KR20090071923A - Method for synchronization using single timesync frame in bridged local area network and appratus thereof - Google Patents

Abstract

A method and an apparatus for synchronizing time of a mobile communication device and a bridge device using a single time sync frame are provided to reduce a delay time in a time control stage by receiving and transmitting time information directly between a network upper layer and a time synchronization layer. A time sync information provider(510) provides reference time information to a time sync layer while operating in a network upper layer. A grand master decision processor(541) performs the grand master decision by using the priority information. A time difference calculating unit calculates the time difference between adjacent devices. A transmission delay time measuring unit measures the time delay time between the apparatus and the adjacent device. A real time application unit(570) receives the time information controlled by using the measured time difference and the transmission delay time and synchronizes the time of the apparatus. The grand master decision processor, the time difference calculator, and the transmission time measuring unit belongs to the time synchronization layer that is a network lower layer. The grand master decision, the time difference measurement, and the transmission delay time measurement are performed by using the single time sync frame.

Description

Method of synchronizing time between a communication terminal and a bridge device using a single time sync frame in a synchronous ethernet and a device thereof

The present invention relates to a method for synchronizing each communication terminal and a bridge device using a single time sync frame in synchronous Ethernet. More specifically, the present invention provides a representative time between communication devices that should guarantee real time in a local area network. The present invention relates to a technique for determining a device and processing all real-time data in time-synchronized manner with all communication devices.

Synchronous Ethernet or Residential Ethernet or Audio / Video Bridging is a technology in progress at the Institute of Electrical and Electronics Engineers (IEEE) 802.1AVB. Synchronous Ethernet is a method of synchronizing a sender and a receiver using a time stamp in the physical layer of the Ethernet with respect to frame synchronization. The time stamp received by the physical layer is used as the reference time, and the new time is applied to all devices in consideration of the difference between the reference time of the sender, the reference time of the receiver, and the transmission delay time. As such, synchronous Ethernet is a next-generation network synchronization technology that can synchronize devices with more accurate time. Synchronous Ethernet's frame synchronization technology ensures precisely synchronized time for multimedia data that should be virtually jitter-free, such as video / audio. For frame synchronization in synchronous Ethernet, a grand master providing a reference reference time among the devices in the network is selected according to the priority of each device, and the reference reference time is provided to other devices in the same network.

Conventional Ethernet provides time synchronization throughout the network based on a single device including a Global Positioning System (GPS) or its own time generating device. Since there is no consideration of jitter or wander that affects the network while the packet is being transmitted, it is overlooked if there is a delay in the transmission packet. Jitter is the amount of change in the pulse signal over a short period of time that has not accumulated from the ideal time. And wonder is the amount of change over a period longer than jitter. Jitter and wonder increase in magnitude as they pass through each device in transit or when phase shifts of unwanted pulse signals occur on the transmission line. Conventional Ethernet can be used within a small office network such as a local area network (LAN) because a delay of less than 1 second occurs.

Therefore, there is a limit to the conventional Ethernet synchronization method applied to the Internet environment. Since the Internet environment can be called a set of LANs, there is more delay than a delay in seconds, and the probability of occurrence of an irregular delay increases according to network conditions. To ensure time synchronization for the Internet environment, Network Time Protocol (NTP) version 3, which is defined as a standard in STD 12 of the Internet Architecture Board (IAB) and Request For Comments (RFC) 1305, published by the Internet Engineering Task Force (IETF). I use it. Each individual device first contacts the world time server to synchronize the time of each individual device before sending packets to other devices over the Internet. The world time server operates on the basis of GMT (Greenwich Mean Time), and the time servers are divided among the countries and distributed evenly. When a reference time is received from a world time server, it first establishes time synchronization on the subnet to which each individual device belongs, then adjusts the local time of the individual device and ensures accurate synchronization up to milliseconds. Since NTP is a time synchronization procedure for the Internet, there is a limit to more accurate synchronization on a LAN. Therefore, we use SNTP (Simple NTP) procedure, a sub-concept of NTP, for more accurate time synchronization in narrow networks such as LAN.

1 is a view for explaining the operation of the SNTP according to the prior art.

As shown in FIG. 1, the SNTP is responsible for the synchronization procedure between the time server 110 and the time client 120. SNTP 130 operates in the Media Access Control (MAC) layer 150 and achieves more accurate time synchronization than NTP using a callback function. The callback function takes a packet transmitted from the upper layer and the packet by using a pointer to a buffer of a packet generated at the upper layer, the application layer, and the time information taken from the application layer to the MAC layer 150 as two parameters. The used time is used as the time stamp 160 of the physical layer. The time client 120 uses this information as its time stamp 160 and transmits it to the upper layer through the SNTP 130.

SNTP uses callback functions to provide better time synchronization than conventional Ethernet and Ethernet using NTP. However, due to the influence of jitter and wonder on the intermediate apparatus such as the switch 170 and the transmission line 180 between the time server and the time client, there is a problem in that the accuracy of synchronization is limited.

This problem may be defined by Equation 1 below.

은 타임 클라이언트(120)에서 패킷을 발생시켰을 때의 시간이고,

는 타임 클라이언트(120)에서 패킷을 보내어 타임 서버(110)가 패킷을 물리 계층에서 전송 받았을 때의 시간이다.

는 타임 클라이언트(120) 내의 발진소자에 대한 주파수 변화의 영향이다. 이 값은 발진소자 자체적인 정확도, 온도 등의 영향으로 인해 중심 주파수의 변동, 시간이 경과함에 따라 발진 소자 주파수 자체 특성의 변화 등이 있다.

는 두 장치 사이의 전송 중에 발생하는 지터나 원더의 영향을 말하며, 중간 노드의 처리 과정 및 전송 선로(180) 상에서 발생하는 지터나 원더로 이해할 수 있다. here,

Is the time when the packet is generated by the time client 120,

Is the time when the time client 120 sends the packet and the time server 110 receives the packet at the physical layer.

Is the effect of the frequency change on the oscillation element in the time client 120. This value includes the oscillation device's own accuracy, temperature fluctuations, and the oscillation device's frequency characteristics change over time.

Refers to the influence of jitter or wonder occurring during transmission between the two devices, and can be understood as jitter or wonder occurring on the process line of the intermediate node and on the transmission line 180.

That is, in the case of the conventional Ethernet or SNTP, there is no compensation for such a difference in time, so it cannot be used for hard real-time systems such as factory automation systems.

In order to solve this problem, a new synchronization method called IEEE 1588 Precision Time Protocol (PTP) has been proposed. IEEE 1588 PTP is a standard for a Precision Clock Synchronization Protocol for Networked Measurement and Control Systems. It is a protocol for equalizing time information of interconnected devices. IEEE 1588 PTP achieves accurate time synchronization by using the difference between the reference times of two devices and the transmission delay time that occurs when a packet is transmitted between the two devices. Therefore, recently, it has been used as a technique for synchronizing the time in the device that is in charge of the control of factory automation system using a robot.

2 is a view for explaining the operation of the IEEE 1588 PTP.

As shown in FIG. 2, there is a master device 210 that provides a reference time and a slave device 220 that establishes synchronization by synchronizing its time information with the master device in the network. The master device 210 synchronizes the slave device 220 at its own time, using Sync. Messages and Follow Up messages (231, 232, 233, 234). The master device 210 periodically transmits its synchronization information to all slave devices 220 in the network. The slave device 220 receives the Follow Up message 231 from the master device 210 to obtain a time difference and adjusts its own time (240). However, since there is no information on the transmission delay time between the two devices, accurate synchronization cannot be achieved. Accordingly, the slave device 220 transmits a Delay Request message 250 to the master device 210, and the master device 210 responds with a Delay Response message 260 by putting its current time in a message in response thereto. . As a result, the slave device 220 can know the transmission delay time. Next, the slave device 220 obtains its exact synchronization time using the Follow Up message 233 transmitted from the master device 210, and calculates its own time. Change using (270). The changed message is delivered to the upper layer of the physical layer in the same manner as SNTP so that the correct time is available to the application layer. Therefore, IEEE 1588 PTP can guarantee accurate synchronization by solving the above problems.

IEEE 1588 PTP can guarantee accurate synchronization in local area networks. Switches connected directly to the router synchronize their subnets using a single reference time, and then each individual device finally synchronizes using this synchronization information. As such, the IEEE 1588 synchronizes even the shortest individual device while synchronizing among several switches, so that the synchronization procedure is very complicated as shown in FIG. As a result, the complexity of the implementation increases.

