KR20130056820A - Apparatus and method for measuring delay - Google Patents

Abstract

PURPOSE: A delay measuring device and a method thereof are provided to correct delay errors generated according to frame transmission and reception in a second location when both-ways delay time is measured between a first and a second location. CONSTITUTION: An overhead insertion unit(42) inserts a time stamp into the overhead of a multi-frame transmitted from a first location to a second location. An overhead extraction unit(44) extracts the time stamp from the overhead of the multi-frame received from the second location. The time stamp includes delay error information from the second location. A delay measuring unit(40) measures both-ways delay time between the first location and the second location by using the inserted time stamp and the extracted time stamp. The delay measuring unit corrects the measured both-way delay time by using the extracted delay error information. [Reference numerals] (40) Delay measuring unit; (42) Overhead insertion unit; (44) Overhead extraction unit

Description

Delay measuring device and method thereof {Apparatus and method for measuring delay}

The present invention relates to an optical transmission network, and more particularly, to a signal delay measurement technique in an optical transmission network.

High-speed interfaces, such as Fiber Channel and Common Public Radio Interface (CPRI), allow for delay-sensitive client signals to be accommodated in Optical Transport Networks (OTNs). The ability to measure delays is required.

According to one embodiment, a delay measuring method and apparatus for measuring a precise delay time are proposed.

According to an embodiment, a delay measuring apparatus may include an overhead insertion unit inserting a time stamp into an overhead of a multiframe to be transmitted from a first position to a second position, and a second from the overhead of the multiframe received from the second position. An overhead extracting unit for extracting a time stamp including delay error information at a position, and measuring a round trip delay time between the first position and the second position using the inserted time stamp and the extracted time stamp, the extracted delay error It includes a delay measuring unit for correcting the measured round trip delay time using the information.

According to another exemplary embodiment, a delay measuring apparatus may include an overhead extractor extracting a timestamp from an overhead of a multiframe received from a first position at a second position, and a timestamp extracted through the overhead extractor at a first position. And an overhead inserting unit inserted into the overhead of the multiframe to be transmitted to, and inserting the delay error information at the second position together, and a delay measuring unit calculating the delay error information to be inserted into the overhead of the multiframe.

According to another embodiment, a delay measuring method includes inserting a time stamp into an overhead of a multiframe at a first position and transmitting the timestamp to a second position, and receiving and receiving a multiframe from a second position at the first position. Extracting a timestamp including delay error information at the second position from the overhead of the multiframe, and measuring a round trip delay time between the first position and the second position using the inserted timestamp and the extracted timestamp But correcting the measured round trip delay time using the extracted delay error information.

According to another embodiment, a delay measuring method includes receiving a multiframe from a first position at a second position, extracting a time stamp from overhead of the received multiframe, and transmitting the extracted time stamp to the first position And inserting a delay error value at a second position together with the delay of the multiframe, and transmitting a multiframe inserted at the time stamp including the delay error value to the first position. do.

According to an embodiment of the present disclosure, when measuring the round trip delay time between the first position and the second position, the round trip delay time may be accurately measured by correcting a delay error generated by the transmission and reception of the frame at the second position. In addition, interoperability with existing delay measuring devices is ensured, and delay resolution with high resolution is possible using only one overhead byte.

1 is an exemplary view showing a network system according to an embodiment of the present invention;
2 is a reference diagram illustrating a signal shape according to a delay calculation path according to an embodiment of the present invention;
3 is a structural diagram showing an ODU multiframe according to an embodiment of the present invention;
4 is a configuration diagram of a delay measuring apparatus according to an embodiment of the present invention;
5 is a configuration diagram of an overhead insertion unit according to an embodiment of the present invention;
6A to 6C are structural diagrams of an overhead of an ODU frame according to an embodiment of the present invention;
7 is a structure diagram of PM & TCM bytes of overhead of an ODU frame according to another embodiment of the present invention;
8 is a structure diagram of PM & TCM bytes of overhead of an ODU frame according to another embodiment of the present invention;
9 is a flowchart illustrating a delay measuring method at a local location according to an embodiment of the present invention;
10 is a flowchart illustrating a delay measuring method at a remote location according to an embodiment of the present invention.

