Delay measuring device

Abstract

This invention makes it possible to suppress an increase in power consumption by terminals as a delay time is measured, in accordance with the connection state between a network and the terminals. A delay measuring unit 22 transmits probe packets 51 to terminals to be measured, performs active measurement, and ascertains the delay time. A terminal transmission packet monitoring unit 16 monitors the presence / absence of a packet 50 and the number of packets, from each terminal to a server 11. When the transmission interval of the packets 50 becomes equal to or longer than the time of an idle timer, a monitoring setting unit 21 excludes the corresponding terminal from the terminals to be measured and stops the probe packet transmission to the excluded terminal. Even when the transmission interval of the probe packets 51 is short, a terminal excluded from the terminals to be measured can move to a sleep state and power consumption can be suppressed.

Description

Delay measurement device

[0001] The present invention relates to a delay measurement device for measuring communication delay times that occur when data communication is performed between each terminal connected to a network and the network.

[0002] In a network compatible with the high-speed communication standard 5G (5th generation mobile communication system), various communication requirements are required when each terminal (UE: User Equipment) accesses the network, such as high-capacity broadband, a large number of session connections, and ultra-low latency and high quality. For example, to provide a network that meets the latency requirements for terminals, it is necessary to measure the latency between the terminal and the network and reflect the measurement results in network control to meet the latency requirements.

[0003] There are two generally known methods for measuring delay times between a network and a terminal: active measurement and passive measurement (see Non-Patent Document 1). For example, in the network 41 shown in FIG. 1A, a data transfer unit 17 of a transfer device 13A controls data transfer between each of the terminals 12-1 to 12-3 and a server 11 on the network 41. An observation unit 14 built into this transfer device 13A can measure delay times by passively observing packets 50 sent and received by each of the terminals 12-1 to 12-3. This type of measurement is called passive measurement.

[0004] On the other hand, the network 42 shown in FIG. 1B is equipped with a dedicated measuring device 15 for measuring delay times. In this configuration, the measuring device 15 actively sends probe packets 51 to each of the terminals 12-1 to 12-3, separate from the packets 50 sent and received by each of the terminals 12-1 to 12-3 for communication. The probe packets 51 sent by the measuring device 15 arrive at each of the terminals 12-1 to 12-3 via the forwarding device 13B. In response to the probe packets 51, each of the terminals 12-1 to 12-3 sends a dedicated packet to the measuring device 15. By using the probe packets 51, the measuring device 15 can measure the delay time for each terminal. This type of measurement is called active measurement.

[0005] In the case of passive measurement as described above, delay time can be measured without affecting the operation of each terminal. However, the observation unit 14 needs to record and process packets 50 sent and received by each of the terminals 12-1 to 12-3. Therefore, as the number of terminals and the amount of traffic increase, the load on the transfer device 13A, which is the observation point, increases.

[0006] In the case of the above-described active measurement, the increase in load due to delay measurement is relatively small even when the number of terminals or traffic volume increases, because the transfer device 13B only increases the transfer processing of the probe packets 51. However, each terminal must add processing to respond to the probe packets 51 in order to measure delay.

[0007] Meanwhile, devices connected to mobile networks are equipped with a Radio Resource Control (RRC) function, which reduces power consumption by disconnecting wireless connections if there is no communication for a certain period of time.

[0008] In this RRC, the terminal undergoes state transitions as shown in Figures 2A and 2B (see Non-Patent Document 2). That is, in the case of LTE (Long Term Evolution), as shown in Figure 2A, the terminal undergoes state transitions between two states: a "radio resource control connected" state ST11 and a "radio resource control idle" state ST12. When a radio connection is established, the terminal transitions to the "radio resource control connected" state ST11, and when the radio connection is released, the terminal transitions to the "radio resource control idle" state ST12.

[0009] In the case of 5G NR (New Radio), as shown in Fig. 2B, the state transitions among three types: a "radio resource control connected" state ST21, a "radio resource control idle" state ST22, and a "radio resource control inactive" state ST23. In the "radio resource control inactive" state ST23, the terminal releases the radio connection, but the network side holds the connection information, so the time until reconnection can be shorter than in the "radio resource control idle" state.

