JPH08331148A - Atm policing device - Google Patents

Abstract

PURPOSE: To exactly monitor cell traffic by a small capacity hardware by providing a means changing the subtraction rate of a specified counter in accordance with the elapsed time from the arrival time of a cell. CONSTITUTION: This device is composed of a counter counting up every arrival of a cell and counting down in accordance with a preliminarily fixed subtraction rate and a means abolishing the cell received after the count value of this counter exceeds threshold. The device is provided with a means changing the subtraction rate in accordance with the elapsed time from the time of the cell arrival. The changing means includes a timer 9 which is set by the arrival of the cell, plural subtraction rate generation circuits 3 and a selector 10 switching the subtraction rate generation circuits in accordance with the counted time T of the timer. Therefore, when the state that the cells concentratedly arrive neglecting desirable cell interval is synchronizingly generated, the control that the concentration is not permitted is enabled for the cell concentrately arriving on the second and succeeding times.

Description

Detailed Description of the Invention

[0001]

The present invention relates to an asynchronous transfer mode (Async
Used for information transfer by hronous Transfer Mode (hereinafter referred to as "ATM"). In particular, usage parameter control (Usage Parameter Control) that monitors and controls user traffic
Control, hereinafter referred to as "UPC") technology.

UPC is a virtual channel (VC)
After the virtual path (VP) is set, it is monitored whether or not the inflowing cells from the connection into the network violate the previously declared value, and the violating cell is discarded at that point, or Alternatively, it refers to a control in which a tag is added, the tag is transferred to the network, and is discarded according to the congestion state in the network. Such control is called policing control, and a device that executes policing control is called a policing device.

[0003]

2. Description of the Related Art Conventionally, as a technique for controlling polishing,
The leaky bucket method is well known. The leaky bucket method monitors the cell flow by the depth of the "bucket with holes". This is shown in FIG. FIG. 7 is a diagram for explaining the principle of the leaky bucket. Depth B
_The cells flowing into the bucket of _a are sent into the network at a constant rate corresponding to the leakage magnitude R _a . If the inflow is too high, the bucket overflows and the cell is discarded.

A circuit of a conventional example for realizing this rehearsal bucket system will be described with reference to FIG. FIG. 8 is a block diagram of a conventional polishing apparatus. This circuit includes a cell identification unit 1, an up / down counter 2, a subtraction timer 3, a comparison circuit 4, a threshold circuit 5 and a cell discard unit 6. The cell identification unit 1 determines whether or not the arriving cell is a valid cell, and when it is a valid cell, the up / down counter 2
Up. The subtraction timer 3 periodically measures the leakage magnitude R
_The up / down counter 2 is down according to the subtraction rate corresponding to a. The comparison circuit 4 compares the value of the up / down counter 2 with the value of the threshold circuit 5, and when the value of the up / down counter 2 exceeds the value of the threshold circuit 5, outputs a discard instruction to the cell discard unit 6. , The value of the up / down counter 2 is subtracted by that amount.

In the signal of the user in ATM, in addition to the main information, a plurality of types of ancillary information called sub-components exist for each user. Examples of sub-components include OAM (Operation Administration and
Mentenance) cells and alarm cells that are issued when a failure occurs. As an example of the OAM cell, like a MC cell (monitoring cell), a cell in which parity of those cells is inserted into 128 main information cells is added to form a block of 129 cells, and cell loss or bit error in the network Is available (B-ISDN technology, published by Ohmsha in October 1993). These subcomponents are inserted asynchronously with the main information. This is shown in FIG. FIG. 9 is a diagram showing main information and subcomponents. Main information and sub-components are collectively called components.

[0006] If there is more than one component in the signal of the user, the size R _a and depth B _a bucket leakage in conventional leaky bucket scheme, T ₁ the cell spacing in the main information, the burst tolerance ( maximum value) tau ₁ of fluctuations of the cell, the cell interval respectively T _2, T ₃ of each subcomponent, ..., T _c, respectively tau ₂ burst tolerance, tau _3, ..., when the tau _c, R _a = 1 / T ₁ + 1 / T ₂ + ... + 1 / T _c = 1 / T _a B _a = (1 + τ ₁ / T ₁ ) + (1 + τ ₂ / T ₂ ) + ... +
(1 + τ _c / T _c ).

[0007]

However, in the conventional leaky bucket method, when the user signal includes a plurality of components, it is possible to pass traffic that is difficult to predict due to the malicious intention of the user. For example, a component in the case of two are found the cell interval T _1, T ₂ of the two components, which is _{T a = T 1 · T 2} / (T 1 + T 2) <T 1, T 2 Nevertheless, two cells can pass the bucket during 2T _a . When there are three components, three cells can be passed during 3T _a .

In a large number of policing devices, if the concentration of cells as described above is allowed, a situation in which a large number of cells arrive at the ATM switch and other subsequent devices almost at the same time tends to occur. As A
Either a TM switch or other device that follows is equipped with a large-capacity buffer, or it is unavoidable to discard a large number of cells.