Hereinafter, with reference to the accompanying drawings will be described embodiments of the present invention; In the following description of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear. In addition, the terms described below are defined in consideration of the functions of the present invention, and this may vary depending on the intention of the user, the operator, or the like. Therefore, the definition should be based on the contents throughout this specification.

1 is an exemplary view showing a network system 1 according to an embodiment of the present invention.

Referring to FIG. 1, the network system 1 includes a plurality of nodes. Many nodes transmit signals over the network. The present invention is to measure the transmission delay time of a signal using a signal transmitted between nodes. In this case, the network is an optical transport network (OTN), and the transmission signal may be an optical data unit (ODUk (k = 0,1,2,3,4, flex) frame). have.

1 shows a master node 10 at a local site and a slave node 12 at a remote site. The master node 10 and the slave node 12 each include a transmitter 100 and 122 for transmitting a signal and a receiver 102 and 120 for receiving a signal. Here, the master node 10 is a subject that transmits a signal to the slave node 12 for the delay measurement of the present invention, the slave node 12 is a target for receiving a signal from the master node 10.

As shown in FIG. 1, when a master node 10 at a local location transmits a signal to a remote location, the slave node 12 at the remote location loops back the received signal and transmits the signal back to the local location. The master node 10 at the local location may measure a signal transmission delay using the received signal. That is, the master node 10 measures the time until the master node 10 transmits a signal at the A position in FIG. 1 and the result is looped back from the slave node 12 at the B position. In this case, the round trip delay may be measured by calculating the time difference between A and B. Assuming that the transmission and reception paths are almost the same, half of the measured round trip delay time may be referred to as a unidirectional propagation delay.

Meanwhile, in ITU-T SG15, in order to measure the real-time round trip delay time using the signal transmission method of FIG. Defines the PM (Path Monitor) & TCM (Tandem Connection Monitor) fields. That is, a toggle signal of 1 bit is defined to measure the round trip delay time of the ODU signal in not only one ODU path section but also up to six ODU TCM sections. The PM & TCM byte contains one DMp bit and up to six DMt bits. At this time, when the master node 10 wants to measure the round trip delay time in the ODU path section, the master node 10 toggles the signal of DMp, which is the 7th bit among the PM & TCM bytes. That is, when the DMp signal is 0, it is toggled to 1, and when the DMp signal is 1, it is toggled to 0. The master node 10 counts the clock of the ODU frame to measure the delay from the point of time toggled at the local position to the point at which the toggled signal loops back from the remote position.

The toggle signal and the clock count of the ODU frame can be used to measure the round trip delay time of the ODU frame. The transmitter 100 and the receiver 102 of the master node 10 at the local location and the transmitter 122 at the remote location can be measured. ) And the receiver 120 do not have the same clock or frame phase difference, and thus a delay measurement error may occur over a frame period. That is, the signal toggled at the local location is extracted by the receiver 12 of the remote location, and the transmitter 122 at the remote location is inserted into the DMp of the overhead of the ODU frame and transmitted to the local location again. Delay error of one frame may occur. In addition, since there is an error between a frame for transmitting a DMp and a frame for receiving a DMp at a local location, the delay measurement resolution (resoultion) of 2.5 times or more of an ODU frame is achieved even if the maximum is 1/2. For example, ODU0 has a delay measurement error approaching 250 us. When delay conditions of less than 100 us must be met, features with high delay measurement resolution make it impossible to ensure that the delay performance is met.

In the delay measurement method of FIG. 1, even if the clock is counted using a precision clock divided by the OSC (oscillator) or ODU transmission rate in order to increase the delay measurement resolution, the receiving unit 120 of the remote location receives the data from the frame received from the local location. When the toggle signal is extracted and the extracted toggle signal is inserted into the overhead DMp of the transmission frame through the transmitter 122 and transmitted to the local location, a delay error of at least one ODU frame occurs due to a time difference between the transmission and reception frames.

