WO2019196425A1

WO2019196425A1 - Method and apparatus for credibility assessment of network packet delay measurement, and storage medium

Info

Publication number: WO2019196425A1
Application number: PCT/CN2018/118024
Authority: WO
Inventors: 周华良; 郑玉平; 徐建松; 姜雷; 王凯; 李友军
Original assignee: 国电南瑞科技股份有限公司; 国电南瑞南京控制系统有限公司
Priority date: 2018-04-11
Filing date: 2018-11-28
Publication date: 2019-10-17
Also published as: CN108667686A; CN108667686B

Abstract

Disclosed are a method and apparatus for credibility assessment of network packet delay measurement, and a storage medium. The method provides the measurement based on two indexes of a packet, i.e., a reasonable value of total link delay and a relative error value of total link delay, and a computing method, and provides an engineering usage and threshold determination method for determining a confidence interval of a network packet delay measurement value using a statistical method, thereby providing a credible basis for the credibility assessment of a network packet delay measurement result, ensuring the effective and reliable use of an essential power service packet (a network SV packet or the like) of a smart transformer station, and improving the running reliability of a secondary power device.

Description

Method, device and storage medium for evaluating credibility of network message delay measurement

Cross-reference to related applications

The present application is filed on the basis of the Chinese Patent Application No. 20110032 141, the entire disclosure of which is hereby incorporated by reference.

Technical field

The invention belongs to the field of power system automation, and relates to a method, a device and a storage medium for evaluating the reliability of network packet delay measurement.

Background technique

With the in-depth application of technical standards such as IEC61850 in substations, Ethernet is widely used for connection between power secondary devices. The introduction of Ethernet communication greatly simplifies the interface of power secondary equipment, realizes the sharing of internal data of substation, and promotes Implementation of advanced application functions in substations. However, Ethernet data transmission has the problem of uncertain network delay, which is unacceptable for the use of some power service data. For example, the sampling value (SV, Sampled Value) of the protection device must be based on the accurate time of sampling. Implementation, a common method for solving this problem in the related art is to realize data synchronization between power secondary devices on time based on an external global positioning system (GPS).

With the advancement of computer technology and microelectronic technology, the delay measurement of Ethernet packet transmission path based on hardware technology has become a reality. The transmission delay of the Ethernet packet in the network node can be calculated by using the time difference between the packet receiving time and the sending time. The transmission delay of the Ethernet packet between the network nodes can be mutually transmitted through the nodes and recorded simultaneously. The time information of the round-trip message is calculated using a certain algorithm. The emergence of equipment with network packet delay measurement function makes the SV network data synchronization of the power secondary equipment no longer dependent on the external GPS clock, and the reliability is obviously improved.

In the related art, the method for real-time measurement of message delay is derived based on the basic principle of Ethernet communication, for example, real-time delay value in the bottom layer of data communication through Field Programmable Gate Array (FPGA) technology. Measurement and correction. Since the delay value modified by the FPGA needs to be forwarded with the same message frame, a delay correction domain needs to be added in the message protocol, which is different from the standard Ethernet protocol; the more device nodes the message passes through, The possibility that the delay correction value produces an error is also greater. In addition, multiple service packets may be simultaneously sent and received in a multi-service co-port network such as an SV, a Generic Object Oriented Substation Event (GOOSE), or a Manufacturing Message Specification (MMS). The sudden change of packet traffic and network storms may adversely affect the delay measurement accuracy and delay accumulation of the message. Although the principle of packet delay measurement technology is becoming more and more mature, the credibility of packet delay measurement results is still a problem to be solved.

Summary of the invention

In view of this, the embodiment of the present invention is to provide a method, an apparatus, and a storage medium for evaluating the credibility of network packet delay measurement.

The embodiment of the present invention is intended to provide a method for evaluating the credibility of network packet delay measurement, including:

Set the reasonable value of the total link delay of the network packet and the relative error of the total link delay of the network packet.

Calculate the sum of the fixed delay of the source node sampling, the reasonable value of the packet forwarding of the single node, and the reasonable delay of the packet transmission path, and use it as the reasonable value of the total link delay of the network packet;

The relative error of the sum of the packet forwarding delay and the transmission path delay between nodes is taken as the median, and the packet delay error of all nodes is summed and the arithmetic mean is taken as the total link delay. Difference

Calculate the mode number in the statistical sample of the reasonable value of the total link delay of the network packet multiplied by the threshold coefficient, and use the corresponding calculation result as the engineering threshold of the total link delay value, and reflect the network packet transmission through the engineering threshold coefficient. Real-time status;

Calculate the engineering link threshold coefficient of the total link delay of the network packet multiplied by the engineering threshold coefficient, and use the corresponding calculation result as the engineering threshold of the total link delay relative error, and reflect the measurement accuracy state of the network system by the engineering threshold coefficient. .

The above embodiments of the present invention have the following beneficial effects:

1) The credibility indicator of the packet delay measurement value can be evaluated online in real time.

2) Network packet delay measurement results can be measured by quantitative indicators.

3) While ensuring that the measured value of the packet delay is within a certain measurement accuracy range, the occurrence of unreasonable extreme values due to the actual network uncertainty is avoided.

4) Engineering threshold parameters can reflect the trend of network traffic.

In the above solution, the reasonable value of the total link delay in the network packet is calculated based on the local clock in real time, and is independent of the external clock.

In the above solution, the absolute delay value of the network packet transmission delay is measured based on the external GPS/Bei Dou (BD) clock and the relative difference of the reasonable value of the total link delay is calculated.

In the above solution, the reasonable value of the total link delay value T _all is as follows:

The intelligent electronic device (IED, Intelligent Electronic Device) source node analog-to-digital converter (ADC, Analog-to-Digital Converter) samples a fixed delay of T ₀ , and the reasonable delay of each single node adjacent forwarding delay is t _i , t _i is the cumulative value of the reasonable delay value t _i1 between the single node and the reasonable delay value t _i2 of the message transmission path, that is, t _i =t _i1 +t _i2 ;t _(n+1)2 refers to a reasonable delay value of the packet transmission path between the n+1 node and the n+2 node;

The total link delay error value δ _all index formula is as follows:

The single-node delay relative error δ _i is the absolute error of the measured value t _i between the single-node forwarding and the transmission link delay relative to the true delay value.

In the above solution, based on the real-time statistics total link delay reasonable value sample, firstly determine the value M of the total link delay measurement value T _all of the network packet based on the statistical method, and take the total link on this basis. The extended engineering threshold coefficients α and β constitute a confidence interval of the total link delay [α*M, β*M]; wherein the engineering threshold coefficient β reflects the influence of the network packet flow change on the packet delay measurement, that is, Perceive the traffic flow situation in the network through the threshold coefficient of the project;

Taking the engineering threshold coefficient γ of the total link delay error value, the actual engineering threshold is γ*δ _all ;

The reliability of the network SV packet delay measurement is evaluated online based on the engineering threshold of the reasonable value of the total link delay and the delay error value. If the relative error of the reasonable value of the total link delay is less than γ*δ _all , Within the confidence interval [α*M, β*M], the total link delay is considered to be trustworthy.

In the above solution, a high-performance packet receiving and transmitting control clock is provided to a dedicated media access controller (MAC) module having a packet time stamping and delay correction function through a global clock network in the FPGA chip. The module records the time of receiving and sending network packets according to the local clock. The local clock module has punctuality and anti-error functions to ensure the reliability of the timestamp generator function.

An embodiment of the present invention further provides a credibility evaluation apparatus for network packet delay measurement, including:

a memory configured to store a credibility evaluation of network packet delay measurements;

The processor is configured to run the program, where the program is executed to perform the credibility evaluation method of the network packet delay measurement provided by the embodiment of the present invention.

