JPH0715459A - Method and apparatus for discrimination of effective cell in redundant-path coupling unit of asynchronous-transfer-mode switch - Google Patents

Abstract

PURPOSE: To identify a valid cell in the redundant path connection unit of an asynchronous transfer mode switch having a double switching substrate. CONSTITUTION: A plane in which the final cell to be transmitted for a specific call is derived is identified (a), whether or not a serial number attached to the cell is larger than a serial number stored in a storage device is checked (c), whether or not the final cell to be transmitted for the specific call comes from the same plane is checked (d), and whether or not the cell is overlapped by the final cell to be allowed to reach to the plane is checked (e). When the (e) or (c) is true, and the (d) is not true, the cell is transmitted to an output storage device, and the serial number of the cell is stored in the storage device.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for identifying a valid cell in a redundant path coupling unit of an asynchronous transfer mode switch having a dual switching plane.

[0002]

2. Description of the Prior Art In a known type of validity checking device, a redundant path coupling unit searches for a serial number assigned to each data cell and the serial number matches the serial number stored in RAM. It is adapted to detect whether or not it is greater than or equal to 1. If both of these conditions are met, the cell is considered valid and its sequence number is incremented.

[0003]

One disadvantage of this type of validity checking is that if the same two consecutive cells are lost from both planes, the redundant path combining unit causes the sequence count to cycle. It does not allow any cell paths until. The sequence of 64 cells is as follows.

Plane 0 data 1, 2, 3, 4 ─── 6
3, 0, 1, 2 plane 1 data 1, 2, 3, 4 ─── 6
3, 0, 1, 2 if, for example, cells 2 and 3 are lost in both planes, the following cells 4, 5, 6-63,
0 and 1 are rejected in the cycle resulting in 64
All cells are lost. As a result, the original cell loss error condition is unnecessarily postponed.

[0005]

SUMMARY OF THE INVENTION One object of the present invention is to provide a method and apparatus for identifying valid cells which eliminates the above disadvantages. According to the present invention, in a method of identifying a valid cell in a redundant path combining unit in asynchronous transfer mode with dual switching planes, a) the plane from which the last cell to be sent for a call of a particular cell is derived. Identify, b) check if the sequence number assigned to that cell is greater than the sequence number stored in storage, and c) the last cell to be sent for a particular call is derived from the same plane. , D) check if the cell is a duplicate of the last cell arriving at this plane, and e) if c) is true and d) is not true. , Sending the cell to an output storage device and storing the serial number of the cell in the storage device.

Furthermore, according to the invention, in an apparatus for carrying out said method, transceiver means adapted to receive and transmit data, a plane identification data and a cell sequence number connected to the transceiver means. A first storage device configured to store, and for presenting at an addressed location within the first storage device,
A second storage device configured to store a call identifier used to address the first storage device and a serial number for the particular call; a serial number from the second storage device and the first storage device Accepts serial numbers from
And a first comparator for comparing the serial number, a serial number from the second storage device and a serial number from the first storage device, accepted via an incrementer that increments the serial number by 1, and A second comparator configured to compare numbers, the first comparator and the second comparator, and the first storage device according to the output signal generated from the first comparator and the second comparator. And a cell receiving logic circuit configured to generate a read / write control signal for the same.

[0007]

An embodiment of the present invention will be described below with reference to the accompanying drawings. Referring to FIG. 1, each drop line IL is connected to the exchange termination device ET. A data cell for a call accepted via the drop line IL is sent to both switching planes P0 and P1, then switched to the output of the respective plane and sent to the redundant path checking unit RPCU. Therefore, the redundant path checker RPCU accepts the duplication of each cell and the accepted cell P from plane 0.
It is intended to decide whether the cell P1 received from 0 or plane 1 should be sent to the leader OL or discarded as a duplicate.

The redundant path checking unit RPCU performs this operation by executing an algorithm. Each cell is numbered serially so that duplicate cells can be identified. The redundant path inspection device RPCU has a built-in search RAM 1 as shown in FIG. Stored in RAM 1 is a serial number for each cell at some address identified by the virtual channel indicator VCI used to identify the call. The VCI and serial number are temporarily stored in the shift register 2.
This VCI is used to address RAM1
Then, the next serial number is written in the RAM under the control of the cell receiving logic circuit 3 together with the plane identifier PI in which the last cell is received. This serial number is sent to the first comparator 4 and the second comparator 5. The first comparator 4 and the second comparator 5 also accept from RAM 1 the expected sequence number and plane identifier PI stored for the VCI.

The serial number sent from RAM 1 to comparator 5 is incremented by 1 by circuit 6. The output signals from comparators 4 and 5 are sent to cell acceptance logic 3 to control the read / write operations of RAM1. The plane identifier PI is sent to the RAM 1 via the line 7.
Further, the cell receiving logic circuit 3 is connected to the RAM via the line 8.
Accept the cycle start signal. Data is written to RAM1 and read from RAM1 by transceiver TC. RAM1 is controlled by the microprocessor.

An example of the manner in which the cell reaches the redundant path check device RPCU is as follows. 1,2,3,4,5,6 plane 0 1,2,3,4,5,6 plane 1 The above represents a sequence of cells for plane 0 and plane 1. Assuming that cells 1 and 2 of plane 0 are accepted and cells 5 are valid, the cells with the above lines will be lost due to a failure or error and will not arrive at the redundant path checker RPCU. Since the redundant path inspection device expects the serial number of the cell 3, it is out of order. Cell 1 of plane 1
And 2 are rejected because they are duplicates of cells 1 and 2 accepted on plane 0.

The above circuit performs the following algorithm. The algorithm fills in the plane from which the last cell to send for a particular VCI was derived. If the cell arrives, for example, from plane 0, and its sequence number is not greater than the sequence number stored in RAM1, two more checks are made as follows. 1) Was the last cell to pass for this VCI derived from this plane?

2) Is this cell a duplicate of the last cell arriving on this plane? This can be detected by checking whether the serial number of this cell is the same as the serial number stored in RAM1. If 1) is true and 2) is not true, this cell is sent to the transceiver output F1F0 (first in first out) and the sequence number stored in RAM1 is the sequence number of this cell.

The redundant path checker RPCU accepts the cell if the sequence number of the cell is the next number in the sequence. The serial number written in RAM1 is the serial number of the accepted cell. This algorithm is shown in pseudo code as follows: BEGIN Plane-sent-bit: = 0; (Set up variables) Ram-seq-no: = 63; When cell arrives on plane do Begin Acceptance Loop If cell-seq-no <> RAM-seq-no then Begin Normal acceptance If cell-seq-no = RAM-seq-no + 1 then Begin Cell-accepted: = True; RAM-seq-no: = cell-seq-no; Plane-sent-bit: = This-plane; End; Out of Sequence If Plane-sent-bit = This-plane then Begin Cell-accepted: = True; Out-of-sequence: = True; RAM-seq-no: = cell-seq-no; End; End; Else IF Plane-sent -bit = This-plane then Duplicate-cell-alarm: = True; END. END. Variable cell-seq-no Serial number of this incoming cell RAM-seq-no Held in RAM for this VCI Sequence number Plane-sent-bit The plane in which the last cell for this VCI was accepted This-plane The plane in which this cell was derived (0 or 1) Cell- accepted Whether or not this cell is being sent to output F1F0 Control variables that describe Duplicate-cell-alarm Indicating that the duplication is a cell of the last cell on this call on the plane arrived in the microprocessor.

Out of sequence cells lost,
That is, it indicates to the microprocessor that the cells sent are out of sequence (out of sequence). This algorithm does not cause the sequence loss of module 64 due to the circumstances described above with respect to the prior art, and the performance in other circumstances is equal to that of the previously used algorithm.

[Brief description of drawings]

FIG. 1 is a diagram showing a part of an asynchronous mode switch incorporating a dual switching plane.

FIG. 2 is a diagram showing a portion of the hardware incorporated in a redundant path coupling unit necessary to carry out the method of the present invention.

[Explanation of symbols]

 1 Search RAM VCI Virtual channel indicator RPCU Redundant path check device 2 Shift register 3 Cell receiving logic circuit 4 Comparator 5 Comparator 7 line 8 line

Claims (2)

[Claims] 1. A method of identifying valid cells in a redundant path combining unit of an asynchronous transfer mode switch having dual switching planes, comprising: a) identifying the plane from which the last cell to be sent for a particular call was derived; b) check if the sequence number assigned to that cell is not greater than the sequence number stored in storage, and c) if the last cell to be sent for a particular call is from the same plane. , D) check if the cell is a duplicate of the last cell to arrive in this plane, and e) if c) is true and d) is not true,
A method including the steps of sending the cell to an output storage device and storing the serial number of the cell in the storage device. 2. Apparatus for performing the method of claim 1, wherein the transceiver means is configured to receive and transmit data, and the plane means is connected to the transceiver means and stores plane identification data and cell sequence number data. A first storage device configured to perform, and a first storage device for presenting at an addressed location within the first storage device.
A second storage device configured to store a call identifier used to address the storage device and a serial number for the particular call; a serial number from the second storage device and the first storage device A first comparator configured to accept a sequence number and to compare the sequence numbers and a sequence number from the second storage device and a sequence number from the first storage device increment the sequence number by one. A second comparator configured to receive through the incrementer and to compare the sequence numbers, the first comparator and the second comparator being connected, and the first comparator and the second comparator.
A cell receiving logic circuit configured to generate a read / write control signal for the first memory device in response to the output signal generated from the comparator.