Even if the resolution of the delay measurement is precisely lowered, since the receiver 120 and the transmitter 122 of the remote location are not synchronized with each other, the DMp signal extracted from the receiver 120 of the remote location is transmitted through the transmitter 122 of the remote location. An additional delay occurs randomly within the ODU 1 frame before being inserted into the transmitted ODU frame as a DMp signal, causing a delay error within the ODU frame period.

To solve this problem, the master node 10 inserts a toggle signal for measuring delay into the DM byte position of the overhead of the ODU frame and transmits it to the slave node 12. The toggle signal is extracted from the receiving unit 120 of the slave node 12 and then inserted into the DM byte position of the overhead of the ODU frame of the transmitting unit 122 of the slave node 12 and returned. As shown in FIG. 1, since the transmitters 100 and 122 use independent clocks, and the receivers 102 and 120 extract the clocks from the transmitted signals, frame timings in transmission and reception do not coincide with each other. Considering this, the process of transmitting the toggle signal along the path of FIG. 1 is as shown in FIG. 2.

2 is a reference diagram illustrating a signal shape according to a delay calculation path according to an embodiment of the present invention.

1 and 2, when the local position receives a start command command (for example, start command = 1) 200 for starting a delay measurement from the outside, the toggled signal is transmitted to the DM overhead position of the ODU frame. And the ODU frame inserted with the toggle signal to the remote location. 2 is an example toggled from 0 to 1. At this time, when the remote location receives the ODU frame from the local location, the toggle signal is extracted from the DM overhead of the received ODU frame, the extraction time corresponds to the propagation delay (210) shown in FIG. Subsequently, the DM overhead value extracted from the remote location is carried back to the DM overhead location of the ODU frame and returned to the local location. However, since the transmission / reception frame timings are different from each other as shown by reference numeral 220, the positions of the DM overheads for transmitting and receiving are not the same in time. Accordingly, a bypass delay by Y (= Diff) 230 occurs as a whole. The delay error Y 230 is a maximum time interval of one frame, and the value may be different for each measurement. The present invention is for delay measurement having a high resolution according to the correction of the above-described delay error Y (230) during the round trip delay time measurement, an embodiment of the ODU frame transmitted for the delay measurement is shown in FIG. same.

3 is a structural diagram illustrating an ODU multiframe according to an embodiment of the present invention.

Referring to FIGS. 2 and 3, when the delay value Y 240 is subtracted from the delay value X 240 measured at the local position during the round trip delay time measurement, the precise delay value 250 may be calculated. However, since the local error cannot know how much the delay error Y 230 is, the delay error Y 230 must be received from the remote location. However, since the delay measurement overhead of a typical frame has only one byte for delay measurement, there is no space for transmitting the delay error Y 230. You can simply increase the overhead bytes, but this will use overhead inefficiently and even modify the frame shape. Accordingly, the present invention has the multiframe structure of FIG. 3 so that only one byte of an overhead of a frame can be used without modifying the existing frame shape.

Referring to FIG. 3, the multiframe structure of the present invention is composed of a plurality of frames. Among them, a flag 300 having a fixed value (for example, 0xB9) is located at the DM overhead position of the first frame. The flag performs the same function as the frame alignment signal (FAS) of the frame. That is, it is possible to determine which frame receives the first DM overhead of the frame through flag reception, so that it is possible to predict what data is received in the next frame. The second frame uses a toggle signal 310 at the DM overhead byte position. Finally, the third and fourth frames have a Diff at the DM overhead byte position. Diff is a delay error Y 230 that is 16 bits and corresponds to a transmission / reception time difference at a remote location. That is, in the third frame, the 9th to 16th bits, Diff [15: 0] (320), are inserted into the Diff. In the fourth frame, the 1st to 8th bits of the Diff, that is, Diff, are inserted. Insert [7: 0] 330. However, when inserting the Diff for the first time from the local location, 0 value is inserted. Your own signal can be looped back from the remote location. The delayed loop difference is 0. If you insert a value other than 0, an error will occur as much as the difference.

Meanwhile, the remote location receives the multiframe from the local location, and determines the multiframe location by detecting a flag from the DM overhead byte location in the first frame of the received multiframe. The remote position is stored to transmit the toggle signal to the local position again when the value of the DM overhead of the second frame is toggled, and the toggle signal stored in the second DM overhead byte of the multiframe of the remote position is inserted. Measure the Diff value, the delay error until Thereafter, Diff [15: 8] and Diff [7: 0] values are inserted into DM overhead bytes over the third and fourth frames.

According to an embodiment, the local location may determine the multiframe location by detecting a flag at the overhead byte location of the first frame of the multiframe received from the remote location. The X count is stopped when the value of the DM overhead of the second frame is toggled. The Diff value (Y value) is extracted from the DM overhead bytes of the third and fourth frames. In addition, the local position measures an accurate delay value by subtracting the received Y value from the X value counted at the local position.

4 is a configuration diagram of a delay measuring apparatus 4 according to an embodiment of the present invention.

Referring to FIG. 4, the delay measuring apparatus 4 includes a delay measuring unit 40, an overhead inserting unit 42, and an overhead extracting unit 44. The delay measuring device 4 may be located at a master node at a local location or a slave node at a remote location.

The delay measuring unit 40 receives a DM_master or DM_slave, which is a command indicating whether the corresponding node is a master node or a slave node of delay measurement, and transmits the same to the overhead inserting unit 42.

According to an embodiment of the present disclosure, when the corresponding node is a slave node, the delay measuring unit 40 does not perform a delay measurement, and a toggle signal extracted by the overhead extractor 44 is inserted into the overhead inserting unit 42. Control to be delivered to the master node. The overhead extractor 44 transmits rcvd_DM_pos, timing information at the time when a toggle signal is received from the master node, to the overhead inserter 42, and then to the delay measurer 40, and delay delayer 40. Starts the Diff count.

On the other hand, when the corresponding node is a master node, the delay measuring unit 40 generates a Start_DM signal and transmits it to the overhead insertion unit 42 when receiving a delay measuring start command from the outside. The overhead inserting unit 42 receiving the Start_DM signal from the delay measuring unit 40 inserts a toggle signal into the overhead of the transmission frame. The overhead inserting unit 42 transmits the Count_DM signal, which is timing information at the time of insertion, to the delay measuring unit 40. The delay measuring unit 40 starts a delay measurement count.

The overhead extractor 44 extracts the toggle signal rcvd_DM from the overhead of the received frame, and transfers the extracted rcvd_DM signal to the delay measurement unit 40. The delay measurement unit 40 stops the delay measurement count when the rcvd_DM signal received from the overhead extractor 44 is toggled. In addition, the overhead extractor 44 extracts the rcvd_Dm_comp Y value, which is a Diff value, from the DM overhead of the received frame, and transmits the extracted rcvd_Dm_comp Y value to the delay measuring unit 40. Then, the delay measuring unit 40 may calculate an accurate round trip delay time by subtracting the rcvd_Dm_comp Y value from the delay value X.

5 is a configuration diagram of an overhead insertion unit 42 according to an embodiment of the present invention.

Referring to FIG. 5, the overhead inserter 42 includes a first multiplexer 422, a second multiplexer 424, and a third multiplexer 426.

When the node is the master node, the first multiplexer 422 of the overhead inserter 42 inserts a Diff value of 0x0000 into the overhead of the multiframe to be transmitted to the slave node, and the second multiplexer 424 The toggle signal is inserted at the overhead of the multiframe to be transmitted to the slave node. In contrast, when the corresponding node is a slave node, the first multiplexer 422 inserts the Diff value measured by the Diff delay measurement unit 40 to the overhead to be transmitted to the master node, and the second multiplexer 424 The toggle signal rcvd_DM extracted through the overhead extractor 44 is inserted in the overhead to be transmitted to the master node.

The third multiplexer 426, when the node is the master node, flags (0x89), DM toggle, Diff [15: 8], Diff [according to the MF count timing so that the overhead to be transmitted to the slave node is inserted in the multiframe. 7: 0] allow the signal to be selected. In contrast, when the corresponding node is a slave node, the delay measuring unit 40 receives the rcvd_DM_pos, which is a reception timing signal of the toggle signal extracted from the overhead extracting unit 44, and starts a Diff count. When the overhead insertion timing generator 420 inserts the toggle signal into the overhead and generates the timing signal and transmits the timing signal to the delay measuring unit 40, the delay measuring unit 40 inserts the toggle signal into the timing signal. To stop the Diff count. In this case, the calculated Diff value is transmitted to the first multiplexer 422.

6A through 6C are structural diagrams of overhead of an ODU frame according to an embodiment of the present invention.

Referring to FIG. 6A, a seventh column in a first row of an OTN frame defines a multiframe alignment sequence (hereinafter referred to as MFAS) for identifying a multiframe. Since there is no MFAS signal in the ODU frame in the embodiment of FIG. 3, a flag byte is defined to generate its own multiframe from one byte of DM overhead. However, since the OTN frame in the embodiment of FIG. 6A can determine the multiframe using the MFAS byte, a separate flag byte is not required for DM overhead.

6B and 6C are enlarged views of the PM & TCM field of FIG. 6A. In the embodiments of FIGS. 6B and 6C, the PM & TCM field includes a toggle signal DMp, so that delay measurement of one ODU path and six ODU TCMs can be independently performed. DMt1,... The definition of DMt6 uses the existing standard method. However, only the 0th multiframe of the 16 multiframes inserts the DMp and DMti toggle signals. It is not necessary to insert the toggle signals in the other multiframes. Of course, it can also be inserted into the first multiframe.

The first multiframe can be designated as Reserved (RES) byte. In the second to third multiframes, a delay measurement, that is, a Diff value when looping back an ODU path signal at a remote location can be inserted. This overhead is temporarily referred to as BDp (Bypass Delay). In the fourth to fifth multiframes, the delay measurement, or Diff value, when looping back the ODU TCM 1 signal at the remote location can be inserted. This overhead is temporarily designated BDt1 (Bypass Delay). In this way, BDt2 for the 6th to 7th multiframes, BDt3 for the 8th to 9th multiframes, BDt4 for the 10th to 11th multiframes, BDt5 for the 12th to 13th multiframes, and BDt6 bytes for the 14th to 15th multiframes. Can be inserted.

7 is a structural diagram of PM & TCM bytes of overhead of an ODU frame according to another embodiment of the present invention.

Referring to FIG. 7, the 8th bit, which is reserved (RES) byte in the 0th multiframe, is used as a delay indicator (700) byte for mutual compatibility with the existing delay measuring apparatus. do. In other words, when the DI value is 0, only toggle signals such as DMp and DMti are inserted into the PM & TCM byte regardless of the multiframe, so as to maintain compatibility with existing devices. If 1 is inserted as the DI value, it is determined that the improved delay measuring apparatus is supported and the BDp and BDti overhead values are inserted in the multiframe as shown in FIG.

8 is a structural diagram of PM & TCM bytes of overhead of an ODU frame according to another embodiment of the present invention.

In FIG. 6 and FIG. 7, the first multiframe is a reserved byte. In FIG. 8, 16 bits of the BDp and the BDTi can be expanded to 17 bits as shown by the reference numeral 800. This means that if you use a very high clock for high resolution, 16 bits of BDp or BDti may not be enough, so you can add one measurement bit while maintaining 16 multiframes. Of course, if 17 bits are not enough, 16 multiframes can be increased to 32 multiframes or more.

9 is a flowchart illustrating a delay measuring method at a local location according to an embodiment of the present invention.

Referring to FIG. 9, the delay measuring apparatus at the local position inserts a toggle signal and delay error information into the overhead of the multiframe (900) and starts a delay measurement count at the insertion time (910). The inserted delay error information value may be zero. Subsequently, the multiframe in which the toggle signal is inserted in the overhead is transmitted to the remote location (920).

Subsequently, the multiframe is received from the remote location at the local location (930), and a timestamp including the toggle signal and the delay error information at the remote location is extracted from the overhead of the received multiframe (940). In this case, when the extracted toggle signal is toggled, the delay measurement count ends (950), and the round trip delay time between the local position and the remote position is measured by using the inserted time stamp and the extracted time stamp (960). The extracted delay error information is a count value from the overhead extraction time to the overhead insertion time at the remote location. In the round trip delay measurement step 960, the delay measuring apparatus subtracts the delay error value extracted from the overhead of the multiframe received from the remote position from the delay measurement measured from the delay measurement start time to the delay measurement end time. Accurate round trip delay time can be measured.

10 is a flowchart illustrating a delay measuring method at a remote location according to an embodiment of the present invention.

Referring to FIG. 10, the delay measuring apparatus receives 1000 a multiframe from a local location at a remote location and extracts a toggle signal from the overhead of the received multiframe at 1010. In operation 1020, the delay error measurement starts when the toggle signal is extracted. Subsequently, the extracted toggle signal is inserted into the overhead of the multiframe to be transmitted to the local location, and the delay error value measured at the remote location is also inserted (1030). The delay error value is a clock count value from the toggle signal extraction time to the toggle signal insertion time at the remote position. Subsequently, the multi-frame having the time stamp including the delay error value inserted in the overhead is transmitted (1040).

So far, the present invention has been described with reference to the embodiments. Those skilled in the art will appreciate that the present invention can be implemented in a modified form without departing from the essential features of the present invention. Therefore, the disclosed embodiments should be considered in an illustrative rather than a restrictive sense. The scope of the present invention is defined by the appended claims rather than by the foregoing description, and all differences within the scope of equivalents thereof should be construed as being included in the present invention.

10: master node 12: slave node
40: delay measuring unit 42: overhead insertion unit
44: overhead extraction unit

Claims (20)

An overhead insertion unit for inserting a time stamp into the overhead of the multiframe to be transmitted from the first position to the second position;
An overhead extracting unit for extracting a time stamp including delay error information at the second position from the overhead of the multiframe received from the second position; And
A delay measuring unit configured to measure a round trip delay time between the first position and the second position using the inserted time stamp and the extracted time stamp, and correct the measured round trip delay time using the extracted delay error information ;
Delay measuring device comprising a. The method of claim 1,
The overhead insertion unit inserts a time stamp in the overhead of each frame of the multi-frame to be transmitted to the second position, and the inserted time stamp includes a toggle signal and delay error information for starting a delay measurement. Delay measuring device characterized in that the value of the delay error information is zero. The method of claim 1,
The overhead extractor extracts a timestamp from the overhead of each frame of the multiframe received from the second position, and the extracted timestamp is a toggle signal for terminating a delay measurement and delay error information at the second position. Wherein the extracted delay error information is a clock count value from an overhead extraction time point at the second position to an overhead insertion time point. 3. The method of claim 2,
The time stamp inserted into the overhead of the multi-frame to be transmitted to the second position further comprises a flag value for recognizing the multi-frame at the second position. 3. The method of claim 2,
And a timestamp inserted into the overhead of the multiframe to be transmitted to the second position further comprises a multiframe alignment sequence value for recognizing the multiframe at the second position. 3. The method of claim 2,
The timestamp inserted into the overhead of the multi-frame to be transmitted to the second position further comprises a delay indicator value for compatibility with other delay measuring device. The method of claim 6, wherein the overhead insertion portion
When the delay indicator value is 0, only the toggle signal is inserted into the overhead of the multiframe for compatibility with the other delay measuring device. When the delay indicator value is 1, the delay error together with the toggle signal in the overhead of the multiframe. Delay measuring device characterized in that the insertion of information. The method of claim 1,
The overhead inserter inserts a toggle signal and delay error information into each overhead of the multiframe to be transmitted to the second position.
And the overhead extractor extracts a toggle signal and delay error information from each overhead of the multiframe received from the second position. The method of claim 8, wherein the delay measuring unit
Delay measurement is started at the time of inserting the toggle signal of the overhead inserting unit,
When the toggle signal extracted through the overhead extractor is toggled, the delay measurement is terminated,
And a delay measuring apparatus measuring a round trip delay time by subtracting a delay error value extracted through the overhead extracting unit from a delay measuring value measured from a delay measuring start to a delay measuring end time. An overhead extractor for extracting a time stamp from the overhead of the multiframe received from the first position at the second position;
An overhead insertion unit for inserting a time stamp extracted through the overhead extraction unit into an overhead of a multiframe to be transmitted to the first position, and inserting delay error information at the second position together; And
A delay measuring unit calculating delay error information to be inserted into the overhead of the multiframe;
Delay measuring device comprising a. The method of claim 10, wherein the overhead insertion portion
A time stamp is inserted into the overhead of each frame of the multi-frame to be transmitted to the first position, and the inserted time stamp includes a toggle signal for terminating the delay measurement and delay error information at the second position. Delay measuring device. The method of claim 11,
The delay error information value extracted by the overhead extractor from the overhead of the multiframe received from the first position is 0,
The delay error information inserted by the overhead inserter into the overhead of the multiframe to be transmitted to the first position is a delay counting device which is a clock count value from the overhead extraction time point to the overhead insertion time point at the second position. . 11. The method of claim 10,
The delay error information inserted into the overhead of the multi-frame to be transmitted to the first position is delay error information for each of the optical data unit path and the plurality of optical data unit tandem connection monitor. The method of claim 10, wherein the delay measuring unit
And a clock count starts at an overhead extraction time point of the overhead extractor and ends a clock count at an overhead insertion point of the overhead inserter. Inserting a timestamp at the overhead of the multiframe at the first location and transmitting it to the second location;
Receiving a multiframe from the second location at the first location and extracting a timestamp including delay error information at the second location from the overhead of the received multiframe; And
Measuring a round trip delay time between the first position and the second position using the inserted time stamp and the extracted time stamp, and correcting the measured round trip delay time using the extracted delay error information;
Delay measuring method comprising a. 16. The method of claim 15, wherein sending to the second location
Inserting a time stamp in the overhead of each frame of the multiframe to be transmitted to the second position,
The inserted timestamp includes a toggle signal for starting delay measurement and delay error information at the second position, wherein the delay error information has a value of zero. The method of claim 15, wherein extracting the time stamp
Extract a timestamp from the overhead of each frame of the multiframe received from the second location,
The extracted timestamp includes a toggle signal for terminating a delay measurement and delay error information at the second position, and the extracted delay error information is from an overhead extraction time point at the second position to an overhead insertion time point. Delay measurement method characterized in that the clock count value of. The method of claim 15, wherein correcting the measured round trip delay time comprises:
Starting a delay measurement at the time of inserting a toggle signal into the overhead of the multiframe to be transmitted to the second position;
Terminating the delay measurement when the toggle signal extracted from the overhead of the multiframe received from the second position is toggled; And
Measuring a round trip delay time by subtracting a delay error value extracted from overhead of a multiframe received from the second position from a delay measurement value measured from a delay measurement start time to a delay measurement end time;
Delay measuring method comprising a. Receiving a multiframe at a second location from the first location and extracting a timestamp from the overhead of the received multiframe;
Inserting the extracted timestamp into an overhead of a multiframe to be transmitted to the first position, and inserting a delay error value at the second position together; And
Transmitting, to the first location, a multiframe having a timestamp including the delay error value inserted at overhead;
Delay measuring method comprising a. 20. The method of claim 19, wherein inserting the delay error values together
Inserting a time stamp in the overhead of each frame of the multi-frame to be transmitted to the first position,
The inserted timestamp includes a toggle signal for terminating the delay measurement and delay error information at the second position, and the inserted delay error information is from the overhead extraction time point at the second position to the overhead insertion time point. Delay measurement method characterized in that the clock count value of.

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