KR19990053245A - Rate control method using backward explicit congestion notification bit in frame relay network matching device - Google Patents

Abstract

1. TECHNICAL FIELD OF THE INVENTION

The present invention relates to a rate control method using backward explicit congestion notification bits.

2. The technical problem to be solved by the invention

An object of the present invention is to provide a method of controlling a rate using backward explicit congestion notification bits (BECN) for efficient management of network resources and minimizing the probability of frame loss when data traffic of a user is congested when interworking with a frame relay exchange.

3. Summary of Solution to Invention

The present invention provides a method of controlling a rate in a frame relay network matching device, the method comprising: initializing the number of receptions of the first predetermined value and the second predetermined value of the backward explicit congestion notification bit, initializing the transmission rate to the agreed information transmission rate, and Receiving a first step; A second step of decreasing a transmission rate step by step according to the number of receptions of the first predetermined value of a backward explicit congestion notification bit of a received frame; And a third step of increasing a transmission rate step by step according to the number of receptions of the second predetermined value of a backward explicit congestion notification bit of a received frame.

4. Important uses of the invention

The present invention is used for a rate control method in a frame relay network matching device.

Description

Rate control method using backward explicit congestion notification bit in frame relay network matching device

The present invention relates to a rate control method using backward explicit congestion notification bits in a frame relay network matching device.

Information Communication Processing System (ICPS) is a gateway system that connects user terminal using telephone network and information service center based on packet-switched network (Hinet-P) to search, collect and store various information.

The user terminal is intended for personal computers (PCs) or high-tel terminals with 2400- to 28800-bps modems, and the Information Service Center uses 56kbps lines to provide X.25 public packet services. Conventional communication processing system uses X.25 packet switching network as data network, so it is expected to increase the number of users of personal computer (PC) communication, improve the performance of user terminals, and request multimedia services such as voice, graphics, and image. Circuit expansion between the system and the packet-switched network becomes inevitable.

Therefore, it is required to develop a frame relay network matching device that guarantees high-speed information providing service to personal computer (PC) communication users and is easily expandable and easy to manage even when expanding the data delivery network system according to the increase in subscriber capacity. .

However, since the conventional frame relay network is implemented to omit error and flow control functions and to perform only minimal processing, in some cases, a large amount of user data transmitted to the frame relay exchange may be congested and packet loss may occur. There is a problem that there is no flow control or congestion control method.

Accordingly, the present invention has been made to solve the above-mentioned problems of the prior art, and a user of a communication processing system connected to a telephone network or a comprehensive information communication network can retrieve information of an information provider connected to a frame relay network. In case of interlocking with frame relay switch in frame relay network matching device of high-capacity communication processing system, in order to efficiently manage network resources and minimize probability of frame loss, reverse explicit congestion notification bit (BECN) It is an object of the present invention to provide a transmission rate control method for controlling a transmission rate by using.

1 is an exemplary configuration diagram of a mass communication processing system to which the present invention is applied.

2 is an exemplary configuration diagram of a frame relay network matching device of FIG. 1.

3 is a structural diagram showing a frame format of a frame relay;

4 is an explanatory diagram for explaining an explicit congestion notification method used in a frame relay network.

5 is a flow diagram of an embodiment of a rate control method using backward explicit congestion notification bits in accordance with the present invention.

* Explanation of symbols for main parts of the drawings

101: telephone network switch 102: telephone network matching device

105: high speed switching connection device 106: frame relay network matching device

107 frame relay network switch

The method of the present invention for achieving the above object, in the transmission rate control method in the frame relay network matching device, initializes the number of reception of the first predetermined value and the second predetermined value of the reverse explicit congestion notification bit, Initializing the data rate to an agreed information rate and receiving a frame; A second step of decreasing a transmission rate step by step according to the number of receptions of the first predetermined value of a backward explicit congestion notification bit of a received frame; And a third step of increasing a transmission rate step by step according to the number of receptions of the second predetermined value of a backward explicit congestion notification bit of a received frame.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is an exemplary configuration diagram of a mass communication processing system to which the present invention is applied.

