WO2012155663A1

WO2012155663A1 - Method and network apparatus for adjusting frequency based on ieee 1588 protocol

Info

Publication number: WO2012155663A1
Application number: PCT/CN2012/072761
Authority: WO
Inventors: 庞贺
Original assignee: 中兴通讯股份有限公司
Priority date: 2011-05-16
Filing date: 2012-03-22
Publication date: 2012-11-22
Also published as: CN102185686B; CN102185686A

Abstract

Disclosed are a method and network apparatus for adjusting the frequency based on IEEE 1588 protocol. The method comprises: a transparent clock(TC) device, according to the master clock information and locally stamped time information which are carried by a received IEEE 1588 protocol packet, calculates the frequency difference between itself and the master clock device; if the frequency difference satisfies the predetermined condition, the locally stamped frequency will be adjusted to the same frequency with the master clock information carried by the IEEE 1588 protocol packet using the frequency difference. The present invention improves frequency accuracy of TC device efficiently, and reduces cost at the same time.

Description

Method and network device for adjusting frequency based on IEEE 1588 protocol

Technical field

The present invention relates to the field of data communications, and in particular to a method and network device for adjusting frequency based on the IEEE 1588 protocol. The present invention is particularly applicable to the IEEE 1588 V1 protocol and the IEEE 1588 V2 protocol, and is applicable to one step (single-step clock) and two step (two Step clock) mode.

Background technique

The IEEE 1588 protocol is a precision clock synchronization protocol standard for network measurement and control systems. It uses the PTP (Precision Clock Synchronization) protocol with an accuracy of microseconds. At present, the intermediate devices in the network of the IEEE 1588 protocol are BC (Border Clock) devices and TC (transparent clock) devices. The TC devices are relatively simple in design, convenient in application, and have a small CPU load on the intermediate devices. The majority of digital communication manufacturers use. The TC device mainly implements the transparent transmission of the IEEE 1588 protocol in the IEEE 1588 protocol network, and the resident time of the IEEE 1588 protocol packet in the TC device is hit into the packet to ensure the final OC (Ordinary clock) or The accuracy of BC's time synchronization, so the accuracy of the TC dwell time is related to the accuracy of the entire network clock.

In order to ensure the accuracy of the TC dwell time, there are two main ways: 1. The entire network uses synchronous Ethernet technology, and the TC recovers the frequency through the Ethernet as the drive clock for the dwell time. As long as the line is not broken, you can always guarantee a stable clock. 2. The TC device is stamped with hardware to provide a stable frequency input, with a high-level crystal oscillator as input. But these two methods have their shortcomings: The first method requires the main clock to support synchronous Ethernet, providing a stable frequency output for the entire network. The 1588 protocol output port of the main clock must support synchronous Ethernet, and drive its own switching chip or PHY (Physical Layer) to ensure the frequency of the line output is stable. If a TC device in the network incorrectly selects the line recovery clock, it will cause the TC devices of the following nodes to lock at the wrong frequency and is not easy to find. The second method has a cost problem.

Summary of the invention

The technical problem to be solved by the embodiments of the present invention is to provide an adjustment frequency based on the IEEE 1588 protocol. Rate method and network device to effectively improve the frequency accuracy of the TC device.

In order to solve the above technical problem, an embodiment of the present invention provides a method for adjusting a frequency based on an IEEE 1588 protocol, including:

The transparent clock device calculates the frequency difference of the device relative to the main clock device according to the received master clock information and the local stamping time information carried in the IEEE 1588 protocol packet.

If it is determined that the frequency difference satisfies a predetermined condition, the frequency of the local stamp is adjusted to be the same frequency as the main clock information carried by the IEEE 1588 protocol packet by using the frequency difference.

The above method also has the following features: The transparent transmission clock device calculates the frequency difference of the device relative to the main clock device by the following formula: ((Tt2-Tt 1 )-(Tm2-Tml )) / (Tm2-Tml ) ,

Tml and Tm2 are the main clock information carried in the first and second IEEE1588 protocol messages, respectively, and Ttl and Tt2 are the devices that the first and second IEEE1588 protocol messages are received. Time information.

The above method further has the following features: if the transparent transmission clock device is an intermediate-level transparent transmission clock device that is not directly connected to the main clock device, the transparent transmission clock device calculates a frequency difference between the device and the main clock device. Previously, it also included:

The time information of the local stamp is corrected according to the dwell time carried by the IEEE 1588 protocol message.

