JPH114231A - Loop back cell control system and device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To test the normality of an ATM network containing the specification of a fault part by means of one transmission/reception of a loop back cell. SOLUTION: An ATM device 1a judges a transmission line to be normal by transmitting the loop back cell having a position ID=C where it is looped back in an ATM device 1c to a going path and receiving the loop back cell from a return path within prescribed time. An ATM device 1b holds a content in a monitor means 3b and transmits it to down stream as it is at the time of receiving the loop back cell in the going route. Then, it generates the loop back cell where the position ID=B of the self-device is added and to the content and transmits it to the return path when the loop back cell is not returned to the return route within prescribed time. The ATM device 1a judges whether the loop back cell is received or not and the normality of a loop back range containing the fault part based on position ID in the loop back cell when it is received.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a loopback cell control system, and more particularly, to a loopback cell control system and apparatus used for testing the normality of a transmission line or the like in ATM transmission.

[0002]

2. Description of the Related Art Conventionally, this kind of loop-back cell control system is used for testing the normality of an ATM transmission line in an ATM network.

FIG. 4 is a block diagram showing a conventional example of the present invention. In the figure, the ATM network has a plurality of ATs.
M devices 1a to 1c and a transmission line.
The M devices 1a to 1c include time management units 2a to 2c and loopback control units 5a to 5c, respectively.

[0004] As shown in FIG. 2, for example, an ATM cell can be composed of a 5-byte ATM header and a 48-byte information field. The ATM header has a logical path identifier VPI (Virtual Path Identifier) of 12 bits and a logical channel identifier VCI (Virtual Channel Identifier).
Identifier) is composed of 16 bits, a 3-bit payload part PT (Payload Type), a 1-bit cell loss priority CLP (Cell Loss Priority), and a 1-byte header error control unit HEC (Header Error Control). In this case, the ATM header is related to the inter-network interface. In the case of the user network interface, a 4-bit flow control unit GFC (Generic Flow Control) is provided after 1 byte defined in the device.
The VPI has a 12-bit configuration.

[0005] The loopback test is performed using a loopback cell which is a cell for loopback. ITU-T
Recommendation I. FIG. 3 shows the format of a loopback cell, such as 610. In FIG. 3, the OAM & function type indicates that this cell is an OAM (Operatio) for loopback.
n And Maintenance) Indicates a cell. The loopback display is displayed before this cell is turned back (outbound path “1”)
Or after returning (return route “0”). The correlation tag indicates the relationship between cells. The loopback position ID indicates the position ID of the device at which the loopback cell is to be turned back.
The source ID is the position I of the device that transmitted the loopback cell.
D is shown. CRC-10 is an operation result of CRC (Cyclic Redundancy Check) -10 for a portion other than the ATM header, and is used for detecting an error in cell information.

The operation of the conventional example having the above-described configuration will be described with reference to a loopback test in which the ATM device 1a turns the ATM device 1c back.

The loopback control means 5a of the ATM device 1a sets the loopback display to "1", sets the loopback position ID to the position ID (C) of the ATM device 1c to be looped back, and sets the source ID to its own. Equipment (own AT
A loopback cell is generated as the position ID (A) of the (M apparatus). OAM type & being a loopback cell
This is performed by setting the function type to a predetermined value. The value given by the administrator is inserted as the correlation tag. C
RC-10 performs an operation on the cell payload to determine its value. The generated loopback cell is added to the idle time between user cells on the transmission line after adding the VPI and VCI to be tested.

[0008] The loopback control means 5a includes:
When the loopback cell is inserted into the transmission path, the time management unit 2a is notified of the transmission of the loopback cell. The time management unit 2a holds the time at which the transmission of the loopback cell was notified, and measures the elapsed time. Loopback control means 5 even if a predetermined time-out period has elapsed
If the notification of the arrival of the loopback cell does not come from a, a timeout is notified to the loopback control means 5a. Here, the timeout time is determined, for example, according to Recommendation I.T. It is fixedly determined in advance on the network as indicated by 610 as 5 seconds.

The loop-back control means 5b of the ATM device 1b receives the loop-back cell from the ATM device 1a and recognizes that the cell is before the loop-back because the loop-back indication is "1". However, since the loopback position ID in the loopback cell is different from the position ID (B) of the own ATM device, the loopback cell is passed as it is.

The loopback control means 5 of the ATM device 1c receives the loopback cell from the ATM device 1b, determines that the loopback display is "1", and that the loopback position ID is the position ID of the own ATM device. (C) is detected, and a return loopback cell in which the loopback display is rewritten to “0” is generated. CRC
For -10, the result of the operation performed on the payload is inserted again. The return loopback cell is also inserted in the idle time between the user cells on the return transmission line. On the return path, the loopback control means 5b of the ATM device 1b recognizes that the loopback display of the loopback cell is "0". However, since the loopback position ID is different from the position ID (B) of the own ATM device, the loopback is performed. Pass the back cell as it is.

The loopback control means 5a of the ATM device 1a determines that the loopback display of the received loopback cell is "0" and the source ID is the position ID of the own ATM device.
(A), and confirms that the correlation tag is the same as the value inserted in the forward path, recognizes that the loopback was performed normally, and loops the time management means 2a. Notify backsell arrival.

The time management means 2a stops measuring the elapsed time and clears the measured value in response to the notification of the arrival of the loopback cell. If the loopback cell does not return to the ATM device 1a due to a failure or the like, a timeout is notified from the time management unit 2a to the loopback control unit 5a, and the loopback control unit 5a recognizes that the loopback has failed. The AT
If there is any abnormality between the M device 1b and the ATM device 1c and the loopback fails, the ATM device 1b
a is an AT which is a transit device on the way to identify a faulty location.
A loop-back test is performed by the M device 1b,
After confirming that the route to the M device 1b is normal, the AT
It is determined that there is an abnormality between the M device 1b and the ATM device 1c.

[0013]

In the above-described loop-back control method, if there is an abnormality in a transmission line or the like, the cell does not return from any place in one test, so that the loop-back cell can be normally operated up to the waypoint. Since it is not possible to determine whether or not the data has been transmitted, a loopback test must be repeatedly performed for each waypoint in order to identify a faulty part of the route.

It is an object of the present invention to provide a loopback control system and apparatus which enables a test of the normality of an ATM network including the identification of a fault location by transmitting and receiving a loopback cell once.

[0015]

In order to solve the above-mentioned problem, a loopback cell control system according to the present invention provides a method for specifying an ATM network comprising a round-trip transmission line and an ATM device.
In a loopback cell control method for determining the normality of a loopback range by transmitting a loopback cell from a TM device, an ATM through which the loopback cell passes
The device holds the contents of the outward loopback cell, and adds the position ID of its own ATM device based on the retained data when the downstream loopback cell does not return from the downstream ATM device. It is characterized in that cells are generated and transmitted on the return path.

Further, the A
When the loopback cell is not received from the return path within the set timeout period from the time when the contents of the loopback cell on the outward path is held, the TM apparatus determines the position I of the own ATM apparatus.
The method is characterized in that the loopback cell to which D is added is generated and transmitted on the return path.

Further, the specific ATM device determines whether or not the loopback cell is received within a predetermined timeout period, and determines the position ID of the ATM device of the received loopback cell.
The normality of the loopback range is determined based on

An ATM device according to the present invention is an ATM device comprising loopback control means connected to a round-trip transmission line and time management means connected to the loopback control means, wherein the loopback control means comprises: A loopback cell including the position ID of the ATM device to be backed up is generated and transmitted to the forward transmission line, and the time elapsed from the transmission time of the loopback cell is measured by the time management means. The normality of the ATM network is determined based on whether or not a loopback cell is received from the return path and the position ID of the ATM device of the received loopback cell.

An ATM apparatus comprising a loop-back control means connected to a round-trip transmission path, a time management means and a monitor means connected to the loop-back control means, wherein the loop-back control means receives the received forward path. The data of the loop-back cell is held in the monitor means and transmitted to the transmission path of the forward path, and the time elapsed from the reception time of the loop-back cell is measured by the time management means. If a back cell is received, the loop back cell is transmitted to the return path. If no return loop back cell is received within the timeout period, the own ATM is transmitted based on the data of the monitor means.
It is characterized in that a loopback cell including the position ID of the device is generated and transmitted to the return path.

The loopback cell control method of the present invention and A
The TM device works as follows. ATM to be looped back from loopback control means of specific ATM device
The loopback cell in which the position ID of the device and the time information (transmission time) obtained from the time management means are written is transmitted to the forward path of the round-trip transmission path. In the ATM device serving as a waypoint, the loopback control unit receives the loopback cell, holds the content in the monitor unit, and determines the timeout in the ATM device based on the current time obtained from the time management unit and the information on the transmission time. Calculate the time and send the loopback cell downstream. When the forward loopback cell reaches an ATM device that matches the assigned loopback position ID, the loopback cell is looped back by the loopback control means.

