CN108880722B - Clock synchronization method, system and optical transmission equipment - Google Patents
Clock synchronization method, system and optical transmission equipment Download PDFInfo
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- CN108880722B CN108880722B CN201710325947.3A CN201710325947A CN108880722B CN 108880722 B CN108880722 B CN 108880722B CN 201710325947 A CN201710325947 A CN 201710325947A CN 108880722 B CN108880722 B CN 108880722B
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- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04J—MULTIPLEX COMMUNICATION
- H04J3/00—Time-division multiplex systems
- H04J3/02—Details
- H04J3/06—Synchronising arrangements
- H04J3/0635—Clock or time synchronisation in a network
- H04J3/0638—Clock or time synchronisation among nodes; Internode synchronisation
- H04J3/0658—Clock or time synchronisation among packet nodes
- H04J3/0661—Clock or time synchronisation among packet nodes using timestamps
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Abstract
The invention discloses a method and a device for clock synchronization, wherein the method comprises the following steps: and the first equipment sends the local clock information to the second equipment through the overhead of Flexe so as to enable the second equipment to carry out clock synchronization according to the local clock information of the first equipment. According to the invention, the first equipment sends the local clock information to the second equipment through the overhead of Flexe, so that the second equipment performs clock synchronization according to the local clock information of the first equipment, the transmission of the time information message is completed through overhead frame sending, the transmission process is not influenced by different optical fiber lengths, the clock synchronization can be accurately realized, and the following problems in the prior art are solved: when time information is transmitted, because the lengths of a plurality of lines of optical fibers corresponding to the flexE interface are different, the link delay will be changed continuously, and the larger the difference of the lengths of the optical fibers is, the larger the jitter of time synchronization is, and the clock synchronization cannot be realized.
Description
Technical Field
The present invention relates to the field of communications, and in particular, to a method, a system, and an optical transmission device for clock synchronization.
Background
Due to its flexibility, the FlexE interface finds an increasingly wide range of applications, for example, in fronthaul networks. However, due to the flexibility, the time information generated at the client side cannot be fixedly transmitted on one line, and if the lengths of optical fibers of several lines of FlexE are different, the link delay will be changed continuously, the time synchronization will also jitter, and if the difference of the lengths of the optical fibers is larger, the jitter of the time synchronization is also larger, and accurate time synchronization cannot be realized.
Disclosure of Invention
The invention provides a clock synchronization method, a clock synchronization system and optical transmission equipment, which are used for solving the following problems in the prior art: when time information is transmitted, because the lengths of a plurality of lines of optical fibers corresponding to the Flexe interface are different, the link delay will be changed continuously, and the larger the difference of the lengths of the optical fibers is, the larger the jitter of time synchronization is, so that accurate clock synchronization cannot be realized.
To solve the above technical problem, in one aspect, the present invention provides a clock synchronization method, including: the first equipment sends the local clock information to the second equipment through the overhead of Flexe so that the second equipment performs clock synchronization according to the local clock information of the first equipment.
Optionally, the sending, by the first device, the local clock information to the second device through the overhead of the FlexE includes: the first equipment generates a first time stamp according to local time and generates a time information message according to the first time stamp and first residence time; the first equipment adds the time information message into reserved fields of a plurality of overhead frames; the first device splits each overhead frame into a plurality of overheads; and the first equipment inserts each split overhead into a data stream sent to the second equipment according to the Flexe standard.
Optionally, the generating, by the first device, the first timestamp according to the local time includes: and the first equipment determines the first timestamp according to the local time corresponding to the sending position of the overhead frame where the message header of the time information message or the message header of the last time information message sent adjacently to the first equipment is located.
On the other hand, the invention also provides a clock synchronization method, which is characterized by comprising the following steps: the second device receives the overhead of the first device Flexe; the second device extracts the clock information in the overhead of the first device FlexE for clock synchronization.
