KR20030057890A - Device for Switching Automatically in ATM Switching System - Google Patents

Abstract

PURPOSE: An automatic switching device for an ATM(Asynchronous Transfer Mode) switch is provided to sense a packet error and select a link automatic switching through probability, when fault is generated in a dual port of a switch board of the ATM switch. CONSTITUTION: A CRC(Cyclic Redundancy Check)-32 logic generating unit(10) generates a CRC-32 logic signal, and transmits the generated CRC-32 logic signal to an object card through a link. CRC-32 check units(20,30) receive CRC-32 signals from the object card, and transmit counter signals and CRC-32 error state information to a dual logic(40). The dual logic(40) receives the counter signals and CRC-32 error state information from the CRC-32 check units(20,30), monitors a packet error, and generates a link switching execution command. A selecting unit(50) receives the link switching execution command, selects a link to be automatically switched, and transmits a signal to a switch device.

Description

Device for Switching Automatically in ATM Switching System

The present invention relates to an automatic switching device in an ATM switch. Especially, in the event of a failure of a redundant port in a switch board in an ATM switch, an ATM to probably select a link automatic switching through packet error detection on a packet basis The present invention relates to an automatic switching device in an exchanger.

In general, as shown in Fig. 1, the ATM switch is connected to the switch card A, the switch card B by the four link cables to the subscriber card A and the subscriber card B.

The switch card A is connected with links one by one from the subscriber card A and the subscriber card B, and the switch card B is also connected with one link from the subscriber card A and the subscriber card B to form a full cross.

The switch card A receives a P_link_A and an R_link_A from the subscriber card A and selects one of them.

That is, the switch card A and the switch card B output packets from the subscriber card A on two links, and receive the output packets.

In addition, the switch card A and the switch card B output packets from the subscriber card B on two links, and receive the output packets.

The switch card A and the switch card B, which have received the packet output from the subscriber card, decide which link to select. The decision conditions include whether the link is connected, the state of mounting the subscriber card, and the operator's command.

When the switch card and the subscriber card are connected and functioning normally, if one of the two links connected to the switch card is disconnected or one of the two subscriber cards is powered off, the switch card detects this condition and automatically changes the link selection. In addition, link switching occurs even when an operator's link selection change command occurs.

However, if a link failure occurs due to an error of a packet in the link itself, link switching is not automatically performed because a detection circuit does not exist, and after the operator reports this error status and confirms an error in the link, The transfer operation is not performed until a transfer command is issued.

This operation process takes a considerable amount of time to switch to packet loss and implies that the conditions for selecting a redundant link are limited.

That is, when the selection condition is selected by the link disconnection of the link and the link selection command of the operator, and an error on the data in the link itself occurs, a large number of packets are lost without being automatically switched.

The present invention has been made to solve the above-mentioned general problems, and its object is to probabilistically select a link automatic switching through packet error detection on a packet basis in the event of a failure of a redundant port in a switch board in an ATM switch. It is.

1 is a view showing an automatic switching device in a conventional AT switch.

2 is a view showing an automatic switching device in an ATM switch according to an embodiment of the present invention.

3 is a more detailed view of the FPGA of FIG.

Figure 4 illustrates an FPGA redundancy logic flow in accordance with the present invention.

* Description of the symbols for the main parts of the drawings *

10: CRC (Cyclic Redundancy Check) -32 logic generation unit

20, 30: CRC (Cyclic Redundancy Check) -32 check part

40: redundancy logic

50: selection unit

The automatic switching device in the AT switch according to the embodiment of the present invention for achieving the above object generates a CRC logic to generate a cyclic redundancy check (CRC) logic to transmit to the other card through the link Wealth; A CRC check unit for receiving a CRC from an opponent card and checking the CRC, and for transmitting a counter and cyclic redundancy check (CRC) ERROR status information to the redundancy logic; Redundancy logic for receiving a counter and CRC ERROR status information from the CRC check unit and generating a link switching execution command by monitoring packet errors in units of packets; And a selection unit for receiving a link switching execution command from the redundancy logic, combining the combinations, selecting a link to be automatically switched, and delivering the link to the switch device.

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

As shown in FIG. 2, the automatic switching device of the ATM switch according to an embodiment of the present invention adds a field-programmable gate array (FPGA) to a conventional structure to detect an error of a packet in a link, and automatically switches and reports the packet. Configure to facilitate.