The loopback control means of the ATM device on the return path determines whether or not the loopback cell is received within the timeout time calculated by the own ATM device, and at the time of timeout, the contents of the loopback cell held in the monitor means. Then, a loopback cell in which the position ID of the own ATM device is added to the above is generated, and the loopback cell is looped back to the specific ATM device. The loopback cell is the specified ATM from the return path.
Returning to the device, the loopback control means determines the normality of the transmission path including the fault location.

The loopback control means of the specific ATM device determines whether or not the loopback cell is received within the timeout period, and determines the AT of the predetermined loopback range based on the loopback position ID of the received loopback cell.
Determine the normality of the M network. Even when a loopback cell is received, if the loopback position ID is different from the loopback position ID at the time of transmission, the path to the ATM device of the position ID is normal and a fault occurs at the destination. Is determined.

[0023]

Next, the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of the present invention.

Reference numerals 1a to 1c denote ATM devices which are connected to a reciprocating transmission line. Of the constituent elements of the ATM devices 1a to 1c, 2a to 2c are time management means, 3a
Reference numerals 3c to 3c denote monitoring means, and 4a to 4c denote loopback control means.

The time management means 2a to 2c are connected to the loopback control means 4a to 4c, respectively, and provide current time information in response to requests from the loopback control means 4a to 4c. Further, the time management units 2a to 2c measure the elapsed time from the time when the transmission of the loopback cell is notified from the loopback control units 4a to 4c, and the timeout time given from the loopback cell control units 4a to 4c. When the time has elapsed, a timeout is notified to the loopback control means 4a to 4c.

The monitoring means 3a to 3c are connected to the loopback control means 4a to 4c, respectively, and hold the contents of the cells provided from the loopback control means 4a to 4c as data. ~ 4
All or part of the stored data is provided to the loopback cell control means 4a to 4c in response to the request of c.

The loop-back control means 4a to 4c
Time management means 2a to 2c and monitor means 3a to 3c respectively
3c and the transmission path, when the time becomes the starting point of the loopback test, the current time information is obtained from the time management means 2a to 2c, the transmission time information is added to the loopback cell, and inserted into the transmission path. Further, the loop-back control means 4a to
4c gives the received loopback cell data to the monitor means 3a to 3c when it becomes a route point of loopback, and holds the data. Also, the transmission time information of the loopback cell is obtained from the contents of the received loopback cell, the current time information is obtained from the time management means 2a to 2c, and the time-out time is calculated as a transit point. Thereafter, the loopback cell is sent downstream. If no loopback cell turned back on the return path is detected by the time-out period, the data of the loopback cell is extracted from the monitoring means 3a to 3c, the loopback position ID is changed, and the loopback position ID is changed. To the location ID of the ATM device
To insert a loopback cell on the return path. Also, when the loopback point is set, the loopback position I
A loopback cell is generated without rewriting D and inserted into the return path.

Next, the operation of this embodiment will be described with reference to AT.
The ATM device 1 transmits a loopback cell from the M device 1a.
The case of folding back at c will be described as an example.

Loopback control means 4 of ATM device 1a
a generates the OAM & function type of the loopback cell, the loopback display, the correlation tag, the loopback position ID (C), and the source ID (A). Further, it obtains information on the current time from the time management means 2a and generates a transmission time. After performing a CRC-10 operation on the data, assembling a loopback cell and adding VPI and VCI to be tested as shown in the cell format examples of FIGS. Insert at free time. Note that AT
In the M transmission line, the band that can be used by the user is limited with respect to the band of the transmission line, and it is general that a vacant cell indicating a normal vacancy is inserted in the remaining band, and the loopback cell is It is inserted between user cells by overwriting empty cells.

When the loopback control means 4a inserts a loopback cell into a transmission line, the loopback control means 4a
Notify a of the timeout time of the loopback test and the cell transmission. All the time management means 2a to 2c on the ATM network are adjusted to indicate the same time at the same time. The timeout time of the loopback test is fixedly determined on the ATM network as in the conventional example.

The time management means 2a holds the time when the transmission of the loopback cell is notified as in the conventional example, and measures the elapsed time thereafter. If the arrival of a loopback cell is not received from the loopback control unit 4a even after the timeout period given by the loopback control unit 4a has passed, the timeout is notified to the loopback control unit 4a.

The loopback cell inserted on the transmission path is received by the ATM device 1b. The loopback control means 4b of the ATM device 1b receives the loopback cell from the ATM device 1a, and recognizes that the cell is before the loopback because the loopback display is "1". Further, since the loopback position ID in the loopback cell is different from the position ID (B) of the own ATM device, the loopback control means 4b determines that the current position is a transit point and performs the following operation. That is, the loopback control unit 4b holds the cell transmission time of the loopback cell, and then copies the VPI, VCI, OAM & function type, correlation tag, and source ID of the cell data, and monitors the data.
Notify.

The ATM device 1a obtains the current time from the time management means 2b and calculates the current time from the transmission time of the loopback cell.
From the ATM device 1b to the ATM device 1b, and the timeout time in the ATM device 1b. Here, as the setting of the timeout time, for example, if the loopback cell transmission time is Ta, the current time is Tb, and the timeout time of the loopback test, that is, the timeout time in the ATM device 1a is To, a theoretical value is obtained. The timeout time Tob 'in the ATM device 1b is Tob' = To
−2 × (Tb−Ta). When the ATM device 1b causes a timeout before the ATM device 1a, the actual time-out time Tob is set to Tob = Tob'-α, where α is a predetermined margin value.

After the calculation of the timeout period, the loopback cell is inserted between the user cells by overwriting the empty cell on the transmission path of the outward path again.

After transmitting the loopback cell, the time management unit 2b is notified of the cell transmission, and a timeout time is given.

The time management means 2b is provided with the time management means 2
As in a, the time at which the transmission of the loopback cell is notified is held, and the elapsed time thereafter is measured. When the arrival of the loopback cell has not been notified from the loopback control unit 4b even after the timeout period given by the loopback control unit 4b, the timeout is notified to the loopback control unit 4b.

The monitor means 3b holds the data notified from the loopback control means 4b and gives the held data at the time of the request from the loopback control means 4b. The monitoring unit 3b includes, for example, a storage unit using a memory or a register and a control unit including an address counter for reading and writing data in the storage unit in accordance with a write request or a read request from the loopback control unit. Can be configured.

Next, the loopback control means 4c of the ATM device 1c receives the loopback cell from the ATM device 1b, and indicates that the loopback display is "1" and that the loopback position ID is of the own ATM device. Position ID (C)
Is detected, and a return loopback cell is generated. For the return loopback cell, the loopback display is rewritten to “0”, and VPI, VCI, OAM & function type, correlation tag, loopback position ID, source ID
For, the contents of the outward loopback cell are copied as they are. For CRC-10, the result of the operation performed on the payload is inserted again. Loopback control means 4
In c, a loopback cell on the return path is inserted between user cells by overwriting an empty cell on the transmission path on the return path.

On the return path, the loopback control means 4b of the ATM device 1b recognizes that the loopback display of the loopback cell is "0" as in the conventional example, but the source ID is the own ATM device ID (B ), The loop-back cell is passed as it is. Further, the loopback control unit 4b notifies the time management unit 2b of the arrival of the loopback cell, and the time management unit 2b stops the elapsed time measurement and clears the measurement value by the notification of the loopback cell arrival.

However, in the ATM device 1b, if the loopback control unit 4b receives a timeout notification from the time management unit 2b before receiving the loopback cell, the loopback control unit 4b performs the following operation.

The data of the loopback cell held in the outward path is obtained from the monitor means 3b, the loopback display is set to “0”, and the loopback cell is generated with the loopback position ID as the position ID (B) of the own ATM device. .

With respect to CRC-10, the result calculated for the payload is inserted again, and the generated loop-back cell is inserted between the user cells by overwriting the empty cell on the return transmission line.

Next, in the ATM device 1a, when the loopback control means 4a receives the loopback cell, the loopback display of the loopback cell is "0", and the source ID is the position ID of its own ATM device ( (A) is confirmed, and if it is confirmed that the correlation tag and the loopback position ID are the same as the values inserted in the outward path, it is recognized that the loopback has been performed normally.

Then, the loopback control means 4a notifies the time management means 2a of the arrival of the loopback cell, and the time management means 2a stops the measurement of the elapsed time by the notification of the arrival of the loopback cell and clears the measured value. .

If the loopback control means 4a recognizes that the loopback position ID of the received loopback cell is different from the value inserted in the forward path, the ATM having the same device ID as the received loopback position ID is used.
An alarm is issued assuming that an abnormality has occurred before the apparatus, and the received loopback position ID is displayed or notified to a predetermined department.

