CN104993900A - Synchronous correction method based on IEEE1588 clock model - Google Patents

Abstract

The invention discloses a synchronous correction method based on an IEEE1588 clock model, and belongs to the technical field of communication. The method comprises the following steps: (1) acquiring the moment point of the IEEE1588 clock model to obtain each timestamp; (2) acquiring the relation between the time of a server and the time of a client through the IEEE1588 clock model, and acquiring the relation among the timestamps in Sync message sending and receiving processes in combination with a PTP (Picture Transfer Protocol); (3) performing difference operation based on the relation among the timestamps; and (4) acquiring the asymmetrical offset of an nth exchange process according to a first-order difference value given in the step (3), moving an average filter through exponential weighting in order that value theta is close to zero, and finishing correction between the server and the client. According to the method, a conventional thought is jumped out, and compensation is performed once again on the basis of the IEEE1588 clock model, so that the problem of end-to-end time non-synchronization is solved, and end-to-end interaction time becomes symmetrical.

Description

A kind of synchronization correction method based on IEEE1588 clock models

Technical field

The present invention relates to a kind of clock synchronous correction method, belong to communication technical field.

Background technology

Adopt an IEEE1588v2 and specially designed clock recovery mechanism to provide and reach the microsecond even clock synchronization accuracy of submicrosecond rank.And this is all based on a very important hypothesis, from master clock to the propagation delay time of the packet from clock and the propagation delay time from clock to master clock equal.But in reality, communication path is non complete symmetry, this is mainly due to delay and the queueing delay of different forwards and reverse link.The difference of packet delay is mainly because the difference queuing engineering of the packet of the element (as switch and router) in communication network causes.This is especially useful in timing and transmits and adopt end to end system, and assisting from network the impact alleviating queueing delay without any the timing of form.

The asymmetry of propagation delay has become the significant challenge solving clock synchronization issue.In network chronograph mechanism, boundary clock (BC) and transparent clock (TC) can eliminate the asymmetry of delay in the following two cases.First scene, the forward of variable queueing delay and reverse path; Second scenario, wraps in the asymmetry caused with different paths in each direction by timing data.It should be noted that time support scheme (BC and TC) is due to physical links different between network element, can not correct the asymmetry of delay.

For solving the asymmetry problem postponed in prior art, the expansion of extensive work has in mind to claim sex chromosome mosaicism with the army solving physical link, rarely has the research to the problem of QIA in end to end system transmission.

Summary of the invention

The technical problem to be solved in the present invention is, not enough for prior art, proposes a kind of synchronization correction method with secondary calibration flow process based on IEEE1588 clock models, to solve the asymmetric problem of time between master-salve clock.

The present invention is the technical scheme solving the problems of the technologies described above proposition: a kind of synchronization correction method based on IEEE1588 clock models, performs following steps:

1) moment point of described IEEE1588 clock models is obtained;

Master clock is at T ₁[n] moment point sends with T ₁the Sync message of [n] timestamp is to from clock, and the moment point receiving described Sync message from clock is T ₂[n], and stamp time stamp T 2 [n] for described Sync message;

Send with the DelayReq message of T3 [n] timestamp to master clock from clock in T3 [n] moment point, the moment point that master clock receives described DelayReq message is T4 [n], and stamps time stamp T 4 [n] for described DelayReq message;

Time stamp T 4 [n] to be embedded in the n-th DelayResp message and to propagate into from clock by master clock, completes the n-th exchange process;

At the end of all n exchange process all, whole PTP message switching terminates;

Wherein, n is positive integer;

2) relation between time S (t) of server and time C (t) of client is obtained by described IEEE1588 clock models, S (t)=(1+ α) C (t)+θ (1)

Obtain described Sync message in conjunction with PTP protocol and formula (1) to send and each timestamp relational expression in receiving course,

T ₁[n]+d _f+q _f[n]＝(1+α[n])T ₂[n]+θ[n] (2)

Described DelayReq message sends and each timestamp relational expression in receiving course,

T ₄[n]-d _r-q _r[n]＝(1+α[n])T ₃[n]+θ[n] (3)

