CN110933096A - Software-defined network time service system and time service method - Google Patents

Software-defined network time service system and time service method Download PDF

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Publication number
CN110933096A
CN110933096A CN201911236057.0A CN201911236057A CN110933096A CN 110933096 A CN110933096 A CN 110933096A CN 201911236057 A CN201911236057 A CN 201911236057A CN 110933096 A CN110933096 A CN 110933096A
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time
data packet
timestamp
network element
client
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李洪星
寿国础
薛俊礼
李登魁
张晓东
胡怡红
刘雅琼
郭志刚
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Beijing University of Posts and Telecommunications
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Beijing University of Posts and Telecommunications
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L69/00—Network arrangements, protocols or services independent of the application payload and not provided for in the other groups of this subclass
    • H04L69/28—Timers or timing mechanisms used in protocols

Abstract

The embodiment of the invention provides a software-defined network time service system and a time service method, wherein the system comprises: the time service system comprises a time service controller, a time server, a time client and a plurality of network elements, wherein the time client is used for sending a request data packet to the time server; the network element is used for forwarding the request data packet and sending a third time data frame to the time service controller, the time server is used for sending a response data packet to the time client and sending a second time data frame to the time service controller, the network element is also used for sending a fourth time data frame to the time service controller, the time client is also used for sending a first time data frame to the time service controller, the time service controller is used for calculating a time deviation value between the time server and the time client and sending the second time service data packet with the time deviation value to the time client; the time client is also used for correcting the local clock according to the time deviation value. The embodiment of the invention can improve the network time service precision.

Description

Software-defined network time service system and time service method
Technical Field
The invention relates to the technical field of network time synchronization, in particular to a software-defined network time service system and a time service method.
Background
In the prior art, a network time service system generally includes a time client, a plurality of network elements and a time server, and time synchronization is realized between the time server and the time client through protocol interaction. Taking an NTP (Network Time protocol) system as an example, a Time client first sends a request data packet and records a first timestamp of the request data packet leaving the Time client, the request data packet is forwarded by a plurality of Network elements and arrives at a Time server, and then the Time server sends a response data packet, which includes a second timestamp of the request data packet arriving at the Time server and a third timestamp of the response data packet leaving the Time server, the response data packet is forwarded by the plurality of Network elements and arrives at the Time client, and the Time client records a fourth timestamp of the response data packet arriving at the Time client. Under the condition that the network time delay between the request data packet transmitted from the time client to the time client (uplink) and the network time delay between the response data packet transmitted from the time server to the time client (downlink) are the same, the time client calculates the time deviation value between the time client and the time server according to the recorded first time stamp, the fourth time stamp, the second time stamp and the third time stamp carried in the response data packet, and corrects the local clock according to the time deviation value. PTP (Precision Time Protocol) system Protocol procedures are similar to NTP.
In fact, the uplink and downlink network time delays are often unequal, and PDVs (Packet data delays) are often present, so that the time deviation value calculated according to the method proposed in the prior art has a deviation from the actual time deviation value, which affects the time service precision.
Disclosure of Invention
The embodiment of the invention aims to provide a software-defined network time service system and a software-defined network time service method, which can improve the network time service precision. The specific technical scheme is as follows:
in a first aspect, an embodiment of the present invention provides a software-defined network time service system, where the system includes: the time service system comprises a time service controller, a time server and a time client which are respectively in communication connection with the time service controller, and a plurality of network elements which are sequentially in communication connection between the time server and the time client, wherein the network elements are respectively in communication connection with the time service controller;
the time client is used for sending a request data packet to the time server;
the network element is configured to forward the request data packet and send a third time data frame to the time service controller, where the third time data frame carries a first time stamp when the request data packet arrives at the network element and a second time stamp when the request data packet leaves the network element;
the time service controller is configured to obtain a time service path through a global view of an SDN controller, and receive the third time data frame sent by each network element in the time service path, where the global view is used to describe a topological relationship among the time service controller, the time server, the time client, and the plurality of network elements in the SDN;
the time server is configured to receive the request data packet forwarded by the network element, send a response data packet to the time client, and send a second time data frame to the time service controller, where the second time data frame carries a sixth timestamp of the request data packet arriving at the time server and a seventh timestamp of the response data packet leaving the time server;
the network element is further configured to forward the response data packet, and send a fourth time data frame to the time service controller, where the fourth time data frame carries a third timestamp of the arrival of the response data packet at the network element and a fourth timestamp of the departure of the response data packet from the network element;
the time service controller is configured to receive the second time data frame and the fourth time data frame sent by each network element in the global view;
the time client is further configured to receive the response data packet forwarded by the network element, and send a first time data frame to the time service controller, where the first time data frame carries a fifth timestamp of the request data packet leaving the time client and an eighth timestamp of the response data packet arriving at the time client;
the time service controller is further configured to receive the first time data frame, calculate the time offset value between the time server and the time client according to the first time stamp, the second time stamp, the third time stamp, the fourth time stamp, the fifth time stamp, the sixth time stamp, the seventh time stamp, and the eighth time stamp, and send a second time service data packet carrying the time offset value to the time client;
and the time client is also used for receiving the second time service data packet and correcting a local clock according to the time deviation value.
Optionally, the network element is further configured to:
recording the first timestamp of the request data packet arriving at the network element, and adding the first timestamp to the three-time data frame; recording the second timestamp of the request data packet leaving the network element, and adding the second timestamp to the third time data frame; recording the third timestamp of the response data packet arriving at the network element, and adding the third timestamp to the fourth time data frame; and recording the fourth time stamp of the response data packet leaving the network element, and adding the fourth time stamp to the fourth time data frame.
Optionally, the time client is further configured to:
after the request data packet is sent to the time server, recording the fifth timestamp of the request data packet leaving the time client, and adding the fifth timestamp to the first time data frame; the time client is further configured to record an eighth timestamp that the response packet arrives at the time client after receiving the response packet forwarded by the network element, and add the eighth timestamp to the first time data frame.
Optionally, the time server is further configured to:
after receiving the request data packet forwarded by the network element, recording the sixth timestamp of the request data packet arriving at the time server, and adding the sixth timestamp to the second time data frame; the time server is further configured to record the seventh timestamp that the response packet leaves the time server after sending the response packet to the time client, and add the seventh timestamp to the second time data frame.