Further, the loopback control means 4a also issues an alarm when a loopback cell that can be regarded as normal is not received within the timeout period, and displays a timeout or notifies a predetermined department.

For example, the ATM device 1b and the ATM device 1c
When there is a failure between the ATM device 1a and the ATM device 1a,
The loopback cell sent to the device 1c is A
Although it is not looped back from the TM device 1c, A
The timeout occurs in the TM device 1b before the ATM device 1a, and the ATM device 1b loops back the loopback cell based on the value held from the forward loopback cell. In this case, the loopback control means 4a of the ATM device 1a determines that the loopback cell is received within the timeout period and the loopback position ID is the value C at the time of transmission.
Loopback position I received with the alarm
The value B of D is displayed or notified to a predetermined department. Thus, it is possible to confirm that the transmission path is normal up to the ATM device 1b and that a failure has occurred between the ATM device 1b and the ATM device 1c.

When there is a failure between the ATM device 1a and the ATM device 1b, the loopback cell transmitted from the ATM device 1a does not return to the ATM device 1a within the timeout period. Therefore, a warning and a timeout are displayed from the loopback control device 4a of the ATM device 1a or a notification is sent to a predetermined department. This makes it possible to confirm that a failure has occurred in the transmission path up to the ATM device 1b.

[0049]

As described above, according to the present invention,
The ATM device through which the loop-back cell passes holds the contents of the loop-back cell on the outward route, and when the loop-back cell does not return from the return route of the downstream ATM device within the time-out period, the content held on the loop-back cell is also restored. And own ATM
Since the loopback cell to which the position ID of the device is added is generated and transmitted to the return path, the presence / absence of reception of the return loopback cell and the position ID of the received loopback cell are checked in the ATM device which has transmitted the loopback cell. Thus, it is possible to perform a normality test of the transmission line including the identification of the abnormal part of the transmission line by transmitting and receiving a single loopback cell.

[0050]

[Brief description of the drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention.

FIG. 2 is a diagram illustrating a configuration example of an ATM cell.

FIG. 3 is a diagram showing a format of a loopback cell.

FIG. 4 is a block diagram showing a conventional example.

[Explanation of symbols]

1a, 1b, 1c, 5a, 5b, 5c ATM device 2a, 2b, 2c, 6a, 6b, 6c Time management means 3a, 3b, 3c Monitoring means 4a, 4b, 4c, 7a, 7b, 7c Loopback control means

Claims (5)

[Claims] An AT comprising a round-trip transmission line and an ATM device
In a loopback cell control method in which the normality of the loopback range is determined by transmitting a loopback cell from a specific ATM device in the M network, the ATM device through which the loopback cell passes holds the contents of the outward loopback cell. Then, when the return loopback cell is not folded back from the downstream ATM device, it is necessary to generate a loopback cell to which the position ID of the own ATM device is added based on the held contents and transmit the loopback cell to the return route. Characterized loopback cell control method. 2. The ATM device through which the loopback cell passes, when the loopback cell is not received from the return route within a set timeout period from the time when the contents of the forward loopback cell is held, the ATM device determines the position ID of the own ATM device. 2. The loopback cell control method according to claim 1, wherein the added loopback cell is generated and transmitted on a return path. 3. The specific ATM device determines whether a loopback cell is received within a predetermined timeout period, and determines the position ID of the ATM device of the received loopback cell.
3. The loopback cell control method according to claim 1, wherein the normality of the loopback range is determined based on the following. 4. An ATM device comprising loopback control means connected to a reciprocating transmission line and time management means connected to said loopback control means, wherein said loopback control means is an ATM device to be looped back. Location ID
Is generated and transmitted to the transmission path on the outward path, and the elapsed time is measured by the time management means from the transmission time of the loopback cell, and the loopback cell is received from the return path within a predetermined timeout time. An ATM device that determines whether the ATM network is normal based on whether the operation is performed and a position ID of the ATM device of the received loopback cell. 5. An ATM device comprising a loopback control means connected to a reciprocating transmission line, a time management means and a monitor means connected to the loopback control means, wherein the loopback control means receives a received forward path. The content of the loopback cell is held in the monitor means and sent to the transmission path of the forward path, and the time elapsed from the reception time of the loopback cell is measured by the time management means. If a back cell is received, the loop back cell is sent to the return path. If no loop back cell for the return path is received within the timeout period, a loop back including the position ID of the own ATM device is performed based on the contents of the monitor means. An ATM device for generating a cell and transmitting the cell to a return path.