[0010] In the "radio resource control connected" states ST11 and ST21, the terminal maintains a radio connection, and therefore consumes a large amount of power. In the "radio resource control idle" states ST12 and ST22 and the "radio resource control inactive" state ST23, the terminal releases the radio connection, and therefore consumes a small amount of power. In other words, the "radio resource control idle" states ST12 and ST22 and the "radio resource control inactive" state ST23 are sleep states.

[0011] Two examples of terminal operation timing when actively measuring latency are shown in Figures 3A and 3B. Each terminal can transition from a normal operating state to a sleep state within a specified time by measuring the elapsed time using its own idle timer.

[0012] The example shown in Fig. 3A assumes a case where the transmission interval Tp1 of the probe packets 51 is longer than the fixed time Tid measured by the idle timer. The example shown in the lower part of Fig. 3 assumes a case where the transmission interval Tp2 of the probe packets 51 is shorter than the fixed time Tid measured by the idle timer.

[0013] The operation example shown in Figure 3A will now be described. After processing and responding to probe packet 51 that appears at time t1, the terminal ends communication at time t2 and starts counting the idle timer. Then, at time t3, the idle timer completes counting a fixed time (Tid), allowing the terminal to transition to a sleep state. Next, at time t4, probe packet 51 is transmitted from the measuring device, but since the terminal is in a sleep state section Ts, the probe packet 51 does not reach the terminal, and the terminal maintains the sleep state until, for example, time t5.

[0014] Next, the operation example shown in Figure 3B will be described. After processing and responding to probe packet 51 that appears at time t21, the terminal ends communication at time t22 and starts counting the idle timer. When the next probe packet 51 appears at time t23, the terminal is in a normal operating state, so it processes and responds to this probe packet 51. Furthermore, since the terminal resets the operation of the idle timer at time t23, the terminal does not transition to a sleep state even after a certain time Tid has elapsed since time t21. The terminal also operates in the same manner as above in response to probe packet 51 that occurs at time t25.

[0015] In other words, if the transmission interval Tp2 of the probe packets 51 is shorter than the fixed time Tid of the idle timer, the terminal will need to process a response to the probe packets 51, and will therefore be unable to transition to a sleep state. Therefore, even in a situation where transmission and reception of normal data packets is not necessary, the power consumption of the terminal cannot be reduced. Meanwhile, Non-Patent Document 3 discloses a means for acquiring the wireless connection state (connected state or sleep state) of each UE from the 5G core.

[0016] "Common Functions of Network Management", Institute of Electronics, Information and Communication Engineers "Forest of Knowledge", Group 5, Part 9, Chapter 3, Internet<URL:https: / / www.ieice-hbkb.org / files / ad_base / view_pdf.html?p= / files / 05 / 05gun_09hen_03.pdf> "Outline of the 5th Generation Mobile Communication System", A2A Research Institute, Inc., May 2018., Internet<URL:http: / / www.a2a.jp / resources / 5G_System.pdf> E. Lyczkowski, C. Sauer, MR Sama and W. Kiess, "Avoiding Keep-Alive Messages by exposing 5G Channel State Information to Applications", 2021 26th IEEE International Conference on Emerging Technologies and Factory Automation (ETFA ), Vasteras, Sweden, 2021, pp. 1-6, doi: 10.1109 / ETFA45728.2021.9613279.

[0017] By utilizing the technology disclosed in Non-Patent Document 3, for example, the measuring device 15 shown in FIG. 1 can determine whether the wireless connection of a terminal is already open before transmitting a probe packet 51. However, even when utilizing the technology disclosed in Non-Patent Document 3, once the measuring device 15 starts transmitting the probe packet 51, it is not possible to determine whether the wireless connection can be released. Therefore, as with the example operation shown in the lower part of FIG. 3, it is not possible to avoid a situation in which the terminal is unable to transition to a sleep state due to the influence of the probe packet 51. In other words, it is not possible to prevent the terminal's power consumption from increasing due to the influence of the probe packet 51.

[0018] On the other hand, when the above-mentioned passive measurement is adopted, the delay time can be measured without affecting the operation of each terminal, so an increase in power consumption at the terminal can be avoided. However, as the number of terminals and traffic volume increase, the load on the transfer device 13A, which is the observation point, increases. Therefore, it is desirable to adopt active measurement in networks such as the high-speed communication standard 5G.

[0019] The present invention has been made in consideration of the above situation, and aims to provide a delay measurement device that can easily suppress the increase in power consumption of each terminal that occurs when measuring delay time, depending on the connection status of the terminal.

