KR20010003644A - Method for detecting satate of duplicated link in atm exchange system - Google Patents

Abstract

PURPOSE: A method for detecting duplexed link states in an asynchronous transfer mode(ATM) exchange system is provided to rapidly detect a link error generation and an error recovery to minimize cell losses and system errors caused by link errors in a cell transmission between a duplexed subscriber device and a switch device. CONSTITUTION: If a power of a subscriber device is turned on, an asynchronous transfer mode(ATM) exchange system sets up a reference state signal, a link state signal and a count enable signal as initial values. Whenever a reference cell starting signal which displays a cell start from the subscriber device is applied to a switch device, the ATM exchange system adds a value of the link state signal to a value of the reference state signal. Whenever the reference call starting signal is applied, the ATM exchange system compares the value of the link state signal and the value of the reference state signal. If the value of the link state signal is equal to the value of the reference state signal, the ATM exchange system applies a count enable signal to initialize a count value. Whenever a reference pulse is applied, the ATM exchange system increases the count value. The ATM exchange system constantly keeps a link normal signal which displays a current link state until the count value is counted as a set up value. The ATM exchange system decides that a current link is an abnormal link, and switches the current link with another normal link by the link normal signal.

Description

How to detect the status of a redundant link in an asynchronous transmission mode switching system {METHOD FOR DETECTING SATATE OF DUPLICATED LINK IN ATM EXCHANGE SYSTEM}

The present invention relates to a method of detecting a state of a redundant link in an asynchronous transmission mode switching system, and more particularly, to a method of detecting an error occurrence and a recovery state of a redundant link between a subscriber matching device and a switch device.

Typically, the interface medium between the subscriber registration device and the switch device is called a link, through which cells between the two devices are transmitted. This link section is duplicated according to the characteristics of each communication system. When an error is detected in the currently used link during operation, the other link is selected and the cell is transmitted. In this way, when one of the two redundant links is used and an abnormal state is detected on the link, selecting another normal link is called link switching.

In general, a link for high speed data transmission adds maintenance information to data to be transmitted to detect an error that may occur on the transmission link, and performs a recovery procedure accordingly. This method adds a parity bit or complex CRC for maintenance information. However, this requires more speed than the original data transmission rate due to the addition of maintenance information, which complicates the hardware of the transmitter and the receiver, thereby increasing the cost.

Accordingly, an object of the present invention is to provide a method for detecting a link error without adding a separate hardware logic such as parity or CRC to detect a link error in an asynchronous transmission mode switching system.

Another object of the present invention is to provide a method for detecting an error of a redundant link using an SOC signal in an asynchronous transmission mode switching system.

It is still another object of the present invention to provide a method for immediately detecting a link error without a separate calculation process in case of a link error in an asynchronous transmission mode switching system.

It is another object of the present invention to provide a method for quickly switching to a normal link in detecting an error of a redundant link in an asynchronous transmission mode switching system.

The present invention for achieving the above object is to quickly detect when an error occurs in the link of the switch block currently in operation to switch to a link in a normal state, and to control the link by notifying the controller even when the error occurs link recovery It is characterized by.

1 is a schematic configuration diagram of a part to which the present invention is applied in an asynchronous transmission mode switching system.

2A is a control flow diagram for managing a reference status signal in accordance with the present invention.

2B is a control flow diagram for managing link state signals in accordance with the present invention.

2C is a control flow diagram for managing a count enable signal in accordance with the present invention.

2D is a control flow diagram for managing a link normal signal in accordance with the present invention.

3 is a waveform diagram of a signal when a link in accordance with the present invention is normal;

4 is a waveform diagram of a signal when a link is abnormal and restored to normal in accordance with the present invention.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. In addition, in the following description of the present invention, if it is determined that a detailed description of a related known function or configuration may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted.

1 is a schematic configuration diagram of a part to which the present invention is applied in an asynchronous transmission mode switching system, and detects a state of a link between a subscriber matching device 100 and a switch device 110 to select a normal link.

Referring to FIG. 1, an operation of selecting a normal link by detecting a state of a link between the subscriber matching device 100 and the switch device 110 in the asynchronous transmission mode switching system according to the present invention will be described. The ATM subscriber registration device 100 includes a control unit 101, a reference clock generation unit 102, a link error detection / selection unit 103, and an LVDS reception unit 104, 105. The controller 101 receives a reference clock from the reference clock generator 103 and provides a reference pulse necessary for link selection to the link error detection / selection unit 103 (or a link error). The detection / selection unit may perform the above function) The link error detection / selection unit 103 reports the link selection result and the link error / recovery result. At this time, the reference clock is 4.096 MHz (optionally changeable), and the reference pulse is used to count the time for which the link reaches a steady state at 8kHz (optionally changeable) by dividing the reference clock. The link error detection / selection unit 103 selects a link using the link error / recovery state detection from the LVDS receivers 104 and 105 and the result. The LVDS receivers 104 and 105 are redundant and receive data from the ATM switch device 110. In case of using LVDS device, it takes more than a few milliseconds to reach steady state during link switching. It is excellent in power consumption and can transmit and receive data at high speed.