In order to prevent this, it has been considered to monitor and control each subcomponent by using a separate leaky bucket. A conventional example for that purpose will be described with reference to FIG. FIG. 10 is a block diagram of a conventional polishing apparatus. In this configuration, the component separating unit 7 separates the main information from the individual sub-components, and the leaky bucket 8 provided for each component.
Monitor each traffic from ₁ to 8 _c . When transmitting cells from the leaky buckets 8 ₁ to 8 _c , the cells are transmitted so that the cell interval does not become narrower than a specified value. The cell discard unit 6 discards the violating cell.

However, when a leaky bucket is provided for each component as described above, it is possible to accurately regulate the leaky bucket, but on the other hand, there is a drawback that a large amount of hardware is required as the number of components increases.

The present invention has been made under such circumstances, and an object of the present invention is to provide an ATM policing apparatus capable of accurately monitoring cell traffic with a small amount of hardware. An object of the present invention is to provide an ATM policing apparatus capable of reducing the cell loss rate in an ATM network.

[0012]

The present invention provides a counter that counts up each time a cell arrives and counts down according to a predetermined subtraction rate, and a cell that arrives after the count value of this counter exceeds a threshold value. It is an ATM policing device having means for discarding.

Here, the feature of the present invention resides in that a means for changing the subtraction rate according to the elapsed time from the arrival time of the cell is provided.

The changing means switches the timer (9) reset by the arrival of a cell, a plurality of subtraction rate generation circuits (3), and the subtraction rate generation circuit according to the measurement time (T) of the timer. It is desirable to include a selector (10).

Thus, for example, when a state in which cells arrive in a concentrated manner ignoring a desired cell interval occurs periodically, it is possible to perform control such that concentration is not allowed for cells that arrive in a concentrated manner after the second time. , It is possible to maintain a desired cell spacing in the ATM network.

[0016]

In the policing device, the counter is incremented each time a cell arrives and the counter is decremented according to a predetermined subtraction rate. As a result, when a cell arrives at a rate exceeding a predetermined rate, the count value of the counter goes in the up direction, and eventually exceeds the threshold value set as the upper limit value. By discarding the cells that have arrived when the count value exceeds the threshold value, it is possible to prevent the cell flow exceeding the specified value from flowing into the ATM network.

In the present invention, the subtraction rate for counting down the counter is changed when the cells arrive at the desired interval and when the cells arrive intensively while ignoring the desired interval. For example, if cells are arriving at the desired intervals, do a fast countdown,
When the cells are arriving intensively ignoring the desired interval, the countdown is controlled to be delayed.

That is, when cells arrive at a desired interval, it is preferable to decrease the value of the counter quickly so as to wait for the arrival of subsequent cells, but cells arrive intensively and periodically. Occasionally, the counter value is slowly decreased so that the counter value exceeds the threshold value due to the subsequent count-up by cells that arrive intensively. As a result, it is possible to discard some of the cells that have subsequently arrived intensively.

Therefore, since it is possible to regulate the transmission of cells ignoring the desired cell interval, it is possible to avoid the situation in which cells arrive intensively at the device following the polishing device. As a result, the loss rate of cells in the device following the polishing device can be reduced. Further, it is not necessary to provide a large capacity buffer used for compensating for the decrease in cell loss rate.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The configuration of an embodiment of the present invention will be described with reference to FIG. FIG. 1 is a block diagram of an apparatus according to the present invention.

The present invention provides a counter 2 that counts up each time a cell arrives and counts down according to a predetermined subtraction rate, and means for discarding a cell that arrives after the count value of the counter 2 exceeds a threshold value. The ATM policing device is provided with the cell discarding unit 6 of FIG.

Here, the features of the present invention are that a timer 9 is reset by the arrival of a cell as a means for changing the subtraction rate according to the elapsed time from the arrival time of the cell, and two subtraction rate generations. It is provided with subtraction timers 3 ₁ and 3 ₂ which are circuits, and a selector 10 which switches the subtraction timers 3 ₁ or 3 ₂ according to the measurement time (T) of the timer 9.

Next, the operation of the embodiment of the present invention will be described. FIG. 2 is a diagram for conceptually explaining the operation of the embodiment of the present invention. FIG. 3 is a diagram showing the state of the subtraction rate. Also in the polishing apparatus of the embodiment of the present invention, as described in the conventional example, water is accumulated in the bucket upon arrival of cells. When the water in the bucket exceeds _a certain threshold value B _a , the cell is determined to be in violation and the disposal process is performed. The water in the bucket has a subtraction rate R
Leak at ₁ or R ₂ . Subtraction rate R ₁ or R ₂
Changes the two values based on the instruction of the timer 9.

As shown in FIG. 3, the leak by subtracting the rate R ₁ and cell arrives, but subtraction rate R ₁ continues only during the time T, the transition to the subtraction rate R _2. The subtraction rate R ₂ continues to be stable, but is reset by the arrival of a cell and returns to the subtraction rate R ₁ again.