Optionally, the extracting, by the second device, clock information in the overhead of the FlexE of the first device includes: the second equipment extracts overheads from the received data stream and records a timestamp corresponding to each overhead; the second equipment reconstructs overhead frames according to the extracted overhead frames and obtains a time information message according to the reconstructed overhead frames, wherein the time information message carries a first timestamp and a first residence time of the time information message sent by the first equipment; the second equipment determines a first time stamp according to the time information message and determines a second time stamp according to the time of receiving a message header of the time information message corresponding to the first time stamp; the second device determines a first time offset based on the first timestamp, the second timestamp, and the first residence time.
Optionally, determining a second timestamp according to the time of receiving the packet header of the time information packet corresponding to the first timestamp, including: determining the cost of a message header of the time information message; and determining the time stamp corresponding to the overhead as the second time stamp.
Optionally, after the second device determines a first time deviation according to the first timestamp, the second timestamp, and the first residence time, the method further includes: and the second device adds a third timestamp to the local clock information and sends the local clock information to the first device through the overhead of Flexe.
In another aspect, the invention also provides a computer storage medium having a computer program stored thereon, wherein the computer program is adapted to perform the steps of the method according to any one of claims 1 to 7 when executed by a processor.
In another aspect, the present invention further provides an optical transmission apparatus, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the execution of the computer program by the processor is to implement the steps of the above method.
In another aspect, the present invention further provides a system for clock synchronization, including:
the device comprises a master device and a slave device, wherein both the master device and the slave device are provided with Flexe interfaces; wherein the content of the first and second substances,
the master device sends first local clock information to the slave device through the overhead of Flexe, wherein the first local clock information comprises a first residence time and a first timestamp;
the slave device determines a second timestamp and a second residence time according to the received overhead, determines a third residence time according to the first residence time and the second residence time, and feeds back second local clock information to the master device through the overhead of Flexe, wherein the second local clock information comprises a fourth residence time and the third timestamp;
the master device receives and determines a fourth timestamp and the fifth residence time according to the received overhead, determines a sixth residence time according to the fourth residence time and the fifth residence time, and feeds back third local clock information to the slave device through the overhead of Flexe, wherein the third local clock information comprises the sixth residence time and the fourth timestamp;
the slave device determines a total time offset according to the fourth residence time, the sixth residence time, the first time stamp, the second time stamp, the third time stamp and the fourth time stamp, and adjusts a local time according to the total time offset.
According to the invention, the first equipment sends the local clock information to the second equipment through the overhead of Flexe, so that the second equipment performs clock synchronization according to the local clock information of the first equipment, the transmission of the time information message is completed through overhead frame sending, the transmission process is not influenced by different optical fiber lengths, the clock synchronization can be accurately realized, and the following problems in the prior art are solved: when time information is transmitted, because the lengths of a plurality of lines of optical fibers corresponding to the Flexe interface are different, the link delay will be changed continuously, and the larger the difference of the lengths of the optical fibers is, the larger the jitter of time synchronization is, and the clock synchronization cannot be realized.
Drawings
FIG. 1 is a flow chart of a method of clock synchronization in a first embodiment of the present invention;
FIG. 2 is a detailed flowchart of a method for clock synchronization according to a second embodiment of the present invention;
FIG. 3 is a schematic diagram of a clock synchronization apparatus according to a third embodiment of the present invention;
FIG. 4 is a schematic diagram of another clock synchronization apparatus according to a third embodiment of the present invention;
FIG. 5 is a block diagram of an implementation of example 1 in a fourth embodiment of the present invention;
fig. 6 is a schematic diagram of a message format in example 1 according to a fourth embodiment of the present invention;
FIG. 7 is a block diagram of another implementation of the fourth embodiment 1 of the present invention;
fig. 8 is a block diagram of the implementation of the transmission direction of embodiment 2 in the fourth embodiment of the present invention;
fig. 9 is a block diagram of the implementation of the receiving direction of embodiment 2 in the fourth embodiment of the present invention;
fig. 10 is an internal message format sent from the component 2 to the component 1 according to the fourth embodiment of the present invention;
fig. 11 shows an internal message format sent from the component 1 to the component 2 according to the fourth embodiment of the present invention.
