodes inside each edge cloud are used as client ends for clock synchronization, the service end of a certain edge cloud is selected among the edge clouds as a top-level clock source, the service ends of other edge clouds are used as the client ends of the top-level clock source, network message receiving and sending are performed between the client ends and the service ends to realize network time service, and finally, the physical machine synchronizes the clock to the virtual machine. The invention can simultaneously realize clock synchronization among the edge clouds, the interior of the edge clouds and between the physical machine and the virtual machine.
Description
Technical Field
The invention relates to the field of cloud computing virtualization, in particular to a multi-stage clock synchronization method facing an edge cloud.
Background
The edge cloud computing is an open cloud platform integrating network, computing, storage and application core capabilities at one side close to an object or a data source, and provides services nearby. The edge cloud is composed of server nodes distributed in the same region, specifically processes service requests of local users, and rapidly and flexibly provides cloud computing services for the users. The edge cloud generally operates in actual scenes such as vehicle-mounted scenes, temporary command posts (such as disaster relief) and the like. In an actual scene, a plurality of edge clouds generally exist in a certain area, and are interconnected and intercommunicated through a network. For business or application software, such as a disaster relief command center, messages and instructions need to be accurately transmitted among a plurality of edge clouds, the problem of clock synchronization needs to be solved for realizing cooperative work, otherwise, inaccuracy of the messages and the instructions may be caused, and cooperative scheduling work of the command center is influenced.
Clock synchronization under an edge cloud scene has three problems at present: first, how to achieve clock synchronization between edge clouds; secondly, how to realize internal clock synchronization of the edge cloud; third, how to achieve clock synchronization between the physical machine and the virtual machine.
Disclosure of Invention
The invention aims to provide a multistage clock synchronization method facing edge clouds, which can simultaneously realize clock synchronization among the edge clouds, inside the edge clouds and between a physical machine and a virtual machine.
In order to solve the technical problem, the technical scheme adopted by the invention is as follows: a multi-level clock synchronization method facing to edge clouds comprises three levels, namely clock synchronization between edge clouds, clock synchronization inside the edge clouds and clock synchronization of a physical machine and a virtual machine, wherein network time service is performed between the edge clouds and inside the edge clouds by adopting a central architecture, a server is selected inside each edge cloud as a service end of the clock synchronization, other nodes inside each edge cloud are used as client sides of the clock synchronization, network message transceiving is performed between the client sides and the service ends to achieve the network time service, the service end of a certain edge cloud is selected between the edge clouds as a top-level clock source, the service ends of other edge clouds are used as the client sides of the top-level clock source, network message transceiving is performed between the top-level clock source and the client sides to achieve the network time service, and finally, the physical machine synchronizes the clock to the virtual machine.
Further, the clock synchronization process between the physical machine and the virtual machine is as follows: s11, executing periodically according to the detection period, firstly, acquiring the time of the physical machine and the time of the virtual machine; s12), calculating the clock error of the physical machine and the virtual machine, judging whether the clock error exceeds the threshold value of forced synchronization, if so, carrying out forced synchronization, then waiting for the next detection period, and if not, executing the next step; s13), judging whether the clock error exceeds the maximum allowable error threshold, if not, not carrying out synchronization, waiting for the next detection period, otherwise, executing the next step; s14), calculating a correction step DeltaTime/(N-1), wherein DeltaTime is the clock error calculated in the step S12, N is the maximum iteration number, and then performing N-1 iteration synchronization by taking the correction step as a period so as to correct the time of the virtual machine; s15), after circularly iterating for N-1 times, recalculating the clock error of the physical machine and the virtual machine self-check for the Nth time, and determining whether the clock error is within the maximum allowable error threshold value, if the clock error is not within the maximum allowable error threshold value, ending the iterative synchronization, otherwise, forcibly synchronizing the time of the physical machine and the virtual machine, and ending the clock synchronization of the current round.
Further, the network time service process is as follows: s21), the server side firstly initiates a network delay detection process, encapsulates a local timestamp T1 into a network message and sends the network message to the client side; s22), after receiving the server message, the client records the current receiving time T2 of the client; s23), before the client sends back to the server, the T1, the T2 and the sending time T3 are packaged into a network message to be sent; s24), after receiving the message fed back by the client, the server records the receiving time T4; s25), calculating network delay ND = (T2-T1 + T4-T3)/2; s26), carrying out rationality verification on the network delay, setting the maximum value of the one-way network delay as MAXND, if ND is greater than MAXND, then detecting again, if ND is less than MAXND, then the network delay is effective, and executing the next step; s27), the server side starts to execute the network time service process, the client side correction time is packaged into a network message and is sent to the client side, and the client side correction time is the sum of the local time of the server and the network delay; s28), after receiving the network message, the client analyzes the correction time and sets the correction time to the local; s29), the client side packages the local time after correcting the time and sends the local time to the server side for confirmation; s210), after receiving the confirmation sent by the client, the server calculates the clock error, if the clock error is less than the maximum allowable error threshold, the synchronization is finished, otherwise, the next round of synchronization is started.
Further, network time service is carried out based on a UDP network protocol.
Further, the forced synchronization and the iterative synchronization between the physical machine and the virtual machine are realized through interprocess communication.
Further, the service end clock of each edge cloud is from Beidou equipment, an internet clock or a previous-level clock server.
The invention has the beneficial effects that: the invention can provide a complete clock synchronization scheme for the edge cloud scene, and the scheme comprises the following steps: synchronization between edge clouds, within edge clouds, and physical and virtual machines. Network time service method based on UDP protocol is adopted between edge clouds and inside the edge clouds, so that efficient clock synchronization can be carried out through the UDP protocol, and high-precision clock synchronization is realized through a delay compensation method. And the physical machine and the virtual machine are synchronized in real time, so that the clock precision of the virtual machine is ensured.
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FIG. 1 is a diagram of a synchronization architecture for a multi-level clock;
FIG. 2 is a flow chart of physical machine and virtual machine clock synchronization;
FIG. 3 is a flow chart of network time service.
Detailed Description
The invention is further described with reference to the following detailed description of embodiments and with reference to the accompanying drawings.
Example 1
This embodiment 1 discloses a multi-stage clock synchronization method facing edge clouds, which can simultaneously implement clock synchronization between edge clouds, inside the edge clouds, and between a physical machine and a virtual machine.
As shown in fig. 1, for a synchronization architecture diagram of a multi-level clock, an edge cloud a is selected from a plurality of edge clouds as a top-level clock source, an a1 server is selected from the edge cloud a as a clock synchronization server, a2 and A3 are selected as a current-level clock synchronization client, an edge cloud B, C is selected as a lower-level clock client, B1 and C1 are selected as respective internal clock synchronization servers, a1 is responsible for synchronizing to a current-level a2 and a current-level A3 and a lower-level B1 and C1, B1 is responsible for synchronizing to a B2 and a B3 client, C1 is responsible for synchronizing to a C2 and a C3 client, and finally, each server synchronizes the clock to a virtual machine. In fig. 1, the a1 server, the a2 server, and the A3 server are all physical machines on which virtual machines run, similarly, the B1 server, the B2 server, and the B3 server are physical machines on which virtual machines run, and the C1 server, the C2 server, and the C3 server are physical machines on which virtual machines run.
The clock synchronization between the physical machine and the virtual machine provided in this embodiment refers to clock synchronization between the physical machine in the edge cloud and the virtual machine running thereon, and since the clock accuracy of the virtual machine cannot be guaranteed, real-time synchronization must be performed by the physical machine, and the synchronization modes are divided into two types: the first group is forced synchronization, and when the error between the clock of the virtual machine and the clock of the physical machine exceeds a threshold value, the virtual machine and the physical machine are immediately synchronized; the second is iterative synchronization, in which clock error detection is performed according to a fixed period, for example, clock error is detected once in 10 seconds, if the clock error is smaller than a threshold, clock synchronization is not performed, and if the clock error is larger than the threshold, clock synchronization is corrected, and it is known that the clock error is smaller than the threshold, and synchronization is stopped.
As shown in fig. 2, the specific process of clock synchronization between the physical machine and the virtual machine is as follows:
step 1: the method comprises the steps of executing periodically according to a detection period, firstly calling a local API by a virtual machine to obtain local system time, and then obtaining physical machine time through a virtual channel;
step 2: calculating a clock error DeltaTime of the physical machine and the virtual machine, judging whether the clock error DeltaTime exceeds a threshold (FTH) of forced synchronization, if so, carrying out forced synchronization, then waiting for the next detection period, and if not, continuing to execute the next step;
step 3: judging whether the maximum allowable error threshold (MAXTH) is exceeded or not, if not, not carrying out synchronization, waiting for the next detection period, otherwise, starting iterative synchronization;
step 4: after the iteration synchronization starts, carrying out N-1 iterations according to the maximum iteration number N, wherein the correction time step is DeltaTime/(N-1) every time;
step 5: after circularly iterating for N-1 times, recalculating the DeltaTime for the Nth time, determining whether the DeltaTime reaches the range of the MAXTH, if the DeltaTime does not exceed the threshold, ending the iteration synchronization, otherwise, continuing to execute the next step;
step 6: and performing forced synchronization on the last iteration, and finishing the clock synchronization of the current round.
In this embodiment, the forced synchronization and the iterative synchronization between the physical machine and the virtual machine are realized by inter-process communication.
The implementation provides a network time service method based on a UDP protocol to realize clock synchronization between edge clouds and inside the edge clouds, a C/S (client/server) architecture mode is adopted, a server side provides time service for all clients once according to a fixed period (such as 1 minute), and due to the fact that certain time delay exists when clock data are transmitted through a network, particularly among the edge clouds, the time delay is relatively large, otherwise high-precision synchronization cannot be achieved. The invention adopts a delay compensation method to realize high-precision clock synchronization, namely, network detection is firstly carried out through UDP messages, network delay is calculated, and finally, the clock data and the network delay are added to be used as an accurate clock.
As shown in fig. 3, the specific process of network time service is as follows:
step 1: the server firstly initiates a network delay detection process;
step 2: encapsulating the local timestamp T1 into a UDP message and sending the UDP message to the client;
step 3: after receiving the server message, the client records the current receiving time T2 of the client;
step 4: before the client sends back to the server, packaging T1, T2 and sending time T3 into UDP messages for sending;
step 5: after receiving the message fed back by the client, the server records the receiving time T4;
step 6: calculating network delay ND = (T2-T1 + T4-T3)/2;
step 7: carrying out rationality verification on network delay, wherein generally the one-way network delay is in millisecond level, setting the maximum value of the one-way network delay as MAXND, if ND is greater than MAXND, detecting again, and if ND is less than MAXND, the network delay is effective;
step 8: the server side starts to execute a network time service process;
step 9: the server side corrects the time of the client side: the local time of the server and the network delay are packaged into a UDP message and sent;
step 10: after receiving the message, the client analyzes the correction time and sets the correction time to the local;
step 11: after the time is corrected by the client, the local time is packaged and then sent to the server for confirmation;
step 12: after receiving the acknowledgement sent by the client, the server calculates the clock error, and if the clock error is smaller than the maximum allowable error threshold (MAXTH), the synchronization is ended, otherwise, the next round of synchronization is started.
In this embodiment, the server clock of each edge cloud is from the beidou device, the internet clock or the upper-level clock server.
The method can simultaneously realize clock synchronization among the edge clouds, the interior of the edge clouds and between the physical machine and the virtual machine, and provides a complete clock synchronization scheme for the edge cloud scene. And the precision of clock synchronization is ensured through a delay compensation and a real-time synchronization mode between the physical machine and the virtual machine.
The foregoing description is only for the basic principle and the preferred embodiments of the present invention, and modifications and substitutions by those skilled in the art are included in the scope of the present invention.
Claims (6)
1. A multi-stage clock synchronization method facing to edge cloud is characterized in that: the method comprises the steps of clock synchronization between edge clouds, clock synchronization inside the edge clouds and clock synchronization of a physical machine and a virtual machine, wherein network time service is performed between the edge clouds and inside the edge clouds by adopting a central architecture, a server is selected inside each edge cloud as a service end of the clock synchronization, other nodes inside the edge clouds are used as client ends of the clock synchronization, network message receiving and sending are performed between the client ends and the service ends to achieve network time service, the service end of a certain edge cloud is selected between the edge clouds to serve as a top clock source, the service ends of other edge clouds serve as the client ends of the top clock source, network message receiving and sending are performed between the top clock source and the client ends to achieve network time service, and finally, the physical machine synchronizes the clock to the virtual machine.
2. The edge cloud-oriented multi-stage clock synchronization method of claim 1, wherein: the clock synchronization process between the physical machine and the virtual machine is as follows: s11, executing periodically according to the detection period, firstly, acquiring the time of the physical machine and the time of the virtual machine; s12), calculating the clock error of the physical machine and the virtual machine, judging whether the clock error exceeds the threshold value of forced synchronization, if so, carrying out forced synchronization, then waiting for the next detection period, and if not, executing the next step; s13), judging whether the clock error exceeds the maximum allowable error threshold, if not, not carrying out synchronization, waiting for the next detection period, otherwise, executing the next step; s14), calculating a correction step DeltaTime/(N-1), wherein DeltaTime is the clock error calculated in the step S12, N is the maximum iteration number, and then performing N-1 iteration synchronization by taking the correction step as a period so as to correct the time of the virtual machine; s15), after circularly iterating for N-1 times, recalculating the clock error of the physical machine and the virtual machine self-check for the Nth time, and determining whether the clock error is within the maximum allowable error threshold value, if the clock error is not within the maximum allowable error threshold value, ending the iterative synchronization, otherwise, forcibly synchronizing the time of the physical machine and the virtual machine, and ending the clock synchronization of the current round.
3. The edge cloud-oriented multi-stage clock synchronization method of claim 1, wherein: the network time service process comprises the following steps: s21), the server side firstly initiates a network delay detection process, encapsulates a local timestamp T1 into a network message and sends the network message to the client side; s22), after receiving the server message, the client records the current receiving time T2 of the client; s23), before the client sends back to the server, the T1, the T2 and the sending time T3 are packaged into a network message to be sent; s24), after receiving the message fed back by the client, the server records the receiving time T4; s25), calculating network delay ND = (T2-T1 + T4-T3)/2; s26), carrying out rationality verification on the network delay, setting the maximum value of the one-way network delay as MAXND, if ND is greater than MAXND, then detecting again, if ND is less than MAXND, then the network delay is effective, and executing the next step; s27), the server side starts to execute the network time service process, the client side correction time is packaged into a network message and is sent to the client side, and the client side correction time is the sum of the local time of the server and the network delay; s28), after receiving the network message, the client analyzes the correction time and sets the correction time to the local; s29), the client side packages the local time after correcting the time and sends the local time to the server side for confirmation; s210), after receiving the confirmation sent by the client, the server calculates the clock error, if the clock error is less than the maximum allowable error threshold, the synchronization is finished, otherwise, the next round of synchronization is started.
4. The edge cloud-oriented multi-stage clock synchronization method according to claim 1 or 3, characterized in that: the network time service is carried out based on a UDP network protocol.
5. The edge cloud-oriented multi-stage clock synchronization method of claim 2, wherein: the forced synchronization and the iterative synchronization between the physical machine and the virtual machine are realized through interprocess communication.
6. The edge cloud-oriented multi-stage clock synchronization method of claim 1, wherein: the service end clock of each edge cloud is from Beidou equipment, an internet clock or a previous-level clock server.
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| CN202010157183.3A CN111294135B (en) | 2020-03-09 | 2020-03-09 | Edge cloud-oriented multi-stage clock synchronization method |
| PCT/CN2020/098659 WO2021179480A1 (en) | 2020-03-09 | 2020-06-29 | Edge cloud-oriented multistage clock synchronization method |
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Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN111835449A (en) * | 2020-07-30 | 2020-10-27 | 山东超越数控电子股份有限公司 | Local area network high-precision clock synchronization method and device based on PTP (precision time protocol) |
| CN111901417A (en) * | 2020-07-28 | 2020-11-06 | 山东超越数控电子股份有限公司 | Time synchronization system based on vehicle-mounted edge cloud environment and implementation method |
| CN112904932A (en) * | 2021-05-08 | 2021-06-04 | 鹏城实验室 | Clock synchronization method, board card, computer storage medium and terminal equipment |
| CN113055149A (en) * | 2021-02-20 | 2021-06-29 | 郑州中科集成电路与信息系统产业创新研究院 | Time synchronization and frequency synchronization method under radio frequency transceiver cascade system |
| WO2021179480A1 (en) * | 2020-03-09 | 2021-09-16 | 山东超越数控电子股份有限公司 | Edge cloud-oriented multistage clock synchronization method |
| CN113691342A (en) * | 2021-09-13 | 2021-11-23 | 上海云轴信息科技有限公司 | Method and system for time synchronization of virtualization platform |
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| CN114327855A (en) * | 2021-10-18 | 2022-04-12 | 阿里云计算有限公司 | Service method and system for downtime migration of edge node |
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| WO2021179480A1 (en) * | 2020-03-09 | 2021-09-16 | 山东超越数控电子股份有限公司 | Edge cloud-oriented multistage clock synchronization method |
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| CN113691342A (en) * | 2021-09-13 | 2021-11-23 | 上海云轴信息科技有限公司 | Method and system for time synchronization of virtualization platform |
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| CN111294135B (en) | 2021-06-08 |
| WO2021179480A1 (en) | 2021-09-16 |
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