[0020] The delay measurement device of the present invention is characterized by comprising: a data transfer unit that controls data communication between each terminal connected to a network and the network; a delay measurement unit that measures the communication delay time between each terminal and the network using a predetermined probe packet; a terminal transmission packet monitoring unit that individually monitors whether or not each terminal transmits a packet, excluding responses to the probe packet, for each terminal; and a monitoring setting unit that reflects the monitoring status of the terminal transmission packet monitoring unit in the control of the probe packet sent by the delay measurement unit.

[0021] According to the delay measurement device of the present invention, the increase in power consumption of each terminal that accompanies delay time measurement can be suppressed according to the connection status of the terminal. That is, the monitoring status of the terminal transmission packet monitoring unit is reflected in the control of the probe packets sent by the delay measurement unit, so that the transmission of probe packets can be suppressed for terminals that are not transmitting or receiving packets other than probe packets. This makes it possible to transition terminals whose power consumption should be suppressed to a sleep state.

[0022] FIG. 1 is a block diagram showing an example of the configuration of a network that performs passive measurement. FIG. 2 is a block diagram showing an example of the configuration of a network that performs active measurement. FIG. 3 is a state transition diagram showing the state of a terminal in radio resource control. FIG. 4 is a state transition diagram showing the state of a terminal in radio resource control. FIG. 5 is a time chart showing an example of the operation timing of a terminal when actively measuring delay time. FIG. 6 is a time chart showing an example of the operation timing of a terminal when actively measuring delay time. FIG. 7 is a block diagram showing an example of the configuration of a network that includes a delay measurement device according to an embodiment of the present invention. FIG. 8 is a flowchart showing an overview of an example of the operation of a delay measurement device according to an embodiment of the present invention. FIG. 9 is a flowchart showing the first half of the detailed operation of a delay measurement device according to an embodiment of the present invention. FIG. 10 is a flowchart showing the second half of the detailed operation of a delay measurement device according to an embodiment of the present invention.

[0023] An embodiment of the present invention will be described below with reference to the accompanying drawings. <Network Configuration Example> Fig. 4 shows an example configuration of a network 43 including a delay measurement device 20 according to an embodiment of the present invention. The delay measurement device according to the embodiment is configured by the delay measurement device 20 and a terminal-transmitted packet monitoring unit 16 shown in Fig. 4. Note that the configuration of the delay measurement device 20 and the location of the terminal-transmitted packet monitoring unit 16 can be changed as necessary.

[0024] The network 43 can provide various communication services to each user using the server 11 connected to this network 43. Each user's terminal 12-1, 12-2, 12-3 is connected to the transfer device 13C. In addition, since each terminal 12-1, 12-2, 12-3 is assumed to be a mobile terminal such as a smartphone compatible with the 5G standard, it is important that the terminal automatically transitions to a sleep state when not actually communicating to reduce its own power consumption. Note that when there is no particular distinction between the terminals 12-1, 12-2, 12-3, they will simply be referred to as terminal 12.

[0025] The transfer device 13C performs a transfer process to relay packets 50 so that communication can be established between the server 11 and each of the terminals 12-1, 12-2, and 12-3 connected to the network 43. The transfer device 13C of this embodiment is also equipped with a special terminal transmission packet monitoring unit 16.

[0026] The network 43 is provided with a delay measurement device 20 for measuring delay times in communications between the terminals 12-1, 12-2, and 12-3 and the network 43. The delay measurement device 20 includes a monitor / setting unit 21 and a delay measurement unit 22.

[0027] The delay measurement unit 22 has a function of measuring the delay time of each of the terminals 12-1, 12-2, and 12-3 in a manner similar to the above-mentioned "active measurement" by using a probe packet 51 that is different from a normal packet 50. The monitoring setting unit 21 has a function of automatically setting the monitoring state of the delay measurement unit 22 according to the situation.

[0028] The specific functions of the monitoring setup unit 21 are as follows: (1) The monitoring setup unit 21 receives, from the operator terminal 30 operable by an operator, the IP address (terminal address) of the terminal to be measured for delay and the fixed time (Tid) of the idle timer set for the terminal 12 corresponding to the terminal address. If the idle timer has a unique value independent of the terminal 12, the unit receives that value. (2) The monitoring setup unit 21 sets each terminal address received from the operator terminal 30 as a delay measurement target in the delay measurement unit 22. (3) The monitoring setup unit 21 performs monitoring setup for each terminal address with the terminal-transmitted packet monitor 16 by communicating a control signal C1. (4) The monitoring setup unit 21 acquires the number of transmitted packets for each terminal address from the terminal-transmitted packet monitor 16 at regular intervals by communicating a control signal C2. (5) The monitoring setup unit 21 changes the delay measurement target in the delay measurement unit 22 based on the results acquired from the terminal-transmitted packet monitor 16. (5-1) When an increase in the number of transmitted packets is not observed within the idle timer time for a terminal address that is a measurement target in the delay measurement unit 22, the monitoring setting unit 21 excludes the terminal address from the measurement target in the delay measurement unit 22. (5-2) When an increase in the number of transmitted packets is observed for a terminal address that has been excluded from the measurement target in the delay measurement unit 22, the monitoring setting unit 21 adds the terminal address to the measurement target in the delay measurement unit 22.

[0029] On the other hand, the delay measurement unit 22 has the function of sending a probe packet 51 to each terminal address set as a measurement target by the monitoring setting unit 21, and measuring the delay time for each terminal 12 based on the time it takes for a response to be returned.

[0030] The terminal transmission packet monitoring unit 16 records, for each address, the number of packets transmitted by each terminal address set as a measurement target by the monitoring setting unit 21. Furthermore, in response to an inquiry from the monitoring setting unit 21, the terminal transmission packet monitoring unit 16 returns the observed value of the number of transmitted packets for each terminal address at the time of inquiry.

[0031] Each of the terminal transmission packet monitoring unit 16, the monitoring setting unit 21, and the delay measurement unit 22 can be configured as dedicated hardware, or as a program that can be executed by a control computer.

[0032] <Overview of Operation of Delay Measurement Device> An overview of the operation of the delay measurement device 20 in Fig. 4 is shown in Fig. 5. The operation shown in Fig. 5 will be described below. In the first step S01, an instruction is sent from the operator terminal 30 to the monitoring and setting unit 21, and the time value of the idle timer that manages the time until transition to a sleep state is determined for each terminal 12 that is the target of delay measurement. Each terminal 12 is managed so that the IP address assigned to it is identified as the terminal address.

[0033] In the next step S02, the monitor setting unit 21 sets the delay measurement unit 22, and controls the delay measurement unit 22 to periodically transmit probe packets 51 for each terminal 12 that is the target of delay measurement.

[0034] In step S03, the monitoring setting unit 21 notifies the terminal-transmitted packet monitoring unit 16 of the IP address of each terminal 12 to be monitored by using the control signal C1 shown in FIG.

[0035] In step S04, terminal-transmitted packet monitor 16 monitors whether or not packets 50 are being transmitted from terminal 12 to server 11, distinguishing between the IP addresses of each monitored terminal 12. In step S05, monitor setting unit 21 periodically obtains from terminal-transmitted packet monitor 16 the monitoring results of whether or not packets are being transmitted for each terminal 12.

[0036] In step S06, based on the monitoring results for each terminal 12 acquired by the monitoring setting unit 21 in step S05, the monitoring setting unit 21 determines that a terminal 12 that has not transmitted packets 50 for a period equal to or longer than the idle timer value determined in step S01 can transition to a low power consumption state (sleep state), and excludes the terminal 12 from the delay measurement targets. Then, the monitoring setting unit 21 controls the delay measurement unit 22 to reflect the exclusion result.

[0037] In step S07, if the monitoring setting unit 21 detects transmission of a packet 50 for a terminal 12 that was excluded from the delay measurement targets in step S06, the monitoring setting unit 21 adds the terminal 12 to the delay measurement targets again. Then, the monitoring setting unit 21 controls the delay measurement unit 22 to reflect the result of the addition.

[0038] 6A and 6B show detailed examples of operation in the delay measurement device 20. The examples of operation shown in Fig. 6A and 6B are described below. In step S11, the operator terminal 30 sends an instruction to the monitoring setting unit 21, and for each terminal 12 to be subjected to delay measurement, the IP address (terminal address) and the time value of the idle timer to be assigned to the corresponding terminal 12 are individually determined.

[0039] In step S12, the monitoring setting unit 21 configures the delay measurement unit 22 in accordance with the instructions given in step S11, and controls the delay measurement unit 22 to periodically transmit probe packets 51 for each terminal 12 to be subjected to delay measurement.

[0040] In step S13, the monitoring setting unit 21 notifies the terminal transmission packet monitoring unit 16 of the IP addresses of each terminal 12 to be monitored using the control signal C1 shown in Figure 4, and the terminal transmission packet monitoring unit 16 assigns each terminal 12 to be monitored.

[0041] In step S14, the monitoring setting unit 21 inquires of the terminal-transmitted packet monitoring unit 16 about the number of transmitted packets for each terminal to be monitored. In step S15, the terminal-transmitted packet monitoring unit 16 notifies the monitoring setting unit 21 of the number of transmitted packets for each terminal to be monitored as a response. In step S16, the monitoring setting unit 21 calculates the difference ΔNp between the previously obtained result and the currently obtained result for the number of transmitted packets for each terminal to be monitored.

[0042] The processes in the following steps S17 to S19 are respectively executed by the monitoring setting unit 21 for each address of the terminal 12 that is the target of delay measurement. In step S181, the monitoring setting unit 21 determines whether or not the number of transmitted packets has increased from the value of the difference ΔNp calculated in step S16, and if it has increased, the process proceeds to step S175, and if it has not increased, the process proceeds to step S182.

[0043] In step S182, the monitoring setting unit 21 compares the transmission interval between packets 50 with the time on the idle timer. Specifically, the monitoring setting unit 21 compares the time from the last time the number of transmitted packets increased to the time the current measurement result was obtained with the time on the idle timer. If the transmission interval between packets 50 is less than the time on the idle timer, the process proceeds to step S184; if this condition is not met, the process proceeds to step S183.

[0044] In step S185, the monitoring setting unit 21 determines whether the currently processing terminal 12 is a target for delay measurement. If the currently processing terminal 12 is not a target for delay measurement, the process proceeds to step S186. If the currently processing terminal 12 is a target for delay measurement, the process proceeds to step S184.

[0045] In step S183, the monitoring setup unit 21 excludes the currently processing terminal 12 from the terminals 12 targeted for delay measurement, and controls the result so as to reflect the operation of the delay measurement unit 22. With this control, the delay measurement unit 22 switches to a state in which it does not periodically transmit probe packets 51 to the terminals 12 excluded from the delay measurement targets. In step S184, the monitoring setup unit 21 maintains the currently processing terminal 12 as the terminal 12 targeted for delay measurement, and continues the current delay measurement state.

[0046] In step S186, the monitoring setting unit 21 adds the currently processing terminal 12 as a terminal 12 to be subjected to delay measurement, and controls the result to be reflected in the operation of the delay measurement unit 22. With this control, the delay measurement unit 22 switches to a state in which it periodically transmits probe packets 51 to the terminal 12 that has been switched from being a non-subject to delay measurement to being a subject to delay measurement.

[0047] After executing steps S17 to S19, the monitoring setting unit 21 waits for a certain period of time in the next step S20 before proceeding to step S14. Therefore, the monitoring setting unit 21 grasps the transmission status of packets 50 in each monitored terminal 12, and performs control that reflects the comparison result between the packet transmission interval and the idle timer time, and whether or not the number of transmitted packets has increased. As a result, a terminal 12 whose packet transmission interval becomes greater than the idle timer time and which is in a state where it is desirable to transition to a sleep state is excluded from the delay measurement targets, and the delay measurement unit 22 switches to a state where it does not transmit probe packets 51 to that terminal 12. A terminal 12 to which a probe packet 51 is not transmitted from the delay measurement unit 22 does not need to receive and process the probe packet 51, and therefore autonomously transitions to a sleep state, thereby reducing its own power consumption.

[0048] Furthermore, if a terminal 12 that has been excluded from the delay measurement targets transmits a packet 50, the terminal 12 is added to the delay measurement targets in step S186 due to an increase in the difference ΔNp, and the delay measurement unit 22 switches to a state in which it periodically transmits a probe packet 51 to the terminal.

[0049] <Characteristics of the Delay Measurement Device> The characteristic features of the delay measurement device of the present invention are listed below in [1] to [4]. [1] A delay measurement device comprising: a data transfer unit (17) that controls data communication between each terminal (12) connected to a network (43) and the network (43), a delay measurement unit (22) that measures a communication delay time between each terminal (12) and the network (43) using a predetermined probe packet (51), a terminal-transmitted packet monitoring unit (16) that individually monitors for each terminal whether or not a packet is transmitted from each terminal, excluding responses to the probe packet (51), and a monitoring setting unit (21) that reflects the monitoring status of the terminal-transmitted packet monitoring unit in the control of the probe packet sent by the delay measurement unit.

[0050] According to the delay measurement device having the configuration described in [1] above, delay time is measured by active measurement using probe packets 51. Therefore, even if the number of terminals or traffic volume increases, the load on the data transfer unit due to delay measurement is relatively small. In particular, the terminal-transmitted packet monitor unit does not need to monitor the contents of each passing packet 50; it only monitors whether or not packets 50 are transmitted and the number of packets, so high-load processing is not required. Furthermore, the monitor setting unit reflects the monitoring status of the terminal-transmitted packet monitor unit in the control of the probe packets sent by the delay measurement unit, so that the transmission of probe packets to each terminal can be appropriately controlled according to the situation. As a result, each terminal can autonomously transition to a sleep state when not communicating, thereby reducing power consumption.

[0051] [2] The delay measurement device described in [1] above, wherein the monitoring setting unit (21) identifies whether at least each terminal can transition to a sleep state in which it operates in a power-saving manner based on the monitoring status of the terminal transmission packet monitoring unit, and stops sending the probe packets to terminals that can transition to a sleep state.

[0052] According to the delay measurement device having the configuration [2] above, a terminal that can transition to a sleep state is identified and the transmission of the probe packet to the corresponding terminal is stopped, so that the corresponding terminal no longer needs to process the probe packet and can autonomously transition to a sleep state.

[0053] [3] The delay measurement device described in [1] above, wherein the monitoring setting unit (21) compares the packet transmission interval of each terminal with the time of the idle timer of the corresponding terminal, and excludes the corresponding terminal from the measurement of communication delay time if the packet transmission interval is large.

[0054] According to the delay measurement device having the configuration described in [3] above, terminals with large transmission intervals between packets 50 are excluded from the measurement of communication delay time, and therefore transmission of the probe packets to the excluded terminals is stopped. As a result, the excluded terminals no longer need to process the probe packets and can autonomously transition to a sleep state.

[0055] [4] The delay measurement device described in [3] above, wherein when the monitoring setting unit (21) detects an increase in the number of packets sent by each terminal, if the corresponding terminal is not a target for measuring communication delay time, the corresponding terminal is added to the targets for measuring communication delay time.

[0056] According to the delay measurement device having the configuration [4] above, even if a terminal has been excluded from the measurement of communication delay time, it can be automatically added as a terminal to be measured after the terminal resumes transmitting packets 50.

[0057] 11 Server 12, 12-1, 12-2, 12-3 Terminal 13A, 13B, 13C Transfer device 14 Observation unit 15 Measurement device 16 Terminal transmission packet monitoring unit 20 Delay measurement device 21 Monitoring setting unit 22 Delay measurement unit 30 Operator terminal C1, C2 Control signal 41, 42, 43 Network P0 Packet 51 Probe packet Tp1, Tp2 Probe packet transmission interval

Claims

1. A delay measurement device comprising: a data transfer unit that controls data communication between each terminal connected to a network and the network; a delay measurement unit that measures communication delay times between each terminal and the network using predetermined probe packets; a terminal-transmitted packet monitoring unit that individually monitors whether or not each terminal transmits a packet, excluding responses to the probe packets; and a monitoring setting unit that reflects the monitoring status of the terminal-transmitted packet monitoring unit in the control of the probe packets sent by the delay measurement unit.

2. The delay measurement device according to claim 1, wherein the monitoring setting unit identifies whether at least each of the terminals can transition to a sleep state in which it operates in a power-saving manner based on the monitoring status of the terminal transmission packet monitoring unit, and stops transmitting the probe packets to terminals that can transition to a sleep state.

3. The delay measurement device according to claim 1, wherein the monitoring and setting unit compares the packet transmission interval of each terminal with the time of the idle timer of the corresponding terminal, and excludes the corresponding terminal from the measurement of communication delay time if the packet transmission interval is large.

4. The delay measurement device according to claim 3, wherein when the monitoring setting unit detects an increase in the number of packets sent by each terminal, if the terminal in question is not subject to measurement of communication delay time, the monitoring setting unit adds the terminal in question to the subjects of measurement of communication delay time.

Images