Returning to FIG. 1, the description will be continued. The apparatus according to the embodiment of the present invention includes a cell identification unit 1 as means for monitoring a transmission signal including a cell of main information and a cell of additional information, an up / down counter 2, and subtraction timers 3 ₁ and 3 ₂ . A cell discard unit 6 that includes a comparison circuit 4 and a threshold circuit 5, and that serves as means for discarding the cell when the difference between the amount of arriving cells and the allowable traffic amount exceeds a predetermined value, A timer 9 for measuring the timing of switching the subtraction rate R ₁ or R ₂ and a selector 10 are provided.
With such a configuration, the leaky bucket monitors the difference between the amount of incoming cells and the amount of cells corresponding to the amount of traffic allowed for this connection.

Here, the traffic parameters of the main signal are (T ₁ , τ ₁ ), the traffic parameters of the other subcomponents are (T ₂ , τ ₂ ), (T ₃ , τ ₃ ), ...
And T _i is the peak cell interval, and τ _i is the CDV tolerant (maximum fluctuation value). At this time, the magnitude R _1, R ₂ and depth B _a leakage leaky _{bucket, R 1 = 1 / T 1} R 2 = 1 / T 2 + 1 / T 3 + ... = Σ1 / T i B a = Σ (1 + τ _i / T _i ). However, Σ represents the sum of i = 1 to c, and c is the total number of components.

FIG. 4 is a diagram showing the arrival status of cell traffic and the value of the counter. The horizontal axis shows the arrival status of cells,
The vertical axis shows the counter value. FIG. 4A is an example in which the sub-components are asynchronously inserted in the worst situation, and the counter value is barely B _a (threshold value). It should be noted that these were considered to have no fluctuation (CDV = 0). FIG. 4B shows an example in which the user tries to insert a malicious and irregular pattern, which is rejected by the policing device. In the example of FIG. 4B, it can be seen that the leak rate changes from R ₁ to R ₂ after a time T.

FIG. 5 is a diagram showing transit traffic patterns of a conventional policing device for user traffic and the policing device of the present invention. FIG. 5A is a traffic pattern that may be transmitted by the user.
FIG. 5B shows a traffic pattern that can occur when a conventional single bucket is used, and FIG. 5C shows a pattern obtained by the polishing apparatus of the present invention. In conventional polishing equipment,
For example sends a 3 cells between 3T _a, there can be passed a pattern to repeat it. On the other hand, the polishing apparatus of the present invention does not allow such traffic patterns to pass. FIG. 5 (c) shows a pattern that seems to be the worst passing pattern.

FIG. 6 is a diagram showing a comparison of the monitoring accuracy between the polishing apparatus of the present invention and the conventional one. Here, it is shown how much the pattern after passing through the policing device has an impact on the buffer of the first stage switch when the number of subcomponents is 1, 2, and 4. Although it depends on the number of sub-components, it can be seen that the polishing apparatus of the present invention can perform accurate polishing as compared with the conventional one. This makes it possible to reduce the cell loss rate in the ATM switch and other devices in the ATM network connected to the latter stage of the polishing device. Also,
The buffer size for compensating the reduction of the cell loss rate can be reduced.

[0030]

As described above, according to the present invention,
Cell traffic can be monitored accurately with a small amount of hardware. Thereby, the cell loss rate in the ATM network can be reduced.

[Brief description of drawings]

FIG. 1 is a block configuration diagram of an apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram for conceptually explaining the operation of the embodiment of the present invention.

FIG. 3 is a diagram showing a state of a subtraction rate.

FIG. 4 is a diagram showing arrival status of cell traffic and a counter value.

FIG. 5 is a diagram showing transit traffic patterns of a conventional policing device and a policing device of the present invention for user traffic.

FIG. 6 is a diagram showing a comparison of monitoring accuracy between the polishing apparatus of the present invention and a conventional polishing apparatus.

FIG. 7 is a diagram for explaining the principle of a leaky bucket.

FIG. 8 is a block configuration diagram of a conventional polishing device.

FIG. 9 is a diagram showing main information and sub-components.

FIG. 10 is a block configuration diagram of a conventional polishing device.

[Explanation of symbols]

1 cell identification part 2 up-down counter 3,3 _1, 3 ₂ subtraction timer 4 comparator circuit 5 threshold circuit 6 cell discarding unit 7 the component separating unit 8 ₁ to 8 _C leaky bucket 9 timer 10 Selector

Claims (2)

[Claims] 1. A counter equipped with a counter that counts up each time a cell arrives and counts down according to a predetermined subtraction rate, and means for discarding a cell that arrived after the count value of this counter exceeded a threshold value.
An ATM policing device, characterized in that it comprises means for changing the subtraction rate according to the time elapsed from the arrival time of the cell. 2. The changing means comprises a timer (9) reset by the arrival of a cell, a plurality of subtraction rate generation circuits (3), and the subtraction rate generation circuit according to a measurement time (T) of the timer. Selector for switching (10)
The ATM polishing apparatus according to claim 1, further comprising: