JPH08242239A - Cell flow rate monitoring system for atm network - Google Patents

Abstract

PURPOSE: To attain cell flow rate measurement and monitor considering the number of active connections by judging the start of a burst based upon a condition that the length of a virtual queue is more than fixed time in a non- zero state. CONSTITUTION: Each of virtual queue length storing parts 7 to 10 in respective cell flow rate excess judging parts 2 to 5 adds the arrival frequency of cells in each arrival of a cell, subtracts a fixed rate from the added cell arrival frequency and finds out the added/subtracted result as virtual queue length. Each of burst judging parts 11 to 14 judges the start of a burst when the nonzero state of the virtual queue length is continued for a prescribed period or more. When the value of the virtual queue length is reduced less than the minimum value of the virtual queue length for a prescribed period going back from a current point of time, the end of the burst state is judged. In said constitution, the generation of misjudgement that the instantaneous extension of the virtual queue length due to the simultaneous arrival of cells from plural connections is judged as the start of a burst can be prevented and the flow rate of cells accurately be monitored.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a wide band ISDN (Inte
ATM (Asynchronous Transfer) used for grated Services Digital Network
Mode, Asynchronous Transfer Mode) The present invention relates to a traffic measurement technique in switching, and more particularly to a cell flow rate monitoring system of an ATM network suitable for accurately monitoring a cell flow rate.

[0002]

2. Description of the Related Art In an ATM used for data transfer in a broadband ISDN, various kinds of information such as images and voices are divided into short fixed-length blocks with a header called "cell", and efficiency is divided into units. Well multiplexed. This cell is dynamically allocated in time, and the communication speed can be variably set by changing the number of allocated cells, and information such as an image whose generated information amount greatly changes with time is centrally transmitted. be able to.

Further, in the network exchange processing of information, since the cell switch performs channel identification based on the header, the speed can be increased by hardware. In such cell transfer control, network resources are appropriately allocated when a call is accepted. However, even if network resources are properly allocated at the time of accepting a call, the bursty traffics may overlap each other and the quality may momentarily not be satisfied. That is, in the cell switch, a buffer is arranged as a save memory in case of a cell collision, but due to overlapping bursty traffic, the number of cells exceeding the capacity of the buffer is input and the cells in the buffer are input. The cell is discarded due to the overflow, and as a result, the quality of cell transfer is deteriorated. In order to prevent this, it is necessary to monitor the input cell.

Regarding such cell overflow, for example,
W. The document "Data communications by Fisher et al.
using ATM: architectures, protocols, and resource m
anagement ”(IEEE Communication Magazine, August 1994 issue), pp. 24-33. Here, each connection repeats the active state and the inactive state, and when sending cells from the active connection at regular intervals, cell overflow in the multiplexing buffer when multiple connections are multiplexed has sufficient buffer capacity. If so, it is described that the effect of the bandwidth of the active connection exceeding the line capacity is larger than the effect of the simultaneous arrival of cells from each connection.

Conventionally, as a cell flow rate monitoring technique, the number of cells in a time window of a certain size is monitored, or the queue length is added every time a cell arrives and subtracted at a certain rate. What is called a leaky bucket is common. In the technology that monitors the cell flow rate by considering the number of active connections with the number of cells in the monitoring (time) window of a certain size, if the transmission interval of cells from the connection and the monitoring window length match , The number of cells observed in the monitoring window represents the number of active connections, regardless of the phase difference between the time window and the transmission time of the cell of the connection of interest.

However, in general, the cell transmission intervals are different for each connection, so that it is difficult to match the monitoring window length with the cell transmission intervals of all the connections. When the monitoring window length does not match the cell transmission interval, the number of cells observed in the monitoring window fluctuates every moment depending on the phase difference between the monitoring window and the cell transmission interval from the connection. In this way, when monitoring the number of cells in a monitoring window of a certain size,
It is difficult to monitor considering the number of active connections.