The above method further has the following features: the step of the transparent transmission clock device determining that the frequency difference satisfies a predetermined condition comprises:

Determining that the frequency difference is greater than a threshold, or

Determining that the frequency difference is continuously preset a number of times greater than a threshold value.

The foregoing method has the following features: The IEEE 1588 protocol packet is a synchronization packet or a follow-up packet.

In order to solve the above problems, the present invention further provides a network device as a transparent transmission clock device, including:

a clock source module, configured to provide frequency information to the time stamp module; and after receiving the frequency difference output by the micro control module, adjusting the frequency information to the IEEE 1588 by using the frequency difference The main clock information carried in the protocol packet is the same frequency;

The timestamp module is configured to timestamp the IEEE 1588 protocol packet according to the frequency information provided by the clock source module after receiving the IEEE 1588 protocol packet;

The micro control module is configured to calculate a frequency difference of the device relative to the main clock device according to the main clock information carried in the IEEE 1588 protocol message and the time information of the local punctuation, and if it is determined that the frequency difference satisfies a predetermined condition, The frequency difference is output to the clock source module.

The above network device also has the following features:

The micro control module calculates the frequency difference of the device relative to the main clock device by the following formula:

((Tt2-Ttl)-(Tm2-Tml))/(Tm2-Tml),

The above network device also has the following features:

The micro control module, when the network device is an intermediate-level transparent transmission clock device that is not directly connected to the main clock device, is used for calculating a frequency difference of the device relative to the main clock device, according to the The resident time carried in the IEEE 1588 protocol packet corrects the time information of the local stamping.

The above network device also has the following features:

The micro control module determines that the frequency difference satisfies the predetermined condition, specifically: determining that the frequency difference is greater than a threshold, or determining that the frequency difference is continuously preset to be greater than a threshold.

The above network device also has the following features:

The IEEE 1588 protocol packet is a synchronization packet or a follow-up packet.

In summary, the embodiments of the present invention provide a method and a network device for adjusting a frequency based on the IEEE 1588 protocol, which can effectively improve the frequency accuracy of the TC device and reduce the cost. BRIEF abstract

1 is a schematic diagram of a network device as a TC device according to an embodiment of the present invention; 2 is a flowchart of a method for adjusting a frequency based on an IEEE 1588 protocol according to an embodiment of the present invention;

3 is a schematic diagram of a network topology according to an embodiment of the present invention;

4 is a flow chart of monitoring the quality of synchronous Ethernet frequency recovery according to an application example of the present invention. Preferred embodiment of the invention

Embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be noted that, in the case of no conflict, the features in the embodiments and the embodiments in the present application may be arbitrarily combined with each other.

FIG. 1 is a schematic diagram of a network device as a TC device according to an embodiment of the present invention. As shown in the figure, the following modules are included:

The clock source module is configured to provide frequency information to the TC device. In this embodiment, the frequency information is provided to the timestamp module. After receiving the frequency difference output by the micro control module, the frequency information is adjusted to be the frequency information by using the frequency difference. The same frequency as the main clock information carried in the IEEE 1588 protocol text;

a timestamp module, configured to timestamp the IEEE 1588 protocol packet according to the frequency information provided by the clock source module, and also to send the IEEE 1588 protocol packet to the TC device after receiving the IEEE 1588 protocol packet The dwell time Ti is hit in the message and then transmitted out;

Wherein, the micro control module calculates the frequency difference of the device relative to the main clock device by the following formula:

((Tt2-Ttl)-(Tm2-Tml))/(Tm2-Tml),

The micro control module is further used to calculate a frequency difference between the device and the main clock device before the network device is an intermediate-level transparent transmission clock device directly connected to the main clock device. The time information of the local stamping is corrected according to the dwell time carried by the IEEE 1588 protocol message. The IEEE 1588 protocol message is a SYNC (sync) message or a FOLLOWJJP (follow) message.

The clock source module of this embodiment can use a crystal oscillator that does not require high precision performance.

Generally, in the networking, there are only one or two master clocks in the entire network. In the network, the device that sends the IEEE1588 protocol packet to the next-level device has two models, BC and TC. The TC device in this embodiment may be a PTN. (Packet Transport Network), switch, router, base station, etc. Network node device that can transparently transmit IEEE1588 protocol packets.

