JP3307528B2 - Alarm cell processing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an OAM (Operation and Maintenance) in an ATM (Asynchronous Transfer Mode) switching technology which forms the core of a next generation communication network, B-ISDN (Broadband Integrated Services Digital Network). Regarding functions.

2. Description of the Related Art In an ATM network, high-speed data transfer is enabled by converting various information such as voice, moving image, data, and the like into fixed-length packets called cells and handling them integrally in the network. The layer that handles multiplexing and switching of cells in the B-ISDN protocol is called an ATM layer, and an information transmission path in the ATM layer, that is, an ATM connection is usually a VP (Virtual Path).
It has a two-stage configuration in which a plurality of VC (Virtual Channel) connections are multiplexed on the connection. The VC connection is a connection established between terminals, and the VP connection is a connection established between exchanges in order to bundle and process a plurality of VC connections. ATM in operation of ATM network
Fault monitoring of connections is very important.

[0003]

2. Description of the Related Art An OAM cell is used for monitoring a failure of an ATM connection (hereinafter simply referred to as a connection). That is, when a node (such as an ATM switch) on the connection between the calling terminal and the called terminal detects a failure in the transmission line, the node sends an AIS (alarm display signal) cell to the called side. The called terminal notified of the occurrence of the failure by the AIS cell returns an RDI (far-end reception failure) cell to the calling side and sends it out. As a result, all nodes on the connection between the originating terminal and the receiving terminal are notified of the failure.

FIG. 7 is a diagram showing an example of a case where a failure occurs on a cell transmission path and an alarm cell is transmitted. AT
A VP relay device for relaying a VP connection is provided between the M exchange (1) and the ATM exchange (2).
A transmission path (1) is provided as a physical layer connection between the TM exchange (1) and the VP relay device, and the VP relay device and the AT
A transmission line (2) is provided between the M exchange (2) and a VP connection between the ATM exchange (1) and the ATM exchange (2) is established therein. If the VP connection (1) fails and cell transmission becomes impossible, the VP connection
The relay device sends a VP-AIS cell to the ATM exchange (2) to notify the downstream side of the failure of the VP connection. Upon receiving the VP-AIS cell, the ATM switch (2) determines that the VP connection to which the VP-AIS cell has been transmitted has entered an alarm state, and usually notifies the maintenance person of the network or the host processor of the occurrence of the alarm.

FIG. 8 is a state transition diagram showing transition conditions between an alarm state and a normal state of a connection. If the ATM switch or the like receives at least one alarm cell, it can determine that the connection through which the alarm cell has been transmitted has transitioned from the normal state to the alarm state, and does not receive the alarm cell for 3 seconds or more. , A user cell or a cell to be determined for recovery of an alarm condition (hereinafter simply referred to as a user cell)
Is received even in one cell, it can be determined that the connection has recovered from the alarm state to the normal state. Further, the alarm cell is usually generated at one second intervals. In the example of FIG. 7, when the VP relay device detects a failure in the transmission line (1), it sends out a VP-AIS cell to the ATM exchange (2) at one-second intervals through the VP connection established therein. I do. On the other hand, if the ATM switch (2) receives at least one VP-AIS cell, the ATM switch (2) determines that the VP connection has transitioned to the alarm state, and thereafter, the VP-AIS is received for at least three seconds after the last reception of the VP-AIS cell. If no cell is received, or if a user cell is received within 3 seconds, it is determined that the VP connection has recovered to a normal state.

In an ATM switch or the like, time is measured by a timer in order to perform state management based on the above transition conditions.
That is, if an alarm cell arrives from a connection in a normal state, it is determined that the connection has transitioned to the alarm state, and timer counting is started. Thereafter, the timer count value is reset every time an alarm cell arrives at one second intervals. The timer count starts from 0 seconds, but if the timer count value exceeds 3 seconds from the last arrival of the alarm cell, it is determined that the connection has been restored to a normal state. However, if a user cell arrives from the connection before the timer count value exceeds 3 seconds, it is determined that the connection has recovered to a normal state at that time.

FIGS. 9 and 10 are diagrams showing examples of connection state transitions. FIG. 9 shows an example in which the connection recovers from the alarm state to the normal state because the alarm cell does not arrive for 3 seconds. When one alarm cell arrives from the connection in the normal state, the ATM switch determines that the connection has transitioned to the alarm state, notifies the network maintenance person of the state change, resets the timer count value, and resets the timer count value. Start counting. Thereafter, since the second and third alarm cells arrive at one second intervals, the timer count value is reset each time and the timer count is started from 0 seconds. However, since the alarm cell did not arrive after the third alarm cell and the timer count value exceeded 3 seconds, A
The TM exchange determines that the connection has transitioned from the alarm state to the normal state, and notifies the maintenance person or the like of the network of the state change.

FIG. 10 shows an example in which the connection recovers from the alarm state to the normal state due to the arrival of the user cell. As in the case of FIG. 9, the ATM exchange determines the transition of the connection to the alarm state upon arrival of the first alarm cell, notifies the network maintenance person or the like of the state change, starts timer counting, and starts the second and second timers. Each time three alarm cells arrive, the timer count value is reset and the timer count is started from 0 seconds. However, since the user cell arrives before the timer count value exceeds 3 seconds after the arrival of the third alarm cell, the ATM exchange determines that the connection has transitioned from the alarm state to the normal state, and performs maintenance of the network. Notify the state change to others.

When a repeater is provided between the ATM exchanges, the transmission line between the ATM exchange and the repeater is usually provided with a duplex structure of a system 0 (working system) and a system 1 (standby system). If the transmission line 0 becomes incapable of transmission due to the occurrence of a failure, the relay device detects this failure and immediately executes automatic transmission line switching to switch to the transmission line 1 system.

[0010]

However, if a physical layer failure (for example, a disconnection of a transmission cable) occurs while a certain connection is in an alarm state, the cell stops arriving from the connection, so that the alarm cell is not activated for three seconds. There is a problem that it is erroneously determined that the connection has recovered from the alarm state to the normal state due to the condition of no reception. FIG. 11 shows an example of a case where it is erroneously determined that the connection is restored to the normal state in the configuration shown in FIG. When the VP repeater detects a failure in the transmission line (1), it sends out VP-AIS cells to the ATM switch (2) at one-second intervals, whereby the ATM switch (2)
Determines that the VP connection has entered an alarm state. However, if a physical layer failure occurs in the transmission line (2) in this state, the VP connection becomes impossible to transmit, so that the VP-AIS cell does not arrive at the ATM exchange (2). For this reason, the ATM switch (2) uses the VP-AIS
Three seconds after the last reception of the cell, it is determined that the VP connection has recovered from the alarm state to the normal state, and a maintenance person or the like of the network is notified of the recovery.

A problem also arises when the VP relay device automatically switches the duplex transmission path. An example thereof will be described with reference to FIGS. As shown in FIG.
When a VP relay device relays a redundant transmission line between the M exchange (1) and the ATM exchange (2), if a physical layer failure occurs in the transmission line 0 and transmission becomes impossible, the VP relay device When this failure is detected, switching to the transmission line 1 system is performed immediately. At this switching, the VP connection on the transmission line is momentarily disconnected, so the VP relay device notifies the VP connection of the failure. V in the downstream direction to
Transmit the P-AIS cell. However, immediately after that, the transmission path is switched and the VP connection is restored to the normal state, and the VP relay device stops sending the VP-AIS cell.
Only about cells are transmitted.

FIG. 13 shows an example of a connection state transition in such a case. When the VP repeater performs automatic transmission path switching, one alarm cell arrives at the ATM exchange (2) accordingly, so that the ATM exchange (2)
The transition of the P connection from the normal state to the alarm state is detected, and this is notified to a maintenance person or the like. However, immediately after that, the transmission path is switched and the VP connection returns to the normal state, and the user cell arrives at the ATM exchange (2).
The ATM switch (2) detects the transition of the VP connection from the alarm state to the normal state, and notifies the maintenance person or the like of the transition. As described above, when a transmission line failure that immediately recovers occurs in a distant place, a connection state change notification that is not so necessary is continuously performed, and there is a problem that a load of network processing increases.

