JP2003348106A - Bandwidth measurement system, network node apparatus, bandwidth measurement method, and network - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a bandwidth measurement system capable of enhancing the availability of a network. <P>SOLUTION: The network node apparatus 101 continuously transmits a measurement packet to its own apparatus. The network node apparatus 101 detects the measurement packet returned to the network node apparatus 101 via network node apparatuses 102 to 104 from received data to measure an data amount D of the measurement packet received within a prescribed time T. The network node apparatus 101 transmits data from a terminal 101-a to a transmission destination node apparatus at a transmission rate of (data amount D/ prescribed time T). <P>COPYRIGHT: (C)2004,JPO

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a bandwidth measurement system, a network node device, a bandwidth measurement method, and a network, and more particularly, to a bandwidth measurement system in a ring network.

[0002]

2. Description of the Related Art A ring network (circular network), which is a packet transfer network, is constructed so that data packets can be transferred without being discarded, especially in the network.

In such a ring network,
Generally, in the network node device in the network, a buffer is prepared to absorb a difference in operating frequency of each device and a data packet is transferred, so if an abnormal state such as congestion occurs for some reason, Packets are discarded due to overflow of those buffers.

[0004] In recent years, ring networks have been used for various purposes, and there is a demand for enhancing reliability and avoiding discarding of data packets generated in the network.

[0005] In order to meet this demand, for example, IEEE
As disclosed in E Draft 802.3ae, the data transmission speed of the interface of the network node device is predetermined. In other words, the data transmission speed is set to a value smaller than the transmission line speed in order to enable the transfer even if the transmission line speed fluctuates in advance within the allowable frequency deviation standard. If the data transmission speed is followed, packets will not be discarded in the network even if the operating frequency of each device varies within the range of the standard.

FIG. 6 shows a configuration of such a conventional network node device. In FIG. 6, a conventional network node device includes idle (idle) detection circuits 50 and 60 and buffer write circuits 51 and 61.
, Buffers 52 and 62, and buffer read circuit 70
, An idle sending circuit 71 and an operation clock generator 72
It is composed of

The idle detection circuit 50 extracts a clock from a signal input from another network node device via a transmission line, and detects idle data. id
The le detection circuit 60 extracts a clock from an input signal from a terminal device which is a lower device of the device itself, and
Find the data. The idle data is used for various controls such as clock extraction.

The buffer write circuit 51 writes only data packets other than the idle data detected by the idle detection circuit 50 into the buffer 52 at a timing according to the clock extracted by the idle detection circuit 50.
The buffer writing circuit 61 writes only data packets other than the idle data detected by the idle detection circuit 60 into the buffer 62 at a timing according to the clock extracted by the idle detection circuit 60.

The buffer read circuit 70 reads a packet written in the buffer 52 or 62 at a timing according to the operation clock from the operation clock generator 72. For example, packets are alternately read from the buffers 52 and 62. The packet may be read preferentially from one of the buffers 52 and 62, that is, if the packet is stored in the one buffer, the packet may be preferentially read from that buffer.

The idle sending circuit 71 outputs the packet read by the buffer reading circuit 70 to the transmission line, and inserts idle data at a timing when there is no packet and outputs the packet to the transmission line.

Here, when the clock extracted from the input signal from the transmission line is earlier than the operation clock of the operation clock generator 72, the write position of the buffer 52 catches up with the read position and overflow occurs. Therefore, the buffer write circuit 51 stops writing to the buffer 52 when the relationship between the write position and the read position of the buffer 52 is in a state immediately before the write position catches up with the read position. Then, the buffer read circuit 70
When the data is read from the buffer 52 and the write position and the read position are separated by a predetermined interval, the buffer write circuit 51 restarts the writing to the buffer 52.

[0012]

In the apparatus shown in FIG. 6, the data transmission speed of the data passing through the buffer 62 is the minimum value of the transmission line speed, that is, 10 Gbps-100 pp.
It is predetermined to a value smaller than m. For this reason, in order to prevent the packet from being discarded, it is necessary to always keep this data transmission speed regardless of the actual transmission line speed in this network node device, so that the reading from the buffer 62 is performed. The idle transmission circuit 71 transmits an amount of idle data corresponding to the difference between the actual transmission line speed and the predetermined data transmission speed.
To be inserted.

As a result, if there is a difference between a predetermined data transmission speed and the operating frequency of the network node device actually configuring the network, the bandwidth of the transmission path is wasted. is there.

An object of the present invention is to provide a bandwidth measurement system, a network node device, a bandwidth measurement method, and a network, which can increase the use efficiency of a network.

[0015]

SUMMARY OF THE INVENTION A bandwidth measuring system according to the present invention is a bandwidth measuring system in a network constituted by a plurality of network node devices. Sending means for sending to the path, receiving means for receiving the measurement data arriving via the path, and available bandwidth of the path based on the measurement data received within a predetermined time by the receiving means And measuring means for measuring

The network node device according to the present invention comprises:
A network node device constituting a network, comprising: sending means for continuously sending measurement data to a predetermined path on the network; receiving means for receiving the measurement data arriving via this path; Measuring means for measuring the available bandwidth of the path based on the measurement data received by the receiving means within a predetermined time.

A bandwidth measuring method according to the present invention is a bandwidth measuring method in a network constituted by a plurality of network node devices, and a transmitting step of continuously transmitting measurement data to a predetermined path on the network. And a receiving step of receiving the measurement data arriving via the path, and a measurement step of measuring an available bandwidth of the path based on the measurement data received within a predetermined time by the reception step. It is characterized by including.

[0018] The network according to the present invention is a network composed of a plurality of network node devices, wherein each of the plurality of network node devices continuously sends measurement data to a predetermined path on the network. Sending means, receiving means for receiving the measurement data arriving via the path, and measurement for measuring the available bandwidth of the path based on the measurement data received within a predetermined time by the receiving means Means.

The operation of the present invention is as follows. The measurement data is continuously transmitted to a predetermined path of a network constituted by a plurality of network node devices. Based on the measurement data received within a predetermined time by passing through this route, the available bandwidth of this route is measured. That is, the data amount of the measurement data received within a predetermined time is measured. This is the amount of data that could actually pass through this path without being discarded, and corresponds to the available bandwidth of this path.

By measuring the available bandwidth in this way, it is possible to obtain a transmission speed that allows data newly transmitted to the path to pass through the path without being discarded. Thus, it is possible to increase the efficiency of network use.

[0021]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram showing a configuration of a ring network according to an embodiment of the present invention. In FIG. 1, a ring network is constructed by network node devices 101, 102, 103 and 104. Terminal devices 101-a, 102-a, 103-a, and 104-a, which are lower-level devices, are connected to each network node device. For example, when transferring a packet from the device 101 to the device 103, the device 102 or the device 104
Have to go through.

FIG. 2 is a diagram showing the configuration of each network node device shown in FIG. 2, each network node device shown in FIG. 1 has an idle (idle)
Detecting circuits 10 and 20, buffer writing circuits 11 and 21, buffers 12 and 22, buffer reading circuit 30, idle sending circuit 31, measuring packet generating circuit 32, measuring packet receiving circuit 33, selector 34 and an operation clock generator 35.

The operation clock generator 35 generates an operation clock of the own device and supplies it to each unit in the own device.

The idle detection circuit 10 extracts a clock from a signal input from another network node device via a transmission line, and detects idle data. id
The le detection circuit 20 extracts a clock from an input signal from a terminal device which is a lower device of the device itself, and
Find the data. For example, in the network node device 101 shown in FIG. 1, a signal from the network node device 102 or 104 is
And the signal from the terminal device 101-a is idle
The signal is input to the detection circuit 20.

When the normal mode is set, the buffer write circuit 11 detects the idle detected by the idle detection circuit 10.
Data packets other than data (real packets, measurement packets) are written to the buffer 12 in synchronization with the clock extracted by the idle detection circuit 10. When the measurement mode is set, the buffer writing circuit 11 writes only the actual packet in the received data to the buffer 12 in synchronization with the clock extracted by the idle detection circuit 10 and also writes the received data for measurement. Packet receiving circuit 3
Output to 3.

The buffer write circuit 21 writes only data packets other than the idle data detected by the idle detection circuit 20 into the buffer 22 in synchronization with the clock extracted by the idle detection circuit 20.

The buffer reading circuit 30 synchronizes the buffer 12 with the operation clock from the operation clock generator 35.
Alternatively, the packet stored in 22 is read. For example, packets are read from the buffers 12 and 22 alternately. The packet may be preferentially read from one of the buffers 12 and 22. That is, if a packet is stored in the one buffer, the packet may be preferentially read from that buffer. When reading a packet from the buffer 22 when the normal mode is set, the buffer reading circuit 30 controls the reading speed according to the measurement result by the measurement packet receiving circuit 33.

When the packet read out by the buffer readout circuit 30 is received, the idle sending circuit 31 outputs the packet as it is to the selector 34, and when not received, inserts the idle data and outputs it to the selector 34. I do.

The measurement packet generator 32 generates a measurement packet based on the operation clock from the operation clock generator 35 and outputs it to the selector 34. The selector 34 is
According to the set mode, the idle transmission circuit 31
And the output of the measurement packet generation circuit 32 are selected and output to the transmission line. Measurement packet receiving circuit 3
3 measures the available bandwidth of the ring network based on the data received from the buffer writing circuit 11 and outputs the measurement result to the buffer reading circuit 30.

FIG. 4A shows a format example of a real packet which is real data, FIG. 4B shows a format example of a measurement packet, and FIG. 4C shows a format example of idle data. I have. As shown in FIGS. 4A to 4C, each network node device can identify each data by the 1-byte header portion of each data.

Next, the operation of this embodiment will be described with reference to the drawings. First, the operation of a single network node device constituting a ring network according to an embodiment of the present invention will be described. There are two operation modes of the network node device shown in FIG. 2, a normal mode and a measurement mode. First, the operation of the network node device when setting the normal mode will be described.

In the network node device shown in FIG. 2, when the operation mode is set to the normal mode,
The idle detection circuits 10 and 20 extract a clock from the received data by a predetermined method. Further, the idle detection circuits 10 and 20 detect data packets and idle data from the received data based on the extracted clock.

The buffer write circuits 11 and 21
Only data packets are written to the buffers 12 and 22 based on the detection results of the e detection circuits 10 and 20. Buffer 12,
Reference numeral 22 denotes a FIFO type memory, for example, which stores a data packet according to an instruction from the buffer writing circuits 11 and 21 and outputs a data packet according to an instruction from the buffer reading circuit 30.

The buffer read circuit 30 synchronizes the operation of the buffer 12 with the operation clock from the operation clock generator 35.
Or, read the data packet from 22. However, when reading data from the buffer 22 in which data from the terminal device is stored, the buffer reading circuit 30 does not allow the data reading speed (transmission speed) to exceed the measurement result by the measurement packet receiving circuit 33. Control the reading speed. For example, when data in one storage area of the buffer 22 is read, reading is stopped for a plurality of clocks according to the measurement result, and then reading is performed again.

Here, if the speed at which the buffer reading circuit 30 reads from the buffer 12 is faster than the speed at which the buffer writing circuit 11 writes to the buffer 12,
The data packet stored in the buffer 12 does not stay. On the other hand, when the data packet is late, the data packet starts to stay in the buffer 12.
2 is full. When the buffer 12 is full, the buffer write circuit 11 stops writing to the buffer 12. Thereafter, when the buffer reading circuit 30 reads from the buffer 12 to make room in the buffer 12 again, the buffer writing circuit 11 restarts writing to the buffer 12.

When the data packet read by the buffer reading circuit 30 is input, the idle sending circuit 31 outputs the data packet to the selector 34 as it is. The idle sending circuit 31 outputs idle data to the selector 34 when a data packet is not received from the buffer reading circuit 30. The selector 34 ignores the data from the measurement packet generation circuit 32 and outputs the data from the idle transmission circuit 31 to the transmission line as it is.

Next, the operation of the network node device shown in FIG. 2 when the measurement mode is set will be described. In the network node device shown in FIG. 2, when the operation mode is set to the measurement mode, the measurement packet generation circuit 3
2 continuously generates and outputs measurement packets based on the operation clock from the operation clock generator 35. At this time, no idle data is inserted. That is,
When the measurement mode is set, a plurality of measurement packets are continuously output from the measurement packet generation circuit 32 without inserting idle data between them. The measurement packet is created in a predetermined length and format as shown in FIG. 4B, and an identifier that can be distinguished from other data (real packet, idle data) is added.

The selector 34 ignores the data from the idle transmission circuit 31 and outputs the data from the measurement packet generation circuit 32 to the transmission line as it is. The idle detection circuit 10 extracts a clock from the received data by a predetermined method. The idle detection circuit 10 detects a data packet and idle data from the received data based on the extracted clock. Buffer writing circuit 11
Writes only the actual packet in the received data to the buffer 12 based on the detection result of the idle detection circuit 10, and outputs the received data to the measurement packet receiving circuit 33. Note that only the measurement packet in the received data may be output to the measurement packet receiving circuit 33.

FIG. 3 is a diagram showing a configuration of the measurement packet receiving circuit 33 shown in FIG. 3, the measurement packet receiving circuit 33 includes a measurement packet detecting circuit 33-.
1 and a counter 33-2. The measurement packet detection circuit 33-1 includes the buffer write circuit 11
Detects the measurement packet from the data received from, and outputs the detection result to the counter 33-2. Counter 33-2
Counts the number of measurement packets received during the predetermined time T based on the detection result of the measurement packet detection circuit 33-1 and outputs the count result to the buffer reading circuit 30.

For example, a 32-bit counter (not shown) that uses the operation clock from the operation clock generator 35 as a clock is operated, and counts how many measurement packets have arrived while the counter makes one round. This count value is output to buffer read circuit 30. Since the data length of the measurement packet is predetermined as shown in FIG. 4B, the total data amount of the measurement packet received during the predetermined time T is obtained from this count value.
The buffer reading circuit 30 uses the count value during the predetermined time T as the reading speed of the buffer 22.

Next, the operation of the entire ring network of FIG. 1 constructed by the network node device shown in FIG. 2 that performs the above-described operation will be described with reference to FIGS. Here, the network node device 1
The operation of transferring a packet from 01 to the network node device 103 via the network node device 102 will be described.

In FIGS. 1 and 2, the network node device 101 operates in the measurement mode before the network node device 101 transfers the real packet from the terminal device 101-a to the network node device 103. At this time, the other network node devices 102, 1
03 and 104 are each operating in the normal mode.

As described above, in the network node device 101 whose operation mode is set to the measurement mode, the measurement packet generation circuit 32 continuously transmits the measurement packet in accordance with the operation clock of the operation clock generator 35. To 102.

In the network node device 102 whose operation mode is set to the normal mode, the measurement packet from the network node device 101 is written into the buffer 12 by the operations of the idle detection circuit 10 and the buffer writing circuit 11. The measurement packet stored in the buffer 12 is read out by the buffer readout circuit 30 in synchronization with the operation clock of the operation clock generator 35, and is output to the network node device 103 via the idle transmission circuit 31 and the selector 34. You.

At this time, if the operation clock of the operation clock generator 35 of the device 102 is earlier than the operation clock of the operation clock generator 35 of the device 101,
When the reading speed of the buffer 12 in the device 102 is higher than the writing speed, all the measurement packets output by the device 101 pass through the device 102 and are output to the device 103.

On the other hand, if the operation clock of the device 102 is slower than the operation clock of the device 101, that is, if the read speed of the buffer 12 in the device 102 is lower than the write speed,
Overflows, so that packet discarding occurs in the device 102.

Since the operation mode of the network node device 102 is set to the normal mode, the buffer 22 for storing the actual packet from the terminal device 102-a is stored.
Is also read out and output to the network node device 103.

Subsequently, in the network node device 103 whose operation mode is set to the normal mode, data packets (real packets and measurement packets) from the network node device 102 are similarly written into the buffer 12, and Actual packets from the terminal device 103-a are written into the buffer 22, and these packets are sequentially read out by the buffer reading circuit 30 and output to the network node device 104.

At this time, if the operation clock of the device 103 is faster than the operation clock of the operation clock generator 35 of the device 102, all the measurement packets arriving through the device 102 are output to the device 104, and If the operation clock of 103 is slower than the operation clock of the device 102, the packet is discarded due to the overflow.

The same operation is performed in the network node device 104 whose operation mode is set to the normal mode, whereby the data packet from the network node device 103 is output to the network node device 101.

In the network node device 101 whose operation mode is set to the measurement mode, the measurement packet received via the network node devices 102, 103 and 104 is converted into the measurement packet detecting circuit 33- of FIG.
1, the counter 33- in FIG.
2 counts the number of measurement packets received during the predetermined time T. Thereby, the total data amount D of the measurement packets received during the predetermined time T is obtained.

Since this count value is the number of measurement packets output from the device 101, passed through the devices 102, 103 and 104, and actually returned to the device 101 again, the network node device 101 sets the (data amount D If the actual packet from the terminal device 101-a is transmitted to the network at a transmission speed equal to or less than the (predetermined time T), the packet can be transmitted to the destination network node device without being discarded in the network. That is,
(Data amount D / predetermined time T) corresponds to the available bandwidth (remaining bandwidth) of the network.

The counter 33-2 in FIG. 3 outputs the count value to the buffer read circuit 30. When the count value is output to the buffer read circuit 30, the operation mode of the network node device 101 returns to the normal mode. In network node device 101 in which the operation mode is set to the normal mode, buffer read circuit 30
Stores the actual packet from the terminal device 101-a in the buffer 2
When reading data from No. 2, the read speed is controlled so as not to exceed the speed of (data amount D / predetermined time T). Therefore, the read actual packet reaches the network node device 103 via the network node device 102 without being discarded on the way.

FIG. 5 is a diagram showing a flowchart of the above-mentioned bandwidth measuring operation. 1 and 5, the network node device 1 whose operation mode is set to the measurement mode
In step S1, the measurement packet is continuously transmitted to the transmission path of the ring network (step S1). The transmission source network node device 101 is connected to the other network node devices 102 to 10 configuring the ring network.
Then, the measurement packets that have returned after passing through Step 4 are detected from the received data (Step S2), whereby the measurement packets received during the predetermined time T are counted (Step S3). In this way, the available bandwidth of the network is measured. Then, the network node device 10
When sending data from the terminal device 101-a, which is a lower device of the own device, 1 controls the sending speed according to the measurement result by the bandwidth measurement.

As described above, according to the embodiment of the present invention, the available bandwidth of the ring network is measured, and the actual packet is transmitted to the network at a speed corresponding to the measured bandwidth. It does not occur and the network utilization efficiency is good. Further, unlike the related art, there is no need to suppress the sending speed in anticipation of the worst value, so that the available data speed increases.

Further, as shown in the present embodiment, the operation clocks of the respective network node devices are independent of each other, and the network operator can obtain the above-mentioned effects without managing and operating the operation clocks. Because of this, network operation flexibility is high.

In the embodiment of the present invention, the device 101 transmits the measurement packet to the device 10 via the devices 102 to 104.
By transferring back to 1, the available bandwidth of the entire network is measured. However, the terminal device 101-a is transmitted from the device 101 to the device 103 via the device 102.
When transferring the real packet from the terminal device 101-
a does not pass through the device 104, so the device 101 is not the available bandwidth of the entire network.
It suffices to measure the available bandwidth of the path from to the device 103 via the device 102. Therefore, in this case, the device 101 transfers the measurement packet to the device 103 via the device 102, and the device 103 counts the number of measurement packets received during the predetermined time T, whereby the device 101 The available bandwidth of the route to the device 103 via the device 102 may be measured, and this may be notified to the device 101.

Since the available bandwidth changes with the aging of the operation clock of each network node device, the available bandwidth may be measured at predetermined time intervals during operation of the network.

The measurement of the available bandwidth may be performed when the network is started. When the network is started, there is no data flowing on the network. Therefore, in the device 102, when the operation clock of the device 102 is slower than the operation clock of the device 101, the buffer 12 of the device 102 overflows, and the device 102 of the measurement packets output by the device 101 when the network is started up. Only the band corresponding to the read speed synchronized with the operation clock of 102 passes through the device 102 and is output to the device 103.

Similarly, in the device 103, when the operation clock of the device 103 is slower than the operation clock of the device 102, the reading speed synchronized with the operation clock of the device 103 among the measurement packets arriving through the device 102 is set. Only the corresponding band is output to the device 104.

Similarly, when the device 104 operates, the measurement (data amount D / predetermined time T) by the device 101 indicates that the device 1 constituting the ring network
Of the devices 01, 102, 103 and 104, the read speed from the buffer 12 of the device having the slowest operation clock is obtained.

As described above, the data rate (data amount D / predetermined time T) measured at the time of starting up the network should be the slowest transfer rate among the devices. If the real packet from 101-a is to be transferred, the buffer 12
Does not overflow, and all real packets reach the device 103.

[0064]

The effect of the present invention is that the utilization efficiency of the network can be improved. The reason is,
Continuously sending measurement data to a predetermined path of a network constituted by a plurality of network node devices,
This is because the available bandwidth of this route is measured based on the measurement data received within a predetermined time by passing through this route.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a ring network according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating a configuration of each network node device of FIG. 1;

FIG. 3 is a diagram showing a configuration of a measurement packet receiving circuit 33 of FIG. 2;

FIG. 4 is a diagram showing a format example of each data;
(A) shows a format example of an actual packet, (b) shows a format example of a measurement packet, and (c) shows an id.
4 shows a format example of le data.

FIG. 5 is a flowchart illustrating a bandwidth measuring operation according to an embodiment of the present invention.

FIG. 6 is a diagram showing a configuration of a conventional network node device.

[Explanation of symbols]

10,20 idle detection circuit 11, 21 Buffer writing circuit 12,22 buffers 30 Buffer readout circuit 31 idle sending circuit 32 Measurement packet generator 33 packet receiver for measurement 33-1 Measurement packet detection circuit 33-2 Counter 34 Selector 35 Operation clock generator 101-104 network node device 101-a to 104-a terminal device

   ────────────────────────────────────────────────── ─── Continuation of front page    F term (reference) 5K030 GA13 GA14 HA08 HC01 HD02                       JA10 JT03 KA03 KX12 LC09                       LC11 MB02 MC03                 5K031 AA02 BA03 CB10 DB03 DB07                       EA11                 5K035 AA01 DD01 EE21 GG02 JJ05

Claims (29)