The large capacity communication processing system dials a call from the exchange to the communication processing system when the personal computer (PC) communication users connected to the telephone network switch 101 dial a specific number for the communication processing service, and the telephone network matching device (TNAS: Telephone). Network Access Subsystem 102 is connected to the communication processing system. The telephone network matching device 102 serves as a hub for connecting a telephone network interface (TNIF) 103 having a trunk interface function and a modem function corresponding to a sub highway of a telephone network switch and a serial subscriber port to a system bus. Communication Processing Module (CPM) 104, which is responsible for the Transparant Asynchronous Xmitter-receiver Interface (TAXI) serial interface for interfacing user-specific information to the data network, and through 32 TAXI ports. High Speed Switching Fabric (HSSF) 105 for high speed packet switching, Frame Relay Network Access Subsystem (FNAS) 106 for connection to Frame Relay network, Frame Relay It is composed of an exchange 107 and an information provider (IP).

The difference between the existing communication processing system and the mass communication processing system is that the HSSF 105 is placed inside the system for data network matching. The fast switching interface 105 accommodates 10 telephone network matching devices 102 located between the telephone network matching device (TNAS) 102 and the frame relay network matching device (FNAS) 106 and having a processing capacity of 96 subscriber units. It is a 32-port internal switch that can use 20 ports for data network matching and 2 ports for operation management.

96 subscriber capacity, which is the capacity of subscribers of telephone network that can be handled by existing small capacity communication processing system, was expanded to 960 subscribers in large capacity communication processing system. A high speed switching interface 105 based on a serial interface has been added. The high speed switching access device is connected to the subscriber I / O unit through the TAXI interface and performs inter-processor communication between the telephone network matching device 102 and the frame relay matching device 106 using a packet having a variable length packet size by a protocol defined by itself. It is supposed to be.

FIG. 2 is an exemplary configuration diagram of the frame relay network matching device of FIG. 1 and illustrates a frame relay network matching device for connecting the high speed switching connection device 105 and the frame relay switch 107 of a large capacity communication processing system.

The frame relay network matching device is composed of a system control unit 202, a fast switching connector matching unit 201, and a frame relay network matching unit 203. The system bus (VME bus) uses 32-bit address / data lines. The packet is transmitted between the fast switching connector matching unit 201 and the frame relay network matching unit 203. The system control unit 201 operates as a master in a sub-system, and is in charge of initialization and state setting and operation management for a service relay function between the high speed switching connector matching unit 201 and the frame relay network matching unit 203. do.

An operation administration and maintenance (OAM) packet for processing frame relay network data is transmitted between the fast switching interface matching unit 201 and the frame relay network matching unit 203 through a system bus (VME bus). It is processed by the system control unit 202. The fast switching interface matching unit 201 and the frame relay network matching unit 203 request state processing to the system control unit 202 by using a system bus (VME bus) interrupt, and the control unit 202 provides a high-speed operation in an operation program. When receiving a message indicating that data has been recorded in the DRAM area on the switching connection device matching unit 201, the data is transmitted to the transmission packet memory area of the frame relay network matching unit 203, and conversely, the frame relay network matching unit ( Upon receiving a message indicating that data has been received in the receiver packet memory area of the receiving unit 203, the data received by the frame relay network matching unit 203 is transmitted to the transmitting side DRAM area on the fast switching connection matching unit 201. .

The high speed switching connector matching unit 201 processes a function corresponding to a high speed communication unit (HSCU) of the high speed switching connector 105, and the high speed switching connector 105 and the TAXI differential serial interface. Connected. In addition, it processes the function of receiving data from the high speed switching connection device 105 and storing the data in the receiving buffer, and converts the data received from the information provider 108 into a packet form for processing by the high speed switching connection device 105 for transmission. Perform the function. Frame relay network matching device has the function to send / receive the packet by inter-processor communication (IPC) and internal shared memory to the control board in charge of host function through system bus (VME bus) internally in the system. It is a matching device. The system as a whole takes the form of the high speed switching junction matching unit 201 on the frame relay network matching unit and the high speed switching junction matching unit of the telephone network matching unit communicating at both ends, and is responsible for packetizing / repacketizing data per user channel. Doing.

3 is a structural diagram showing a frame format of a frame relay, in which a forward explicit congestion notification bit (hereinafter referred to as "FECN") used for frame relay congestion control and a backward explicit congestion notification bit ( Backward Explicit Congestion Notification (hereinafter referred to as "BECN"), Discard eligibility bit (DE), Data Link Connection Identifier (DLCI), Command / Reponse bit (C / R), and the location of the address extension BIT (EA).