In addition, when individual devices are connected by using multiple bridge devices, as shown in FIG. 2, the slave device 220 completes time adjustment and synchronizes itself to provide neighboring devices with the same time information as the master device 210. Therefore, a delay occurs in the time adjustment step, there is a problem that can not provide a time synchronization of less than microseconds.

3 is a diagram for describing a time synchronization procedure of IEEE 802.1AVB.

Each bridge device includes a time synchronization upper layer 310 providing time synchronization to a network upper layer and a time synchronization processor 320 for each port operating for each port of the bridge. The time synchronization upper layer 310 finally synchronizes time using the time synchronization information transmitted from the time synchronization processor 320 for each port. The time synchronization processor 320 for each port calculates a time synchronization difference by reflecting different transmission delay times from neighboring bridges. When the initial network is set up or there is a change of the grand master, the announce message 330 is transmitted to all the bridge and the terminal devices to the neighbor devices. At this time, the grand master is determined using the time synchronization information priority in the announce message 330. The device determined as the grand master (bridge) sends a sync message 34 containing a reference time to all devices in synchronous Ethernet in 10 ms periods, and all slave devices synchronize their time based on the information of this reference time. . For more accurate synchronization, each device sends a Pd_Req (Pdelay_Req: Propagation delay request) message 350, a Pd_Resp (Pdealy_Resp: Propagation delay response) message 360, and a Pd_Resp_Follow_Up (Pdelay_Resp_Follow_Up: Propagation delay response follow up) message 370. By using this method, the transmission delay time between neighboring devices is measured every 100ms. Instead of immediately processing the sync message 340 after receiving it, the wait time is briefly used using the Follow_Up message 380 to apply the measurement value of the transmission delay time. The intermediate slave writes a new time stamp and provides time synchronization information to the next neighboring slave.

Although time synchronization of IEEE 802.1AVB can provide more accurate time synchronization than IEEE 1588 PTP, it follows the concept of IEEE 1588 PTP and uses the message format used in more complicated network. Also, considering the situation of the local area network, this uses a lot of messages unnecessarily.

Thus, a plurality of control frames for the time synchronization of the IEEE 802.1AVB puts a lot of load in the synchronous Ethernet and the disadvantage that the processing time in the device for processing each control frame unnecessarily increases.

One embodiment of the present invention is to solve the above-described problems, and an object of the present invention is to provide a synchronous Ethernet layer structure in which a network upper layer and a time synchronization layer can directly exchange time information.

One embodiment of the present invention is to solve the above-described problem, and an object of the present invention is to provide a single time sync frame for time synchronization in synchronous Ethernet.

One embodiment of the present invention is to solve the above problems, to provide a method for time synchronization of synchronous Ethernet, determine the grand master, calculate the transmission delay time using a single time sync frame and time synchronization It aims to do it.

As a technical means for achieving the above-described technical problem, a time synchronization information providing unit for providing reference time information to the time synchronization layer while operating in a network upper layer, and a grand master decision processing unit for performing grand master determination using priority information A time difference calculator for calculating a time difference between the device and a neighboring device, a transmission delay time measuring unit for measuring a transmission delay time between the device and a neighboring device, and an adjustment using the measured time difference and the transmission delay time And a real-time application unit for receiving the received time information and synchronizing the time of the device, wherein the grand master decision processing unit, the time difference calculation unit, and the transmission time measuring unit belong to a time synchronization layer, which is a network lower layer, and uses a single time sync frame. Grand Master decision, time This measurement provides a synchronous Ethernet will provide time synchronization of devices that perform transmission delay time measurements.

In addition, the second aspect of the present invention is to generate a field group for the classification of the time sync frame, to create a field group for determining the grand master and to measure the time difference and the transmission delay time used for time synchronization It provides a method for generating a time sync frame comprising the step of generating a field group.

In addition, the third aspect of the present invention includes the steps of determining the grand master using the priority information, performing the time synchronization by measuring the reference time of the grand master, the inherent time and transmission delay time of each device, The priority information, the reference time of the grand master, and the transmission delay time are recorded in a single time sync frame and are exchanged between the grand master and the slave.

According to one of the problem solving means of the present invention described above, since the network upper layer and the time synchronization layer can directly exchange time information, the time synchronization step can be simplified to reduce the delay time in the time adjustment step.

In addition, according to one of the problem solving means of the present invention described above, since a time synchronization can be performed in a synchronous Ethernet using a single time sync frame, the number of transmission of frames for time synchronization is reduced, and the processing load and Link occupancy is reduced, which simplifies time synchronization.

Therefore, in synchronous Ethernet, each device can synchronize time more accurately and quickly, and has the effect of ensuring the real-time service is improved.

DETAILED DESCRIPTION Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention. In the drawings, parts irrelevant to the description are omitted in order to clearly describe the present invention, and like reference numerals designate like parts throughout the specification.

Throughout the specification, when a part is "connected" to another part, this includes not only "directly connected" but also "electrically connected" with another element in between. . In addition, when a part is said to "include" a certain component, which means that it may further include other components, except to exclude other components unless otherwise stated.

Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

4 is a block diagram of synchronous Ethernet according to an embodiment of the present invention.

As shown in FIG. 4, synchronous Ethernet according to an embodiment of the present invention includes a terminal device 410, a bridge device 420, and an Ethernet communication medium 430.

The terminal device 410 generates the real time data and the single time sync frame and processes the real time data and the single time sync frame received from another device.

A single time sync frame is one frame for time synchronization, which will be described later.

The bridge device 420 receives real-time data and a single time sync frame from each terminal device 410 and delivers the single-time sync frame to the neighboring terminal device 410 and the neighboring bridge device 420.

The bridge device 420 may include, for example, multiple ports, and is divided into a master port for delivering a single time sync frame to a neighboring device and a slave port for receiving and synchronizing time with a single time sync frame. Can be.

The Ethernet communication medium 430 connects the terminal device 410 and the bridge device 420 or connects the bridge device 420 and the bridge device 420.

Of each of the terminal devices 410 and the bridge devices 420 mentioned above, for example, one device serving to provide a reference synchronization time for the entire synchronous Ethernet becomes a grand master, and all other devices are timed. For synchronization, it is a slave that matches its time synchronization value with the grand master's time synchronization value.

5 is a block diagram of each layer of synchronous Ethernet according to an embodiment of the present invention.

As shown in FIG. 5, a layer of synchronous Ethernet according to an embodiment of the present invention may include, for example, a time synchronization information providing unit 510, a transport layer 520, a network layer 530, a time synchronization layer ( 540, data link layer 550 and physical layer 560, real-time application 570.

The time synchronization information providing unit 510 serves to provide reference time information while operating in a network upper layer.

The reference time information is information for time synchronization, and may include, for example, atomic time information, Global Positioning System (GPS) information, ground station information, NTP (Network Time Protocol) information, and the like. Means a radio station for wireless communication.

The transport layer 520 refers to a layer providing data transmission service, and the network layer 530 serves to provide connectivity and path selection between two systems located at different locations.

The time synchronization layer 540 records priority information and time synchronization information of each terminal device 410 and the bridge device 420, and the information is neighbored through the data link layer 550 and the physical layer 560. It serves to deliver to the device.

The priority information refers to information on priority for determining the grand master.

In addition, the time synchronization information may be transmitted to the time synchronization layer 540 without being affected by the transport layer 520 and the network layer 530, for example.

In other words, the reference time information provided by the time synchronization information providing unit 510 may be directly transmitted to the time synchronization layer 540.

On the other hand, the time synchronization layer 540 includes, for example, a grand master decision processing unit 541, a time difference calculation unit 542, and a transmission delay time measuring unit 543.

The grand master decision processing unit 541 determines priority information in a time sync frame received from a neighboring device, and then determines whether to operate as a grand master or a slave, and among the various ports, a master port and a slave port. It determines the operation of the furnace.

The time difference calculator 542 calculates a reference time difference between the neighboring device and its own reference time using the same time sync frame.

In addition, the transmission delay time measuring unit 543 measures the transmission delay time applied to each port. In this case, when performing the function of the intermediate bridge, the transmission delay time measuring unit 543 determines the reference time differently by measuring the transmission delay time of the medium for each port.