[Claims] 1. A bandwidth measuring system in a network comprising a plurality of network node devices, comprising: sending means for continuously sending measurement data to a predetermined route on the network; Receiving means for receiving the measurement data, and measuring means for measuring an available bandwidth of the path based on the measurement data received within a predetermined time by the receiving means. Bandwidth measurement system. 2. The bandwidth measuring system according to claim 1, wherein said measuring means measures a data amount of said measurement data received within said predetermined time by said receiving means. 3. The data length of the measurement data is predetermined, and the measurement means counts the number of the measurement data received within the predetermined time by the reception means. The bandwidth measurement system according to claim 2, wherein 4. The network node device according to claim 1, further comprising control means for controlling a transmission speed of actual data to be transmitted to the path according to a measurement result of the measurement means. Bandwidth measurement system. 5. The bandwidth measurement system according to claim 4, wherein the actual data is data from a lower device connected to the network node device. 6. The bandwidth according to claim 1, wherein the bandwidth measurement is performed at a time of starting up the network or at predetermined time intervals during operation of the network. Width measuring system. 7. The bandwidth measurement system according to claim 1, wherein said network is a ring network. 8. A network node device constituting a network, comprising: transmitting means for continuously transmitting measurement data to a predetermined path on the network; and receiving the measurement data arriving via this path. A network node device comprising: receiving means; and measuring means for measuring an available bandwidth measurement of the path based on the measurement data received by the receiving means within a predetermined time. 9. The network node device according to claim 8, wherein said measuring means measures a data amount of said measurement data received within said predetermined time by said receiving means. 10. The data length of the measurement data is predetermined, and the measurement means counts the number of the measurement data received within the predetermined time by the reception means. The network node device according to claim 9, wherein 11. The network node device according to claim 8, further comprising control means for controlling a transmission speed of actual data to be transmitted to said path according to a measurement result of said measurement means. 12. The network node device according to claim 11, wherein the actual data is data from a lower device connected to the device. 13. The network according to claim 8, wherein the bandwidth measurement is performed at a time of starting up the network or at predetermined time intervals during operation of the network. Node device. 14. The network node device according to claim 8, wherein said network is a ring network. 15. A method for measuring bandwidth in a network comprising a plurality of network node devices, comprising: a transmitting step of continuously transmitting measurement data to a predetermined path on the network; Receiving the measurement data, and measuring the available bandwidth of the path based on the measurement data received within a predetermined time by the reception step. Bandwidth measurement method. 16. The bandwidth measuring method according to claim 15, wherein the measuring step measures a data amount of the measurement data received within the predetermined time by the receiving step. 17. The data length of the measurement data is predetermined, and the measurement step counts the number of the measurement data received within the predetermined time by the reception step. Item 17. The bandwidth measuring method according to Item 16. 18. The network node device according to claim 15, further comprising a control step of controlling a transmission speed of actual data transmitted to the path according to a measurement result of the measurement step. Bandwidth measurement method. 19. The bandwidth measuring method according to claim 18, wherein the actual data is data from a lower device connected to the network node device. 20. The bandwidth according to claim 15, wherein the bandwidth measurement is performed at a time of starting up the network or at predetermined time intervals during operation of the network. Width measurement method. 21. The bandwidth measuring method according to claim 15, wherein said network is a ring network. 22. A network constituted by a plurality of network node devices, wherein each of the plurality of network node devices continuously sends measurement data to a predetermined path on the network, Receiving means for receiving the measurement data arriving via the path, and measurement means for measuring an available bandwidth of the path based on the measurement data received within a predetermined time by the reception means; A network, characterized in that: 23. The network according to claim 22, wherein said measuring means measures a data amount of said measurement data received within said predetermined time by said receiving means. 24. The data length of the measurement data is predetermined, and the measurement means counts the number of the measurement data received within the predetermined time by the reception means. 24. The network according to claim 23, wherein: 25. The apparatus according to claim 22, wherein each of the plurality of network node devices has a control unit for controlling a transmission speed of actual data transmitted to the path according to a measurement result of the measurement unit. 24. The network according to any of 24. 26. The network according to claim 25, wherein the actual data is data from a lower device connected to the own node device. 27. The network according to claim 22, wherein the bandwidth measurement is performed at a time of starting up the network or at a predetermined time interval during the operation of the network. . 28. The network according to claim 22, wherein said network is a ring network. 29. A network comprising the bandwidth measurement system according to claim 1. Description: