KR20000074220A - Method for selecting duplicated link in atm swiching system - Google Patents

Abstract

PURPOSE: A method for selecting duplicated links in an asynchronous transfer mode(ATM) switching system, is provided to check errors in one link and to select the other link without errors. CONSTITUTION: If a cable is connected, whether a start of cell(SOC) signal exists is decided. If the SOC signal does not exist, whether a cell exists is decided. If a cell exists, whether a back-pressure signal is normal is decided. If the back-pressure signal is normal, whether a present link is under operation is decided. If the present link is under operation, whether a user requests a change of a port is decided. If the user requests a port change, the present link is stood by and change to another port is performed.

Description

METHODO FOR SELECTING DUPLICATED LINK IN ATM SWICHING SYSTEM}

The present invention relates to a method of selecting a redundant link in an asynchronous transmission mode switch, and more particularly, to a method of selecting a normal link by determining an error for a duplicated link.

Asynchronous Transfer Mode (hereinafter referred to as ATM) switches typically switch high speed ATM cells transmitted on multiple ports. When the ATM switch is used as an edge switch, in order to provide various kinds of services, ATM cells transmitted from multiple ATM I / Os of various types are multiplexed / demultiplexed to match the switch. In this case, a number of ATM I / O boards are matched with a switch board, which increases the size of the system, and thus a cable is generally used to connect them. However, if there is a problem with the cable when data is sent and received at high speed, a large amount of data will be lost. Therefore, in the ATM switching system, ATM switch ports and ATM I / O boards are dually connected to improve stability and reliability.

1 illustrates a structure of a cable for connecting a conventional ATM switch board and an ATM I / O board.

Referring to FIG. 1, in order to transmit data through a cable, the transmitting side serializes several bits of data and converts the data into a differential signal having a good noise characteristic. In addition, the clock is also switched to a differential signal. On the contrary, the receiving side parallelizes them in synchronization with a clock. However, the differential signal is shielded with a ground signal in order to strengthen the influence of general noise and EMI. When this cable was opened, there was no way for the upper level application to know.

Accordingly, an object of the present invention is to provide a method for selecting a link by grasping a cable connection state between a switch and an I / O in an ATM switching system.

Another object of the present invention is to provide a method of selecting a port by determining an error of a redundant link in an ATM switching system.

It is still another object of the present invention to provide a method for checking an error of a link and selecting an error-free link to improve the stability and reliability of an ATM switching system.

The present invention for achieving the above object is characterized by selecting the link in which the error does not occur among the redundant link by checking the error that may occur in the link when the redundant link is formed in the ATM switching system.

1 is a cable structure for connecting between a conventional switch board and the input and output board.

2 is a cable and connector connection structure for the cable open alarm according to the present invention.

3 is a bit configuration diagram of one port according to the present invention;

4 is a circuit diagram for detecting a start error of a cell in accordance with the present invention.

5 is a structural diagram of a cell for general switching.

6 is a control flow diagram for selecting a redundant link according to an embodiment of the present invention.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. First of all, in adding reference numerals to the components of each drawing, it should be noted that the same reference numerals are used as much as possible even if displayed on different 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.

2 shows a connection structure of a cable and a connector for knowing a cable open alarm according to the present invention.

Referring to FIG. 2, the middle ground line is separated from the shield ground of the connector, and the cable connection detecting units 210 and 220 determine the connection state of the cable according to the applied voltage so that the upper application can know. Make sure In addition, it is possible to determine whether each board has a hernia or not, so that it is possible to determine whether the hernia by the board or cable hernia.

3 illustrates data and control signals transmitted and received by an ATM switch board and an I / O board according to an embodiment of the present invention.

Referring to FIG. 3, in an embodiment of the present invention, data transmits and receives ATM cells in nibble units (4 bits). The backpressure signal is a signal for controlling the flow between links. The backpressure signal is used to give data (i.e., from receiving data to giving data). The back press signal applies a "low" signal to the next clock "high" after 6 clocks after the start of cell (SOC) signal is generated, and generates the priority (priority) of the cells that should not be sent. In this way, after the SOC signal is always generated, the back-pressor signal is always checked to see if "high" and "low" are received at the 6th and 7th clocks to see if the signal is faulty. . The SL_ACT signal is a signal that indicates whether the switch link is active or stand-by. In a specific embodiment of the present invention, when the SL_ACT signal is defined as being "low", it is defined as being in operation when the SL_ACT signal is "high". The serializer 310 serializes data and control signals and transmits them in synchronization with a clock signal at a transmitting side. On the other hand, the deserializer 320 deserializes the transmitted data in accordance with the clock signal at the receiving side.

When the ATM switch board and the ATM I / O board exchange ATM cells with each other, SOC signals are sent to each other to indicate the starting point of the cells. However, if the SOC signal cannot be transmitted or received due to a cable or any other cause, a serious problem arises in that the synchronization of the cells is not known and the cells cannot be exchanged with each other, so that an error thereof can be detected for the stability of the system. As shown in Fig. 4, a circuit for detecting an error in receiving the other party's SOC signal is configured.

Referring to FIG. 4, it is determined whether an error occurs by detecting an SOC signal transmitted from a counterpart port. The D flip-flops 410, 420, 430, and 440 shift the high signal whenever the SOC signal applied to the clock changes. The D flip-flops 41, 420, 430, and 440 are cleared by receiving the RX_SOC signal received from the counterpart. If the RX_SOC signal is normally received, the SOC_ERR signal is always in a high state, and if it is not normally received, the SOC_ERR signal is changed to a low state. Here, the two D flip-flops 410 and 420 and the two D flip flops 430 and 440 below are to keep the RX_SOC signal 'high' or 'low' so that the SOC_ERR signal does not appear abnormally. The number of such D flip-flops can be changed depending on how much the margin for the error of the RX_SOC signal is decreased.

In general, the ATM switch prioritizes each cell in order to satisfy a Quality of Service for each service, and manages it using a queue. In this case, contention may occur when a cell having the same priority inputted to multiple ports to the switch is outputted to the same switch output port for the same cell time. The back presser signal controls flow by notifying the input port not to be sent during the next cell time so that a cell is not lost due to a buffer overflow due to a competition in a switch. According to a specific embodiment of the present invention, a signal is placed and the ATM switch board and the ATM I / O board periodically transmit and receive this information. The back presser signal is generated to send data. Therefore, it is used as information for determining whether there is an error in this link by checking whether the back presser signal according to the present invention occurs periodically.

FIG. 5 shows the structure of a typical cell tagged in front of an ATM cell so that the ATM cell can be routed on an ATM switch board.

In this case, the purpose of the tag is whether a cell exists (for example, '10XX' means a cell exists, '01XX' means a meaningless cell), a cell's priority level, and a switch structure. Gives routing information.

6 is a control flowchart for detecting an error of a link and selecting a link according to an embodiment of the present invention.

A method of selecting a link by detecting an error of the link according to an embodiment of the present invention will be described with reference to FIG. 6. In step 600, it is determined whether the cable is connected. At this time, the cable connection detection unit 210, 220 as shown in Figure 2 can determine the connection state of the cable. If it is determined that the cable is not connected, in step 605, a cable connection error process is performed. If the cable is not connected, select the other link on the same switch port.

If it is determined that the cable is connected, in step 610, it is determined whether there is an SOC signal transmitted from the router for one cell time. At this time, the presence or absence of the SOC signal can be determined by the detection circuit as shown in FIG. If it is determined that the SOC signal does not exist, it is processed as an error of the SOC signal in step 615. In other words, if an SOC signal error occurs, select the other link on the same switch port.

If it is determined that the SOC signal exists, it is determined whether a cell exists in step 620. In this case, as shown in FIG. 5, the tag of the cell is checked to see if the cell exists, and if the cell does not exist, it is checked whether an idle cell is sent. If it is determined that the cell does not exist, it is treated as an error of the link in step 625. Since a link failure has occurred, select the other link on the same switch port.

If it is determined that the cell exists, it waits for a predetermined time (six clocks in the embodiment of the present invention) in step 630 and an error occurs by checking the backpressor signal in steps 640 and 650. Judge whether or not. That is, after a predetermined time elapses, if it is determined that the back press signal is not high in step 640, it is determined that an error of the back press signal occurs. In addition, after a predetermined time elapses, if the back press signal is high in step 640 and the back press signal is not low in step 650, it is determined that an error of the back press signal occurs.

If it is determined that an error of the back presser signal has occurred, the process is processed as an error of the back presser signal in step 655. Therefore, if an error of the back press signal occurs, the other link of the same switch port is selected.

If it is determined that no error occurs in the back presser signal, it is determined whether the current link is operating in operation 660 as the SL_ACT signal. When the SL_ACT signal according to the present invention is in the 'low' state, it is determined that the current link is in operation, and in the 'high' state, it is determined that the current link is in the standby state.

If it is determined that the current link is in operation, the SW_CHG signal determines whether there is a request for a port change from the user in step 670. When the SW_CHG signal according to the present invention is in the 'high' state, it is determined that there is a port change request from the user, and in the 'low' state, it is determined that there is no port change request from the user.

If the SW_CHG signal is in the 'low' state, it is determined that there is no port change request from the user, and the current link operates in step 675, and the operation of the step is repeated.

In contrast, when the SW_CHG signal is 'high', it is determined that there is a port change request from the user, and in step 665, the current link is in a standby state, and the other link of the same switch port is selected.

If the current link is determined to be a cable connection error or an SOC signal error or a link error or a back presser signal error in step 680, the step 685 indicates that an error has occurred in the upper link. Generate an interrupt to give. If the link is bad in step 690, the port is changed, and the link monitoring operation for the changed port is repeatedly performed.

As described above, according to the present invention, it is known that an error occurs in a physical medium and a link between an ATM switch board and an ATM I / O board, and thus, a correct port can be selected. Therefore, the present invention can transmit data stably and reliably in configuring an ATM switch.

Claims (6)

A method for selecting a redundant link in an asynchronous transmission mode switching system, A first step of determining whether the cable is connected; If it is determined that the cable is connected, a second process of determining whether a Start Of Cell (hereinafter referred to as SOC) signal exists; If it is determined that the SOC signal does not exist, determining whether a cell exists; A fourth step of determining whether a backpressure signal is normal when it is determined that the cell exists; If it is determined that the back presser signal is normal, a fifth process of determining whether a current link is in operation; If it is determined that the current link is in operation, a sixth process of determining whether there is a port change request from a user; And a seventh step of waiting for the current link and changing to another port, if it is determined that there is a request for changing the port from the user. According to claim 1, If the cable is not connected in the first process, And selecting another link of the same switch port by determining that the cable is in error. The method of claim 1, wherein when no SOC signal is present in the second process, And selecting the other link of the same switch port by determining that the SOC signal is an error. The method of claim 1, wherein the cell does not exist in the third process. The method of selecting a redundant link in an asynchronous transmission mode switching system, further comprising the step of determining the link error and selecting another link of the same switch port. The method of claim 1, wherein when the back press signal is not normal in the fourth process, And selecting the other link of the same switch port based on the error of the back presser signal. The method according to any one of claims 1 to 5, If it is determined that the predetermined error, the method for selecting a duplicated link in the asynchronous transmission mode switching system, characterized in that it further comprises the step of generating an interrupt for notifying that the link has occurred as a link failure.