Link monitoring is implemented as logic by placing an FPGA 100 in each of switch card A, switch card B, and subscriber card A and subscriber card B, and the link monitoring logic is a cyclic redundancy check per packet. To check if there is an error in the data sent to the communication link, restore it, and check each packet to see if there was an error while the packets were on the link, and duplicate this state. It transfers to logic and configures to automatically switch in case of link error.

In addition, the FPGA 100 is configured to perform error monitoring in a packet unit, but is designed to perform link switching by probability as a whole to minimize the system load and packet loss due to repeated link switching during abnormal link operation.

As shown in FIG. 3, the FPGA 100 includes a cyclic redundancy check (CRC) -32 logic generation unit 10, a CRC-32 check unit 20 and 30, a redundancy logic 40, and a selection. The part 50 is provided.

The CRC-32 logic generation unit 10 generates the CRC-32 logic and transmits the CRC-32 logic to a counterpart card (for example, a switch card or a subscriber card) through the P link and the R link, and performs a CRC-32 check on the receiving side. It consists of a kind of coding done.

Two CRC-32 check units 20 and 30 exist, one for each link. The CRC-32 check units 20 and 30 each receive a CRC-32 from an opponent card (for example, a switch card or a subscriber card) and check the result. In this case, the transmitted signal is CNT (COUNT: Count counts packets from 1 to 100 continuously. If CRC ERROR occurs among 100 packets, it is performed to automatically switch the link through the link selector. Logic) and CRC ERROR status information.

The redundancy logic 40 receives the CNT and the CRC ERROR status information from the CRC-32 check units 20 and 30 to perform the redundancy logic.

The CNT and CRC ERROR status information received from the CRC-32 check units 20 and 30 are used as input conditions according to respective states of the redundancy logic 40, as shown in the flowchart of FIG. There are six states (P0, P1, P2, P3, P4, P5), and in each state, state transition occurs in the direction of each arrow according to the input condition.

In the first P0 state, the CRC ERROR is monitored. If a CRC ERROR occurs, it transitions to P1. If the CNT value is 100, it transitions to P0. The CRC ERROR and CNT values are continuously monitored.

At P1, CRC ERROR is monitored. If CRC ERROR occurs, it transitions to P2. If CNT value is 100, it transitions to P0. Otherwise, CRC ERROR and CNT values are continuously monitored in P1 state.

P2, P3, and P4 states also perform the same operations as P0 and P1.

However, if a CRC ERROR occurs in P4 and then transitions to P5, P5 executes a link transfer command, and transfers a transfer signal from the redundancy logic 40 to the selector 50 to perform automatic transfer.

In a circular flow from P0 to P0 and back to P0, all transitions to P5 state means that five CRC ERRORs occurred before the CNT value reached 100. This means that link switching is performed automatically.

Since the redundancy logic 40 receives both the CRC ERROR and the CNT value checked from the two links, there are two state flow diagrams using the same, and combines the link transfer command from the two state flow diagrams and delivers them to the selection unit 50. Automatic switching is realized.

Although the preferred embodiments of the present invention have been described in detail above, it will be understood by those skilled in the art that the present invention may be modified or modified in various ways. Therefore, changes of the embodiments of the present invention will not be able to escape the technical scope of the present invention.

As described above, according to the present invention, in the event of a failure of a redundant port in a switch board in an ATM switch, it is possible to probabilistically select a link automatic switching through packet error detection on a packet basis, thereby resulting in system reliability and packet error. This reduces the error time and minimizes packet loss on the system.

In addition, there is an effect of reducing the system operating cost and improving the system stability.

Claims (3)

A CRC logic generation unit for generating a Cyclic Redundancy Check (CRC) logic and transmitting the link to the other card through a link; A CRC check unit for receiving a CRC from an opponent card and checking the CRC, and for transmitting a counter and cyclic redundancy check (CRC) ERROR status information to the redundancy logic; Redundancy logic for receiving a counter and CRC ERROR status information from the CRC check unit and generating a link switching execution command by monitoring packet errors in units of packets; And a selection unit for receiving a link switching execution command from the redundancy logic, combining the combinations, and selecting a link to be automatically switched to the switch device. The method of claim 1, The redundancy logic uses the counter and the CRC ERROR state information from the CRC checker as an input condition, and monitors the counter and the CRC ERROR as the state transitions according to the corresponding input condition. Automatic transfer device in The method according to claim 1 or 2, The redundancy logic is an automatic switching device in the AT switch, characterized in that the stochastic selection of the link automatic switching through packet error detection on a packet basis.