The data link layer 550 refers to a layer that provides various types of network services, and the physical layer 560 refers to a layer that determines an electrical signal standard for data transmission of a transmission medium and transmits data.

The real time application 570 receives the adjusted time information directly from the time synchronization layer 540 and synchronizes the time of the device.

In other words, the real-time application 570 may receive the adjusted time information directly from the time synchronization layer 540 without going through the network layer 530 and the transport layer 520.

In synchronizing the time, for example, when the device is the bridge device 420, the reference time may be determined differently by measuring the transmission delay time of the medium for each port in the time synchronization layer 540. In addition, the bridge device 420 may transmit time synchronization information to a neighboring device that is bite at a corresponding port with a reference time measured differently for each port.

The transmission delay time refers to a delayed time when a single time sync frame is transmitted from one device to a neighboring device, and a method of measuring the transmission delay time will be described later.

Hereinafter, a structure of a single time sync frame according to an embodiment of the present invention will be described with reference to FIG. 6.

6 is a structural diagram of a single time sync frame according to an embodiment of the present invention.

As illustrated in FIG. 6, a single time sync frame according to an embodiment of the present invention may be, for example, a frame loaded in a payload of an Ethernet frame, and may include 48 bytes, which is a minimum size of an Ethernet frame payload. .

A single time sync frame according to an embodiment of the present invention may include, for example, a protocol type field 601, a time sync type field 602, a version field 603, a frame count field 604, and a reservation field 605. ), Priority field 606, time identifier field 607, hop count field 608, port identifier field 609, transmission period field 610, grand time field 611, request side transmission A delay time field 612, a response side reception delay time field 613, and a response side transmission delay time field 614.

The protocol type field 601, the time sync type field 602, the version field 603, the frame count field 604, and the reservation field 605 are portions 620 for classifying time sync frames.

The protocol type field 601 is a frame used in synchronous Ethernet and can be distinguished from other Ethernet frames. For example, the protocol type field 601 may be 0x88F7.

The time sync type field 602 is a field for identifying a single time sync frame among frames used in synchronous Ethernet. For example, the time sync type field 602 may be 0x10, 0x11, or the like.

For example, when the time sync type field is 0x10, it may be used to provide information about a reference time for grand master and time synchronization, and when it is 0x11, it may be used to measure a transmission delay time.

The version field 603 refers to a field indicating information on a version of a single time sync frame, and may have a value such as 0x01.

The frame count field 604 is used as a unique value for distinguishing time sync frames. For example, each time a single time sync frame is generated and transmitted for each device, the frame count field 604 may have a value of 1 to 256. have.

The reservation field 605 is a field for recording a change in consideration of a change of a single time sync frame.

Meanwhile, the priority field 606, the time discriminator field 607, the hop count field 608, and the port discriminator field 609 are portions 630 for determining the grand master.

The priority field 606 is a field in which a priority for recording the grand master is recorded. The network administrator may, for example, set a high priority of a specific device so that the specific device becomes a grand master.

In the time distinguisher field 607, a uniquely determined value is recorded for each device, and is equal to the MAC address of each device. In other words, since the MAC addresses may be uniquely distinguished, each device may be distinguished from each other through this. In this case, for example, the FFFE after the Organizational Unique Identifier (oui) field represents a MAC address corresponding to IPv4 (Internet Protocol Version 4).

The hop count field 608 is used to be able to determine the path of shortest distance from the grand master. In the bridge device 420, if there are multiple paths according to various ports, time synchronization information transmitted to the path with the shortest hop count may be used. The value of the hop count field 608 may have a value of 0 to 255, for example.

The port identifier field 609 is used to distinguish if there are several ports in the bridge device 420. The bridge device 420 may include, for example, multiple ports, and is divided into a master port for delivering a single time sync frame to a neighboring device and a slave port for receiving and synchronizing time with a single time sync frame. Can be. In addition, the value of the port identifier field 609 may have a value of 1 to 256, for example.

In the transmission period field 610, a period value in which a single time sync frame is transmitted is recorded, and may be set differently according to a network state of synchronous Ethernet. The shorter the transmission period, the more accurate synchronization can be shown. However, the generation of many control frames increases the network congestion and complicates the calculation in the device. Therefore, an appropriate transmission period should be selected in consideration of the range of the synchronous Ethernet and the path length. The value of the transmission period field 610 may be set to 10 ms for time synchronization, and 100 ms for measurement of transmission delay time.