Each signal used in the present invention is as follows.

The power on reset signal (hereinafter referred to as PORESET) is a reset signal when the ATM subscriber apparatus 100 is powered on.

The Reference Start Of Cell (hereinafter referred to as Ref. SOC) signal is a signal indicating the ATM cell start from the ATM subscriber apparatus 100 to the ATM switch apparatus 110.

The Link Start Of Cell (hereinafter referred to as Link. SOC) signal is a signal indicating the ATM cell start from the ATM switch device 110 to the ATM subscriber device 100.

The reference pulse (hereinafter referred to as Ref.pulse) signal is an 8 kHz pulse (which can be arbitrarily changed according to system characteristics).

The count enable signal (hereinafter referred to as Count.enb) is an enable signal for operating a counter.

The Count (hereinafter referred to as Count) signal is a 10-bit (optionally modifiable) counter value based on the Ref.pulse signal.

The link normal signal (hereinafter referred to as Link.normal) is a signal indicating the current link state. If the link is '0', the link is in an abnormal state, and if the link is '1', the link is in a normal state.

The link state signal (hereinafter referred to as Link.state) is a value (3 bits) counted based on the Link.SOC signal.

The reference state signal (hereinafter referred to as Ref.state) is a signal that receives a Link.state value based on the Ref.SOC signal and is 3 bits.

2A-2D illustrate a control flow for detecting and recovering from errors in a redundant link according to the present invention.

First, when power is applied to the system, the ATM subscriber apparatus 100 according to the present invention maintains the state of the PORESET signal at '0' for several ms therefrom, and the initial value is set in this period. After that, the PORESET signal maintains a state of '1', from which control for link error detection / selection is performed.

A process of managing the Ref.state signal according to the present invention will be described with reference to FIG. 2A. In step 211, it is determined whether the PORESET signal is '0'. If it is determined that the PORESET signal is '0', Ref.state is set to an initial value of "110" in step 212. When the Ref.SOC signal is a rising edge in step 213, the value of the Link.state signal is written to the Ref.state signal in step 214. (Ref.state <= Link. state) That is, whenever Ref.SOC signal is applied, the value of Link.state signal is written to Ref.state signal.

Meanwhile, a process of managing the Link.state signal according to the present invention will be described with reference to FIG. 2B. In step 221, it is determined whether the PORESET signal is '0'. If it is determined that the PORESET signal is '0', the initial value of the Link.state signal is set to "0" in step 222. In step 223, it is determined whether the Link.normal signal is '0'. If it is determined that the Link.normal signal is '0', the Link.state signal is maintained as it is in step 224. (Link.state <= Link.state) In contrast, the Link.normal signal is '0'. If not, if the Link.SOC signal is the rising edge in step 225, the value of the Link.state signal is increased in step 226. (Link.state <= Link.state + 1) That is, when the Link.normal signal is '1', the value of the Link.state signal is increased whenever the Link.SOC signal is applied.

Meanwhile, a process of managing the Count.enb signal according to the present invention will be described with reference to FIG. 2C. In step 231, it is determined whether the PORESET signal is '0'. If it is determined that the PORESET signal is '0', the Count.enb signal is set to an initial value of '1' in step 232. If the Ref.SOC signal is the rising edge in step 233, it is determined in step 234 whether the Link.state signal is the same as the Ref.state signal. If it is determined that the Link.state signal is not the same as the Ref.state signal, in step 235, the value of the Count.enb signal is maintained at '1'. In contrast, if it is determined that the Link.state signal is the same as the Ref.state signal, the value of the Count.enb signal is set to '0' in step 236.

Meanwhile, a process of managing the Link.normal signal according to the present invention will be described with reference to FIG. 2D. In step 241, it is determined whether the Count.enb signal is '1'. If the Count.enb signal is determined to be '1', the Count value is set to '1111111111' in step 242, and the Link.normal signal is set to '1'. In contrast, if it is determined that the Count.enb signal is not '1', in step 243, the Count value is set to "0000000000" and the Link.normal signal is set to "0". If the Ref.pulse signal is a rising edge in step 244, it is determined in step 245 whether the Count value is greater than or equal to '0' and less than or equal to '1000'. If the Count value is determined to be greater than or equal to '0' and less than or equal to '1000', in step 246, the Count value is increased (Count <= Count + 1) and the Link.normal signal is set to '0'. In contrast, if it is determined that the Count value is not more than '0' or less than '1000', it is determined whether the Count.enb signal is '1' in step 247. If the Count.enb signal is determined to be '1', the Count value is set to '1111111111' and the Link.normal signal is set to '1'. In contrast, if it is determined that the Count.enb signal is not '1', the Count value is set to '0000000000' and the Link.normal signal is set to '0'.

The operation when the link is in the normal state according to an embodiment of the present invention will be described with reference to FIGS. 2A to 3. First, when the link is in a normal state according to an embodiment of the present invention, the Ref.SOC signal 310 and the Link.SOC signal 330 are repeatedly applied at regular intervals as shown in FIG. 3. . The Ref.state signal 320 is changed to the value of the Link.state signal 340 whenever the Ref.SOC signal 310 is applied. In addition, since the value of the Link.normal signal 360 is '1', the value of the Link.state signal 340 is increased whenever the Link.SOC signal 330 is applied. In addition, when the Ref.SOC signal 310 is applied and the value of the Link.state signal 340 and the Ref.state signal 420 are different from each other, the value of the Count.enb signal 350 is changed to '1'. Keep it at When the value of the Count.enb signal 350 is maintained at '1', the Count value is set to '1111111111' and the Link.normal signal 360 is maintained at '1'. That is, when the link according to the embodiment of the present invention is in a normal state, the Link.normal signal 360 is always maintained at '1', and no link switching is performed.

On the other hand, with reference to Figures 2a to 4 will be described the operation when the link is in an abnormal state and restored to normal according to an embodiment of the present invention. First, when a link is in an abnormal state according to an embodiment of the present invention, Ref. SOC may be caused by cable detachment of the LVDS receivers 104 and 105, detachment of the ATM switch device 110, abnormal power supply of the ATM switch device 110, and the like. The signal is repeated periodically but the Link.SOC signal is not applied. Each time the Ref.SOC signal 410 is applied, the value of the Link.state signal 440 is written to the Ref.state signal 420. However, since the value of the Link.state signal 440 does not increase from the time T1 at which the link error occurs, the value of the Ref.state signal 420 is also the value before the error occurrence of the link of the Link.state signal 440. It will continue to be written. Since the Link.SOC signal 430 is not applied after the link error (after T1), the value of the Link.state signal 440 does not increase and maintains the value before the link error. . In addition, when the Ref.SOC signal 410 is applied, the value of the Link.state signal 440 is compared with the value of the Ref.state signal 420. If an error of the link occurs, the Link.state signal 440 ) And the value of the Ref.state signal 420 are the same, so the value of the Count.enb signal 450 is set to '0'. When it is detected that the value of the Count.enb signal 450 becomes '0', the count value is initialized to '0000000000' and incremented each time the 8kHz Ref.pulse signal is applied. At this time, the Link.normal signal 460 is maintained at '0' during the interval 125ms from the count value '0' to '999' (decimal). This is to ensure sufficient time for the LVDS device to reach a steady state, and how long it counts depends on the characteristics of the device. After counting up to '999', the value of the Count.enb signal 450 is again checked to determine whether the error of the link is recovered or whether the error continues. In conclusion, in case of an abnormal state due to a link error according to an embodiment of the present invention, the link.normal signal is maintained at '0', and the link.normal signal is detected as '0' at the time of the normal link. Transfer. Then, keep the Link.normal signal '0' until the link error is repaired.

On the other hand, if the link in which the error occurred at time T2 is restored, the value of the Link.state signal 440 is increased because the Link.SOC signal 430 is normally applied. Accordingly, the Ref.state signal 420 changes to the value of the Link.state signal 440 when the Ref.SOC signal 410 is applied as the value of the Link.state signal 440 increases. Then, when the value of the Ref.state signal 420 is compared with the value of the Link.state signal 440 when the Ref.SOC signal 410 is applied, the value of the Ref.state signal 420 is Since the value of the Link.statet signal 440 is different, the value of the Count.enb signal 450 is set to '1', and the value of the Link.normal signal 450 is also set to '1'. At this time, the selection decision of the link restored to normal is not dealt with in the present invention.

As described above, the present invention provides a link error occurrence and error recovery in order to minimize cell loss and system error due to a link error between two devices in a cell transmission between a redundant subscriber station and a switch device in an asynchronous transmission mode switching system. Detect quickly. Therefore, the present invention has the advantage of preventing the malfunction of the subscriber apparatus by preventing the inflow of the error data to the system at the time of link switching to increase the continuity and stability of the system.

Claims (3)

A method for detecting a state of a redundant link between a subscriber device and a switch device in an asynchronous transmission mode switching system, Setting a reference state signal, a link state signal, and a count enable signal to initial values when the subscriber device is powered on; Writing a value of the link state signal to a value of the reference state signal whenever a reference cell start signal indicating the start of a cell from the subscriber device to the switch device is applied; Comparing the value of the link state signal with the value of the reference signal each time the reference cell start signal is applied; If the value of the link state signal is equal to the value of the reference state signal, applying the count enable signal to initialize a count value and increasing the count value each time a reference pulse is applied; Maintaining a constant link normal signal indicating a current link state until the count value is counted to a set value; And determining that the current link is an abnormal link with the link normal signal, and switching to another normal link. The method of claim 1, If the value of the link state signal is different from the value of the reference state signal, stopping the count operation and determining that the link state is normal. How to detect it. The method of claim 2, If it is determined whether the current link is normal by the link normal signal, increasing the value of the link state signal whenever a link cell start signal indicating the start of a cell from the switch device to the subscriber device is applied. A method for detecting a state of a redundant link in an asynchronous transmission mode switching system, characterized in that.