CN102394741A

CN102394741A - Method for realizing precision time synchronization based on IEEE1588 and apparatus thereof

Info

Publication number: CN102394741A
Application number: CN2011104184513A
Authority: CN
Inventors: 梁学伟
Original assignee: Hangzhou H3C Technologies Co Ltd
Current assignee: Hangzhou H3C Technologies Co Ltd
Priority date: 2011-12-13
Filing date: 2011-12-13
Publication date: 2012-03-28

Abstract

The invention provides a method for realizing precision time synchronization based on IEEE1588. The method comprises the following steps that: according to a downlink/uplink path delay test message sent from a slave device to a primary device, uplink/downlink data between the primary device and the slave device is switched to the downlink/uplink; after the data is transmitted on the downlink/uplink, a first wavelength is used to transmit the downlink data and a second wavelength is used to transmit the uplink data on the downlink/uplink; through an IEEE1588 protocol, the downlink/uplink path delay can be calculated; through the IEEE1588 protocol, and the uplink, downlink path delay, a time error between the primary device and the slave device can be calculated so that the slave device can realize the precision time synchronization with the primary device according to the calculated time error. The invention simultaneously discloses an apparatus of realizing the precision time synchronization based on the IEEE1588. By using the method for realizing the precision time synchronization based on the IEEE1588 and the apparatus thereof, influences of the asymmetric uplink/downlink on the time synchronization can be avoided and accuracy of the time synchronization can be raised.

Description

Realize the method and apparatus of exact time synchronization based on IEEE1588

Technical field

The present invention relates to network communications technology field, particularly a kind of method and apparatus of realizing exact time synchronization based on IEEE1588.

Background technology

The IEEE1588 agreement is present unique agreement that can realize that split-second precision is synchronous; As shown in Figure 1; Slave unit carries out message through uplink and downgoing line and main equipment and transmits obtaining being used for four time point T1, T2, T3 and T4 of time synchronized, thereby realizes time synchronized.Concrete message transport process can be referring to Fig. 2, and as shown in Figure 2, this process can comprise:

Main equipment sends the Sync message through downgoing line to slave unit, simultaneously, sends the Followup message of the transmitting time T1 that has the Sync message to slave unit through downgoing line;

After slave unit receives the Sync message, write down the T2 time of advent of this Sync message, and from the Followup message, obtain time T 1, simultaneously, at time point T3, slave unit sends the Delay_Req message through uplink to main equipment;

After main equipment receives the Delay_Req message, write down the T4 time of advent of this Delay_Req message, and T4 is carried in the response message Delay_Resp message sends to slave unit through downgoing line;

Slave unit obtains time T 4 from the Delay_Resp message that receives.

Through said process, slave unit can obtain time point T1, T2, T3 and T4, and obtains circuit time delay PathDelay=((T2-T1)+(T4-T3))/2 and the time difference Offset=((T2-T1)-(T4-T3))/2 between the master-slave equipment between the master-slave equipment according to T1, T2, T3 and T4; Wherein, T2-T1=Delay01+ Δ ms, T4-T3=Delay02+ Δ sm, wherein Delay01 is the downgoing line time delay; Delay02 is the uplink time delay; Δ ms is the absolute time difference of slave unit with respect to main equipment, and Δ sm is the absolute time difference of main equipment with respect to slave unit, and Δ ms=-Δ sm; Offset=((T2-T1)-(T4-T3))/2=((Delay01-Delay02)+(Δ ms-Δ sm))/2=(Delay01-Delay02)/2+ (2 Δ sm)/2 is then arranged.

Under the ideal situation, the Offset theoretical value should equal Δ sm, promptly needs Delay01=Delay02, also is that the uplink time delay is identical with the downgoing line time delay.Yet under actual conditions, when especially the up-downgoing circuit was asymmetric, up-downgoing circuit time delay can not guarantee it is identical, and the Offset actual value is not Δ sm thus, thereby causes 1588 timing tracking accuracies obviously to reduce.

Summary of the invention

In view of this, the invention provides a kind of method that realizes exact time synchronization based on IEEE1588, can avoid the asymmetric influence that time synchronized is brought of up-downgoing circuit, the accuracy of raising time synchronized.

The present invention also provides a kind of device of realizing exact time synchronization based on IEEE1588, can avoid the asymmetric influence that time synchronized is brought of up-downgoing circuit, the accuracy of raising time synchronized.

In order to achieve the above object, the technical scheme of the present invention's proposition is:

A kind of method based on IEEE1588 realization exact time synchronization, this method comprises:

Based on the downgoing line delay testing message of sending to main equipment from equipment; After switching to downgoing line transmission with main equipment and from the uplink data between the equipment; On downgoing line respectively with the first wavelength transmission downlink data, with the second wavelength transmission uplink data, calculate the downgoing line time delay through the IEEE1588 agreement;

Based on the uplink delay testing message of sending to main equipment from equipment; After switching to uplink transmission with main equipment and from the downlink data between the equipment; On uplink respectively with the first wavelength transmission downlink data, with the second wavelength transmission uplink data, calculate the uplink time delay through the IEEE1588 agreement;

Obtain the time error between main equipment and the slave unit through IEEE1588 agreement and said uplink and downlink circuit time-delay calculation, make slave unit according to the exact time synchronization between time error realization that calculates and the main equipment.