4 is an explanatory diagram for explaining an explicit congestion notification method used in a frame relay network.

As shown in the figure, when congestion occurs at a node B in the network, the node transmits by setting the FECN in the address region of all frames passing through to '1' (401), and receives such a frame. An end node of one network transmits a BECN of a frame transmitted in a backward channel to '1' to inform a user who transmits the frame that the congestion has occurred (402). The sender receiving the BECN-configured frame lowers the transmission rate according to the regulations to achieve congestion control. At this time, while the FECN or BECN is configured and transmitted, any node in the network must pass it without clearing this bit.

When these FECN and BECN are used independently, the nature of these bits is slightly different. That is, the frame relay network matching unit 203 receiving the frame in which the FECN is set notifies the system control unit 202 of this fact, thereby reducing the credit implemented in the protocol of this area. As a result, this method is a method of performing congestion control on the receiving side. On the other hand, the frame relay network matching unit that receives the frame with the BECN set is a method of congestion control at the transmitting side by notifying the upper layer of this fact and reducing its transmission rate.

On the other hand, X.25 is a network interface consisting of three layer protocol structures, that is, packet layer, link layer, and physical layer, where the main functions of the link layer are flow control and error recovery functions. In the current situation of reliable and fast transmission, the control of the complex link layer in X.25 is a hindrance to the trend of high speed due to reduced overall throughput and high latency.

In order to improve the processing speed problem of X.25, error and flow control functions are omitted in the link layer between the user and the exchange period, and these control functions are delegated to end-to-end users to minimize the processing in the network switching system. When connecting with an information provider through a frame relay network, which is a packet transmission technology that guarantees high speed, it guarantees high-speed information provision service to personal computer (PC) communication users, and can be easily expanded even when expanding the data delivery network system with increasing subscriber capacity. Since the subscriber's data is transmitted through the frame relay network matching device, it is easy to manage and provide reliable information service.

However, since the network is implemented to minimize errors and flow control functions and to perform minimal processing, most of the data passing through the frame relay network matching device is an IP frame for personal computer users to access the Internet. Because of its bursty nature, the amount of user data that enters the frame relay exchange can be congested, resulting in packet loss. Accordingly, the frame relay network matching node needs to detect this and reduce the transmission speed to efficiently manage network resources and control the transmission rate.

FIG. 5 is a flowchart illustrating a method of controlling a rate using a reverse explicit congestion notification bit according to the present invention, and a method of controlling a rate using a reverse explicit congestion notification bit (BECN) in the frame relay network matching unit 106. Referring to FIG. It is shown.

In the rate control method using the backward explicit congestion notification bit (BECN), a step count S is defined as follows.

In the above Equations (1), (2) and (Equation 3), IR _f and IR _b are information rate, Th _f and Th _b are agreed throughput, Bc _f and Bc _b are the agreed burst size, Be _f and Be _b are the excess burst size, Ar _f and Ar _b are the access rate, and F _f / F _b is the ratio of frames received to sent, N202f and N202b are the maximum information area length (max. information size), and EETD is the end-to-end transit delay, and f and b represent forward and backward, respectively.

S is the ratio of the actual number of frames transmitted and received at any moment by the maximum number of frames on the link in each direction in the network. The information rate is a maximum value that can be transmitted and is the sum of the agreed rate and the excess rate. The S value determined by the sender is used to determine when to increase or decrease its transmission rate as follows.

On the other hand, if the BECN receives a frame set to "1", the transmitting side immediately decreases to a transmission rate of the negotiated information rate (CIR; Committed Information Rate), and after that, if the BECN-set frame is continuously received S times, the user The rate should be lowered to the next level of allowed rates. The first step of the “step” ratio is 0.675 × CIR, the second step is 0.5 × CIR, and the third step is 0.25 × CIR.

In the case of receiving the frame with BECN = 0 in S / 2 consecutive times, the transmission rate is increased by 0.125 times the negotiated information rate (CIR).