Optionally, the time service controller is further configured to:
calculating a total time delay of a first network element by using a first preset expression, where the total time delay of the first network element is a time delay generated when the request packet passes through all network elements in the global view, and the first preset expression is:
dSync＝[TEgress(1)-TIngress(1)]+…+[TEgress(N)-TIngress(N)]
in the formula (d)SyncRepresenting a total time delay, T, of said first network elementEgress(1) Said second timestamp, T, representing a first one of all network elementsIngress(1) Said first timestamp, T, representing a first one of all network elementsEgress(N) said second timestamp representing the Nth of said network elements in all network elements,TIngress(N) representing said first timestamp of the nth of said network elements among all network elements, N being the total number of said network elements;
calculating a second network element total time delay by using a second preset expression, where the second network element total time delay is a time delay generated when the response data packet passes through all network elements in the global view, and the second preset expression is as follows:
dDelay_req＝[TE(1)-TIn(1)]+…+[TE(N)-TIn(N)]
in the formula (d)Delay_reqRepresenting a total time delay, T, of said second network elementE(1) Said fourth timestamp, T, representing a first one of all network elementsIn(1) Said third timestamp, T, representing a first one of all network elementsE(N) said fourth timestamp, T, representing the Nth of all network elementsIn(N) said third timestamp for the nth of all network elements, N being the total number of said network elements;
calculating the time compensation value by using a third preset expression, wherein the third preset expression is as follows:
Figure BDA0002304905200000041
in the formula (d)cRepresenting said time compensation value, dSyncRepresenting the total delay of said first network element, dDelay_reqRepresenting the total time delay of the second network element;
and calculating the time deviation value according to the time compensation value, the fifth time stamp, the sixth time stamp, the seventh time stamp and the eighth time stamp.
Optionally, the time service controller is further configured to:
calculating the time deviation value by using a fourth preset expression, wherein the fourth preset expression is as follows:
Figure BDA0002304905200000042
wherein offset represents the time offset value, t2Represents the sixth timestamp, t1Represents the fifth time stamp, t3Represents the seventh timestamp, t4Represents the eighth time stamp, dcRepresenting the time compensation value.
In a second aspect, an embodiment of the present invention provides a software-defined network time service method, which is applied to any one of the software-defined network time service systems described above, where the system includes: the time service system comprises a time service controller, a time server and a time client which are respectively in communication connection with the time service controller, and a plurality of network elements which are sequentially in communication connection between the time server and the time client, wherein the network elements are respectively in communication connection with the time service controller;
the method comprises the following steps:
the time client sends a request data packet to the time server;
the network element forwards the request data packet and sends a third time data frame to the time service controller, wherein the third time data frame carries a first time stamp when the request data packet arrives at the network element and a second time stamp when the request data packet leaves the network element;
the time service controller is configured to obtain a time service path through a global view of an SDN controller, and receive the third time data frame sent by each network element in the time service path, where the global view is used to describe a topological relationship among the time service controller, the time server, the time client, and the plurality of network elements in the SDN;
the time server receives the request data packet forwarded by the network element, sends a response data packet to the time client, and sends a second time data frame to the time service controller, wherein the second time data frame carries a sixth timestamp of the request data packet arriving at the time server and a seventh timestamp of the response data packet leaving the time server;
the network element forwards the response data packet and sends a fourth time data frame to the time service controller, wherein the fourth time data frame carries a third timestamp of the arrival of the response data packet at the network element and a fourth timestamp of the departure of the response data packet from the network element;
the time service controller receives the second time data frame and the fourth time data frame sent by each network element in the global view;
the time client receives the response data packet forwarded by the network element and sends a first time data frame to the time service controller, wherein the first time data frame carries a fifth timestamp of the request data packet leaving the time client and an eighth timestamp of the response data packet arriving at the time client;
the time service controller receives the first time data frame, calculates the time offset value between the time server and the time client according to the first time stamp, the second time stamp, the third time stamp, the fourth time stamp, the fifth time stamp, the sixth time stamp, the seventh time stamp and the eighth time stamp, and sends a second time service data packet carrying the time offset value to the time client;
and the time client receives the second time service data packet and corrects a local clock according to the time deviation value.
Optionally, the method further comprises: the network element records the first time stamp of the request data packet reaching the network element and adds the first time stamp to the three-time data frame; recording the second timestamp of the request data packet leaving the network element, and adding the second timestamp to the third time data frame; recording the third timestamp of the response data packet arriving at the network element, and adding the third timestamp to the fourth time data frame; and recording the fourth time stamp of the response data packet leaving the network element, and adding the fourth time stamp to the fourth time data frame.
Optionally, the method further comprises: after the time client sends the request data packet to the time server, recording a fifth timestamp of the request data packet leaving the time client, and adding the fifth timestamp to the first time data frame; and after receiving the response data packet forwarded by the network element, the time client records an eighth timestamp of the response data packet reaching the time client, and adds the eighth timestamp to the first time data frame.
Optionally, the method further comprises: after receiving the request data packet forwarded by the network element, the time server records the sixth timestamp of the request data packet reaching the time server, and adds the sixth timestamp to the second time data frame; and after sending the response data packet to the time client, the time server records the seventh timestamp of the response data packet leaving the time server, and adds the seventh timestamp to the second time data frame.
Optionally, the step of receiving, by the time service controller, the first time data frame, and calculating the time offset value between the time server and the time client according to the first time stamp, the second time stamp, the third time stamp, the fourth time stamp, the fifth time stamp, the sixth time stamp, the seventh time stamp, and the eighth time stamp includes:
the time service controller calculates a first network element total time delay by using a first preset expression, where the first network element total time delay is a time delay generated when the request data packet passes through all network elements in the global view, and the first preset expression is:
dSync＝[TEgress(1)-TIngress(1)]+…+[TEgress(N)-TIngress(N)]
in the formula (d)SyncRepresenting a total time delay, T, of said first network elementEgress(1) Said second timestamp, T, representing a first one of all network elementsIngress(1) Representing the first of all network elementsSaid first time stamp of the element, TEgress(N) said second timestamp, T, representing the Nth of said network elements among all network elementsIngress(N) representing said first timestamp of the nth of said network elements among all network elements, N being the total number of said network elements;
the time service controller calculates a second network element total time delay by using a second preset expression, where the second network element total time delay is a time delay generated when the response data packet passes through all network elements in the global view, and the second preset expression is as follows:
dDelay_req＝[TE(1)-TIn(1)]+…+[TE(N)-TIn(N)]
in the formula (d)Delay_reqRepresenting a total time delay, T, of said second network elementE(1) Said fourth timestamp, T, representing a first one of all network elementsIn(1) Said third timestamp, T, representing a first one of all network elementsE(N) said fourth timestamp, T, representing the Nth of all network elementsIn(N) said third timestamp for the nth of all network elements, N being the total number of said network elements;
the time service controller calculates the time compensation value by using a third preset expression, wherein the third preset expression is as follows:
Figure BDA0002304905200000071
in the formula (d)cRepresenting said time compensation value, dSyncRepresenting the total delay of said first network element, dDelay_reqRepresenting the total time delay of the second network element;
and the time service controller calculates the time deviation value according to the time compensation value, the fifth time stamp, the sixth time stamp, the seventh time stamp and the eighth time stamp.
Optionally, the step of calculating, by the time service controller, the time offset value according to the time compensation value, the fifth timestamp, the sixth timestamp, the seventh timestamp, and the eighth timestamp includes: the time service controller calculates the time deviation value by using a fourth preset expression, wherein the fourth preset expression is as follows:
Figure BDA0002304905200000072
wherein offset represents the time offset value, t2Represents the sixth timestamp, t1Represents the fifth time stamp, t3Represents the seventh timestamp, t4Represents the eighth time stamp, dcRepresenting the time compensation value.
In the software-defined network time service system and the time service method provided by the embodiment of the invention, the time service controller can receive a third time data frame and a fourth time data frame sent by a plurality of network elements, the third time data frame carries a first time stamp of a request data packet arriving at the network element and a second time stamp of the request data packet leaving the network element, the time delay generated when the request data packet and the response data packet pass through the network elements can be determined and the time delay difference can be calculated through the second data frame and the first data frame, the time service controller can calculate the time deviation value between the time client and the time server according to the third time data frame and the fourth time data frame sent by the plurality of network elements, the first time data frame sent by the time client and the second time data frame sent by the time server, the second time service data packet carrying the time deviation value is sent to the time client, and the time client can correct the local clock according to the time deviation value. When the time deviation value is calculated, the time deviation value calculation method and the time deviation value calculation device fully consider the situation that the time delay generated by the network element is different when the request data packet is transmitted between the time client and the time server and when the response data packet is transmitted between the time server and the time client, so that the time deviation value calculated by the time deviation value calculation method and the time deviation value calculation device are closer to the real time deviation value, and the network time service precision can be improved. Of course, not all of the advantages described above need to be achieved at the same time in the practice of any one product or method of the invention.
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In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.
Fig. 1 is a schematic structural diagram of a software-defined network time service system according to an embodiment of the present invention;
fig. 2 is a schematic structural diagram of a network element according to an embodiment of the present invention;
fig. 3 is a signaling interaction diagram of a software-defined network timing system according to an embodiment of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
In order to better describe the software-defined network time service system provided by the embodiment of the present invention, the following contents are explained first:
the request data packet and the response data packet are both data packets transmitted between the time client and the time server, and the first time service data packet and the second time service data packet are both data packets transmitted between the time service controller and the time client.
The third time data frame and the fourth time data frame are both data frames transmitted between the network element and the time service controller, the first time data frame is a data frame transmitted between the time client and the time service controller, and the second time data frame is a data frame transmitted between the time server and the time service controller.
The first timestamp is a timestamp of a request data packet arriving at the network element, the second timestamp is a timestamp of a request data packet leaving the network element, the third timestamp is a timestamp of a response data packet arriving at the network element, the fourth timestamp is a timestamp of a response data packet leaving the network element, the fifth timestamp is a timestamp of a request data packet leaving time client, the sixth timestamp is a timestamp of a request data packet arriving at the time server, the seventh timestamp is a timestamp of a response data packet leaving time server, and the eighth timestamp is a timestamp of a response data packet arriving at the time client.
As shown in fig. 1, an embodiment of the present invention provides a software-defined network time service system, where the system may include:
the time service system comprises a time service controller, a time server and a time client which are respectively in communication connection with the time service controller, and a plurality of network elements which are sequentially in communication connection between the time server and the time client, wherein the plurality of network elements are respectively in communication connection with the time service controller.
The time service controller may adjust the transmission of a Network time data packet according to information such as a topological relation of each hardware device in an SDN (Software Defined Network), a Network element delay, a clock state, and the like, control an operating state of each hardware device in the SDN, and ensure synchronization accuracy of time client synchronization.
The time server is a computing device with high computing power and capable of providing time services for a plurality of users, the time server may provide time services to the outside through a network, and may obtain a Coordinated Universal Time (UTC) time signal, where the UTC time signal may be obtained from a Global Navigation Satellite System (GNSS), or may be obtained by connecting to a UTC laboratory through an optical fiber, and the time server may convert the obtained UTC time signal into a network time data packet and send the network time data packet to a time client through the network.
The time client is a time-consuming device for providing time service for a terminal user, and the time client and the time server need to be simultaneously accessed into a network, so that the time client can obtain a network time data packet sent by the time server.
The network element is a data packet transmission device for forwarding a data packet transmitted between the time client and the time server, and may be, for example, a bridge, a switch, a router, or other devices.
And the time client is used for sending the request data packet to the time server.
The time client may first send a request data packet to the time server, where the request data packet may be a preset data packet, for example, a preset identifier is set in the preset data packet, and the preset identifier is an identifier for time service, as long as the network element and the time server that receive the request data packet can recognize the preset identifier and send a time data frame accordingly.
As an optional implementation manner of the embodiment of the present invention, after the time client sends the request packet to the time server, the time client may record a fifth timestamp of the request packet leaving the time client, and add the fifth timestamp to the first time data frame, a leaving timestamp field may be set in the first time data frame, and when the time client sends the request packet, and when the request packet reaches an exit of the time client, the time client may record a fifth timestamp of the request packet leaving the time client, and write the fifth timestamp into the leaving timestamp field in the first time data frame.
And the network element is used for forwarding the request data packet and sending a third time data frame to the time service controller.
The third time data frame carries a first time stamp of the request data packet arriving at the network element and a second time stamp of the request data packet leaving the network element.
As shown in fig. 2, as an optional implementation manner of the embodiment of the present invention, an arrival timestamp field and a departure timestamp field may be set in a third time data frame, when a network element forwards a request data packet, when the request data packet arrives at an entry of the network element, the network element may record a first timestamp that the request data packet arrives at the entry, and add the first timestamp to the third time data frame, that is, write the first timestamp into the arrival timestamp field in the third time data frame; when the request packet leaves the network element, that is, when the request packet reaches the network element exit, the network element may record a second timestamp that the request packet leaves the network element, and add the second timestamp to the third time data frame, that is, write the second timestamp into a leaving timestamp field in the third time data frame.
In addition, the third time data frame may also carry information such as an ID of the network element, a local oscillator characteristic, and the like, in addition to the first time stamp and the second time stamp.
And after the network element adds the first time stamp and the second time stamp to the third time data frame, the third time data frame can be sent to the time service controller.
It should be noted that, because the request packet is forwarded by the plurality of network elements when being transmitted between the time client and the time server, each network element may send the corresponding third time data frame to the time service controller.
And the time service controller is used for acquiring a time service path through a global view of the SDN controller and receiving a third time data frame sent by each network element in the time service path. In actual use, the SDN controller may obtain a global view of a network first, and then the timing controller obtains the global view through the SDN controller.
In the embodiment of the invention, the global view is used for describing a topological relation among a time service controller, a time server, a time client and a plurality of network elements in the SDN.
In practical application, the time service controller may receive a third time data frame of a network element that is not connected between the time client and the time server, and therefore, the global view may further include IDs of the network elements, and thus, after receiving the third time data frames sent by the plurality of network elements, the time service controller may determine whether the network element is a network element connected between the time client and the time server according to the IDs of the network elements.
And the time server is used for receiving the request data packet forwarded by the network element, sending a response data packet to the time client and sending a second time data frame to the time service controller.
The second time data frame carries a sixth timestamp of the arrival of the request data packet at the time server and a seventh timestamp of the departure of the response data packet from the time server.
It should be noted that the response packet may be identical to or different from the request packet.
As an optional implementation manner of the embodiment of the present invention, the time server may be further configured to record a sixth timestamp of the request packet arriving at the time server after receiving the request packet forwarded by the network element, and add the sixth timestamp to the second time data frame, and similarly, an arrival timestamp field and a departure timestamp field may also be set in the second time data frame, and write the sixth timestamp into the arrival timestamp field in the second time data frame. The time server may be further configured to record a seventh timestamp that the response packet leaves the time server after sending the response packet to the time client, and add the seventh timestamp to the second time data frame, that is, write the seventh timestamp into a leaving timestamp field in the second time data frame.
And the network element is also used for forwarding the response data packet and sending a fourth time data frame to the time service controller.
The fourth time data frame carries a third timestamp of the arrival of the response data packet at the network element and a fourth timestamp of the departure of the response data packet from the network element.
As an optional implementation manner of the embodiment of the present invention, as shown in fig. 2, when the network element forwards the response packet, the network element may further be configured to record a third timestamp that the response packet arrives at the network element, and add the third timestamp to the fourth time data frame, that is, write the third timestamp into an arrival timestamp field in the fourth time data frame; when the response packet leaves the network element, the network element may be configured to record a fourth timestamp that the response packet leaves the network element, and add the fourth timestamp to the fourth time data frame, that is, write the fourth timestamp into a leaving timestamp field in the fourth time data frame.
And the time service controller is used for receiving the second time data frame and a fourth time data frame sent by each network element in the global view.
The time service controller may be configured to receive the second time data frame sent by the time server and a plurality of fourth time data frames sent by each network element.
And the time client is also used for receiving the response data packet forwarded by the network element and sending a first time data frame to the time service controller.
The first time data frame carries a fifth time stamp of the client terminal requesting the departure time of the data packet and an eighth time stamp of the client terminal responding to the arrival time of the data packet.
As an optional implementation manner of the embodiment of the present invention, the time client is further configured to record an eighth timestamp of an arrival time of the response packet at the time client after receiving the response packet forwarded by the network element, and add the eighth timestamp to the first time data frame.
And the time service controller is also used for receiving the first time data frame, calculating a time deviation value between the time server and the time client according to the first time stamp, the second time stamp, the third time stamp, the fourth time stamp, the fifth time stamp, the sixth time stamp, the seventh time stamp and the eighth time stamp, and sending a second time service data packet carrying the time deviation value to the time client.
In the embodiment of the present invention, since the time service controller receives the third time data frame and the fourth time data frame sent by the multiple network elements, the time service controller may calculate a time delay generated when the request data packet passes through the network elements according to the first time stamp and the second time stamp carried by the multiple third time data frames, calculate a time delay generated when the response data packet passes through the network elements according to the third time stamp and the fourth time stamp carried by the multiple fourth time data frames, and calculate the time compensation value according to the obtained time delay, thereby obtaining the time offset value. In the process of calculating the time deviation value, the time delay generated when the request data packet passes through the network element and the time delay generated when the response data packet passes through the network element are fully considered, so the calculation precision of the time deviation value is higher, and the time service precision is higher.
As an optional implementation manner of the embodiment of the present invention, a first preset expression is used to calculate a total time delay of a first network element, where the total time delay of the first network element is a time delay generated when a request packet passes through all network elements in a global view, and the first preset expression is:
dSync＝[TEgress(1)-TIngress(1)]+…+[TEgress(N)-TIngress(N)]
in the formula (d)SyncRepresenting the total delay, T, of the first network elementEgress(1) Second time stamp, T, representing a first one of all network elementsIngress(1) A first time stamp, T, representing a first of all network elementsEgress(N) a second timestamp, T, representing the Nth of all network elementsIngress(N) represents a first timestamp of an nth network element of all network elements, N being the total number of network elements.
In this embodiment of the present invention, the first total delay of the network element may be total delay of an uplink of the network element or total delay of a downlink of the network element, and correspondingly, the second total delay of the network element may be total delay of a downlink of the network element or total delay of an uplink of the network element.
According to the difference value between the second time stamp and the first time stamp of each network element, the time delay generated when the request data packet passes through the network element can be obtained, and the time delays corresponding to the first network element to the Nth network element in all the network elements are added, so that the total time delay of the first network element can be obtained.
Calculating the total time delay of the second network element by using a second preset expression, wherein the total time delay of the second network element is the time delay generated when the response data packet passes through all network elements in the global view, and the second preset expression is as follows:
dDelay_req＝[TE(1)-TIn(1)]+…+[TE(N)-TIn(N)]
in the formula (d)Delay_reqRepresenting the total delay, T, of the second network elementE(1) Fourth timestamp, T, representing a first one of all network elementsIn(1) Third time stamp, T, representing a first one of all network elementsE(N) a fourth timestamp, T, representing the Nth of all network elementsIn(N) denotes the Nth network of all network elementsAnd a third timestamp of the element, wherein N is the total number of the network elements.
Calculating the time compensation value by using a third preset expression, wherein the third preset expression is as follows:
Figure BDA0002304905200000141
in the formula (d)cRepresents a time compensation value, dSyncRepresenting the total delay of the first network element, dDelay_reqRepresenting the total delay of the second network element. The difference value between the first network element total time delay generated when the request data packet passes through all the network elements and the second network element total time delay generated when the response data packet passes through all the network elements is calculated, and the quotient obtained by dividing the difference value by 2 is the time compensation value.
And calculating a time deviation value according to the time compensation value, the fifth time stamp, the sixth time stamp, the seventh time stamp and the eighth time stamp.
As an optional implementation manner of the embodiment of the present invention, the time service controller is further configured to:
calculating the time deviation value by using a fourth preset expression, wherein the fourth preset expression is as follows:
Figure BDA0002304905200000142
wherein offset represents a time offset value, t2Denotes a sixth time stamp, t1Denotes a fifth time stamp, t3Denotes a seventh time stamp, t4Denotes an eighth time stamp, dcRepresenting the time offset value.
And the time client is also used for receiving the second time service data packet and correcting the local clock according to the time deviation value.
And after receiving the second time service data packet with the time deviation value, the time client can correct the local clock according to the time deviation value.
It should be noted that, for the system in the embodiment of the present invention, the time client is configured to send a request packet, where the request packet is forwarded to the time server via multiple network elements, and the time server is configured to receive the request packet and send a response packet to the time client, where the response packet is forwarded to the time client via multiple network elements. In practical applications, the time server may also be configured to send a request packet, where the request packet arrives at the time client via forwarding of the plurality of network elements, and the time client is configured to receive the request packet and send a response packet to the time server, where the response packet arrives at the time server via forwarding of the plurality of network elements. In this case, the timing controller may calculate the time offset value using a fifth predetermined expression, where the fifth predetermined expression is:
Figure BDA0002304905200000143
wherein offset represents a time offset value, t2Denotes a sixth time stamp, t1Denotes a fifth time stamp, t4Denotes an eighth time stamp, t3Denotes a seventh time stamp, dcRepresenting the time offset value.
In the software-defined network timing system provided in the embodiment of the present invention, the timing controller is capable of receiving a third time data frame and a fourth time data frame sent by a plurality of network elements, the third time data frame carries a first timestamp for requesting a data packet to arrive at the network element and a second timestamp for requesting the data packet to leave the network element, the time delay generated when the request data packet passes through the network elements can be determined through the second data frame and the first data frame, the time service controller can calculate the time deviation value between the time client and the time server according to the third time data frame and the fourth time data frame sent by the network elements, the first time data frame sent by the time client and the second time data frame sent by the time server, the second time service data packet carrying the time deviation value is sent to the time client, and the time client can correct the local clock according to the time deviation value. When the time deviation value is calculated, the time deviation value calculation method and the time deviation value calculation device fully consider the situation that the time delay generated by the network element is different when the request data packet is transmitted between the time client and the time server and when the response data packet is transmitted between the time server and the time client, so that the time deviation value calculated by the time deviation value calculation method and the time deviation value calculation device are closer to the real time deviation value, and the network time service precision can be improved.
In addition, it should be noted that, in the embodiment of the present invention, the request data packet may be a preset data packet, and the preset data packet may carry an identifier for time service, that is, the request data packet may be a data packet based on a non-time protocol, and after the network element receives the request data packet, when it is recognized that the identifier for time service is carried in the request data packet, the request data packet may be forwarded to another network element, and a corresponding data frame may be sent to the time service controller.
Because the system provided by the embodiment of the invention can transmit the request data packet between the time server and the time client, the data packet based on the non-time protocol can also be used for realizing time service; in addition, in the embodiment of the invention, the time server and the time client only need to record the arrival or departure time of the request data packet, and do not need the processing of a higher-layer protocol, so the structures of the time server and the time client can be simplified.
The embodiment of the invention also provides a software-defined network time service system, which can comprise: the time service system comprises a time service controller, a time server and a time client which are respectively in communication connection with the time service controller, and a plurality of network elements which are sequentially in communication connection between the time server and the time client, wherein the plurality of network elements are respectively in communication connection with the time service controller.
And the time client is used for sending the request data packet to the time server and recording a fifth time stamp of the request data packet leaving the time client.
And the network element is used for forwarding the request data packet and sending a third time data frame to the time service controller, wherein the third time data frame carries a first time stamp of the request data packet reaching the network element and a second time stamp of the request data packet leaving the network element.
And the time service controller is used for acquiring a time service path through a global view of the SDN controller and receiving a third time data frame sent by each network element in the time service path, wherein the global view is used for describing a topological relation among the time service controller, a time server, a time client and a plurality of network elements in the SDN.
And the time server is used for receiving the request data packet forwarded by the network element and sending a response data packet to the time client.
The network element is further configured to forward the response data packet, and send a fourth time data frame to the time service controller, where the fourth time data frame carries a third timestamp indicating that the response data packet arrives at the network element and a fourth timestamp indicating that the response data packet leaves the network element.
And the time service controller is also used for receiving a fourth time data frame sent by each network element in the global view, calculating a time compensation value between the time server and the time client according to the first time stamp, the second time stamp, the third time stamp and the fourth time stamp, and sending a first time service data packet carrying the time compensation value to the time client.
In the embodiment of the present invention, the timing controller only needs to calculate the time compensation value, and does not need to calculate the time deviation value, and the calculation formula of the time compensation value here may be the same as that of the time compensation value in the foregoing embodiment.
And the time client is further used for receiving the response data packet, recording an eighth timestamp of the arrival time of the response data packet at the time client, carrying a sixth timestamp of the arrival time of the request data packet at the time server in the response data packet, and a seventh timestamp of the departure time of the response data packet from the time server, receiving the first time service data packet, calculating a time deviation value according to the time compensation value and the fifth timestamp, the sixth timestamp, the seventh timestamp and the eighth timestamp, and correcting the local clock according to the time deviation value.
In the embodiment of the invention, the response data packet carries a sixth timestamp of the request data packet arriving at the time server and a seventh timestamp of the response data packet leaving the time server, so that after the time client receives the response data packet, the time client can calculate the time offset value according to the sixth timestamp and the seventh timestamp carried by the response data packet, the seventh timestamp and the eighth timestamp recorded by the time client and the time compensation value. The calculation formula of the time deviation value here may be the same as that of the foregoing embodiment.
As an optional implementation manner of the embodiment of the present invention, the time client is further configured to send a request time data packet to the time service controller, where the request time data packet carries information of a request sending time compensation value, and after receiving the request time data packet, the time service controller may send a first time service data packet to the time client.
It should be further noted that, for the system in the embodiment of the present invention, the time client is configured to send a request packet, where the request packet is forwarded to the time server via multiple network elements, and the time server is configured to receive the request packet and send a response packet to the time client, where the response packet is forwarded to the time client via multiple network elements. In practical applications, the time server may also be configured to send a request packet, where the request packet arrives at the time client via forwarding of the plurality of network elements, and the time client is configured to receive the request packet and send a response packet to the time server, where the response packet arrives at the time server via forwarding of the plurality of network elements.
In addition, the request packet in the embodiment of the present invention may be a preset packet, or may also be a Network Time Protocol (NTP) packet, or a Precision Time Protocol (PTP) packet, that is, the embodiment of the present invention may be implemented by separating from a universal Time Protocol (NTP or PTP) to implement Network Time service, or may be implemented by implementing Network Time service based on a Time Protocol.
According to the software-defined network time service system provided by the embodiment of the invention, a time service controller calculates a time compensation value between a time server and a time client according to a third time data frame and a fourth time data frame sent by a plurality of network elements, and sends a first time service data packet to the time client, wherein the first time service data packet carries the time compensation value; and the time client responds to a seventh time stamp of the data packet leaving the time server, a fifth time stamp of the request data packet leaving the time client, an eighth time stamp of the request data packet reaching the time client and the time compensation value according to the time compensation value, calculates a time deviation value, and finally corrects a local clock according to the time deviation value, wherein a third time data frame carries the first time stamp of the request data packet reaching the network element and the second time stamp of the request data packet leaving the network element, and the time delay generated when the request data packet passes through the network element can be determined through the second data frame and the first data frame. When the time deviation value is calculated, the time deviation value calculation method and the time deviation value calculation device fully consider the situation that the time delay generated by the network element is different when the request data packet is transmitted between the time client and the time server and when the response data packet is transmitted between the time server and the time client, so that the time deviation value calculated by the time deviation value calculation method and the time deviation value calculation device are closer to the real time deviation value, and the network time service precision can be improved.
The embodiment of the invention provides a software-defined network time service method, which is applied to the software-defined network time service system and comprises the following steps: the time service system comprises a time service controller, a time server and a time client which are respectively in communication connection with the time service controller, and a plurality of network elements which are sequentially in communication connection between the time server and the time client, wherein the plurality of network elements are respectively in communication connection with the time service controller.
As shown in fig. 3, the method for network time service defined by software according to the embodiment of the present invention includes:
s101, the time client sends a request data packet to the time server.
S1021, the network element transmits the request data packet; s1022, the network element sends a third time data frame to the time service controller, where the third time data frame carries a first time stamp of the request data packet arriving at the network element and a second time stamp of the request data packet leaving the network element.
And S103, the time service controller acquires a time service path through a global view of the SDN controller, and receives a third time data frame sent by each network element in the time service path, wherein the global view is used for describing a topological relation among the time service controller, a time server, a time client and a plurality of network elements in the SDN.
S1041, the time server receives the request data packet forwarded by the network element and sends a response data packet to the time client; and S1042, the time server sends a second time data frame to the time service controller, and the second time data frame carries a sixth timestamp of the request data packet arriving at the time server and a seventh timestamp of the response data packet leaving the time server.
S1051, the network element transmits the response data packet; and S1052, the network element sends a fourth time data frame to the time service controller, where the fourth time data frame carries a third timestamp of the response data packet arriving at the network element and a fourth timestamp of the response data packet leaving the network element.
And S106, the time service controller receives the second time data frame and a fourth time data frame sent by each network element in the global view.
S107, the time client receives the response data packet forwarded by the network element and sends a first time data frame to the time service controller, wherein the first time data frame carries a fifth timestamp of the client requesting the departure time of the data packet and an eighth timestamp of the client when the response data packet arrives.
S1081, the time service controller receives the first time data frame, calculates a time deviation value between the time server and the time client according to the first time stamp, the second time stamp, the third time stamp, the fourth time stamp, the fifth time stamp, the sixth time stamp, the seventh time stamp and the eighth time stamp, and sends a second time service data packet with the time deviation value to the time client in S1082.
And S109, the time client receives the second time service data packet and corrects the local clock according to the time deviation value.
As an optional implementation manner of the embodiment of the present invention, the software-defined network time service method provided in the embodiment of the present invention may further include: the network element records a first time stamp of the request data packet reaching the network element, and adds the first time stamp to the three-time data frame; recording a second timestamp of the request data packet leaving the network element, and adding the second timestamp to a third time data frame; recording a third timestamp of the response data packet reaching the network element, and adding the third timestamp to a fourth time data frame; and recording a fourth time stamp of the response data packet leaving the network element, and adding the fourth time stamp to the fourth time data frame.
As an optional implementation manner of the embodiment of the present invention, the software-defined network time service method provided in the embodiment of the present invention may further include: after sending the request data packet to the time server, the time client records a fifth timestamp of the request data packet leaving the time client and adds the fifth timestamp to the first time data frame; and after receiving the response data packet forwarded by the network element, the time client records an eighth timestamp of the arrival time of the response data packet at the time client and adds the eighth timestamp to the first time data frame.
As an optional implementation manner of the embodiment of the present invention, the software-defined network time service method provided in the embodiment of the present invention may further include: after receiving the request data packet forwarded by the network element, the time server records a sixth timestamp of the arrival of the request data packet at the time server, and adds the sixth timestamp to the second time data frame; and after sending the response data packet to the time client, the time server records a seventh timestamp of the response data packet leaving the time server, and adds the seventh timestamp to the second time data frame.
As an optional implementation manner of the embodiment of the present invention, the step of receiving, by the time service controller, the first time data frame, and calculating a time offset value between the time server and the time client according to the first time stamp, the second time stamp, the third time stamp, the fourth time stamp, the fifth time stamp, the sixth time stamp, the seventh time stamp, and the eighth time stamp may include:
the time service controller calculates the total time delay of the first network element by using a first preset expression, the total time delay of the first network element is the time delay generated when the request data packet passes through all network elements in the global view, and the first preset expression is as follows:
dSync＝[TEgress(1)-TIngress(1)]+…+[TEgress(N)-TIngress(N)]
in the formula (d)SyncRepresenting the total delay, T, of the first network elementEgress(1) Second time stamp, T, representing a first one of all network elementsIngress(1) A first time stamp, T, representing a first of all network elementsEgress(N) a second timestamp, T, representing the Nth of all network elementsIngress(N) represents a first timestamp of an nth network element of all network elements, N being the total number of network elements.
The time service controller calculates the total time delay of the second network element by using a second preset expression, the total time delay of the second network element is the time delay generated when the response data packet passes through all network elements in the global view, and the second preset expression is as follows:
dDelay_req＝[TE(1)-TIn(1)]+…+[TE(N)-TIn(N)]
in the formula (d)Delay_reqRepresenting the total delay, T, of the second network elementE(1) Fourth timestamp, T, representing a first one of all network elementsIn(1) Third time stamp, T, representing a first one of all network elementsE(N) a fourth timestamp, T, representing the Nth of all network elementsIn(N) represents a third timestamp of an nth network element of all network elements, N being the total number of network elements.
The time service controller calculates a time compensation value by using a third preset expression, wherein the third preset expression is as follows:
Figure BDA0002304905200000201
in the formula (d)cRepresents a time compensation value, dSyncRepresenting the total delay of the first network element, dDelay_reqRepresenting the total delay of the second network element.
And the time service controller calculates a time deviation value according to the time compensation value, the fifth time stamp, the sixth time stamp, the seventh time stamp and the eighth time stamp.
As an optional implementation manner of the embodiment of the present invention, the step of calculating, by the time service controller, a time deviation value according to the time compensation value, the fifth timestamp, the sixth timestamp, the seventh timestamp, and the eighth timestamp includes:
the time service controller may calculate the time deviation value by using a fourth preset expression, where the fourth preset expression is:
Figure BDA0002304905200000202
wherein offset represents a time offset value, t2Denotes a sixth time stamp, t1Denotes a fifth time stamp, t3Denotes a seventh time stamp, t4Denotes an eighth time stamp, dcRepresenting the time offset value.
In the software-defined network time service method provided by the embodiment of the invention, the time service controller can receive a third time data frame and a fourth time data frame sent by a plurality of network elements, the third time data frame carries a first time stamp of a request data packet arriving at the network element and a second time stamp of the request data packet leaving the network element, the time delay generated when the request data packet passes through the network elements can be determined through the second data frame and the first data frame, the time service controller can calculate the time deviation value between the time client and the time server according to the third time data frame and the fourth time data frame sent by the network elements, the first time data frame sent by the time client and the second time data frame sent by the time server, the second time service data packet carrying the time deviation value is sent to the time client, and the time client can correct the local clock according to the time deviation value. When the time deviation value is calculated, the time deviation value calculation method and the time deviation value calculation device fully consider the situation that the time delay generated by the network element is different when the request data packet is transmitted between the time client and the time server and when the response data packet is transmitted between the time server and the time client, so that the time deviation value calculated by the time deviation value calculation method and the time deviation value calculation device are closer to the real time deviation value, and the network time service precision can be improved.
It is noted that, herein, relational terms such as first and second, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other identical elements in a process, method, article, or apparatus that comprises the element.
All the embodiments in the present specification are described in a related manner, and the same and similar parts among the embodiments may be referred to each other, and each embodiment focuses on the differences from the other embodiments. In particular, for the system embodiment, since it is substantially similar to the method embodiment, the description is simple, and for the relevant points, reference may be made to the partial description of the method embodiment.
The above description is only for the preferred embodiment of the present invention, and is not intended to limit the scope of the present invention. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention shall fall within the protection scope of the present invention.

Claims (10)

1. A software-defined network time service system, the system comprising: the time service system comprises a time service controller, a time server and a time client which are respectively in communication connection with the time service controller, and a plurality of network elements which are sequentially in communication connection between the time server and the time client, wherein the network elements are respectively in communication connection with the time service controller;
the time client is used for sending a request data packet to the time server;
the network element is configured to forward the request data packet and send a third time data frame to the time service controller, where the third time data frame carries a first time stamp when the request data packet arrives at the network element and a second time stamp when the request data packet leaves the network element;
the time service controller is configured to acquire a time service path through a global view of a Software Defined Network (SDN) controller, and receive the third time data frame sent by each network element in the time service path, where the global view is used to describe a topological relation among the time service controller, the time server, the time client, and the plurality of network elements in the SDN;
the time server is configured to receive the request data packet forwarded by the network element, send a response data packet to the time client, and send a second time data frame to the time service controller, where the second time data frame carries a sixth timestamp of the request data packet arriving at the time server and a seventh timestamp of the response data packet leaving the time server;
the network element is further configured to forward the response data packet, and send a fourth time data frame to the time service controller, where the fourth time data frame carries a third timestamp of the arrival of the response data packet at the network element and a fourth timestamp of the departure of the response data packet from the network element;
the time service controller is configured to receive the second time data frame and the fourth time data frame sent by each network element in the global view;
the time client is further configured to receive the response data packet forwarded by the network element, and send a first time data frame to the time service controller, where the first time data frame carries a fifth timestamp of the request data packet leaving the time client and an eighth timestamp of the response data packet arriving at the time client;
the time service controller is further configured to receive the first time data frame, calculate the time offset value between the time server and the time client according to the first time stamp, the second time stamp, the third time stamp, the fourth time stamp, the fifth time stamp, the sixth time stamp, the seventh time stamp, and the eighth time stamp, and send a second time service data packet carrying the time offset value to the time client;
and the time client is also used for receiving the second time service data packet and correcting a local clock according to the time deviation value.
2. The system of claim 1, wherein the network element is further configured to:
recording the first timestamp of the arrival of the request data packet at the network element, and adding the first timestamp to the third time data frame; recording the second timestamp of the request data packet leaving the network element, and adding the second timestamp to the third time data frame; recording the third timestamp of the response data packet arriving at the network element, and adding the third timestamp to the fourth time data frame; and recording the fourth time stamp of the response data packet leaving the network element, and adding the fourth time stamp to the fourth time data frame.
3. The system of claim 1, wherein the time client is further configured to:
after the request data packet is sent to the time server, recording the fifth timestamp of the request data packet leaving the time client, and adding the fifth timestamp to the first time data frame; the time client is further configured to record an eighth timestamp that the response packet arrives at the time client after receiving the response packet forwarded by the network element, and add the eighth timestamp to the first time data frame.
4. The system of claim 1, wherein the timeserver is further configured to:
after receiving the request data packet forwarded by the network element, recording the sixth timestamp of the request data packet arriving at the time server, and adding the sixth timestamp to the second time data frame; the time server is further configured to record the seventh timestamp that the response packet leaves the time server after sending the response packet to the time client, and add the seventh timestamp to the second time data frame.
5. The system of claim 1, wherein the timing controller is further configured to:
calculating a total time delay of a first network element by using a first preset expression, where the total time delay of the first network element is a time delay generated when the request packet passes through all network elements in the global view, and the first preset expression is:
dSync＝[TEgress(1)-TIngress(1)]+…+[TEgress(N)-TIngress(N)]
in the formula (d)SyncRepresenting a total time delay, T, of said first network elementEgress(1) Said second timestamp, T, representing a first one of all network elementsIngress(1) Said first timestamp, T, representing a first one of all network elementsEgress(N) said second timestamp, T, representing the Nth of said network elements among all network elementsIngress(N) representing said first timestamp of the nth of said network elements among all network elements, N being the total number of said network elements;
calculating a second network element total time delay by using a second preset expression, where the second network element total time delay is a time delay generated when the response data packet passes through all network elements in the global view, and the second preset expression is as follows:
dDelay_req＝[TE(1)-TIn(1)]+…+[TE(N)-TIn(N)]
in the formula (d)Delay_reqRepresenting a total time delay, T, of said second network elementE(1) Said fourth timestamp, T, representing a first one of all network elementsIn(1) Said third timestamp, T, representing a first one of all network elementsE(N) said fourth time representing the Nth of all network elementsTimestamp, TIn(N) said third timestamp for the nth of all network elements, N being the total number of said network elements;
calculating the time compensation value by using a third preset expression, wherein the third preset expression is as follows:
Figure FDA0002304905190000031
in the formula (d)cRepresenting said time compensation value, dSyncRepresenting the total delay of said first network element, dDelay_reqRepresenting the total time delay of the second network element;
and calculating the time deviation value according to the time compensation value, the fifth time stamp, the sixth time stamp, the seventh time stamp and the eighth time stamp.
6. The system of claim 1, wherein the timing controller is further configured to:
calculating the time deviation value by using a fourth preset expression, wherein the fourth preset expression is as follows:
Figure FDA0002304905190000032
wherein offset represents the time offset value, t2Represents the sixth timestamp, t1Represents the fifth time stamp, t3Represents the seventh timestamp, t4Represents the eighth time stamp, dcRepresenting the time compensation value.
7. A software-defined network time service method is applied to the software-defined network time service system according to any one of claims 1-6, and the system comprises: the time service system comprises a time service controller, a time server and a time client which are respectively in communication connection with the time service controller, and a plurality of network elements which are sequentially in communication connection between the time server and the time client, wherein the network elements are respectively in communication connection with the time service controller;
the method comprises the following steps:
the time client sends a request data packet to the time server;
the network element forwards the request data packet and sends a third time data frame to the time service controller, wherein the third time data frame carries a first time stamp when the request data packet arrives at the network element and a second time stamp when the request data packet leaves the network element;
the time service controller acquires a time service path through a global view of an SDN controller, and receives the third time data frame sent by each network element in the time service path, wherein the global view is used for describing a topological relation among the time service controller, the time server, the time client and the plurality of network elements in the SDN;
the time server receives the request data packet forwarded by the network element, sends a response data packet to the time client, and sends a second time data frame to the time service controller, wherein the second time data frame carries a sixth timestamp of the request data packet arriving at the time server and a seventh timestamp of the response data packet leaving the time server;
the network element forwards the response data packet and sends a fourth time data frame to the time service controller, wherein the fourth time data frame carries a third timestamp of the arrival of the response data packet at the network element and a fourth timestamp of the departure of the response data packet from the network element;
the time service controller receives the second time data frame and the fourth time data frame sent by each network element in the global view;
the time client receives the response data packet forwarded by the network element and sends a first time data frame to the time service controller, wherein the first time data frame carries a fifth timestamp of the request data packet leaving the time client and an eighth timestamp of the response data packet arriving at the time client;
the time service controller receives the first time data frame, calculates the time offset value between the time server and the time client according to the first time stamp, the second time stamp, the third time stamp, the fourth time stamp, the fifth time stamp, the sixth time stamp, the seventh time stamp and the eighth time stamp, and sends a second time service data packet carrying the time offset value to the time client;
and the time client receives the second time service data packet and corrects a local clock according to the time deviation value.
8. The method of claim 6, further comprising:
the network element records the first time stamp of the request data packet reaching the network element and adds the first time stamp to the three-time data frame; recording the second timestamp of the request data packet leaving the network element, and adding the second timestamp to the third time data frame; recording the third timestamp of the response data packet arriving at the network element, and adding the third timestamp to the fourth time data frame; and recording the fourth time stamp of the response data packet leaving the network element, and adding the fourth time stamp to the fourth time data frame.
9. The method of claim 6, further comprising:
after the time client sends the request data packet to the time server, recording a fifth timestamp of the request data packet leaving the time client, and adding the fifth timestamp to the first time data frame; and after receiving the response data packet forwarded by the network element, the time client records an eighth timestamp of the response data packet reaching the time client, and adds the eighth timestamp to the first time data frame.
10. The method of claim 6, further comprising:
after receiving the request data packet forwarded by the network element, the time server records the sixth timestamp of the request data packet reaching the time server, and adds the sixth timestamp to the second time data frame; and after sending the response data packet to the time client, the time server records the seventh timestamp of the response data packet leaving the time server, and adds the seventh timestamp to the second time data frame.
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