The embodiment of the present invention further provides a storage medium, where the storage medium includes a stored program, wherein the program is executed to perform a credibility evaluation method for the network packet delay measurement provided by the embodiment of the present invention.

DRAWINGS

FIG. 1 is a network packet transmission system for a power secondary device with n nodes according to an embodiment of the present invention.

2 is a network packet delay measurement system implemented by using an FPGA technology according to an embodiment of the present invention.

FIG. 3 is a partial enlarged view of a portion of the MAC module of FIG. 2 according to an embodiment of the present invention.

detailed description

The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It is understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

The invention realizes a real-time evaluation method for the reliability of message delay measurement on the power secondary device, and proposes two technical indexes for evaluating the reliability of the delay measurement of the message, and the method for determining the threshold value of the corresponding project. The measurement and evaluation system is built by FPGA technology to reflect the credibility of the message delay in real time.

A power secondary equipment network message transmission system containing (n + 2) nodes is shown in FIG. Two indicators, the total link delay reasonable value and the total link delay error value, are proposed to measure the credibility of the packet delay measurement.

The total link delay reasonable value T _all is defined as the sum of the fixed delay of the source node sampling, the reasonable value of the packet forwarding of the single node, and the reasonable delay of the packet transmission path.

The formula for the reasonable value of the total link delay T _all is as follows:

Applicable to a power secondary equipment network message transmission system containing (n+2) nodes (ie, n intermediate nodes between the source node and the destination node), where n is an integer greater than or equal to 1.

The fixed delay of the sampling of the intelligent IED source node ADC is T ₀ , and the reasonable delay of each single node adjacent forwarding is t _i , and t _i is a reasonable value of the forwarding delay between the single nodes t _i1 and the message transmission path. The accumulation of the reasonable value t _i2 of the delay, that is, t _i = t _i1 + t _i2 ; t _{(n+1) 2} refers to the time of the message transmission path between the n+1th node and the n+2th node Reasonable value.

The single-node delay relative error δ _i is the absolute error of the measured value t _i between the single node and the transmission link delay relative to the true delay value.

The total link delay error value δ _all is defined as: the average of the arithmetic delays of all single-node message delay relative error values, wherein the delay relative error value δ _{i of} each single node, this application will Defined as the median of the delay vs. error statistics for cumulative messages between single nodes.

The total link delay error value δ _all index formula is as follows:

The total link delay reasonable value T _all and the total link delay error value δ _{all are} calculated in real time based on the local clock of the device, and can reflect the real-time state of the network packet transmission delay.

Based on the real-time statistics of the total link delay reasonable value samples, the statistical value method first determines the value M of the total link delay measurement value T _all of the network packet, and based on this, the engineering threshold of the total link delay is taken. The coefficients α, β constitute a confidence interval [α*M, β*M] of the total link delay. The engineering threshold coefficient β reflects the influence of network packet traffic change on packet delay measurement. That is, the threshold coefficient of the project can sense the traffic trend of the packet in the network, and provides a reference for the state monitoring and alarm of the network itself. .

Taking the engineering threshold coefficient γ of the total link delay error value, the actual engineering threshold is γ*δ _all .

The reliability of the network SV packet delay measurement is evaluated online based on the engineering threshold of the reasonable value of the total link delay and the delay error value, which can improve the judgment of the data delay of the SV network.

In practical engineering applications, the upper and lower bounds of the confidence intervals of the two evaluation indicators predicted by the engineering threshold coefficient are significantly wider than the theoretically obtained confidence interval values and the statistical distribution of the measured values of the system. The practical significance lies in the higher Under the confidence level, the margin of the upper and lower bound prediction results is larger, and the actual engineering application reliability of the delay measurement is higher, that is, while ensuring the delay value within a certain measurement accuracy range, the actual network is avoided. The emergence of irrational extremes brought about by uncertainty.

The network packet delay measurement system can be implemented by using an FPGA technology, or by using an application specific integrated circuit (ASIC) or a system on chip (SoC). The following uses FPGA technology as an example.

The network packet delay measurement system implemented by FPGA technology is shown in FIG. 2 and FIG. 3. The system uses a high-precision crystal clock source to generate a synchronous clock signal, and provides a high-performance message receiving and transmitting control clock to the dedicated MAC module with message timestamp lock and delay correction function through the global clock network in the FPGA chip. The module records the time of receiving and sending network packets based on the local clock. The local clock module has punctuality and error protection to ensure the reliability of the time stamp generator function. The system supports access to an external GPS/BD clock. The SV packet is used as an example to describe the process of implementing packet delay measurement and evaluation.

The source node records the ADC sampling time t _s and the transmission time t _{x of the} SV message transmission, then T ₀ =t _x -t _s .

The MAC address of the SV packet forwarding node is based on the local clock to record the time t _{rx of the} SV message frame header and the time t _tx at which the packet header is forwarded. The reasonable value of the SV packet forwarding delay of the single node is t _i1 =t _Tx -t _rx .

The reasonable delay value t _{i2 of the} SV packet transmission path is determined by the physical path of the packet transmission. The physical path includes the physical layer (PHY, Port Physical Layer), network transformer, twisted pair, optical transceiver, and optical fiber. The delay of the transmission path can be calculated using the method recommended by the IEC61588 standard.

The SV packet forwarding node uses the Frame Transmit Correction Field (FTCF) to transmit the SV packet forwarding delay of the local node to the next node. The FTCF is a 4-byte length field in the header format of the SV message frame. This field is used to store the reasonable link delay of the SV packet. After the forwarding node calculates the reasonable value of the forwarding delay of the node ti, the FTCF of the SV packet is extracted and accumulated, and the FTCF is written back to complete the delay correction of the SV packet forwarding. The total link delay reasonable value T _{all is} obtained by using formula (1).

The MAC module of the SV packet forwarding node uses the external GPS/BD (PPS) clock to measure the absolute time T _(i-1)x and T _{ix of the} received and transmitted messages, and the single node SV packet forwarding delay real time T _{abs -i} =T _ix -T _(i-1)x .

Then, the relative delay of the packet delay of a single node is [T _abs -i-(t _i1 +t _i2 )]/T _abs-i , taking the time delay relative error statistics of several times (such as 20,000 times) between single nodes. Sort by size, take the median in this data sequence as δ _i .

Use δ (2) to get δ _all .

In the statistical sample of the reasonable value of the total link delay, the highest frequency is selected as its mode M, and α and β can be determined according to the network condition. For example, the engineering threshold coefficients α=0.9 and β=5.0 are used to obtain a confidence interval [ M*0.9, M*5.0], the upper and lower limits of the confidence interval are used as engineering thresholds.

In order to ensure the applicability of the engineering application, the engineering threshold value γ=5.0 is taken to obtain the engineering threshold value of the total link delay error 5.0*δ _all .

If the relative error of the reasonable value of the total link delay is less than 5.0*δ _all and falls within the confidence interval [M*0.9, M*5.0], the total link delay is considered to be trustworthy.

In addition, there are many specific implementation methods and approaches of the present invention, and the above description is only a preferred embodiment of the present invention. It should be noted that a number of modifications and refinements may be made by those skilled in the art without departing from the principles of the invention, and such modifications and refinements are also considered to be within the scope of the invention. The components that are not clear in this embodiment can be implemented by the prior art.

Claims

A method for evaluating the credibility of network packet delay measurement, setting a reasonable value of the total link delay of the network packet and a relative error value of the total link delay of the network packet;

Calculate the sum of the fixed delay of the source node sampling, the reasonable value of the packet forwarding of the single node, and the reasonable delay of the packet transmission path, and use it as the reasonable value of the total link delay of the network packet;

The relative error of the sum of the packet forwarding delay and the transmission path delay between nodes is taken as the median, and the packet delay error of all nodes is summed and the arithmetic mean is taken as the total link delay. Difference

Calculate the mode number in the statistical sample of the reasonable value of the total link delay of the network packet multiplied by the threshold coefficient, and use the corresponding calculation result as the engineering threshold of the total link delay value, and reflect the network packet transmission through the engineering threshold coefficient. Real-time status;

Calculate the total link delay relative error value of the network packet multiplied by the engineering threshold coefficient, and use the corresponding calculation result as the engineering threshold of the total link delay relative error, and reflect the measurement accuracy state of the network system through the engineering threshold.
The method for evaluating the credibility of the network packet delay measurement according to claim 1, wherein the reasonable value of the total link delay in the network packet is calculated in real time based on the local clock, and is independent of the external clock.
The credibility evaluation method for network packet delay measurement according to claim 1, wherein: the absolute delay value of the network packet transmission delay is measured based on the external global positioning system GPS/Beidou BD clock, and the total chain is calculated and measured. The relative difference in the reasonable value of the road delay.
The method for evaluating the credibility of network packet delay measurement according to claim 1 or 2 or 3, wherein:

For a network secondary transmission network message transmission system with n+2 nodes, n is an integer greater than or equal to 1;

The formula for the reasonable value of the total link delay T all is as follows:

The fixed delay of the sampling of the analog electronic ADC of the IED source node of the intelligent electronic device is T 0 , and the reasonable delay of each single node adjacent forwarding is t i , and t i is a reasonable value of the forwarding delay between single nodes. The sum of the reasonable delay value t i2 of i1 and the message transmission path, that is, t i = t i1 + t i2 ; t (n+1) 2 refers to the report between the n+1th node and the n+2th node a reasonable value of the delay of the text transmission path;

The total link delay error value δ all index formula is as follows:

The single-node delay relative error δ i is the absolute error of the measured value t i between the single-node forwarding and the transmission link delay relative to the true delay value.
The method for evaluating the credibility of network packet delay measurement according to claim 4, wherein:

Based on the real-time statistics of the total link delay reasonable value samples, the statistical value method first determines the value M of the total link delay measurement value T all of the network packet, and based on this, the engineering threshold of the total link delay is taken. The coefficients α and β constitute a confidence interval of the total link delay [α*M, β*M]; wherein the engineering threshold coefficient β reflects the influence of the network packet flow change on the packet delay measurement, that is, the threshold of the project is passed. The coefficient senses the traffic flow situation in the network;

Taking the engineering threshold coefficient γ of the total link delay error value, the actual engineering threshold is γ*δ all ;

The reliability of the network SV packet delay measurement is evaluated online based on the engineering threshold of the reasonable value of the total link delay and the delay error value. If the relative error of the reasonable value of the total link delay is less than γ*δ all , Within the confidence interval [α*M, β*M], the total link delay is considered to be trustworthy.
The credibility evaluation method for network packet delay measurement according to claim 5, wherein: the dedicated medium access having the message time stamp lock and the delay correction function is performed by the global clock network in the field programmable gate array FPGA chip. The control MAC module provides high-performance packet receiving and sending control clocks. The MAC module records the receiving and sending time of network packets according to the local clock. The local clock module has punctuality and anti-error functions to ensure the reliability of the timestamp function. .
A credibility evaluation apparatus for network packet delay measurement includes:

a memory configured to store a credibility evaluation of network packet delay measurements;

And a processor configured to execute the program, wherein the program is executed to perform a credibility evaluation method for network packet delay measurement according to any one of claims 1 to 6.
A storage medium, the storage medium comprising a stored program, wherein the program is operative to perform a credibility evaluation method for network packet delay measurement according to any one of claims 1 to 6.