KR0146764B1 - Equipment and method for control of abr service by managing buffer using multi stage critical value - Google Patents

Abstract

The present invention relates to an apparatus and method for a flow chair of an ABR service using a buffer management using a multi-level threshold in an asynchronous transmission mode (ATM) network, and to managing a buffer having a multi-level threshold in a switch node. In order to provide an apparatus and method for controlling a flow of an ABR service for generating a reverse RM cell, a forward RM cell management means 21 for detecting a forward RM cell; Reverse RM cell management means 22 for detecting and generating reverse RM cells; Buffering means 24 having a multi-level threshold value; And a first step (401, 402, 409, 410) having a buffer management means (23) for controlling the buffering means (24), for examining a buffer state having a multi-level threshold value; A second step (403 to 408) of generating a reverse RM cell by the switch node itself; and a third step (411 to 416) of increasing or decreasing the subscriber station transmission speed to reduce the buffer size in the switch node. There is an effect that can improve the efficiency of the transmission link in the initial transient state.

Description

Apparatus and method for controlling flow of ABR services using buffer management using multi-level thresholds

1 is a schematic configuration diagram of an ATM system to which the present invention is mounted;

2 is a configuration diagram of an apparatus for controlling flow of an ABR service according to the present invention;

3 is a structural diagram of a buffer in a switch node having a multi-level threshold according to the present invention.

4 is a flowchart illustrating a flow control method of an ABR service according to the present invention.

* Explanation of symbols for main parts of the drawings

21: forward RM cell detector 22: reverse RM cell management unit

23: buffer management unit 24: buffer

The present invention relates to an apparatus and method for controlling flow of an ABR service using buffer management using a multi-level threshold in an asynchronous transfer mode (ATM) network.

In ATM networks, ABR service is bursty and insensitive to transmission delay, but very sensitive to cell loss.The ABR service is fixed in bandwidth allocated at connection establishment such as CBR (Constant Bit Rate) or VBR (Variable Bit Rate) service. It is characterized by the fact that the allocated bandwidth is dynamically changed (variation of transmission rate) by performing flow control according to ATM network situation without using. Since the traffic control technology for the ABR service connection is difficult to predict the input traffic, it is impossible to use preventive control using predefined traffic parameters. The feedback information should be used to directly suppress traffic input.

For the flow control algorithm for transmission rate control, the ATM Forum recently adopted the Enhanced Proportional Rate Control Algorithm (EPRCA) mechanism to standardize the detailed protocol.

EPRCA is a control algorithm based on the closed-loop rate based (CRB) method, which is a response control for the flow control of ABR service in ATM network. Resource management (RM) cell after transmitting N data cells to the source subscriber station Before transmitting and receiving this RM cell backward, the data rate is reduced after every data cell transmission. When the forward RM cell transmitted from the source subscriber station is received again with CI (Congestion Indecator) = 0, which is a parameter that specifies the congestion state by changing to the reverse RM cell via the destination node, the congestion state on the path It is possible to recognize that there is no and to compensate for the reduced transmission rate so far and increase the transmission rate beyond.

On the other hand, the switch node introduces a Mean Allowed Cell Rate (MACR) parameter, which represents the average transmission rate of all ABR service connections, and transmits at a higher allowable cell rate (ACR) than this average network allowed rate. The fairness between the ABR service connections can be maintained by the selective feedback method that reduces the transmission speed only for the ABR service connection being made. When congested at each switch node, the ER (Explicit Rate) specified in the network estimated using the average network allowed rate is transmitted directly to the subscriber station using the RM cell. By transmitting the next data cell at the terminal transmission rate value, the transmission rate is drastically reduced so that the network can be recovered from the congestion state.

However, when the congestion condition occurs in the switch node, this EPRCA mechanism uses the reverse RM cell to directly transmit the subscriber station transmission rate specified in the network to the subscriber station and reduces the transmission rate. The queue length can be continuously increased, and there is a problem that the efficiency of the transmission link is low due to a slow increase in the transmission speed of the subscriber station in the initial transient state.