If the value of S is large, it means that the propagation delay time is large, so that the number of times that control should be done is small. If the value of S is small, it should be controlled frequently because it is a small network with short propagation delay time. According to the definition of S, if the allowable excess data amount Be or throughput Th is large, the S value also becomes large and thus the number of control decreases. However, if the maximum information area length N202 is a large value, the S value becomes small and the number of control increases.

In the implementation of the rate control method using the backward explicit congestion notification bit (BECN), it can be conveniently controlled using a window similar to the control by the rate. Such implementations can measure their provision rate or control the throughput negotiated with the network in relation to the measurement in the call setup period. The rate actually provided is determined by the end-to-end propagation delay time, line access rate, window size and frame size, where S is defined as the time at which one frame is transmitted and acknowledged.

If the BECN is set to 1 and the frame is received, the user reduces the dynamic window to 0.625 times the previous value. If S consecutive frames are received with BECN still being set, the reduction will continue but the window size will not drop below one.

The user may increase the current window by not exceeding the maximum window size when a frame having BECN = 0 is received S / 2 consecutive times.

As shown in the figure, the number of reverse explicit congestion notification bit '0' and the reverse explicit congestion notification bit '1' are initialized to '0', the data rate is initialized to the agreed information rate (501), and the frame is initialized. Receive (502).

Then, it is determined whether the backward explicit congestion notification bit is' 1 '(503), and if it is' 1', the number of reverse congestion notification bits' 0 'is set to' 0 '(504), and the reverse explicit congestion notification bit' After increasing the number of 1's by 1, determine whether nS times (where n is a natural number) of backward explicit congestion notification bit '1' (505) and receives a frame again if not nS times. Decrease the data rate by 0.675 times (contracted information rate x 0.675) (506), and reduce the transmission rate by 0.5 times the agreed information rate (2S) by 2S (507), and agree the transmission rate by 3S. It decreases by 0.25 times the negotiated information transmission rate (the agreed information transmission rate x 0.25) (508).

On the other hand, it is determined whether the backward explicit congestion notification bit is '1' (503), and if it is not '1', the number of backward explicit congestion notification bits '1' is set to '0' (509), and the reverse explicit congestion bit After increasing the number of '0's by 1, it is determined whether the number of the backward explicit congestion notification bits'0' is nS / 2 (where n is a natural number) (510). / 2 increases the transmission rate by 0.125 ⁿ times the negotiated information rate (a negotiated information rate + 0.125 ⁿ x the negotiated information rate) (511).

The present invention described above is capable of various substitutions, modifications, and changes without departing from the spirit of the present invention for those skilled in the art to which the present invention pertains, and the above-described embodiments and accompanying It is not limited to the drawing.

Therefore, the present invention as described above minimizes the probability of frame loss by maintaining congestion in the frame relay network matching device, maintains the quality of service of a telephone network access user, and enables several users to use the network fairly. Minimize the possibility of the user monopolizing the network, simplifying the implementation for both the user and the network, avoiding overloading, and preventing congestion from spreading to other networks or to other exchanges within the network. have.

Claims (3)

In the rate control method in the frame relay network matching device, A first step of initializing the number of receptions of the first predetermined value and the second predetermined value of the backward explicit congestion notification bit, initializing the transmission rate to the agreed information transmission rate and receiving a frame; A second step of decreasing a transmission rate step by step according to the number of receptions of the first predetermined value of a backward explicit congestion notification bit of a received frame; And A third step of increasing a transmission rate step by step according to the number of receptions of the second predetermined value of a backward explicit congestion notification bit of a received frame; Rate control method comprising a. The method of claim 1, The second step, A fourth step of initializing a number of receptions of the second predetermined value of a reverse explicit congestion notification bit if the reverse explicit congestion notification bit of the received frame is the first predetermined value; And A fifth step of decreasing the transmission rate by a predetermined multiple of the negotiated transmission rate step by step according to the number of reception of the first predetermined value of the backward explicit congestion notification bit; Rate control method comprising a. The method according to claim 1 or 2, The third step, A sixth step of initializing the number of receptions of the first predetermined value of the backward explicit congestion notification bit if the backward explicit congestion notification bit of the received frame is the second predetermined value; And A seventh step of increasing the transmission rate by a predetermined multiple of the agreed transmission rate step by step according to the number of reception of the second predetermined value of the backward explicit congestion notification bit; Rate control method comprising a.