2 is a flow chart of a method for adjusting a frequency based on an IEEE 1588 protocol according to an embodiment of the present invention. As shown in FIG. 2, the method includes:

S10. The TC device calculates a frequency difference between the master clock information and the master clock device according to the received master clock information and the local stamping time information carried in the IEEE 1588 protocol packet.

S20. If the TC device determines that the frequency difference satisfies a predetermined condition, the frequency of the local puncture is adjusted to be the same frequency as the main clock information carried in the IEEE 1588 protocol packet by using the frequency difference.

The method utilizes the SYNC and FOLLOW-UP protocols of the original IEEE1588 protocol, and does not require the TC device to transmit redundant messages without modifying the protocol, and can correct the frequency of the TC device while reducing the redundant packets of the link.

FIG. 3 is a schematic diagram of a network topology according to an embodiment of the present invention, as shown in the figure,

The master clock device transmits the IEEE1588 message to the node in the network that needs to be timed through the TC device. The main clock device sends a SYNC message or a FOLLOW-UP message at the time of Tmi, and the Tmi time stamp is carried in the SYNC message or the FOLLOW-UP message.

The first-level TC1 device (the TC device directly connected to the main clock) receives the SYNC message, hits the local timestamp Tti, and simultaneously puts the dwell time Ti in the SYNC message, and records the SYNC message or the FOLLOWJJP message. Time Tmi. The first level TC1 device calculates the frequency error of the local TC through the collected Tmi and Tti. The calculation formula is as follows:

((Tt2-Ttl)-(Tm2-Tml))/(Tm2-Tml),

The frequency offset of the TC device relative to the main clock device per unit time is obtained, and then the local frequency is adjusted to be the same frequency as the main clock.

The second-level TC2 device (intermediate TC device not directly connected to the main clock) receives the TC1 device The transparent SYNC message is also time-stamped Ttti, the Ttti time is corrected by the dwell time Ti of the SYNC message, the corrected Ttti=Ttti-Ti, and the local TC is calculated by the collected Tmi and the corrected Ttti. Frequency error, frequency adjustment.

And so on, all TCs after the third level.

4 is a flow chart of monitoring the quality of synchronous Ethernet frequency recovery according to an application example of the present invention, as shown in FIG. 4:

First, the synchronous Ethernet is turned on, and the frequency of the TC device is recovered through the Ethernet.

Step 101: The TC device receives the IEEE1588 protocol.

Step 102: The TC device determines whether the IEEE1588 protocol packet is a SYNC packet or

FOLLOW - UP message, if yes, then go to step 103, if not, then go to step 101;

Step 103: The TC device calculates a calculated frequency offset of the device relative to the main clock device according to the received master clock information carried by the IEEE 1588 protocol packet and the local stamping time information.

Step 104: The TC device determines whether the frequency deviation of the continuous N times is greater than a threshold. If yes, the process proceeds to step 105. If not, the synchronization trust is set, the detection is continued, and the process returns to step 101.

If the entire network is stable, the value of N can be set larger; if the network is very unstable, the value of N can be set smaller.

Step 105, the frequency deviation is continuously greater than the threshold for N times, and the frequency of the synchronous Ethernet recovery is abnormal, and the synchronous Ethernet untrusted mode is set, and then step 106 is performed;

If the current port frequency is abnormal, you can try other ports that are synchronized with Ethernet recovery. Return to step 101. If all the ports are abnormal, go to step 106.

Step 106: The TC device starts a frequency recovery mechanism, and uses the frequency difference to adjust the frequency of the local stamping to be the same frequency as the main clock information carried in the IEEE 1588 protocol.

During the process of starting the frequency recovery mechanism of the TC device, the synchronous Ethernet process can be automatically switched back to the synchronous Ethernet process by timing, or manually switched to the synchronous Ethernet process, and then the accuracy of the synchronous Ethernet is checked to meet the requirements. Continue to detect the synchronous Ethernet. In the case of low frequency stability, continue to set the frequency recovery mechanism and set the synchronous Ethernet untrusted mode. In the embodiment of the present invention, the time interval of the main clock is calculated by using the SYNC (synchronization) message or the FOLLOWJJP (following) message, the time stamp of the winner clock is received by the TC, the local time interval is calculated, and the frequency difference between the TC and the main clock is calculated by an algorithm. , Compensate the frequency of TC, realize the function of TC high-precision time stamping. The invention has the advantages that the network device is not required to support the synchronous Ethernet, and the high frequency stability can be ensured without using the high-precision constant temperature crystal oscillator, and the quality of the Ethernet recovery clock is detected for the network TC device using the synchronous Ethernet. When the synchronous Ethernet clock quality is not available, switch to the frequency adjustment state to ensure the accuracy and stability of the TC timestamp.