Therefore, the present invention devised to solve the above problems can improve the efficiency of the transmission link in the initial transient state and to manage the buffer having a multi-level threshold in the switch node to reduce the queue length in the switch node switch node An object of the present invention is to provide an apparatus and method for controlling flow of an ABR service using a method capable of rapidly increasing a transmission rate of a reverse RM cell and a subscriber station generated by the UE.

The apparatus of the present invention for achieving the above object is a flow control device of the ABR service mounted on the switch node of the Asynchronous Transfer Mode (ATM) network, the forward RM cell among the cells input from the external subscriber station A forward RM cell detection means for detecting a; Among the cells transmitted from the external destination node to the subscriber station, the reverse RM cell is detected to detect the reverse RM cell to notify the arrival of the reverse RM cell, or instructed to generate the reverse RM cell to generate its own reverse RM cell to generate the subscriber. Reverse RM cell management means for outputting to a terminal; Buffering means for receiving a cell from the forward RM cell detecting means and outputting the cell to the destination node, outputting status information, and having a multi-level threshold value; And when the forward RM cell is detected by the forward RM cell detection means and the reverse RM cell is detected by the reverse RM cell management means, the reverse RM cell is generated according to the state information of the buffering means. And buffer management means for instructing the management means or specifying the subscriber station transmission rate increase rate to notify the parameters of the reverse RM cell.

The method of the present invention for achieving the above object, in the flow control method of the ABR service applied to the flow control apparatus of the ABR service mounted on the switch node of the Asynchronous Transfer Mode (ATM) network, from the subscriber station A first step of examining a buffer state having a multi-step threshold when receiving a forward RM cell or receiving a reverse RM cell from a destination node; A second step of generating, by the switch node itself, a forward RM cell or transmitting a forward RM cell to the destination node when the forward RM cell is received in the first step; And a third step of increasing or decreasing the subscriber station transmission rate according to a buffer state check result when the reverse RM cell is input in the first step.

Hereinafter, with reference to the accompanying drawings will be described an embodiment according to the present invention;

1 is a schematic configuration diagram of an ATM system to which the present invention is mounted. The present invention is installed in a switch of an ATM system, and generates a reverse RM cell by itself at a switch node using a buffer having a multi-level threshold. By rapidly increasing the transmission speed of the subscriber station, the performance of the ERRCA mechanism can be improved.

2 is a block diagram of an apparatus for controlling the flow of an ABR service according to the present invention, which detects a forward RM cell among cells input from an external subscriber station, notifies the buffer manager 23 of the arrival of the forward RM cell, and provides a buffer 24. The detection unit 21 detects the forward RM cell outputting the cell to the subscriber station, and detects the reverse RM cell among the cells transmitted from the external destination node to the subscriber station and notifies the buffer manager 23 of the arrival of the reverse RM cell. In response to the notification from 23, a reverse RM cell management unit 22 which generates its own reverse RM cell and outputs it to the subscriber station, receives the cell from the forward RM cell detection unit 21, outputs the cell to the destination node, and outputs the buffer to the destination node. 24 is notified of the state of the buffer 24, and the buffer 24 and the forward RM cell detection unit 21 having a multi-level threshold is notified that the forward RM cell has been detected and the reverse RM cell management In response to the notification that the reverse RM cell is detected from the 22, instructing the reverse RM cell management unit 22 to generate its own reverse RM cell according to the state of the buffer 24, or designating an increase rate of the subscriber station transmission rate of the reverse RM cell. A buffer manager 23 is provided to notify the parameter.

3 is a structural diagram of a buffer in a switch node having a multi-step threshold according to the present invention, which can be broadly divided into a high threshold controlling a congestion state and a low threshold controlling a transmission rate increase rate of a subscriber station.

The low threshold is composed of a first right threshold value L1 that doubles the transmission rate increase rate of the subscriber station and a second low threshold value L2 that specifies the transmission rate increase rate 1.5 times. Has a buffer structure having four multi-stage threshold values, each consisting of a first high threshold value H1 indicating a congestion state and a second high threshold value H2 indicating a congestion state.

4 is a flowchart illustrating a flow control method of an ABR service according to the present invention.

When the switch node receives the forward RM cell from the subscriber station according to the EPRCA mechanism (401), the state of the buffer 24 having the multi-level threshold value is examined (402) and the number of cells in the buffer is smaller than the first high threshold value H1. If not, the forward RM cell is sent directly to the destination node (408) without generating a reverse RM cell (408).

When the number of cells in the buffer is greater than the first high threshold value H1 (403), as a result of the state investigation of the buffer 24, the subscriber station transmission rate parameter designated by the network to reduce the transmission speed of the subscriber station is expected because a congestion condition is expected. In step 403, the RM cell is generated by using the above-specified parameters (406), and a direct reverse RM cell is transmitted to the subscriber station (407). In step 408, the forward RM cell is continuously transmitted.

As a result of the state investigation of the buffer 24, if the number of cells in the buffer is larger than the second high threshold value H2, the subscriber station transmission rate parameter designated by the network can be rapidly reduced so as to rapidly reduce the transmission rate of the subscriber station to recover from the congestion state. It is designated as 25% of the average network allowed speed (405), and then generates a reverse RM cell by itself using the parameters specified above (406) and transmits the reverse RM cell directly to the subscriber station (407) toward the destination node Continues to transmit the forward RM cell (408).

On the other hand, when the switch node receives the reverse RM cell from the destination node according to the EPRCA mechanism (409), the state of the buffer 24 having the multi-level threshold value is examined (410) and the number of cells in the buffer is the second high threshold value (H2). If it is larger, in order to recover from the congestion state, the subscriber station transmission rate parameter designated by the network is designated as 25% of the average network allowable rate so as to drastically reduce the transmission rate of the subscriber station (411), and the reverse RM cell is transmitted to the subscriber station. (416).

As a result of the state investigation of the buffer 24, if the number of cells in the buffer is larger than the first high threshold value H1, a congestion condition is expected, so that the average subscriber station transmission rate parameter designated by the network is reduced so that the transmission rate of the subscriber station can be reduced. 80% of the allowed speed is specified (412) and the reverse RM cell is transmitted to the subscriber station (416).

As a result of the state investigation of the buffer 24, if the number of cells in the buffer is between the first low threshold value L1 and the first high threshold value H1, the increase of the subscriber station transmission rate is designated as a parameter value according to the existing EPRCA mechanism ( 413. The reverse RM cell is transmitted to the subscriber station (416).

If the number of cells in the buffer is less than the second lower threshold value L2 as a result of the state investigation of the buffer 24, the increase rate of the subscriber station transmission speed is increased by 1.5 times in order to improve the throughput because there is room in the band on the transmission link. A parameter value can be specified (414) and a reverse RM cell is transmitted to the subscriber station (416).

As a result of the state investigation of the buffer 24, when the number of cells in the buffer is smaller than the second low threshold value L2, after specifying a parameter value that can double the subscriber station transmission rate increase rate (415), the reverse RM is transmitted to the subscriber station. The cell is transmitted (416).

The present invention, which is configured and operated as described above, uses a method of generating a reverse RM cell by itself in a switch node using a buffer having a multi-level threshold or increasing a transmission speed of a subscriber station according to a buffer threshold. By reducing the propagation delay, the buffer size in the switch node can be reduced and the efficiency of the propagation link can be improved in the initial transient state.

Claims (7)

An apparatus for controlling flow of an ABR service mounted in a switch node of an Asynchronous Transfer Mode (ATM) network, comprising: forward RM cell detection means (21) for detecting a forward RM cell among cells input from an external subscriber station; A reverse RM that detects a reverse RM cell among cells transmitted from an external destination node to the subscriber terminal and notifies the arrival of a reverse RM cell or is instructed to generate a reverse RM cell and generates its own reverse RM cell and outputs it to the subscriber terminal. Cell management means 22; Buffering means (24) for receiving a cell from the forward RM cell detecting means (21), outputting it to the destination node, outputting status information, and having a multi-level threshold value; And when the forward RM cell is detected from the forward RM cell detection means 21 and the reverse RM cell management means 22 is notified that the reverse RM cell has been detected, according to the state information of the buffering means 24. And a buffer management means 23 for instructing reverse RM cell generation to the reverse RM cell management means 22 or for designating a subscriber station transmission rate increase rate to notify the parameters of the reverse RM cell. Flow control device of ABR service by using buffer management. A flow control method of an ABR service applied to a flow control apparatus of an ABR service mounted on a switch node of an Asynchronous Transfer Mode (ATM) network, the method comprising: receiving a forward RM cell from a subscriber station or a reverse RM cell from a destination node A first step (401, 402, 409, 410) of examining a buffer state having a multi-level threshold value when receiving a; When receiving a forward RM cell in the first step (401, 402, 409, 410), the second step (403 to 403) to generate a reverse RM cell itself or to transmit the forward RM cell to the destination node according to the buffer state check result; 408); And a third step (411 to 416) of increasing or decreasing the subscriber station transmission rate according to a buffer state investigation result when receiving the reverse RM cell in the first step (401, 402, 409, 410). Flow control method of ABR service by buffer management using threshold. 3. The multi-stage threshold according to claim 2, wherein the buffer states of the first steps (401, 402, 409, 410) have a multi-step threshold such as a high threshold for controlling the congestion state and a low threshold for controlling the rate of increase of the subscriber station. How to control flow of ABR service by managing buffer using value. 4. The method of claim 3, wherein the high threshold comprises: a first high threshold (H1) indicating that a congestion condition is expected; And a second high threshold value H2 indicating a congestion state. 4. The method of claim 3, wherein the low threshold comprises: a first low threshold (L1) for designating a rate of increase of the subscriber station as a first predetermined value; And a second low threshold value (L2) for designating a transmission rate increase rate of the subscriber station as a second predetermined value. 3. The method of claim 2, wherein the second steps 403 to 408 include: a fourth step of transmitting a forward RM cell to the destination node if the number of cells in the buffer is less than the first high threshold value H1 as a result of examining the buffer state; Step 408; As a result of examining the buffer status, if the number of cells in the buffer is larger than the first high threshold value H1, the subscriber station transmission rate parameter designated by the network is designated as the first predetermined value of the average network allowance rate, thereby generating a reverse RM cell by itself. Transmitting a reverse RM cell to the subscriber station and transmitting a forward RM cell to the destination node (404, 405 to 408); If the number of cells in the buffer is greater than the second high threshold value (H2), the subscriber station transmission rate parameter designated by the network is designated as the second predetermined value of the average network allowance rate to generate a reverse RM cell. And a sixth step (405 to 408) of transmitting a reverse RM cell to the subscriber station and transmitting a forward RM cell to a destination node. Way. 3. The method of claim 2, wherein the third step (411 to 416), if the number of cells in the buffer is greater than the second high threshold value (H2) as a result of examining the buffer status, the average network allowed for the subscriber station transmission rate parameter designated by the network; A fourth step (411, 416) of designating a first predetermined value of speed and transmitting a reverse RM cell to the subscriber station; As a result of investigating the buffer status, if the number of cells in the buffer is larger than the first high threshold value H1, the subscriber station transmission rate parameter designated by the network is designated as the second predetermined value of the average network allowable rate, and a reverse RM cell is assigned to the subscriber station. A fifth step of transmitting (412, 416); As a result of investigating the buffer status, if the number of cells in the buffer is between the first low threshold value L1 and the first high threshold value H1, the subscriber station transmission speed increase is designated as a parameter value in accordance with the conventional EPRCA mechanism, and is sent to the subscriber station. A sixth step (413, 416) of transmitting reverse RM cells; As a result of examining the buffer status, if the number of cells in the buffer is less than the second low threshold value L2, a parameter value for increasing the subscriber station transmission speed to a third predetermined value is designated and a reverse RM cell is transmitted to the subscriber station. Seventh step (414, 416); And as a result of examining the buffer state, when the number of cells in the buffer is smaller than the second lower threshold value L2, a parameter value for increasing the subscriber station transmission speed to a fourth predetermined value is designated and a reverse RM cell is transmitted to the subscriber station. And an eighth step (415, 416) of transmitting the ABR service flow control method using a buffer management using a multi-level threshold value.