Further, the leaky bucket determines the arriving cell as the excess flow amount when the queue length that is added for each cell arrival and subtracted at a constant rate exceeds a threshold value. This is a technique applied when the flow rate is monitored individually for each connection. It is possible to use this leaky bucket for cell flow rate monitoring considering the number of active connections. However, when the cell flow rate is monitored based on the judgment of the start and end of the burst state depending on whether the queue length that is added at each cell arrival and subtracted at a constant rate is zero or non-zero, multiple connections are If the simultaneous arrival of the cells occurs, the queue length momentarily becomes non-zero but immediately returns to zero, so it is erroneously determined that a very short burst has occurred. Further, the erroneous determination is repeated while the connection continues to send cells. Therefore, it is difficult to judge the burst only by the value of the queue length. Also,
The leaky bucket only determines whether or not the specific rate is exceeded, and it is impossible to evaluate the value of the cell flow rate using the leaky bucket as it is.

[0008]

The problem to be solved is that the prior art cannot measure and monitor the cell flow rate in consideration of the number of active connections. The object of the present invention is to solve these problems of the prior art,
An object of the present invention is to provide an ATM network cell flow rate monitoring system capable of accurately monitoring the cell flow rate.

[0009]

In order to achieve the above object, an ATM network cell flow rate monitoring system of the present invention comprises:
(1) A monitoring system for the flow rate of cells sent from a plurality of connections in an ATM network to one buffer 1. The number of cell arrivals is added for each cell arrival, and the added number of cell arrivals is added. The virtual queue length holding units 7 to 10 that subtract the result of addition and subtraction as a virtual queue length at a constant rate, and the non-zero state of the virtual queue length obtained by the virtual queue length holding units 7 to 10 are for a predetermined period or more. When it continues, the start of the burst state is determined,
After the start of the burst state, the virtual queue length holding units 7-1
The burst determination unit 1 that determines the end of the burst state when the value of the virtual queue length obtained by 0 becomes smaller than the minimum value of the virtual queue length during a predetermined period from the present time
1 to 14 are included at least. (2) In the cell flow monitoring system for the ATM network according to (1), the virtual queue length holding unit 7 is composed of a set of virtual queue length holding units 7 to 10 and burst determination units 11 to 14. 10 to 10 of a plurality of cell flow rate excess determination units 2 to 5 having different virtual queue length subtraction rates, and a plurality of cell flow rate excess determination units 2 to 5 for which the burst determination units 11 to 14 have determined the non-burst state. Of the virtual queue length holding units 7 to 10 that has the lowest subtraction rate of the virtual queue length, and the determined virtual queue length holding units 7 to 10 in the cell flow rate excess determination units 2 to 5 are determined. And a minimum value determination unit 6 which sends out the subtraction rate of as the current cell flow rate evaluation value. (3) In the cell flow monitoring system of the ATM network according to (1) or (2) above, the cell transmission of any one connection is performed for a predetermined period used by the burst determination units 11 to 14. It is characterized in that the interval.

[0010]

In the present invention, the start of burst is determined on the basis that the virtual queue length obtained by the virtual queue length holding unit is non-zero for a certain period of time or longer. That is,
In determining the start of the burst state, protection is performed based on the information on the virtual queue length in a predetermined past period. As a result, a momentary increase in virtual queue length due to simultaneous arrival of cells from a plurality of connections will not be erroneously determined as the start of a burst.

Further, a cell flow rate excess determination section is configured by combining a virtual queue length holding section and a burst determination section, and a plurality of cell flow rate excess determination sections having different virtual queue length subtraction rates are provided. In this configuration, the minimum of the virtual queue length subtraction rates of the cell flow excess determination unit that does not detect the burst state is the cell flow rate or more considering the number of active connections, and the minimum value determination unit determines this minimum value. The subtraction rate of is output as the evaluation value of the cell flow rate. As described above, by providing a plurality of cell flow rate excess determination units having different virtual queue length subtraction rates, it is possible to obtain a cell flow rate in consideration of the number of active connections.