Detailed Description
In order to solve the following problems in the prior art: when time information is transmitted, because the lengths of a plurality of lines of optical fibers corresponding to the Flexe interface are different, the link delay can be changed continuously, and the larger the difference of the lengths of the optical fibers is, the larger the jitter of time synchronization is, and the clock synchronization can not be realized; the invention provides a method, a system and an optical transmission device for clock synchronization, which are described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and do not limit the invention.
A first embodiment of the present invention provides a clock synchronization method, where a flow of the method is shown in fig. 1, and as can be seen in fig. 1, a first device sends local clock information to a second device through an overhead of FlexE, so that the second device can further implement clock synchronization according to the local clock information of the first device.
Specifically, the sending process in fig. 1 may include steps S102 to S106:
and S102, the first equipment generates a first time stamp according to the local time and generates a time information message according to the first time stamp and the first residence time.
The first timestamp is generated according to local time, and the method is used for realizing time synchronization, so that in the process of realizing the process, the first timestamp information represents the sending time of the last sent time information message adjacent to the current time information message to be generated.
S104, the first device adds the time information message to the reserved field of a plurality of overhead frames.
For each overhead frame, there is a reserved field, and this embodiment sets the reserved field as an add time information packet, splits the time information packet, adds the time information packet to each reserved field, and sends the time information packet through the overhead frame.
S106, the first equipment splits each overhead frame into a plurality of overheads, and inserts each split overhead into the data stream sent to the second equipment according to the Flexe standard.
When the first device inserts the overhead frames into the data stream transmitted to the second device, each overhead frame is also transmitted according to a predetermined byte length, and thus each overhead frame is split into a plurality of overhead transmissions.
According to the invention, the first equipment sends the local clock information to the second equipment through the overhead of Flexe, so that the second equipment performs clock synchronization according to the local clock information of the first equipment, the transmission of the time information message is completed through overhead frame sending, the transmission process is not influenced by different optical fiber lengths, the clock synchronization can be accurately realized, and the following problems in the prior art are solved: when time information is transmitted, because the lengths of a plurality of lines of optical fibers corresponding to the Flexe interface are different, the link delay will be changed continuously, and the larger the difference of the lengths of the optical fibers is, the larger the jitter of time synchronization is, and the clock synchronization cannot be realized.
A second embodiment of the present invention provides a clock synchronization method, which is a process executed by a device side waiting for clock synchronization, in which a second device receives overhead of a first device FlexE, and extracts clock information in the overhead of the first device FlexE to perform clock synchronization.
When the second device extracts the clock information in the overhead of the first device FlexE, the specific flow thereof is as shown in fig. 2, and includes steps S202 to S208:
s202, the second device extracts overhead from the received data stream and records a timestamp corresponding to each overhead.
Since the overhead frame is sent according to the predetermined byte, the overhead frame is split into a plurality of overhead messages during sending, so that when the second device determines the time information packet according to the overhead frame in the received data stream, it is necessary to extract the overhead from the received data stream first, and record the timestamp corresponding to each overhead, so as to prepare for subsequently determining the receiving timestamp of the time information packet.
And S204, the second equipment reconstructs the overhead frames according to the extracted overhead frames and obtains a time information message according to the reconstructed overhead frames, wherein the time information message carries a first timestamp and a first residence time of the time information message sent by the first equipment.
And S206, the second device determines a first time stamp according to the time information message, and determines a second time stamp according to the time for receiving the message header of the time information message corresponding to the first time stamp.
When the second timestamp is determined according to the time of receiving the message header of the time information message, the cost of the message header of the time information message needs to be determined first, and then the timestamp corresponding to the cost is determined to be the second timestamp.
And S208, the second device determines a first time deviation according to the first time stamp, the second time stamp and the first residence time.
When the process is implemented, the time deviation is determined according to the first time stamp, the second time stamp and the first residence time by the second equipment, and then the third time stamp is added into the local clock information by the second equipment, and the local clock information is sent to the first equipment through the overhead of Flexe, so that the clock synchronization with the first equipment is implemented subsequently.
In a specific implementation, the first device of the first embodiment of the present invention may be equivalent to a master device, and the second device of the second embodiment may be equivalent to a slave device. The propagation speed of light in the fiber is about 200000km/s, i.e. 0.2 m/ns. The process of synchronizing in 1588E2E mode is illustrated as follows:
assuming that the time of the Sync message during line transmission is delay1, the master device sends a timestamp T1, the slave device receives a timestamp T2, the residence time of the two devices is CF21, the time of the delayreq message during line transmission is delay2, the sending timestamp T3 of the slave device, the receiving timestamp T4 of the master device, the residence time of the two devices is CF34, and the time offset of the slave device with respect to the master device is offset, the following two formulas are obtained:
t1+ CF21+ offset + delay1 ═ T2 (formula 1)
T3+ CF34-offset + delay2 ═ T4 (formula 2)
1588 the traditional formula is:
t1+ CF21+ offset + meandelay T2 (formula 3)
T3+ CF34-offset + meandelay T4 (formula 4)
The offset and meandelay equations are calculated as follows:
the common interface sync and delayreq messages are respectively fixed on a line for transmission, and the difference between delay1 and delay2 can be added to CF21 and CF34 by compensation. And the transmission line of the messages of the flexE interface is not fixed and cannot be compensated.
If the sync message is transmitted on the line 1 for the first time and the sync message is transmitted on the line 2 for the second time, and the lengths of the two lines are different by 20 meters, the value difference of T2-T1-CF is 100ns, and delayreq messages are transmitted on the same line, namely T4-T3-CF34 are unchanged, so that the offset difference calculated twice is 50ns, and the time synchronization can increase the jitter of 50ns due to the uncertain line length. The method of the invention fixes the transmission of the message on the same interface, and the jitter of 50ns does not exist.
A third embodiment of the present invention provides an apparatus for clock synchronization, which may be provided in the first device of the first embodiment described above, and includes: and the overhead sending module is used for sending the local clock information of the first equipment to the second equipment through the overhead of the Flexe so as to enable the second equipment to carry out clock synchronization according to the local clock information of the first equipment. Specifically, fig. 3 shows each working unit of the overhead transmission module, which includes:
the generating unit 10 is configured to generate a first timestamp according to the local time, and generate a time information packet according to the first timestamp and the first residence time; an adding unit 20, coupled to the generating unit 10, configured to add the time information packet to reserved fields of multiple overhead frames; and the inserting unit 30 is coupled to the adding unit 20, and is configured to enable the first device to split each overhead frame into multiple overheads, and insert each split overhead into a data stream sent to the second device according to the FlexE standard.
The generating unit 10 is specifically configured to determine the first timestamp according to a local time corresponding to a sending position of an overhead frame where a packet header of the time information packet or a packet header of a last time information packet sent adjacent to the packet header of the time information packet is located.
An embodiment of the present invention further provides another clock synchronization apparatus, which may be disposed in the second device of the second embodiment, and the apparatus includes: and the clock synchronization module is used for enabling the second equipment to receive the overhead of the first equipment FlexE and extracting clock information in the overhead of the first equipment FlexE so as to perform clock synchronization.
The structure of the clock synchronization module may be as shown in fig. 4, and includes:
the message determining unit 40 is configured to extract overheads from a received data stream, record a timestamp corresponding to each overhead, reconstruct overhead frames according to the extracted overheads, and obtain a time information message according to the reconstructed overhead frames, where the time information message carries a first timestamp and a first residence time of a time information message sent by a clock synchronization device; a time determining unit 50, coupled to the message determining unit 40, configured to determine a first time stamp according to the time information message, and determine a second time stamp according to a time of receiving a message header of the time information message corresponding to the first time stamp; an adjusting unit 60 is coupled to the time determining unit 50 for determining the first time offset based on the first time stamp, the second time stamp and the first dwell time.
In a specific implementation, the time determining unit 50 is specifically configured to determine an overhead of a header of the time information packet, and determine that a timestamp corresponding to the overhead is a second timestamp.
The apparatus may further include means for adding a third timestamp to the local clock information and sending the local clock information to the first device over the overhead of FlexE after determining the first time offset based on the first timestamp, the second timestamp, and the first dwell time.
A fourth embodiment of the present invention provides a system for clock synchronization of a FlexE interface, which solves the problem of excessive time synchronization jitter of the FlexE interface due to the fact that time information cannot be fixed on a line for transmission. The present embodiment will be described in detail below.
A transmission direction device (corresponding to a first device in a first embodiment) according to an embodiment of the present invention includes:
the time information generating unit is used for generating a timestamp according to the local time and packaging the timestamp into the message; the overhead frame generating unit is used for generating overhead frames of all ports and inserting the time information messages into the overhead frames; and the overhead insertion processing unit is used for inserting the overhead frames into corresponding positions of the data stream according to the Flexe standard.
The reception direction device (corresponding to the second device in the second embodiment) of the present invention includes:
the overhead extraction processing unit is used for extracting the overhead in the data stream; an overhead frame reorganization unit for framing the extracted overhead; time information extraction for extracting time information from the overhead frame for time synchronization.
In addition, the synchronizing end may further include a unit for the synchronizing end to synchronize the frequency of the synchronized end, which is not described in detail herein.
Based on the above device, the clock synchronization method provided by the embodiment of the present invention includes the following steps:
after the frequency synchronization is realized, a sending end of the sending direction equipment generates a timestamp according to local time and packages the timestamp into a message with a certain format; the overhead frame generating unit inserts the message into the specified position of the overhead frame according to bytes; the overhead insertion processing unit then inserts the overhead frames into the corresponding positions of the port PHY data streams.
The receiving direction equipment extracts the overhead in the data stream by an overhead extraction processing unit and records a time stamp T of the arrival time of the overhead; the overhead frame recombination unit recombines the extracted overhead and detects whether the overhead position of the time information is the initial byte of the time information message, if so, the T is locked and recorded as TS, and the TS is the arrival time of the time information message; the time information extraction unit extracts the time information message from the overhead frame and extracts the opposite end sending time stamp carried by the time information message from the time information message.
And then, the receiving direction equipment calculates the time deviation according to the arrival time of the message and the time carried in the message, and performs time adjustment so as to realize time synchronization.
In the implementation process, when the sending direction device (synchronizing end) and the receiving direction device (synchronized end) need to exchange time information for multiple times, the above two ends are repeatedly executed for multiple times, so as to finally complete time synchronization.
The embodiment of the invention uses the field of the overhead frame to transmit the time information, thereby effectively avoiding the problem of overlarge jitter caused by large delay difference of lines of different ports of Flexe.
The above process is described in detail below with reference to the accompanying drawings and specific examples.
EXAMPLE 1
The implementation block diagram of the embodiment is shown in fig. 5.
The sending direction device: firstly, a sending time stamp is obtained according to local time and a sending position of the time information message header corresponding to the cost, and the sending time stamp is packaged into the time information message. Then, the time information packet is inserted into a reserved field (i.e., a reserved field) of the FlexE overhead frame in blocks, an overhead frame is generated together with other information, and the overhead frame is inserted into the data stream of the PHY 0. The time information packet may also be inserted into overhead frames of other PHYs.
The receiving direction device: overhead is extracted from a data stream of the PHY0, a timestamp of an overhead position is recorded, an overhead frame is reconstructed according to the extracted overhead, a time information packet is extracted from the overhead frame, and a sending timestamp of an opposite terminal device carried in the packet is obtained.
The synchronization terminal (in this embodiment, the receiving direction device) calculates a time offset according to the obtained transceiving time stamp, and adjusts the local time, thereby achieving time synchronization.
For the sending and receiving of the time information message, the calculation of the time deviation can refer to the mode of 1588E 2E. Since the overhead frame field is dedicated to the time information, the message format of the conventional 1588 can be simplified without performing two-layer ethernet and three-layer IP encapsulation, as shown in fig. 6, matching between the port id of the home terminal and the port id of the opposite terminal can be omitted in processing.
In this embodiment, a 1588 message may also be used to carry time information, and the implementation block diagram is shown in fig. 7. The processing flow is similar to that of embodiment 1, and will not be described in detail here, and the frequency synchronization in fig. 7 can be implemented by means of sync.
In the embodiment, two paths of overheads can be selected to respectively transmit two paths of 1588 messages, one path is used for time synchronization, the other path is used for standby, and when the path with time synchronization has a problem, the standby path can be switched. Thereby realizing the protection switching of time synchronization.
Numerous variations will occur to those skilled in the art without departing from the spirit of the method of the embodiments of the invention.
EXAMPLE 2
This embodiment describes a scheme in which different processing units are respectively implemented in two components. The component 1 realizes the functions of inserting and extracting overhead frames, recombining overhead frames, recording transceiving timestamps and the like. The component 2 realizes the functions of time information message generation, overhead frame generation, timestamp extraction, time synchronization, frequency synchronization and the like. The internal messages of the component 1 and the component 2 are transmitted through the GE port, and the block diagrams of the sending direction and the receiving direction are respectively shown in fig. 8 and fig. 9.
The time information may be transmitted in an overhead reserved field of an optional FlexE line, and in this embodiment, the 0 th line is selected and the time information is added to the overhead reserved field of the PHY 0.
In the sending direction, firstly, the component 2 calculates the sending time of the current message according to the timestamp and the serial number sent by the component 1, and generates a time information message according to the sending time. Then, the time information message is added to the overhead frame, and the overhead frame is encapsulated into the internal message, and the format of the internal message sent by the component 2 to the component 1 is shown in fig. 10. Wherein, the meaning of each field is as follows:
preamble & SDF: ethernet standard definition content
DA: the destination address and value can be configured, and the chip needs to determine the address value of the received message
And SA: source address, value configurable.
TPID: VLAN flag, can be configured, and the default value is: 8100.
priority: priority, configurable, default is 0.
CFI: standard format identifier, configurable, default is 0.
Vlan id: 12 bits, 6 bits high configurable, and 6 bits low indicating the corresponding PHY lane number. 0 is the first PHY, 1 is the second PHY, and so on.
S _ serial number: and adding 1 to each new message by the message sequence number, and circularly counting for identifying the sequence of the messages.
Reserved: and a reserved part, wherein 10 bytes are reserved.
Reserved 1: the first segment in the overhead retains the field contents, and the retained field has 47 bits and is transmitted in 6 bytes (48 bits, low 47 bits are valid, highest bit is not used).
Reserved 2: the second segment of the overhead retains the contents of the fields, which have 13 bits and are transmitted in 2 bytes (16 bits, the lower 13 bits being valid and the highest 3 bits being unused).
Section management: the section level manages the channel overhead information and transmits the information by using 16 bytes.
shim storage: the shim-shim stage manages channel overhead information and is delivered with 24 bytes.
FCS: an Ethernet CRC check portion.
The time information message is divided into 7 bytes, and the higher 9 bits of the Reserved 1 field and the Reserved 2 field of a plurality of messages are respectively inserted.
After receiving the internal message, the component 1 analyzes the overhead frame content carried by the internal message and recombines the overhead frame content, then inserts the overhead frame content into a data stream in blocks, records the time value of the local time 2 when each block is sent, encapsulates the time value into the internal message together with the sequence number of the internal message corresponding to the block, and sends the internal message to the component 2. The message format is shown in fig. 11, and the field meanings are as follows:
preamble & SDF: ethernet standard definition content
DA: the destination address and value can be configured, and the chip needs to determine the address value of the received message.
And SA: source address, value configurable.
TPID: VLAN flag, can be configured, and the default value is: 8100.
priority: priority, configurable, default is 0.
CFI: standard format identifier, configurable, default is 0.
Vlan id: 12 bits, 6 bits high configurable, and 6 bits low indicating the corresponding PHY lane number. 0 is the first PHY, 1 is the second PHY, and so on.
R _ serial number: the PHY receives the packet sequence number, adds 1 to each new packet, and counts cyclically to identify the sequence order of the packets.
R _ timestamp: the content carried by the message is in FLEXE overhead, and a first overhead block in the overhead samples a chip timestamp value when receiving.
Reserved 1: the first segment in the overhead retains the field contents, and the retained field has 47 bits and is transmitted in 6 bytes (48 bits, low 47 bits are valid, highest bit is not used).
Reserved 2: the second segment of the overhead retains the contents of the fields, which have 13 bits and are transmitted in 2 bytes (16 bits, the lower 13 bits being valid and the highest 3 bits being unused).
Section management: the channel overhead information is managed at the stage level and is transmitted by 16 bytes
shim storage: the cost information of the shim-shim level management channel is transmitted by 24 bytes
S _ serial _ number: when the PHY sending end sends FLEXE overhead last time, the serial number carried in the sending message is adopted, and the sending direction reads the content of the sending message last time. The component 2 can know how many messages are sent by the PHY in the component 1 and how many messages are buffered currently through the information.
S _ timestamp: when the PHY sending end sends the FLEXE overhead last time, the message content corresponding to the S _ serial _ number is filled in the FLEXE overhead, and the first overhead block sends the timestamp value of the time chip. Through the S _ serial _ number and the S _ timestamp, the component 2 can know the sending time of the sent message, that is, the sending time of the timestamp value of the time information message in the reserved field, and is used for timestamp correction of the time information message.
FCS: ethernet CRC check part
After receiving the internal message, the component 1 analyzes the internal message, extracts the time information message from the reserved 1 field and the reserved 2 field, recombines the time information message, and further obtains the timestamp in the message; and acquiring the receiving timestamp of the first overhead block from the R _ timestamp field, and calculating the receiving timestamp of the current time information if the extracted time information message content is the message header of the message. Meanwhile, the arrival timestamp is analyzed from the internal message. After the synchronizing end obtains a plurality of groups of timestamps by using a similar method, time deviation can be calculated, and local time is adjusted, so that time synchronization is achieved.
Although the preferred embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, and the scope of the invention should not be limited to the embodiments described above.
Claims (8)
1. A method of clock synchronization, comprising:
the method comprises the steps that a first device sends local clock information to a second device through the overhead of Flexe, so that the second device carries out clock synchronization according to the local clock information of the first device;
the method for sending the local clock information to the second device through the FlexE overhead by the first device includes:
the first equipment generates a first time stamp according to local time and generates a time information message according to the first time stamp and first residence time;
the first equipment adds the time information message into reserved fields of a plurality of overhead frames;
the first device splits each overhead frame into a plurality of overheads;
and the first equipment inserts each split overhead into a data stream sent to the second equipment according to the Flexe standard.
2. The method of claim 1, wherein the first device generating the first timestamp from the local time comprises:
and the first equipment determines the first timestamp according to the local time corresponding to the sending position of the overhead frame where the message header of the time information message or the message header of the last time information message sent adjacently to the first equipment is located.
3. A method of clock synchronization, comprising:
the second device receives the overhead of the first device Flexe;
the second device extracts clock information in the overhead of the first device Flexe to perform clock synchronization;
wherein the second device extracting clock information in the overhead of the first device FlexE includes:
the second equipment extracts overheads from the received data stream and records a timestamp corresponding to each overhead;
the second equipment reconstructs overhead frames according to the extracted overhead frames and obtains a time information message according to the reconstructed overhead frames, wherein the time information message carries a first timestamp and a first residence time of the time information message sent by the first equipment;
the second equipment determines a first time stamp according to the time information message and determines a second time stamp according to the time of receiving a message header of the time information message corresponding to the first time stamp;
the second device determines a first time offset based on the first timestamp, the second timestamp, and the first residence time.
4. The method of claim 3, wherein determining the second timestamp according to a time of receiving a header of the time information packet corresponding to the first timestamp comprises:
determining the cost of a message header of the time information message;
and determining the time stamp corresponding to the overhead as the second time stamp.
5. The method of claim 4, wherein after the second device determines a first time offset based on the first timestamp, the second timestamp, and the first dwell time, further comprising:
and the second device adds a third timestamp to the local clock information and sends the local clock information to the first device through the overhead of Flexe.
6. A computer storage medium on which a computer program is stored, which computer program, when being executed by a processor, carries out the steps of the method of any one of claims 1 to 5.
7. An optical transmission apparatus comprising a memory, a processor and a computer program stored on the memory and executable on the processor, wherein execution of the computer program by the processor is to implement the steps of the method of any one of claims 1 to 5.
8. A system for clock synchronization, comprising:
the device comprises a master device and a slave device, wherein both the master device and the slave device are provided with Flexe interfaces; wherein the content of the first and second substances,
the master device sends first local clock information to the slave device through the overhead of Flexe, wherein the first local clock information comprises a first residence time and a first timestamp;
the slave device determines a second timestamp and a second residence time according to the received overhead, determines a third residence time according to the first residence time and the second residence time, and feeds back second local clock information to the master device through the overhead of Flexe, wherein the second local clock information comprises a fourth residence time and a third timestamp;
the master device receives and determines a fourth timestamp and a fifth residence time according to the received overhead, determines a sixth residence time according to the fourth residence time and the fifth residence time, and feeds back third local clock information to the slave device through the overhead of Flexe, wherein the third local clock information comprises the sixth residence time and the fourth timestamp;
the slave device determines a total time deviation according to the fourth residence time, the sixth residence time, the first time stamp, the second time stamp, the third time stamp and the fourth time stamp, and adjusts local time according to the total time deviation;
the master device encapsulates corresponding local clock information into a time information message, inserts the time information message into a specified position of an overhead frame according to bytes, and inserts the overhead frame into a port PHY data stream so as to send the first local clock information or the third local clock information to the slave device through the overhead of Flexe;
the slave device extracts the overhead in the data stream, recombines the extracted overhead, and extracts the time information message from the overhead frame, so as to determine a second timestamp and a second residence time according to the received overhead, and determine a third residence time according to the first residence time and the second residence time.
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| CN111245542B (en) * | 2018-11-28 | 2022-01-28 | 中兴通讯股份有限公司 | Method for acquiring time stamp and time synchronization system |
| WO2020181462A1 (en) | 2019-03-11 | 2020-09-17 | 华为技术有限公司 | Clock synchronization message interacting method and apparatus |
| CN110634488B (en) * | 2019-10-08 | 2022-04-15 | 北京小米智能科技有限公司 | Information processing method, device and system and storage medium |
| CN112672235A (en) * | 2019-10-15 | 2021-04-16 | 中兴通讯股份有限公司 | Synchronization method, device, equipment and storage medium |
| CN112825493A (en) * | 2019-11-21 | 2021-05-21 | 深圳市中兴微电子技术有限公司 | Timestamp configuration method and device and clock synchronization method and device |
| CN113098645A (en) * | 2019-12-23 | 2021-07-09 | 中兴通讯股份有限公司 | Configuration method and device of synchronization information, network equipment and storage medium |
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