The time migration of the n-th exchange process from clock in formula (2) and formula (3) is θ [n],

$\left\{\begin{array}{c}\mathrm{\θ}\[n\]=\frac{1}{2}(T_1\[n\]+T_4\[n\]-(1+\mathrm{\α}\[n\]\left)\left(T_2\[n\]+T_3\[n\]\right)\right)+\frac{1}{2}(d_f-d_r)+{\mathrm{\θ}}_q\[n\]\\ {\mathrm{\θ}}_q\[n\]=\frac{1}{2}(q_f\[n\]-q_r\[n\])\end{array}\right.$

Wherein,

α is crooked degree coefficient, and the kind k of transmission medium and the length l of propagation path is directly proportional;

α [n] is the crooked degree coefficient of the n-th exchange process;

θ is the time migration from clock;

θ _q[n] is variable queuing delay deviation;

D _ffor master clock is to the physical link delay from clock;

Q _ffor the variable queuing delay of master clock, q _fthe variable queuing delay of the n-th exchange process that [n] is master clock;

D _rfor the physical link delay from clock to master clock;

Q _rfor the variable queuing delay from clock, q _r[n] is the variable queuing delay of volume of the n-th exchange process from clock;

3) based on step 1) in time stamp T ₁[n], T ₂[n], T ₃[n], T ₄[n] carries out calculus of differences and obtains,

ε[n]＝q _f[n]-q _f[n-1]＝(1+α[n])dT ₂[n]-dT ₁[n]

γ[n]＝q _r[n]-q _r[n-1]＝dT ₄[n]-(1+α[n])dT ₃[n]

ε [n] is the variable queuing delay q of the n-th exchange process of master clock _fthe first-order difference of [n],

γ [n] is the variable queuing delay q of the n-th exchange process from clock _rthe first-order difference of [n];

4) by step 3) given by first-order difference value, obtain the asymmetric skew of the n-th exchange process obtained by exponentially weighted moving average (EWMA) filter again average magnitude for average variable queuing delay skew

${\stackrel{\‾}{\mathrm{\θ}}}_{qav}\[n\]=(1-\mathrm{\β}){\stackrel{\‾}{\mathrm{\θ}}}_{qav}\[n-1\]+\mathrm{\β}{\stackrel{\‾}{\mathrm{\θ}}}_{qav}\[n\],$

Wherein, β is hum reduction factor, 0< β <1, by adjustment β, makes θ value level off to zero, completes the synchronous correction of described server and described client.

The improvement of technique scheme is: step 3) afterwards to q _f[n] and q _r[n] is normalized, and with step 3) in the minimum of the variable queuing delay of master clock mentioned and the minimum of variable queuing delay from clock as the reference value of normalized, and obtain q _fand q _rcorresponding normalization amount with

$\begin{array}{c}{q}_{f_{nr}}\&lsqb;n\&rsqb;={\mathrm{\&epsiv;}}_s\&lsqb;n\&rsqb;-\underset{k=n-N}{\overset{k=n}{\min }}\left\{{\mathrm{\&epsiv;}}_s\&lsqb;k\&rsqb;\right\}=q_f\&lsqb;n\&rsqb;-q_f\&lsqb;0\&rsqb;\\ -\underset{k=n-N}{\overset{k=n}{\min }}\left\{q_f\&lsqb;k\&rsqb;-q_f\&lsqb;0\&rsqb;\right\}\\ =q_f\&lsqb;n\&rsqb;-q_{f_{\min }}\&lsqb;n\&rsqb;\end{array}$

$q_{r_{nr}}\&lsqb;n\&rsqb;={\mathrm{\&gamma;}}_s\&lsqb;n\&rsqb;-\underset{k=n-N}{\overset{k=n}{\min }}\left\{{\mathrm{\&gamma;}}_s\&lsqb;k\&rsqb;\right\}=q_r\&lsqb;n\&rsqb;-q_{r_{min}}\&lsqb;n\&rsqb;$

Wherein,

ε _s[n]＝ε _s[n-1]+ε[n]

＝ε _s[n-1]+q _f[n]-q _f[n-1]

＝ε _s[0]+q _f[n]-q _f[0]

γ _s[n]＝γ _s[0]+q _r[n]-q _r[0]

ε _s[0]＝γ _s[0]＝0。

The improvement of technique scheme is: the instantaneous asymmetric skew of the n-th exchange process by the n-th exchange process normalization amount of correspondence with determine ${\stackrel{\&OverBar;}{\mathrm{\&theta;}}}_q\&lsqb;n\&rsqb;=(q_{f_{nr}}\&lsqb;n\&rsqb;-q_{r_{nr}}\&lsqb;n\&rsqb;)/2.$

The improvement of technique scheme is: determine the forward of described PTP message and reverse respectively according to master clock with from the sequence of the variable queuing delay of clock, and determine instantaneous asymmetric skew with the variable queuing delay of forward and reverse variable queuing delay

The improvement of technique scheme is: forward and the reverse data flow of described PTP message are separate.

The present invention adopts the beneficial effect of technique scheme to be: the basis that the present invention is based on IEEE1588 clock models, jump out conventional method on this basis, consider the situation of the time irreversibility between the server that the time error between being eliminated by master-salve clock by compensation method is caused and client; This method mainly considers the time migration brought by master-salve clock, calculated by the timestamp obtained in message transmission procedure on each point, the compensation rate of certainty annuity, to revise time migration (or correction), makes server and client synchronization.And carry out simplified operation by normalization operation time shortened, be convenient to carry out the selection of repeatedly computing and sample size sooner so that the enforcement of backoff algorithm, make it possible to realize faster to hold with hold synchronous.

Accompanying drawing explanation

Below in conjunction with accompanying drawing, the invention will be further described.

Fig. 1 is the master-salve clock transfer process schematic diagram of a kind of synchronization correction method embodiment based on IEEE1588 clock models of the present invention.

Fig. 2 is the backoff algorithm flow process of a kind of synchronization correction method embodiment based on IEEE1588 clock models of the present invention.

Fig. 3 is the branching diagram based on the power distribution network topological structure of OPNET foundation in the embodiment of the present invention.

Fig. 4 is the Comparative result figure A in the embodiment of the present invention.

Fig. 5 is the Comparative result figure B in the embodiment of the present invention.

Fig. 6 is the end-to-end time migration of the message transmissions of the embodiment of the present invention under different β value.

Fig. 7 is the message transmissions end-to-end time delay of the embodiment of the present invention under different β value.

Embodiment

Embodiment

For convenience of describing, the compensation method mentioned in the present invention is called QIA backoff algorithm in the present embodiment.

The present embodiment is a kind of same bearing calibration based on IEEE1588 clock models, wherein the principle of IEEE1588 clock models as shown in Figure 1, by following step, can to based on the correction work realizing master-salve clock synchronization between the server of this modular concept and client

1) moment point of IEEE1588 clock models is obtained;

Master clock is at T ₁[n] moment point sends with T ₁the Sync message of [n] timestamp is to from clock, and the moment point receiving Sync message from clock is T ₂[n], and stamp time stamp T 2 [n] for Sync message;

Send with the DelayReq message of T3 [n] timestamp to master clock from clock in T3 [n] moment point, the moment point that master clock receives DelayReq message is T4 [n], and stamps time stamp T 4 [n] for DelayReq message;

Time stamp T 4 [n] to be embedded in the n-th DelayResp message and to propagate into from clock by master clock, completes the n-th exchange process;

At the end of all n exchange process all, whole PTP message switching terminates;

Wherein, n is positive integer.

After acquisition each point timestamp to master-salve clock between difference compensate, be applied to QIA backoff algorithm as shown in Figure 2;

2) relation between time S (t) of server and time C (t) of client is obtained by IEEE1588 clock models, S (t)=(1+ α) C (t)+θ (1)

In conjunction with PTP protocol, (PTP protocol is the abbreviation of IEEE1588 agreement, the full name of IEEE1588 agreement is " the precise clock synchronization consensus standard of network measure and control system ") and formula (1) Sync message send with receiving course in each timestamp relational expression

T ₁[n]+d _f+q _f[n]＝(1+α[n])T ₂[n]+θ[n] (2)

DelayReq message sends and each timestamp relational expression in receiving course,

T ₄[n]-d _r-q _r[n]＝(1+α[n])T ₃[n]+θ[n] (3)

The time migration of the n-th exchange process from clock in formula (2) and formula (3) is θ [n],

$\left\{\begin{array}{c}\mathrm{\&theta;}\&lsqb;n\&rsqb;=\frac{1}{2}(T_1\&lsqb;n\&rsqb;+T_4\&lsqb;n\&rsqb;-(1+\mathrm{\&alpha;}\&lsqb;n\&rsqb;\left)\left(T_2\&lsqb;n\&rsqb;+T_3\&lsqb;n\&rsqb;\right)\right)+\frac{1}{2}(d_f-d_r)+{\mathrm{\&theta;}}_q\&lsqb;n\&rsqb;\\ {\mathrm{\&theta;}}_q\&lsqb;n\&rsqb;=\frac{1}{2}(q_f\&lsqb;n\&rsqb;-q_r\&lsqb;n\&rsqb;)\end{array}\right.$

Wherein,

α is crooked degree coefficient, and the kind k of transmission medium and the length l of propagation path is directly proportional;

α [n] is the crooked degree coefficient of the n-th exchange process;

θ is the time migration from clock;

θ _q[n] is variable queuing delay deviation;

D _ffor master clock is to the physical link delay from clock;

Q _ffor the variable queuing delay of master clock, q _fthe variable queuing delay of the n-th exchange process that [n] is master clock;

D _rfor the physical link delay from clock to master clock;

Q _rfor the variable queuing delay from clock, q _r[n] is the variable queuing delay of volume of the n-th exchange process from clock;

3) based on step 1) in time stamp T ₁[n], T ₂[n], T ₃[n], T ₄[n] carries out calculus of differences and obtains,

ε[n]＝q _f[n]-q _f[n-1]＝(1+α[n])dT ₂[n]-dT ₁[n]

γ[n]＝q _r[n]-q _r[n-1]＝dT ₄[n]-(1+α[n])dT ₃[n]

ε [n] is the variable queuing delay q of the n-th exchange process of master clock _fthe first-order difference of [n],

γ [n] is the variable queuing delay q of the n-th exchange process from clock _rthe first-order difference of [n];

4) by step 3) given by first-order difference value, obtain the asymmetric skew of the n-th exchange process obtained by exponentially weighted moving average (EWMA) filter (Exponentially Weighted Moving Average Filter) again average magnitude for average variable queuing delay skew

${\stackrel{\&OverBar;}{\mathrm{\&theta;}}}_{qav}\&lsqb;n\&rsqb;=(1-\mathrm{\&beta;}){\stackrel{\&OverBar;}{\mathrm{\&theta;}}}_{qav}\&lsqb;n-1\&rsqb;+\mathrm{\&beta;}{\stackrel{\&OverBar;}{\mathrm{\&theta;}}}_{qav}\&lsqb;n\&rsqb;,$

Wherein, β is hum reduction factor, 0< β <1, by adjustment β, makes θ value level off to zero, completes the synchronous correction of described server and described client.

The present embodiment is in step 3) after to q _f[n] and q _r[n] is normalized, and with step 3) in the minimum of the variable queuing delay of master clock mentioned and the minimum of variable queuing delay from clock as the reference value of normalized, and obtain q _fand q _rcorresponding normalization amount with

$\begin{array}{c}{q}_{f_{nr}}\&lsqb;n\&rsqb;={\mathrm{\&epsiv;}}_s\&lsqb;n\&rsqb;-\underset{k=n-N}{\overset{k=n}{\min }}\left\{{\mathrm{\&epsiv;}}_s\&lsqb;k\&rsqb;\right\}=q_f\&lsqb;n\&rsqb;-q_f\&lsqb;0\&rsqb;\\ -\underset{k=n-N}{\overset{k=n}{\min }}\left\{q_f\&lsqb;k\&rsqb;-q_f\&lsqb;0\&rsqb;\right\}\\ =q_f\&lsqb;n\&rsqb;-q_{f_{\min }}\&lsqb;n\&rsqb;\end{array}$

$q_{r_{nr}}\&lsqb;n\&rsqb;={\mathrm{\&gamma;}}_s\&lsqb;n\&rsqb;-\underset{k=n-N}{\overset{k=n}{\min }}\left\{{\mathrm{\&gamma;}}_s\&lsqb;k\&rsqb;\right\}=q_r\&lsqb;n\&rsqb;-q_{r_{min}}\&lsqb;n\&rsqb;$

Wherein,

ε _s[n]＝ε _s[n-1]+ε[n]

＝ε _s[n-1]+q _f[n]-q _f[n-1]

＝ε _s[0]+q _f[n]-q _f[0]

γ _s[n]＝γ _s[0]+q _r[n]-q _r[0]

ε _s[0]＝γ _s[0]＝0。

The instantaneous asymmetric skew of n-th exchange process of the present embodiment by the n-th exchange process normalization amount of correspondence with determine,

${\stackrel{\&OverBar;}{\mathrm{\&theta;}}}_q\&lsqb;n\&rsqb;=(q_{f_{nr}}\&lsqb;n\&rsqb;-q_{r_{nr}}\&lsqb;n\&rsqb;)/2.$

The present embodiment determines the forward of PTP message and reverse respectively according to master clock with from the sequence of the variable queuing delay of clock, and determine instantaneous asymmetric skew with the variable queuing delay of forward and reverse variable queuing delay

Forward and the reverse data flow of the PTP message of the present embodiment are separate.

Based on said method, set up a power distribution network topological structure based on OPNET in the present embodiment, (OPNET is the popular software for communication simulation as shown in Figure 3, to the comparative analysis of the path delay of time and time deviation, there is preferably analogue simulation effect), adopt a typical branch to contrast effect when between mode when different pairs pair.Wherein comprise a server node (i.e. master node), 8 client nodes (i.e. terminal node) and some routers, telephone net node and relevant link.In whole network topology, server node as website of advocating war be to need pair time client node send corresponding pair according to protocol conventions time message, client node is as terminal node, periodically and server node carries out pair time message interaction, guarantee that local clock is consistent with server node clock.

The quantity of obvious network element and network transport load situation all have important impact to every part of QIA backoff algorithm (QIACA).Herein mainly for topological structure and the loading condition thereof of typical distribution net, corresponding backoff algorithm is adopted to study.Herein mainly for the Sensitivity Analysis of QIACA parameter, and attempt when choosing different crooked degree coefficient α, hum reduction factor β and sample size N, comparative analysis also obtains best compensation of delay effect.Because crooked degree coefficient α is for being approximately a constant, and the value that sample size N gets is the bigger the better, and the value that we get α is herein 0.1, and the value of N to be 20min carry out that contrast is discussed.

Server node in above-mentioned distribution network and the nodal analysis method of client node, containing standard five layer architecture of OSI communication protocol in node, is physical layer, Access Layer, network layer, transport layer and application layer respectively.Wherein, PTP protocol, as the protocol stack in application layer, is positioned on udp layer, transmit pair time message be all encapsulated as UDP/IP bag after transmit in a network.In addition, for agreement during IEEE1588 couple, also need to carry out corresponding parameter configuration to model.

End-to-end time deviation is not transmitted and time delay is analyzed to adopting the IEEE1588 protocol massages of QIA backoff algorithm, Comparative result figure A and B is as shown in Figure 4,5 based on the end-to-end skew of the message transmissions of model in the present embodiment and the successively contrast of message transmissions end-to-end time delay QIA backoff algorithm respectively

The result of display as can be seen from Fig. 4,5, after the QIA backoff algorithm adopting the embodiment of the present invention to mention, its time migration and time delay are all far smaller than the data not adopting QIA backoff algorithm, and it is more effective for the compensation effect of forward and reverse time delay that experiment demonstrates QIA algorithm.

And when hum reduction factor β is 0.0008,0.0009, when 0.0010,0.0011,0.0012, the end-to-end time deviation of overall message transmissions and time delay are respectively as shown in Figure 6 and Figure 7.

Experiment proves in the present embodiment α=0.1 and under the environment of N=20min, when β=0.0010, time migration and time delay are all tending towards minimum value, and wherein time migration is 0.000013s, and time delay value is 0.0000222s, all remains on preferably within accuracy rating.

The QIA backoff algorithm mentioned in the present embodiment, substantially increases precision when to be undertaken pair by IEEE1588 agreement.Adopt QIA backoff algorithm can be undertaken finely tuning to obtain time delay and reporting the most accurately by its corresponding sample size of change, crooked degree coefficient α and hum reduction factor β.

The present invention is not limited to above-described embodiment.All employings are equal to the technical scheme of replacing and being formed, and all drop on the protection range of application claims.

Claims (5)

1., based on a synchronization correction method for IEEE1588 clock models, it is characterized in that performing following steps:

1) moment point of described IEEE1588 clock models is obtained;

Master clock is at T ₁[n] moment point sends with T ₁the Sync message of [n] timestamp is to from clock, and the moment point receiving described Sync message from clock is T ₂[n], and stamp time stamp T 2 [n] for described Sync message;

Send with the DelayReq message of T3 [n] timestamp to master clock from clock in T3 [n] moment point, the moment point that master clock receives described DelayReq message is T4 [n], and stamps time stamp T 4 [n] for described DelayReq message;

Time stamp T 4 [n] to be embedded in the n-th DelayResp message and to propagate into from clock by master clock, completes the n-th exchange process;

At the end of all n exchange process all, whole PTP message switching terminates;

Wherein, n is positive integer;

2) relation between time S (t) of server and time C (t) of client is obtained by described IEEE1588 clock models, S (t)=(1+ α) C (t)+θ (1)

Obtain described Sync message in conjunction with PTP protocol and formula (1) to send and each timestamp relational expression in receiving course,

T ₁[n]+d _f+q _f[n]＝(1+α[n])T ₂[n]+θ[n] (2)

Described DelayReq message sends and each timestamp relational expression in receiving course,

T ₄[n]-d _r-q _r[n]＝(1+α[n])T ₃[n]+θ[n] (3)

The time migration of the n-th exchange process from clock in formula (2) and formula (3) is θ [n],

$\left\{\begin{array}{c}\mathrm{\&theta;}\&lsqb;n\&rsqb;=\frac{1}{2}(T_1\&lsqb;n\&rsqb;+T_4\&lsqb;n\&rsqb;-\left(1+\mathrm{\&alpha;}\&lsqb;n\&rsqb;\right)\left(T_2\&lsqb;n\&rsqb;+T_3\&lsqb;n\&rsqb;\right))+\frac{1}{2}(d_f-d_r)+{\mathrm{\&theta;}}_q\&lsqb;n\&rsqb;\\ {\mathrm{\&theta;}}_q\&lsqb;n\&rsqb;=\frac{1}{2}(q_f\&lsqb;n\&rsqb;-q_r\&lsqb;n\&rsqb;)\end{array}\right.$

Wherein,

α is crooked degree coefficient, and the kind k of transmission medium and the length l of propagation path is directly proportional;

α [n] is the crooked degree coefficient of the n-th exchange process;

θ is the time migration from clock;

θ _q[n] is variable queuing delay deviation;

D _ffor master clock is to the physical link delay from clock;

Q _ffor the variable queuing delay of master clock, q _fthe variable queuing delay of the n-th exchange process that [n] is master clock;

D _rfor the physical link delay from clock to master clock;

Q _rfor the variable queuing delay from clock, q _r[n] is the variable queuing delay of volume of the n-th exchange process from clock;

3) based on step 1) in time stamp T ₁[n], T ₂[n], T ₃[n], T ₄[n] carries out calculus of differences and obtains,

ε[n]＝q _f[n]-q _f[n-1]＝(1+α[n])dT ₂[n]-dT ₁[n]

γ[n]＝q _r[n]-q _r[n-1]＝dT ₄[n]-(1+α[n])dT ₃[n]

ε [n] is the variable queuing delay q of the n-th exchange process of master clock _fthe first-order difference of [n],

γ [n] is the variable queuing delay q of the n-th exchange process from clock _rthe first-order difference of [n];

4) by step 3) given by first-order difference value, obtain the asymmetric skew of the n-th exchange process obtained by exponentially weighted moving average (EWMA) filter again average magnitude for average variable queuing delay skew

${\stackrel{\&OverBar;}{\mathrm{\&theta;}}}_{qav}\&lsqb;n\&rsqb;=(1-\mathrm{\&beta;}){\stackrel{\&OverBar;}{\mathrm{\&theta;}}}_{qav}\&lsqb;n-1\&rsqb;+\mathrm{\&beta;}{\stackrel{\&OverBar;}{\mathrm{\&theta;}}}_{qav}\&lsqb;n\&rsqb;,$

Wherein, β is hum reduction factor, 0< β <1, by adjustment β, makes θ value level off to zero, completes the synchronous correction of described server and described client.

2. a kind of synchronous correction method based on IEEE1588 clock models as claimed in claim 1, is characterized in that: step 3) after to q _f[n] and q _r[n] is normalized, and with step 3) in the minimum of the variable queuing delay of master clock mentioned and the minimum of variable queuing delay from clock as the reference value of normalized, and obtain q _fand q _rcorresponding normalization amount with

$\begin{array}{c}{q}_{f_{nr}}\&lsqb;n\&rsqb;={\mathrm{\&epsiv;}}_s\&lsqb;n\&rsqb;-\underset{k=n-N}{\overset{k=n}{\min }}\left\{{\mathrm{\&epsiv;}}_s\&lsqb;n\&rsqb;\right\}=q_f\&lsqb;n\&rsqb;-q_f\&lsqb;0\&rsqb;\\ -\underset{k=n-N}{\overset{k=n}{\min }}\left\{q_f\&lsqb;n\&rsqb;-q_f\&lsqb;0\&rsqb;\right\}\\ =q_f\&lsqb;n\&rsqb;-q_{f_{\min }}\&lsqb;0\&rsqb;\end{array}$

$q_{r_{nr}}\&lsqb;n\&rsqb;={\mathrm{\&gamma;}}_s\&lsqb;n\&rsqb;-\underset{k=n-N}{\overset{k=n}{\min }}\left\{{\mathrm{\&gamma;}}_s\&lsqb;k\&rsqb;\right\}=q_r\&lsqb;n\&rsqb;-q_{r_{min}}\&lsqb;n\&rsqb;$

Wherein,

ε _s[n]＝ε _s[n-1]+ε[n]

＝ε _s[n-1]+q _f[n]-q _f[n-1]

＝ε _s[0]+q _f[n]-q _f[0]

γ _s[n]＝γ _s[0]+q _r[n]-q _r[0]

ε _s[0]＝γ _s[0]＝0。

3. a kind of synchronization correction method based on IEEE1588 clock models as claimed in claim 2, is characterized in that: the instantaneous asymmetric skew of the n-th exchange process by the n-th exchange process normalization amount of correspondence with determine ${\stackrel{\&OverBar;}{\mathrm{\&theta;}}}_q\&lsqb;n\&rsqb;=(q_{f_{nr}}\&lsqb;n\&rsqb;-q_{r_{nr}}\&lsqb;n\&rsqb;)/2.$

4. a kind of synchronization correction method based on IEEE1588 clock models as claimed in claim 1, it is characterized in that: determine the forward of described PTP message and reverse respectively according to master clock with from the sequence of the variable queuing delay of clock, and determine instantaneous asymmetric skew with the variable queuing delay of forward and reverse variable queuing delay

5. a kind of synchronization correction method based on IEEE1588 clock models as claimed in claim 4, is characterized in that: forward and the reverse data flow of described PTP message are separate.