[0012]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of a configuration according to the present invention of a cell flow rate monitoring system for an ATM network according to the present invention. In FIG. 1, reference numeral 1 is a buffer in which cells from each connection are multiplexed, 2 to 5 are cell flow excess determination units for determining the burst state of the buffer 1 according to the present invention,
Reference numeral 6 is a minimum value determination unit that outputs an evaluation value of the cell flow rate of the buffer 1 based on the determination results of the cell flow rate excess determination units 2 to 5 according to the present invention.

Each of the cell flow rate excess judging units 2 to 5 is composed of a virtual queue length holding unit 7 to 10 and a burst judging unit 11 to 14, respectively, and the virtual queue length holding units 7 to 10 are provided.
Adds "1" each time a cell arrives in buffer 1,
The added value is subtracted at a different constant rate and held as a "virtual queue length". In the present embodiment, the subtraction rate of each of the cell flow rate determination devices 2 to 5 is set to 1/4, 2/4, 3/4, and 4/4 of the cell read speed of the buffer 1, respectively. When the value of the "virtual queue length" becomes zero or less, the value is set to zero. Therefore, assuming that the cell flow rate is input to the buffer 1 having a read speed equivalent to the subtraction rate, the virtual queue length holding units 7 to 10 determine the number of cells stored in the buffer 1. Show.

Further, the burst judgment units 11-14, based on the "virtual queue length" of the virtual queue length holding units 7-10,
The start and end of the burst state of the buffer 1 are determined. That is, it is determined that the burst state has started when the buffer 1 is in the non-burst state at the present time and the “virtual queue length” of the virtual queue length holding units 7 to 10 continues to be non-zero for a predetermined period or longer. To do. On the contrary, when the current buffer is in the burst state and the virtual queue length obtained by the virtual queue length holding units 7 to 10 is smaller than the minimum value of the virtual queue length in the period back a predetermined period from the current time, , The end of the burst state is determined, and the virtual queue length obtained by the virtual queue length holding units 7 to 10 is reset to zero.

The above operation can be formally expressed using the following mathematical expression, where q (t) is the virtual queue length at time t. When a cell arrives at time t, the virtual queue length becomes q (t) = q (t) + a, and the virtual queue length becomes q (t) = max (q (t) -r, 0). Here, "r" is the subtraction rate of the virtual queue length.

Based on the virtual queue length, the burst determination units 11 to 14 determine whether or not the current cell flow rate exceeds the subtraction rate of each virtual skew as follows. A predetermined period, which is the protection time for burst start and end determination, is set to w
Then, in the case where the buffer 1 is in the non-burst state at the present time, if q (t−t ′)> 0, ∀t′ε [0, w], it is determined that the time t is the start of the burst state. When the buffer 1 is in the burst state at the present time, if q (t−t ′)> q (t), ∀t′ε [0, w], then the time “t” is determined to be the end of the burst state. At the same time, q (t) = 0.

As described above, in this embodiment, the virtual queue length holding units 7 to 10 and the burst determination units 11 to 14 are provided,
The judgment of the start of the burst state of the buffer 1 is made based on the information of the virtual queue length in a predetermined past period.
As a result, a momentary increase in virtual queue length due to simultaneous arrival of cells from each connection will not be erroneously determined as the start of a burst.

Next, these virtual queue length holding units 7-1
The operation of the cell flow rate excess determination units 2 to 5 including 0 and the burst determination units 11 to 14 and the minimum value determination unit 6 according to the present invention will be described. If the connection sends cells at a predetermined time interval in the active state, the number of cells sent within the time interval is equivalent to the number of active connections. Then, when the cell flow rate from the active connection is balanced with the read speed of the virtual queue, the virtual queue length takes a non-zero value within the cell transmission interval from one connection, and The virtual queue length changes periodically with the interval as the period.

When the cell flow rate from the active connection exceeds the reading speed of the virtual queue of the buffer 1, the virtual queue length calculated by the virtual queue length holding units 7 to 10 increases and decreases overall, and the virtual queue length increases overall. start. That is, when the transmission interval of cells from one connection is set as a cycle, the minimum value of the virtual queue length within this cycle monotonically increases. On the contrary, when the cell flow rate from the active connection becomes lower than the reading speed of the virtual queue of the buffer 1, the virtual queue length obtained by the virtual queue length holding units 7 to 10 starts to be subtracted as a whole. That is, when the transmission interval of cells from one connection is set as a cycle, the minimum value of the virtual queue length within the cycle is monotonically subtracted.