On the other hand, the grand time field 611, the request-side transmission delay time field 612, the response-side reception delay time field 613 and the response-side transmission delay time field 614 are time-synchronized, and the transmission delay time is measured. Part 640.

The grand time field 611 records a time value of recording a local time of the device determined as the grand master, and other devices may synchronize their time according to the grand time.

The request-side transmission delay time field 612 shows the time when the request-side slave port transmits a single time sync frame toward the neighboring responding master port in calculating the transmission delay time between the master port and the slave port between the devices. Is recorded.

The response side delay time field 613 records the time when the responding master port receives a single time sync frame transmitted from the requesting slave port.

The response side transmission delay time field 614 records the time at which the single time sync frame is delivered from the response master port to the request side slave port.

Hereinafter, a method of synchronizing time using a single time sync frame in synchronous Ethernet according to an embodiment of the present invention will be described with reference to FIG. 7.

7 is a flowchart illustrating a method of time synchronization using a single time sync frame in synchronous Ethernet according to an embodiment of the present invention.

First, when the first synchronous Ethernet network is established, a single time sync frame is used to determine a device to operate as a grand master among the devices, and also a port to operate as a grand port among several ports (S700).

The method of determining the grand master and the grand port will be described later.

Thereafter, neighboring devices transmit and receive a single time sync frame to each other (S702), and calculate a transmission delay time using the time value measured in the transmission and reception process (S704).

Thereafter, time synchronization is achieved using the grand time transmitted from the grand master, the device's own time, and the transmission delay time value determined in the above process (S706).

The method of calculating the transmission delay time and synchronizing the time will be described later.

Hereinafter, a method of determining a grand master according to an embodiment of the present invention will be described with reference to FIG. 8.

8 is a flowchart illustrating a method of determining a grand master according to an embodiment of the present invention.

As shown in FIG. 8, when the first synchronous Ethernet is started to determine the grand master, all the terminal devices 410 and the bridge devices 420 in the synchronous Ethernet transmit a single time sync frame (S800).

Thereafter, each device compares the priority and time discriminator of the single time sync frame while transmitting and receiving a single time sync frame with a neighboring device, and determines whether the grand master determination condition is satisfied (S802).

The above grand master determination condition means that the receiving side can be the grand master when the receiving side priority is higher than the transmitting side priority and the receiving time separator is lower than the transmitting time separator.

If the determination result (S802), the receiving side priority is high, and the receiving time discriminator is low, the receiving device is operated as a grand master (S804), the determination result (S802) receiving priority is low, the receiving side If the time discriminator is high, the receiving device operates as a slave (S806).

If the receiving device operates as a grand master (S804), it is determined whether a new device has been added afterwards (S808).

If no new device is added as a result of the determination (S808), the receiving device continues to operate as a grand master (S804), and if a new device is added (S808), the step S802 is repeated again. The grand master is determined (S802).

On the other hand, when the receiving side device operates as a slave (S806), it is determined whether a single time sync frame has not been received more than three times (S810).

As a result of the determination (S810), if a single time sync frame is not received three or more times, all devices transmit a single time sync frame again (S800), and again determine the grand master, and the determination result (S810), single If the time sync frame is not received less than three times, it is determined whether a new device has been added (S812).

As a result of the determination (S812), when no new device is added, the receiving device continues to operate as a slave (S806). When the determination result (S812) is added a new device, the process is repeated again and again. The grand master is determined (S802).

Hereinafter, a method of determining a master port in a bridge device according to an embodiment of the present invention will be described with reference to FIG. 9.

9 is a flowchart illustrating a method of determining a master port in a bridge device according to an embodiment of the present invention.

As shown in FIG. 9, it is determined whether a port in the bridge device is a port that has received the lowest hop count (S900).

As a result of the determination (S900), when the port is the port that receives the lowest port, the operation is a master port (S902), and when the port is not the port that receives the lowest port, it operates as a slave port ( S904).

The embodiment shown in FIG. 9 may be performed together with the embodiment shown in FIG. 8 when determining the grand master in the intermediate bridge device.

Hereinafter, a method of transmitting and receiving a single time sync frame in order to synchronize time by receiving a single time sync frame from a device determined as a grand master will be described with reference to FIG. 10.

FIG. 10 illustrates a method of transmitting and receiving a single time sync frame for transmission delay time measurement and time synchronization according to an embodiment of the present invention.

As shown in FIG. 10, when synchronous Ethernet is first started, all terminal devices 410 and bridge devices 420 transmit a single sync frame to neighboring devices in the time synchronization layer 540. In the case of transmitting a single sync frame, for example, a device determined as a grand master transmits a single time sync frame in units of 10 ms periods (S1002), and a device determined as a slave device transmits a single time sync frame in units of 100 ms periods. It may transmit (S1004). Therefore, the slave device may apply the reference time of the grand master every 10ms, and measure the transmission delay time every 100ms.

FIG. 11 is a diagram illustrating a method of calculating a transmission delay time using a single time sync frame transmitted and received at a master port and a slave port of each device according to an embodiment of the present invention.

As shown in Fig. 11, each device transmits a single time sync frame to a neighboring device, and then receives the single time sync frame again, for example, to measure a transmission delay time with the neighboring device. can do. In addition, each device may determine a request side transmission delay time field 612, a response side reception delay time field 613, and a response side transmission delay time field 614 among fields of a single time sync frame to measure a transmission delay time. It is available.

The request-side transmission delay time 1104 refers to the time when a single time sync frame is transmitted through the request-side slave port 1100, and the response-side reception delay time 1106 is described above through the response-side master port 1102. The time when the time sync frame is received.

In addition, the return time 1112 refers to a time elapsed after receiving a single time sync frame through the responding master port 1102, processing it, and returning the request to the requesting side.

In addition, the response side transmission delay time 1108 refers to a time for transmitting the single sync frame to the requesting side through the response side master port 1102 after the return time 1112 has elapsed. 1110 denotes a time when a single time sync frame transmitted from the responding master port 1102 is transmitted through the requesting slave port 1100.

In addition, the round trip time 1114 refers to the time taken by the requesting party to transmit the single time sync frame and then to receive it again.

In other words, prior to calculating the transmission delay time, each device first measures the request transmission delay time 1104 and then transmits a single time sync frame to the response master port through the request slave port 1100. The neighboring device receives the single time sync frame through the responding master port 1102 and measures the responding receive delay time 1106.

Thereafter, the neighboring device transmits the single sync frame back to the requesting slave port 1100 through the responding master port 1102, and the time at which the frame is transmitted is the response side transmission delay time field ( 1108).

Thereafter, the requesting slave port 1100 receives the single time sync frame, and measures the requesting reception delay time 1110.

Each device uses the following equation (2) to calculate the transmission delay time.

Round trip time 1114 = request side delay time 1110-request side delay time 1104

Return time 1112 = response side transmit delay time 1108-response side receive delay time 1106

Transmission delay time = (round trip time (1114)-return time (1112)) / 2

The adjusted time information obtained by applying the transmission delay time obtained as described above to the grand time is transmitted to the network upper layer to be applied to the real time application 570. At this time, the adjusted time information is calculated using the following equation (3).

Adjusted time information = Grand time-Unique time for each device-Transmission delay time

The grand time refers to the reference time of the grand master, and the unique time of each device refers to the unique time of each device. In addition, the transmission delay time refers to the transmission delay time calculated for each port.

The above procedure and calculation method can be similarly applied to neighboring slave devices. Therefore, all devices of synchronous Ethernet are adjusted by using the synchronization time information provided by the grand master and applying the transmission delay time of each port between neighboring devices. Time synchronization can be achieved based on time information.

One embodiment of the present invention can also be implemented in the form of a recording medium containing instructions executable by a computer, such as a program module executed by the computer. Computer readable media can be any available media that can be accessed by a computer and includes both volatile and nonvolatile media, removable and non-removable media. In addition, computer readable media may include both computer storage media and communication media. Computer storage media includes both volatile and nonvolatile, removable and non-removable media implemented in any method or technology for storage of information such as computer readable instructions, data structures, program modules or other data. Communication media typically includes computer readable instructions, data structures, program modules, or other data in a modulated data signal such as a carrier wave, or other transmission mechanism, and includes any information delivery media.

The foregoing description of the present invention is intended for illustration, and it will be understood by those skilled in the art that the present invention may be easily modified in other specific forms without changing the technical spirit or essential features of the present invention. will be. Therefore, it should be understood that the embodiments described above are exemplary in all respects and not restrictive. For example, each component described as a single type may be implemented in a distributed manner, and similarly, components described as distributed may be implemented in a combined form.

The scope of the present invention is shown by the following claims rather than the above description, and all changes or modifications derived from the meaning and scope of the claims and their equivalents should be construed as being included in the scope of the present invention. do.

1 is a view for explaining the operation of the SNTP according to the prior art.

2 is a view for explaining the operation of the IEEE 1588 PTP according to the prior art.

3 is a view for explaining a time synchronization procedure of IEEE 802.1AVB according to the prior art.

4 is a block diagram of a synchronous Ethernet according to an embodiment of the present invention.

5 is a block diagram of a synchronous Ethernet layer according to an embodiment of the present invention.

6 is a structural diagram of a single time sync frame according to an embodiment of the present invention;

7 is a flowchart illustrating a method for time synchronization according to an embodiment of the present invention.

8 is a flowchart illustrating a method of determining a grand master according to an embodiment of the present invention.

9 is a flowchart illustrating a method for determining a master port in a bridge device according to an embodiment of the present invention.

10 illustrates a method of transmitting and receiving a single time sync frame for transmission delay time measurement and time synchronization according to an embodiment of the present invention.

11 illustrates a method of calculating a transmission delay time according to an embodiment of the present invention.

Claims (11)

An apparatus for providing time synchronization of synchronous Ethernet, A time synchronization information providing unit operating in a network upper layer and providing reference time information to the time synchronization layer; A grand master decision processing unit that performs grand master decision using priority information, A time difference calculator for calculating a time difference between the device and a neighboring device; A transmission delay time measuring unit measuring a transmission delay time between the device and a neighboring device; The real-time application unit for receiving the time information adjusted by using the measured time difference and the transmission delay time to synchronize the time of the device Including, The grand master decision processing unit, the time difference calculating unit and the transmission time measuring unit belong to a time synchronization layer, which is a network lower layer, and perform a grand master determination, a time difference measurement, and a transmission delay time measurement using a single time sync frame. Device that provides time synchronization for Ethernet. The method of claim 1, When the time synchronization providing apparatus is an intermediate bridge device, the transmission time measuring unit measures the transmission delay time of the medium for each port, synchronous Ethernet time synchronization providing apparatus. The method of claim 1, And the grand master decision processing unit determines a master port and a slave port among a plurality of ports. In the method of generating a time sync frame for time synchronization in synchronous Ethernet, Generating a field group for classifying the time sync frame, Creating a field group for determining the grand master, and Measuring the time difference and transmission delay time to create a group of fields used for time synchronization, Time sync frame generation method comprising a. The method of claim 4, wherein The field group used for the time synchronization, Grand time field, which records the local time of the device determined as the grand master, Request-side transmit delay time field, Response-side receive delay time field and Response side send delay time field The time sync frame generation method comprising a. The method of claim 5, wherein The field group for classifying the time sync frame is And including a protocol type field, a time sync type field, a version field, and a frame count field. The method of claim 5, wherein The field group for grand master determination, A priority field with a recorded priority for determining the grand master, A time identifier field in which the unique identifier of the device is recorded, A hop count field in which the distance from the grand master is recorded and And a port identifier field for distinguishing between master and slave ports in the device. In a method for providing time synchronization in synchronous Ethernet, (a) determining the grand master using the priority information; (b) performing time synchronization by measuring a reference time of the grand master, an inherent time of each device, and a transmission delay time; The priority information, the reference time of the grand master, and the transmission delay time are recorded in a single time sync frame and are exchanged between the grand master and the slave. How to Synchronize Time with Synchronous Ethernet. The method of claim 8, In step (a), the method of synchronizing the Ethernet to determine the grand master further using an identifier for identifying the device. The method of claim 8, In the step (a), it is repeated if the new device is added time synchronization method of synchronous Ethernet. The method of claim 8, In step (b), Measuring request transmission delay time, response reception delay time, response transmission delay time, and request reception delay time.

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