Said based on the downgoing line delay testing message of sending to main equipment from equipment; With main equipment and switch to downgoing line transmission from the uplink data between the equipment and comprise: switch to the main equipment transmitting line from equipment and prepare message; After receiving the switching preparation confirmation message that sends by main equipment; Through the downgoing line transmission, make main equipment perceive after equipment completion switching the uplink data, also the uplink data are passed through the downgoing line transmission;

Said on downgoing line respectively with the first wavelength transmission downlink data, with the second wavelength transmission uplink data, calculate the downgoing line time delay through the IEEE1588 agreement and comprise: slave unit receives by main equipment with first wavelength Sync message that sends and the transmitting time T1 that has the Sync message through downgoing line _DownThe Followup message; After receiving the Sync message, write down the T2 time of advent of this Sync message _Down, and from the Followup message, obtain time T 1 _DownAt time point T3 _Down, send Delay_Req message with second wavelength to main equipment through downgoing line, and receive the T4 time of advent that has the Delay_Req message that returns with first wavelength through downgoing line by main equipment _DownResponse Delay_Resp message, from the Delay_Resp message that receives, obtain time T 4 _DownAccording to T1 _Down, T2 _Down, T3 _DownAnd T4 _DownCalculate downgoing line time delay PathDelay _Down=((T2 _Down-T1 _Down)+(T4 _Down-T3 _Down))/2.

When calculating downgoing line through the IEEE1588 agreement, delay, this method further comprises:

Slave unit switches the recovery message to the main equipment transmitting line; After receiving the switching recovery confirmation message that sends by main equipment; With the uplink data through uplink transmission, make main equipment perceive slave unit accomplish switch after, also the uplink data are passed through uplink transmission.

Said based on the uplink delay testing message of sending to main equipment from equipment; With main equipment and switch to uplink transmission from the downlink data between the equipment and comprise: from equipment to main equipment transmitting line handoff request message; After receiving the switching preparation message that sends by main equipment; Switch confirmation message to the main equipment transmitting line; Make main equipment with downlink data through uplink transmission, from equipment perceive main equipment accomplish switch after, also downlink data is passed through uplink transmission;

Said on uplink respectively with the first wavelength transmission downlink data, with the second wavelength transmission uplink data, calculate the uplink time delay through the IEEE1588 agreement and comprise: slave unit receives by main equipment with first wavelength Sync message that sends and the transmitting time T1 that has the Sync message through uplink _OnThe Followup message; After receiving the Sync message, write down the T2 time of advent of this Sync message _On, and from the Followup message, obtain time T 1 _OnAt time point T3 _On, send Delay_Req message with second wavelength to main equipment through uplink, and receive the T4 time of advent that has the Delay_Req message that returns with first wavelength through uplink by main equipment _OnResponse Delay_Resp message, from the Delay_Resp message that receives, obtain time T 4 _OnAccording to T1 _On, T2 _On, T3 _OnAnd T4 _OnCalculate uplink time delay PathDelay _On=((T2 _On-T1 _On)+(T4 _On-T3 _On))/2.

Saidly delay when calculating uplink through the IEEE1588 agreement, this method further comprises:

Switch the recovery request message from equipment to the main equipment transmitting line; After receiving the switching recovery preparation message that sends by main equipment; Send switching to main equipment and recover confirmation message; Make main equipment that downlink data is transmitted by downgoing line, from equipment perceive main equipment accomplish switch back after, also downlink data is transmitted by downgoing line.

A kind of device of realizing exact time synchronization based on IEEE1588; This device comprises main equipment and the slave unit of being made up of time synchronized unit, control unit, MAC chip, timestamp unit and enhancement unit respectively; Said enhancement unit comprises gate and optical transceiver, wherein

The control unit of said slave unit sends downgoing line delay testing message through time synchronized unit, MAC chip, timestamp unit, gate and the optical transceiver of slave unit to main equipment; So that being switched on the downgoing line, the uplink data between main equipment and the slave unit transmit; On downgoing line; The timestamp unit of said slave unit with the time of the downlink data of first wavelength transmission, the said slave unit time with the second wavelength transmission uplink data, calculates downgoing line time delay through the IEEE1588 agreement according to said main equipment;

The control unit of said slave unit sends uplink delay testing message through time synchronized unit, MAC chip, timestamp unit, gate and the optical transceiver of slave unit to main equipment; So that being switched on the uplink, the downlink data between main equipment and the slave unit transmits; On uplink; The timestamp unit of said slave unit with the time of the downlink data of first wavelength transmission, the said slave unit time with the second wavelength transmission uplink data, calculates uplink time delay through the IEEE1588 agreement according to said main equipment;

The timestamp unit of said slave unit is according to obtaining the time error between main equipment and the slave unit through IEEE1588 agreement and said uplink and downlink circuit time-delay calculation, the exact time synchronization between realization and the main equipment.

The control unit of said slave unit sends downgoing line delay testing message through time synchronized unit, MAC chip, timestamp unit, gate and the optical transceiver of slave unit to main equipment, and transmission comprises on the downgoing line so that the uplink data between main equipment and the slave unit are switched to:

The control unit of slave unit sends downgoing line delay testing message to the time synchronized unit of slave unit; Through MAC chip, timestamp unit and gate, optical transceiver, switch the preparation message to the main equipment transmitting line by the time synchronized unit through uplink;

After the optical transceiver of main equipment receives that circuit switches the preparation message; Circuit is switched the preparation message send to the time synchronized unit through gate, timestamp unit, MAC chip; After packet parsing identification is prepared in switching to circuit by the time synchronized unit, send switching preparation message, switch SBR so that control unit gets into to control unit; Through MAC chip, timestamp unit, gate, optical transceiver, send switching through downgoing line to slave unit and prepare confirmation message simultaneously;

After the slave unit optical transceiver receives that confirmation message is prepared in the switching of being sent by main equipment; Through gate, timestamp unit, MAC chip; With message time of delivery (TOD) lock unit, behind this message of time synchronized unit resolves, send circuit switched message to control unit; After the slave unit control unit was received circuit switched message, the control gate broke off being connected of the optical transceiver that links to each other with uplink;

After the optical transceiver that main equipment links to each other with uplink can not receive opposite end optical transceiver light wave; Send receipts light LOS signal to the main equipment control unit; After the main equipment control unit receives that optical transceiver sends receipts light LOS signal; The control gate breaks off the optical transceiver that links to each other with uplink and is connected; Simultaneously to main equipment time synchronized unit transmitting line handoff completion message, after the circuit handoff completion message is received in main equipment time synchronized unit, send to switch to slave unit through MAC chip, gate, optical transceiver, through downgoing line and accomplish message;

After the slave unit optical transceiver receives that message is accomplished in the switching of being sent by main equipment,, transmit to accomplish the uplink data between main equipment and the slave unit are switched on the downgoing line through gate, MAC chip, with message time of delivery (TOD) lock unit;

Said on downgoing line; The timestamp unit of said slave unit, calculates the downgoing line time delay through the IEEE1588 agreement and comprises with the time of the downlink data of first wavelength transmission, the said slave unit time with the second wavelength transmission uplink data according to said main equipment:

Said slave unit receives by main equipment with first wavelength Sync message that sends and the transmitting time T1 that has the Sync message through downgoing line _DownThe Followup message; After receiving the Sync message, the T2 time of advent of this Sync message of timestamp unit record of slave unit _Down, and from the Followup message, obtain time T 1 _DownAt time point T3 _Down, slave unit sends Delay_Req message with second wavelength to main equipment through downgoing line, and receives the T4 time of advent that has the Delay_Req message that is returned with first wavelength through downgoing line by main equipment _DownResponse Delay_Resp message, the timestamp unit of slave unit obtains time T 4 from the Delay_Resp message that receives _DownThe timestamp unit of slave unit is according to T1 _Down, T2 _Down, T3 _DownAnd T4 _DownCalculate downgoing line time delay PathDelay _Down=((T2 _Down-T1 _Down)+(T4 _Down-T3 _Down))/2.

Said slave unit time synchronized unit also is used for switching recovery message through downgoing line to the main equipment transmitting line through MAC chip, gate, optical transceiver, use second wavelength;

After the main equipment optical transceiver receives that the circuit that is sent by slave unit switches the recovery message; Through gate, timestamp unit, MAC chip; With message time of delivery (TOD) lock unit; After main equipment time synchronized unit resolves circuit switches the recovery message, switch recovery message to main equipment control unit transmitting line, and through MAC chip, gate, optical transceiver; Use first wavelength to send the recovery confirmation message to slave unit, the recovery SBR was switched in entering after the main equipment control unit was received circuit switching recovery message;

The slave unit optical transceiver is received the recovery confirmation message that is sent first wavelength by main equipment; Through gate, MAC chip, with message time of delivery (TOD) lock unit; Slave unit time synchronized unit is through after resolving the recovery confirmation message; Switch restore operation message to slave unit control unit transmitting line, the transmission interface of the optical transceiver that gate 22 and uplink is linked to each other by control unit is connected;

After the main equipment optical transceiver can not receive opposite end optical transceiver light wave; Send receipts light LOS signal to the main equipment control unit; After the main equipment control unit receives that transceiver sends light LOS signal; The receiving interface of the optical transceiver that the control gate links to each other with uplink is connected, and recovers to accomplish message to main equipment time synchronized unit transmitting line simultaneously, after main equipment time synchronized unit receives that circuit recovers to accomplish message; Through MAC chip, gate, optical transceiver, use first wavelength to send to switch and accomplish message to slave unit;

After the slave unit optical transceiver receives that the switching of sending first wavelength by main equipment is ready to complete message; Pass through gate, MAC chip, message is sent to the time synchronized unit, the uplink data between main equipment and the slave unit are switched back uplink transmission to accomplish.

The control unit of said slave unit sends uplink delay testing message through time synchronized unit, MAC chip, timestamp unit, gate and the optical transceiver of slave unit to main equipment, and transmission comprises on the uplink so that the downlink data between main equipment and the slave unit is switched to:

The control unit of slave unit sends uplink delay testing message to the time synchronized unit of slave unit; By the time synchronized unit through MAC chip, timestamp unit and gate, optical transceiver, through uplink to main equipment transmitting line handoff request message;

After the main equipment optical transceiver is received circuit handoff request message; With circuit handoff request message process gate, timestamp unit, MAC chip time of delivery (TOD) lock unit; Behind time synchronized unit resolves identification message; Through MAC chip, gate 11, optical transceiver 11, use λ n wavelength to switch and prepare message to the slave unit transmitting line;

After the slave unit optical transceiver receives that message is prepared in the switching of being sent by main equipment; Through gate, MAC chip; With message time of delivery (TOD) lock unit, behind the slave unit time synchronized unit resolves message, switch confirmation message to the main equipment transmitting line through MAC chip, gate, optical transceiver; Notify slave unit control unit circuit to switch simultaneously and prepare message, switch SBR so that the slave unit control unit gets into;

After the main equipment optical transceiver is received and is switched confirmation message; With message process gate, MAC chip time of delivery (TOD) lock unit; Behind the time synchronized unit resolves message; Sending to control unit can circuit switched message, so that the main equipment control unit is being connected of gate breaks off and downgoing line links to each other optical transceiver, and the transmission interface of the optical transceiver that links to each other with uplink is connected;

After the slave unit optical transceiver can not receive opposite end optical transceiver light wave; Send receipts light LOS signal to the slave unit control unit; After the slave unit control unit receives that transceiver sends newspaper light LOS signal; The control gate breaks off the optical transceiver that links to each other with downgoing line and is connected, and is connected with the receiving interface of the continuous optical transceiver of uplink, to slave unit time synchronized unit transmitting line handoff completion message; And, send switching to main equipment and accomplish message through MAC chip, gate, optical transceiver;

After the main equipment optical transceiver receives that message is accomplished in the switching of being sent by slave unit, through gate, MAC chip, with message time of delivery (TOD) lock unit,, transmit to accomplish the downlink data between main equipment and the slave unit switched on the uplink;

Said on uplink; The timestamp unit of said slave unit, calculates the uplink time delay through the IEEE1588 agreement and comprises with the time of the downlink data of first wavelength transmission, the said slave unit time with the second wavelength transmission uplink data according to said main equipment:

Said slave unit receives by main equipment with first wavelength Sync message that sends and the transmitting time T1 that has the Sync message through uplink _OnThe Followup message; After receiving the Sync message, the T2 time of advent of this Sync message of timestamp unit record of slave unit _On, and from the Followup message, obtain time T 1 _OnAt time point T3 _On, slave unit sends Delay_Req message with second wavelength to main equipment through uplink, and receives the T4 time of advent that has the Delay_Req message that is returned with first wavelength through uplink by main equipment _OnResponse Delay_Resp message, the timestamp unit of slave unit obtains time T 4 from the Delay_Resp message that receives _OnThe timestamp unit of slave unit is according to T1 _On, T2 _On, T3 _OnAnd T4 _OnCalculate uplink time delay PathDelay _On=((T2 _On-T1 _On)+(T4 _On-T3 _On))/2.

Said slave unit time synchronized unit also is used for through MAC chip, gate, optical transceiver, uses second wavelength to switch the recovery request message to the main equipment transmitting line;

After the main equipment optical transceiver receives that the circuit that is sent by slave unit switches the recovery request message; Through gate, timestamp unit, MAC chip; With message time of delivery (TOD) lock unit; After main equipment time synchronized unit resolves is switched the recovery message,, recover to prepare message to the slave unit transmitting line through MAC chip, gate, optical transceiver;

The slave unit optical transceiver receives that the circuit that is sent by main equipment recovers to prepare message; Through gate, MAC chip; With message time of delivery (TOD) lock unit, slave unit time synchronized unit switches recovery to slave unit control unit transmitting line and prepares message through to after recovering the confirmation message parsing; After the slave unit control unit receives that circuit switches restore operation message; Entry-line recovers SBR, simultaneously through MAC chip, gate, optical transceiver, switches the recovery confirmation message to the main equipment transmitting line;

After the main equipment optical transceiver receives that the switching of being sent by slave unit recovers confirmation message; Through gate, timestamp unit, MAC chip; With message time of delivery (TOD) lock unit; Main equipment time synchronized unit resolves is sent the transmitting line restore operation message to the main equipment control unit, after the main equipment control unit is received the circuit restore operation message after switching the recovery confirmation message; Break off being connected of optical transceiver that gate links to each other with uplink, and the transmission interface of the optical transceiver that gate and downgoing line are linked to each other is connected;

After the slave unit optical transceiver can not receive opposite end optical transceiver light wave; Send receipts light LOS signal to the slave unit control unit; After the slave unit control unit received that transceiver sends light LOS signal, the control gate broke off the optical transceiver that links to each other with uplink and is connected, and the receiving interface of the optical transceiver that gate and downgoing line is continuous is connected; Recover to accomplish message to slave unit time synchronized unit transmitting line; After the slave unit lock unit receives that circuit recovers to accomplish message,, switch the completion message to the main equipment transmitting line through MAC chip, gate, optical transceiver;

After the main equipment optical transceiver receives that the switching of being sent by slave unit is ready to complete message,,, the downlink data between main equipment and the slave unit is switched back the downgoing line transmission to accomplish with message time of delivery (TOD) lock unit through gate, MAC chip.

In sum; The method that the present invention adopted based on IEEE1588 realization exact time synchronization; Be to transmit through respectively the uplink data between main equipment and the slave unit being switched on the downgoing line; On downgoing line, calculate the downgoing line time delay through the IEEE1588 agreement; And the downlink data between main equipment and the slave unit switched on the uplink transmit, and delay when on uplink, calculating uplink through the IEEE1588 agreement, with the up-downgoing circuit time delay substitution that calculates according in the existing time error formula that calculates through the IEEE1588 agreement; Obtain the precise time error, make slave unit according to the exact time synchronization between time error realization that calculates and the main equipment.Because the inventive method is through with obtaining time error in the time error of the up-downgoing circuit time delay substitution accurately formula; And be not to think the identical time error that obtains of up-downgoing circuit time delay simply; Therefore, also just avoided because the influence that up-downgoing circuit time delay difference is brought time error, especially when the up-downgoing circuit is asymmetric; Avoid the asymmetric influence that time synchronized is brought of up-downgoing circuit, improved the accuracy of time synchronized.

Description of drawings

Fig. 1 uses the networking sketch map for existing IEEE1588;

Fig. 2 transmits sketch map for message between the existing master-slave equipment;

Fig. 3 is the workflow diagram of method for synchronizing time of the present invention;

Fig. 4 is the structural representation of time synchronism apparatus of the present invention;

Fig. 5 is up-downgoing circuit changing method one a process sketch map of the present invention;

Fig. 6 is up-downgoing circuit changing method two process sketch mapes of the present invention.

Embodiment

In order to solve the technical problem that the present invention proposes, the concrete realization of scheme according to the invention comprises:

According to the downgoing line delay testing message of slave unit to the main equipment transmission; After uplink data between main equipment and the slave unit are switched on the downgoing line transmission; On downgoing line respectively with the first wavelength transmission downlink data, with the second wavelength transmission uplink data, calculate the downgoing line time delay through the IEEE1588 agreement; According to the uplink delay testing message of slave unit to the main equipment transmission; After downlink data between main equipment and the slave unit switched on the uplink transmission; On uplink respectively with the first wavelength transmission downlink data, with the second wavelength transmission uplink data, calculate the uplink time delay through the IEEE1588 agreement; Obtain the time error between main equipment and the slave unit through IEEE1588 agreement and said uplink and downlink circuit time-delay calculation, make slave unit according to the exact time synchronization between time error realization that calculates and the main equipment.

For making the object of the invention, technical scheme and advantage clearer, the present invention is done to describe in detail further below in conjunction with accompanying drawing and specific embodiment.

Fig. 3 is the workflow diagram of the method for synchronizing time that the present invention adopted.As shown in Figure 3, this flow process comprises:

Step 301: according to the downgoing line delay testing message of slave unit to the main equipment transmission; After uplink data between main equipment and the slave unit are switched on the downgoing line transmission; On downgoing line respectively with the first wavelength transmission downlink data, with the second wavelength transmission uplink data, calculate the downgoing line time delay through the IEEE1588 agreement.

In this step, the downgoing line delay testing message of sending to main equipment according to slave unit switches to the uplink data between main equipment and the slave unit that transmission comprises on the downgoing line:

Slave unit (can pass through uplink) switches to the main equipment transmitting line prepares message; After receiving the switching preparation confirmation message that sends by main equipment (can pass through downgoing line); The uplink data are transmitted (being about to pass through the downgoing line transmission through the data of uplink transmission) through downgoing line; After making that main equipment perceives slave unit completion switching, also the uplink data are transmitted through downgoing line.Specifically can for: the transmission data flow of main equipment uses wavelength to be λ n (being first wavelength), and receiving data stream uses wavelength to be λ b (being second wavelength): slave unit switch to be prepared message to main equipment through the uplink transmitting line; After main equipment receives that circuit is prepared message, send switching through downgoing line to slave unit and prepare confirmation message, and SBR is switched in entering; Slave unit switches to transmitting line on the downgoing line through gate after receiving and switching the preparation confirmation message; Simultaneously the single fiber bi-directional optical transceiver in the uplink is closed light, main equipment switching SBR, switches to downgoing line through gate with receiving lines because of after closing light according to the uplink in the single fiber bi-directional optical transceiver perception slave unit.

More specifically, Fig. 4 has provided the structural representation of the time synchronism apparatus that the present invention adopted.As shown in Figure 4; Main equipment in this device and slave unit all comprise time synchronized unit, control unit, MAC chip, timestamp unit and enhancement unit; Wherein the structure of enhancement unit can be referring to Fig. 5; Promptly comprise gate and optical transceiver, in conjunction with Fig. 4 and Fig. 5, concrete up-downgoing circuit handoff procedure is:

The control unit of slave unit sends downgoing line delay testing message to the time synchronized unit of slave unit; And then the time synchronized unit switches preparation message through uplink to the main equipment transmitting line with λ n wavelength through MAC chip (message forwarding chip), timestamp unit and gate 22, optical transceiver 22;

After the optical transceiver 12 of main equipment receives that the circuit of λ n wavelength switches the preparation message; Circuit is switched the preparation message send to the time synchronized unit through gate 12, timestamp unit, MAC chip; After packet parsing identification is prepared in switching to circuit by the time synchronized unit; To control unit send to switch prepare message (control unit receive switch prepare message after; Get into and switch SBR), simultaneously through MAC chip, timestamp unit, gate 11, optical transceiver 11, use λ n wavelength to send to switch to slave unit and prepare confirmation message through downgoing line;

After slave unit optical transceiver 21 is received the switching preparation confirmation message by main equipment transmission λ n wavelength, through gate 21, timestamp unit, MAC chip, with message time of delivery (TOD) lock unit; Behind this message of time synchronized unit resolves, send circuit switched message to control unit, after the slave unit control unit is received circuit switched message; The disconnection of control gate is connected with optical transceiver 22; Simultaneously, optical transceiver 22 is closed luminous, and optical transceiver 21 is opened luminous;

After main equipment optical transceiver 12 can not receive optical transceiver 22 light waves; Send receipts light LOS signal to the main equipment control unit, the main equipment control unit is judged to be at present when switching SBR after receiving that optical transceiver 12 sends receipts light LOS signals; The control gate breaks off and being connected with optical transceiver 12; And close optical transceiver 12 receiving functions, open optical transceiver 11 receiving functions, simultaneously to main equipment time synchronized unit transmitting line handoff completion message; After the circuit handoff completion message is received in main equipment time synchronized unit, send switching through downgoing line to slave unit and accomplish message through MAC chip, gate 11, optical transceiver 11, use λ n wavelength;

After slave unit optical transceiver 21 receives that message is accomplished in the switching of sending λ n wavelength by main equipment,, behind the time synchronized unit resolves message, begin to carry out the measurement of downgoing line time delay through gate 12, MAC chip, with message time of delivery (TOD) lock unit.

Need to prove; When completion is transmitted the uplink data through downgoing line after; Data all can be through the downgoing line transmission, for the differentiating uplink and downlink circuit, at this moment; The data of different directions can be transmitted through different wavelengths, and distinguishing thus is uplink data or downlink data.

Further, after completion switches to downgoing line with uplink, can calculate the downgoing line time delay, specifically can comprise through the IEEE1588 agreement:

Slave unit receives by main equipment with first wavelength Sync message that sends and the transmitting time T1 that has the Sync message through downgoing line _DownThe Followup message; After receiving the Sync message, write down the T2 time of advent of this Sync message _Down, and from the Followup message, obtain time T 1 _DownAt time point T3 _Down, send Delay_Req message with second wavelength to main equipment through downgoing line, and receive the T4 time of advent that has the Delay_Req message that returns with first wavelength through downgoing line by main equipment _DownResponse Delay_Resp message, from the Delay_Resp message that receives, obtain time T 4 _DownAccording to T1 _Down, T2 _Down, T3 _DownAnd T ₄Under calculate downgoing line time delay PathDelay _Down=((T2 _Down-T1 _Down)+(T4 _Down-T3 _Down))/2.

What also need explain is that after calculating the downgoing line time delay through the IEEE1588 agreement, also need switch back uplink transmission with the uplink data between main equipment and the slave unit, comprising:

Slave unit (can pass through downgoing line) switches the recovery message to the main equipment transmitting line; After receiving the switching recovery confirmation message that sends by main equipment (can pass through downgoing line); With the uplink data through uplink transmission (soon passing through uplink transmission) through the data of uplink transmission; Make main equipment perceive slave unit accomplish switch back after, also the uplink data are passed through uplink transmission.Be specially: when calculating downgoing line, delay, slave unit (can pass through downgoing line) switches the recovery message to the main equipment transmitting line; After main equipment was received circuit switching recovery message, (can pass through downgoing line) sent to switch to slave unit and recovers confirmation message, and the entering switching returns to form; Slave unit switches back transmitting line on the uplink through gate after receiving and switching the recovery confirmation message, the luminous work of single fiber bi-directional optical transceiver working line this moment; Single fiber bi-directional optical transceiver in the main equipment perception slave unit switches back to uplink through gate with receiving lines after receiving normally.

More specifically, in conjunction with Fig. 4 and Fig. 5, the uplink data between main equipment and the slave unit are switched back uplink transmission comprise:

Slave unit time synchronized unit switches recovery message through downgoing line to the main equipment transmitting line through MAC chip, gate 22, optical transceiver 21, use λ b wavelength;

After main equipment optical transceiver 11 receives that the circuit that is sent by slave unit switches the recovery message; Through gate 12, timestamp unit, MAC chip; With message time of delivery (TOD) lock unit; After main equipment time synchronized unit resolves circuit switches the recovery message, switch recovery message to main equipment control unit transmitting line, and through MAC chip, gate 11, optical transceiver 11; Use λ n wavelength to slave unit transmission recovery confirmation message, the main equipment control unit is received after circuit switches recovery message and is got into switching recovery SBR;

Slave unit optical transceiver 21 is received the recovery confirmation message that is sent λ n wavelength by main equipment; Through gate 22, MAC chip, with message time of delivery (TOD) lock unit; Slave unit time synchronized unit switches restore operation message through to after recovering the confirmation message parsing to slave unit control unit transmitting line, carries out circuit by control unit and recovers to handle; That is: gate 22 is broken off and being connected of optical transceiver 21; But its transmission interface with optical transceiver 22 is connected, while optical transceiver 21 is closed luminous, and optical transceiver 22 is opened luminous;

After main equipment optical transceiver 11 can not receive the opposite end light wave; Send receipts light LOS signal to the main equipment control unit, after the main equipment control unit receives that transceiver 11 sends light LOS signals, judge to be at present and switch when returning to form; Control gate 12 breaks off and being connected with optical transceiver 11; And its receiving interface with optical transceiver 12 is connected, and close and optical transceiver 11 receiving functions, open optical transceiver 12 receiving functions; Recover to accomplish message to main equipment time synchronized unit transmitting line simultaneously; After main equipment time synchronized unit receives that circuit recovers to accomplish message,, use λ n wavelength to send to switch and accomplish message to slave unit through MAC chip, gate 11, optical transceiver 11;

After slave unit optical transceiver 21 receives that the switching of sending λ n wavelength by main equipment is ready to complete message; Pass through gate 21, MAC chip, message is sent to the time synchronized unit, so far promptly accomplished the process of the uplink data between main equipment and the slave unit being switched back uplink transmission.

Step 302: according to the uplink delay testing message of slave unit to the main equipment transmission; After downlink data between main equipment and the slave unit switched on the uplink transmission; On uplink respectively with the first wavelength transmission downlink data, with the second wavelength transmission uplink data, and calculate the uplink time delay through the IEEE1588 agreement.

In this step, the uplink delay testing message of sending to main equipment according to slave unit switches to the downlink data between main equipment and the slave unit that transmission comprises on the uplink:

Slave unit (can pass through uplink) is to main equipment transmitting line handoff request message; After receiving the switching preparation confirmation message that sends by main equipment (can pass through downgoing line); Switch confirmation message to the main equipment transmitting line; Make main equipment that downlink data is passed through uplink transmission, slave unit also passes through uplink transmission with downlink data after perceiving main equipment completion switching.Specifically can for: the transmission data flow of main equipment uses wavelength to be λ b (i.e. first wavelength), and receiving data stream uses wavelength to be λ n (i.e. second wavelength): slave unit is to main equipment (can pass through uplink) transmitting line handoff request message; After main equipment was received circuit handoff request message, (can pass through downgoing line) sent to switch to slave unit and prepares message, and gets into the switching SBR; After slave unit is received and is switched the preparation message; Switch confirmation message to the main equipment transmitting line; Make main equipment transmitting line switched on the uplink, simultaneously the single fiber bi-directional optical transceiver in the downgoing line is closed light, after slave unit closes light according to the downgoing line in the single fiber bi-directional optical transceiver perception main equipment through gate; Switching SBR, receiving lines is switched to uplink because of through gate.

More specifically, up-downgoing circuit handoff procedure can be referring to Fig. 4 and Fig. 6, and in conjunction with Fig. 4 and Fig. 6, up-downgoing circuit handoff procedure is:

The slave unit control unit sends uplink delay testing message to slave unit time synchronized unit; Slave unit time synchronized unit uses λ n wavelength to pass through uplink to main equipment transmitting line handoff request message through MAC chip, gate 22, optical transceiver 22;

After main equipment optical transceiver 12 is received the circuit handoff request message of λ n wavelength; With message process gate 12; MAC chip time of delivery (TOD) lock unit; Behind the main equipment time synchronized unit resolves identification message,, use λ n wavelength to switch and prepare message to the slave unit transmitting line through MAC chip, gate 11, optical transceiver 11;

After slave unit optical transceiver 21 is received the switching preparation message by main equipment transmission λ n wavelength; Through gate 21, MAC chip, with message time of delivery (TOD) lock unit, behind the slave unit time synchronized unit resolves message; Use λ n wavelength to switch confirmation message through MAC chip, gate 22, optical transceiver 22 to the main equipment transmitting line; Notify slave unit control unit circuit to switch simultaneously and prepare message, the slave unit control unit gets into and switches SBR after receiving circuit switching preparation message;

After main equipment optical transceiver 12 is received the switching confirmation message of λ n wavelength; Through gate 12, MAC chip time of delivery (TOD) lock unit, behind the time synchronized unit resolves message, sending to control unit can circuit switched message with message; The main equipment control unit receive can circuit switched message after; Carry out the circuit hand-off process, that is: gate 11 breaks off and being connected of optical transceiver 11, and its transmission interface with optical transceiver 12 is connected; While optical transceiver 11 is closed luminous, and optical transceiver 12 is opened luminous;

After slave unit optical transceiver 21 can not receive the opposite end light wave, send receipts light LOS signal, after the slave unit control unit receives that transceiver 21 sends newspaper light LOS signals to the slave unit control unit; Judge and be at present when switching SBR; The control gate breaks off and being connected with optical transceiver 21, but is connected with the receiving interface of optical transceiver 22, and closes optical transceiver 21 receiving functions; Open optical transceiver 22 receiving functions; Simultaneously to slave unit time synchronized unit transmitting line handoff completion message, after the slave unit lock unit is received the circuit handoff completion message, through MAC chip, gate 22, optical transceiver 22; Use λ n wavelength to send to switch and accomplish message to main equipment, and entry-line latency measurement state;

Main equipment optical transceiver 12 through gate 12, MAC chip, with message time of delivery (TOD) lock unit, behind the time synchronized unit resolves message, begins to carry out the latency measurement of uplink after receiving the switching completion message by slave unit transmission λ n wavelength.

The same with step 301, after completion switched to uplink with downgoing line, data all can be passed through uplink transmission; Likewise, for the differentiating uplink and downlink circuit, at this moment; The data of different directions can be transmitted through different wavelengths, and distinguishing thus is upstream data or downlink data.

Further, after completion switches to uplink with downgoing line, can calculate the uplink time delay, specifically can comprise through the IEEE1588 agreement:

Slave unit receives by main equipment with first wavelength Sync message that sends and the transmitting time T1 that has the Sync message through uplink _OnThe Followup message; After receiving the Sync message, write down the T2 time of advent of this Sync message _On, and from the Followup message, obtain time T 1 _OnAt time point T3 _On, send Delay_Req message with second wavelength to main equipment through uplink, and receive the T4 time of advent that has the Delay_Req message that returns with first wavelength through uplink by main equipment _OnResponse Delay_Resp message, from the Delay_Resp message that receives, obtain time T 4 _OnAccording to T1 _On, T2 _On, T3 _OnAnd T4 _OnCalculate uplink time delay PathDelay _On=((T2 _On-T1 _On)+(T4 _On-T3 _On))/2.

What also need explain is that after calculating the uplink time delay through the IEEE1588 agreement, also need switch back the downgoing line transmission with the downlink data between main equipment and the slave unit, comprising:

Switch the recovery request message from equipment (can pass through uplink) to the main equipment transmitting line; After receiving the switching recovery preparation message that sends by main equipment (can pass through uplink); Send switching to main equipment and recover confirmation message; Make main equipment that downlink data is transmitted by downgoing line, from equipment perceive main equipment accomplish switch back after, also downlink data is transmitted by downgoing line.Be specially: when calculating uplink, delay, slave unit (can pass through uplink) switches the recovery request message to the main equipment transmitting line; After main equipment received that circuit switches the recovery request message, (can pass through uplink) sent to switch to slave unit and recovers to prepare message, and then slave unit sends to switch to main equipment and recover confirmation message, and got into to switch and return to form; Main equipment switches back receiving lines on the downgoing line through gate after receiving and switching the recovery confirmation message, the luminous work of single fiber bi-directional optical transceiver working line this moment; Single fiber bi-directional optical transceiver in the slave unit perception main equipment switches back to downgoing line through gate with transmitting line after receiving normally.

More specifically, in conjunction with Fig. 4 and Fig. 6, the downlink data between main equipment and the slave unit is switched back the downgoing line transmission comprises:

Slave unit time synchronized unit uses λ n wavelength to switch the recovery request message to the main equipment transmitting line through MAC chip, gate 22, optical transceiver 22;

After main equipment optical transceiver 12 is received the circuit switching recovery request message by slave unit transmission λ n wavelength; Through gate 12, timestamp unit, MAC chip; With message time of delivery (TOD) lock unit; After main equipment time synchronized unit resolves is switched the recovery message,, use λ b wavelength to recover to prepare message to the slave unit transmitting line through MAC chip, gate 11, optical transceiver 12;

Slave unit optical transceiver 22 is received the circuit recovery preparation message that is sent λ b wavelength by main equipment; Through gate 21, MAC chip; With message time of delivery (TOD) lock unit, slave unit time synchronized unit switches recovery to slave unit control unit transmitting line and prepares message through to after recovering the confirmation message parsing; After the slave unit control unit receives that circuit switches restore operation message; Entry-line 1 recovers SBR, simultaneously through MAC chip, gate 22, optical transceiver 22, uses λ n wavelength to switch to the main equipment transmitting line and recovers confirmation message;

After main equipment optical transceiver 12 is received the switching recovery confirmation message by slave unit transmission λ n wavelength; Through gate 12, timestamp unit, MAC chip, with message time of delivery (TOD) lock unit, after main equipment time synchronized unit resolves is switched the recovery confirmation message; Send the transmitting line restore operation message to the main equipment control unit; After the main equipment control unit was received the circuit restore operation message, disconnection gate 11 was connected with optical transceiver 12, and its transmission interface with optical transceiver 11 is connected; While optical transceiver 12 is closed luminous, and optical transceiver 11 is opened luminous;

After slave unit optical transceiver 22 can not receive the opposite end light wave; Send receipts light LOS signal to the slave unit control unit, after the slave unit control unit receives that transceiver 22 sends light LOS signals, judge that being in circuit at present switches when returning to form; Control gate 21 breaks off and being connected with optical transceiver 22; Its receiving interface with optical transceiver 21 is connected, and closes and optical transceiver 22 receiving functions, open optical transceiver 21 receiving functions; Recover to accomplish message to slave unit time synchronized unit transmitting line simultaneously; After the slave unit lock unit receives that circuit recovers to accomplish message,, use λ n wavelength to switch and accomplish message to the main equipment transmitting line through MAC chip, gate 22, optical transceiver 22;

After main equipment optical transceiver 12 receives that the switching of sending λ n wavelength by slave unit is ready to complete message; Through gate 12, MAC chip; With message time of delivery (TOD) lock unit, so far promptly accomplished the process of the downlink data between main equipment and the slave unit being switched back the downgoing line transmission.

Step 303: obtain the time error between main equipment and the slave unit through IEEE1588 agreement and said uplink and downlink circuit time-delay calculation, make slave unit according to the exact time synchronization between time error realization that calculates and the main equipment.

The said time error that obtains between main equipment and the slave unit through IEEE1588 agreement and said uplink and downlink circuit time-delay calculation comprises: calculate Offset=(PathDelay according to the IEEE1588 agreement _Down-PathDelay _On)/2+ (2 Δ sm)/2 is with PathDelay _DownAnd PathDelay _OnSubstitution Offset can obtain the time error between main equipment and the slave unit, thereby makes slave unit according to the exact time synchronization between time error realization that calculates and the main equipment.

Need to prove how to calculate Offset and in background technology, introduced, repeat no more according to the IEEE1588 agreement.

So far, promptly accomplished the whole workflow of method for synchronizing time of the present invention.

Based on said method; The further describing that provides in the face of Fig. 4 down for time synchronism apparatus of the present invention; As can be seen from Figure 4, this device comprises main equipment and the slave unit of being made up of time synchronized unit, control unit, MAC chip, timestamp unit and enhancement unit respectively, and said enhancement unit comprises gate and optical transceiver; Wherein

Further; The control unit of said slave unit sends downgoing line delay testing message through time synchronized unit, MAC chip, timestamp unit, gate and the optical transceiver of slave unit to main equipment, and transmission comprises on the downgoing line so that the uplink data between main equipment and the slave unit are switched to:

After the slave unit optical transceiver receives that message is accomplished in the switching of being sent by main equipment,, transmit to accomplish the uplink data between main equipment and the slave unit are switched on the downgoing line through gate, MAC chip, with message time of delivery (TOD) lock unit.

Particularly; Said on downgoing line; The timestamp unit of said slave unit, calculates the downgoing line time delay through the IEEE1588 agreement and comprises with the time of the downlink data of first wavelength transmission, the said slave unit time with the second wavelength transmission uplink data according to said main equipment:

Further, said slave unit time synchronized unit also is used for switching to the main equipment transmitting line through downgoing line through MAC chip, gate, optical transceiver, use second wavelength and recovers message;

Likewise; The control unit of said slave unit sends uplink delay testing message through time synchronized unit, MAC chip, timestamp unit, gate and the optical transceiver of slave unit to main equipment, and transmission comprises on the uplink so that the downlink data between main equipment and the slave unit is switched to:

After the main equipment optical transceiver receives that message is accomplished in the switching of being sent by slave unit, through gate, MAC chip, with message time of delivery (TOD) lock unit,, transmit to accomplish the downlink data between main equipment and the slave unit switched on the uplink.

Further, said slave unit time synchronized unit also is used for through MAC chip, gate, optical transceiver, uses second wavelength to switch the recovery request message to the main equipment transmitting line;

So far, promptly obtained the time synchronism apparatus that the present invention adopted.

In a word; The method that the present invention adopted based on IEEE1588 realization exact time synchronization; Transmit through respectively the uplink data between main equipment and the slave unit being switched on the downgoing line; On downgoing line, calculate the downgoing line time delay through the IEEE1588 agreement; And the downlink data between main equipment and the slave unit switched on the uplink transmit, and delay when on uplink, calculating uplink through the IEEE1588 agreement, with the up-downgoing circuit time delay substitution that calculates according in the existing time error formula that calculates through the IEEE1588 agreement; Obtain the precise time error, make slave unit according to the exact time synchronization between time error realization that calculates and the main equipment.Because the inventive method is through with obtaining time error in the time error of the up-downgoing circuit time delay substitution accurately formula; And be not to think the identical time error that obtains of up-downgoing circuit time delay simply; Therefore, also just avoided because the influence that up-downgoing circuit time delay difference is brought time error, especially when the up-downgoing circuit is asymmetric; Avoid the asymmetric influence that time synchronized is brought of up-downgoing circuit, improved the accuracy of time synchronized.Further, the inventive method is to implement data transmission link by slave unit to switch, and has avoided message dropping, can onlinely carry out non-measurement being prolonged in time-delay.

The above is merely preferred embodiment of the present invention, and is in order to restriction the present invention, not all within spirit of the present invention and principle, any modification of being made, is equal to replacement, improvement etc., all should be included within the scope that the present invention protects.

Claims

1. method that realizes exact time synchronization based on IEEE1588 is characterized in that this method comprises:

2. method according to claim 1 is characterized in that,

3. method according to claim 2 is characterized in that, when calculating downgoing line through the IEEE1588 agreement, delays, and this method further comprises:

4. method according to claim 1 is characterized in that,

5. method according to claim 4 is characterized in that, saidly delays when calculating uplink through the IEEE1588 agreement, and this method further comprises:

6. device of realizing exact time synchronization based on IEEE1588; It is characterized in that; This device comprises main equipment and the slave unit of being made up of time synchronized unit, control unit, MAC chip, timestamp unit and enhancement unit respectively; Said enhancement unit comprises gate and optical transceiver, wherein

7. device according to claim 6; It is characterized in that; The control unit of said slave unit sends downgoing line delay testing message through time synchronized unit, MAC chip, timestamp unit, gate and the optical transceiver of slave unit to main equipment, and transmission comprises on the downgoing line so that the uplink data between main equipment and the slave unit are switched to:

8. device according to claim 7 is characterized in that,

9. device according to claim 6; It is characterized in that; The control unit of said slave unit sends uplink delay testing message through time synchronized unit, MAC chip, timestamp unit, gate and the optical transceiver of slave unit to main equipment, and transmission comprises on the uplink so that the downlink data between main equipment and the slave unit is switched to:

10. device according to claim 9 is characterized in that,