Therefore, if the virtual queue length holding units 7 to 10 and the burst determination units 11 to 14 are set as a set and a plurality of cell flow rate excess determination units 2 to 5 having different virtual queue length subtraction rates are provided, a burst state is created. The minimum one of the virtual queue length subtraction rates of the undetected cell flow rate excess determination units (11 to 14) is equal to or higher than the cell flow rate in consideration of the number of active connections, and the minimum value determination unit 6 determines this minimum value. The subtraction rate is output as the evaluation value of the cell flow rate.

As described above with reference to FIG. 1, in the cell flow monitoring system of the ATM network of the present embodiment, the virtual queue length that is added every time a cell arrives in the buffer and is subtracted at a constant rate. The burst start is determined based on the fact that it is non-zero for a certain period of time or longer. As a result, it is possible to eliminate the effect of the instantaneous increase in the virtual queue due to the simultaneous arrival of cells from a plurality of connections, and it is possible to correctly determine whether or not a burst exceeding the subtraction rate has occurred. Further, by providing a plurality of cell flow rate excess determination units 2-5 having different virtual queue length subtraction rates, it is possible to monitor the cell flow rate in consideration of the number of active connections at the present time.

The present invention is not limited to the embodiment described with reference to FIG. 1, and various modifications can be made without departing from the spirit of the invention. For example, in this embodiment, four cell flow rate excess determination units are provided, but the number is not limited to four. The virtual queue length subtraction rate is also set to "1/4" to "4/4" in the present embodiment, but the increase of the virtual queue length when one cell arrives is set to "4", and each virtual queue is The subtraction value of may be set to "1" to "4". As described above, the circuit configuration becomes simpler when the arithmetic operation is performed with an integer.

[0023]

According to the present invention, the cell flow rate can be measured and monitored in consideration of the number of active connections, and the cell flow rate can be accurately monitored.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a configuration according to the present invention of a cell flow rate monitoring system for an ATM network of the present invention.

[Explanation of symbols]

1: buffer, 2-5: cell flow rate excess determination unit, 6: minimum value determination unit, 7-10: virtual queue length holding unit, 11-1
4: Burst determination section

Claims (3)

[Claims] 1. A system for monitoring the flow rate of cells sent to a buffer from a plurality of connections in an ATM network, wherein the number of cell arrivals is added for each arrival of the cell, and the added number of cell arrivals is calculated. A virtual queue length holding unit that subtracts at a constant rate and obtains the addition / subtraction result as a virtual queue length, and a burst when a non-zero state of the virtual queue length obtained by the virtual queue length holding unit continues for a predetermined period or more. After determining the start of the state, after the start of the burst state, the value of the virtual queue length obtained by the virtual queue length holding means is smaller than the minimum value of the virtual queue length during the predetermined period from the present time. A cell flow rate monitoring system for an ATM network, characterized in that it has at least burst judgment means for judging the end of the burst state. 2. The cell flow monitoring system for an ATM network according to claim 1, comprising a set of said virtual queue length holding means and said burst judgment means, and further comprising a virtual queue length in said virtual queue length holding means. Among the plurality of cell flow rate excess determination means having different subtraction rates and the plurality of cell flow rate excess determination means for which the burst determination means determines the non-burst state, the virtual queue length of the virtual queue length holding means A minimum value determination means is provided for determining the one having the lowest subtraction rate, and transmitting the subtraction rate of the virtual queue length of the virtual queue length holding means in the determined cell flow rate excess determination means as the current cell flow rate evaluation value. AT characterized by
Cell flow monitoring system for M network. 3. A cell flow rate monitoring system for an ATM network according to claim 1, or 2.
A cell flow rate monitoring system for an ATM network, wherein the predetermined period used by the burst determination means is a cell transmission interval of the arbitrary one connection.