One of ordinary skill in the art will appreciate that all or a portion of the above steps may be accomplished by a program instructing the associated hardware, such as a read-only memory, a magnetic disk, or an optical disk. Alternatively, all or part of the steps of the above embodiments may also be implemented using one or more integrated circuits. Correspondingly, each module/unit in the above embodiment may be implemented in the form of hardware or in the form of a software function module. The invention is not limited to any specific form of combination of hardware and software.

The above is only a preferred embodiment of the present invention, and of course, the present invention may be embodied in various other embodiments without departing from the spirit and scope of the invention. Corresponding changes and modifications are intended to be included within the scope of the appended claims.

Industrial applicability

The embodiment of the invention provides a method and a network device for adjusting a frequency based on the IEEE 1588 protocol, which can effectively improve the frequency precision of the TC device and reduce the cost.

Claims

Claim

1. A method for adjusting a frequency based on an IEEE 1588 protocol, comprising:

The transparent clock device calculates the frequency difference between the transparent clock device and the main clock device according to the received master clock information and the local stamping time information carried in the IEEE 1588 protocol packet.

When it is judged that the frequency difference satisfies a predetermined condition, the frequency of the local stamp is adjusted by the frequency difference to be the same frequency as the main clock information carried in the IEEE 1588 protocol.

2. The method according to claim 1, wherein the transparent transmission clock device calculates a frequency difference of the device relative to the main clock device by:

((Tt2-Ttl)-(Tm2-Tml))/(Tm2-Tml),

Tml and Tm2 are the main clock information carried in the first and second IEEE1588 protocol messages respectively, and Ttl and Tt2 are respectively the first and second IEEE1588 protocols received by the transparent transmission clock device. Time stamping information.

The method according to claim 1 or 2, wherein, if the transparent transmission clock device is an intermediate-level transparent transmission clock device that is not directly connected to the main clock device, the transparent transmission clock device calculates the device Before the frequency difference of the main clock device, the method further includes:

4. The method according to claim 1, wherein the transparent transmission clock device determines that the frequency difference satisfies a predetermined condition comprises:

Determining that the frequency difference is greater than a threshold, or

5. The method according to claim 1 or 2 or 4, wherein

6. A network device as a transparent transmission clock device, comprising a clock source module, a time stamp module and a micro control module, wherein:

The clock source module is configured to: provide frequency information to the time stamp module; and after receiving the frequency difference output by the micro control module, adjust the frequency information to the IEEE by using the frequency difference The primary clock information carried in the 1588 protocol packet is the same as the frequency;

The timestamp module is configured to: timestamp the IEEE 1588 protocol packet according to the frequency information provided by the clock source module after receiving the IEEE 1588 protocol packet;

The micro control module is configured to: calculate a frequency difference of the transparent clock device relative to the main clock device according to the main clock information carried in the IEEE 1588 protocol packet and the time information of the local stamping, when determining the frequency difference The predetermined condition is satisfied, and the frequency difference is output to the clock source module.

7. The network device according to claim 6, wherein

The micro control module is configured to calculate a frequency difference of the transparent transmission clock device relative to the main clock device by:

((Tt2-Ttl)-(Tm2-Tml))/(Tm2-Tml),

8. The network device according to claim 6 or 7, wherein

The micro control module is further configured to: before the network device is an intermediate-level transparent transmission clock device directly connected to the main clock device, before calculating a frequency difference between the device and the main clock device, according to the The resident time carried in the IEEE 1588 protocol packet corrects the time information of the local stamping.

9. The network device according to claim 6, wherein

The micro control module is further configured to determine that the frequency difference satisfies a predetermined condition in the following manner: determining that the frequency difference is greater than a threshold value, or determining that the frequency difference is continuously preset to be greater than a threshold value.

10. The network device according to claim 6 or 7 or 9, wherein