SUMMARY OF THE INVENTION The present invention has been made in view of such a problem, and in monitoring the failure of an ATM connection, the state of the ATM connection is erroneously determined due to the occurrence of a physical layer failure, or the transmission path failure that immediately recovers. An object of the present invention is to prevent the load of network processing from being increased due to the accompanying unnecessary notification.

[0014]

FIG. 1 is an explanatory view of the principle according to the present invention. In order to solve the above-mentioned problem, in the present invention, as shown in FIG.
An alarm cell monitoring unit 101 for monitoring an arrival state of an alarm cell for each ATM connection; and an alarm cell monitoring unit 101
Based on the monitoring result, the ATM connection in which the alarm cell arrives at a time interval within a predetermined time is determined to be in the alarm state, and the ATM connection in which the alarm cell has not arrived for the predetermined time or more is determined to be in the normal state. A physical layer failure detecting unit 103 that detects a physical layer failure when a physical layer failure related to an ATM connection determined to be in an alarm state is detected until the physical layer failure is recovered. The state management unit 102 is provided with the alarm cell processing apparatus 100 that determines the ATM connection to be in an alarm state regardless of the monitoring result of the alarm cell monitoring unit 101. The alarm cell processing device 1
The time measurement timer is further incorporated in the configuration of 00.
It is possible. At this time, the alarm cell monitoring unit 101
Failure and recovery of each connection on the input highway
Alarm cells for each connection to monitor old
And the arrival of the user cell, and the state management unit 102
Notify the measurement timer. Physical layer failure detection unit 103
Is the input highway physical layer failure occurrence and recovery
And notifies the time measurement timer. Time measurement timer
Indicates that the connection in the alarm state is in the normal state.
Timer that measures the time to detect recovery to
You. In other words, the time measurement timer is
When the cell notification is received,
Start timer counting, and count
Immediately stops and stops before the timeout.
When the alarm cell detection notification of the connection is received, the timer
Reset the count value and start the timer count from 0 seconds
I do. Therefore, the time measurement timer times out
This changes the connection from the alarm state to the normal state.
Recovery is detected. However, the time measurement timer
When notified of the occurrence of a physical layer failure, the
Timer for all connections included on the ear
Counting is temporarily stopped, and recovery from the physical layer
When notified , restart those timer counts . State tube
Management unit 102
When an alarm cell detection notification is received, the connection
It is determined that the status has transitioned to the
Sends a signal notifying the status change to the processor, etc.,
After that, the time measurement timer 12
Time out or from the connection
When the arrival of the user cell is notified, the connection
Is determined to have returned to the normal state, and a notification signal of the state change is issued.
Send out. In this way, the time measurement timer
When harm occurs, the timer count is temporarily stopped, and
When restarting the timer count at recovery, the timer at the stop
Counting from the count value and restarting from 0 seconds
Is possible.

In the present invention, as shown in FIG. 1B, as a second embodiment, an alarm cell monitoring unit 201 which monitors the arrival state of alarm cells for each ATM connection and counts the number of alarm cells arriving. And a state management unit 202 that determines, based on the monitoring result of the alarm cell monitoring unit 201, that the ATM connection at which the alarm cell has arrived is in the alarm state. After the ATM connection transitions from the normal state to the alarm state, Until a predetermined number of alarm cells are counted for an ATM connection,
An alarm cell processing device 200 that does not perform alarm notification for an M connection is provided.

[0016]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 2 is a diagram showing a configuration of an alarm cell processing device as one embodiment of the present invention. The alarm cell processing device 1 is provided in, for example, an ATM exchange, and includes a connection failure detection unit 10, a physical layer failure detection unit 11, a time measurement timer 12, and a state management unit 13.

The connection fault detecting unit 10 detects the arrival of an alarm cell or a user cell for each connection to monitor the occurrence and recovery of a fault on each connection on the input highway. Notify. The physical layer failure detection unit 11 detects occurrence and recovery of a physical layer failure on the input highway and notifies the time measurement timer 12 of the detection.

The time measurement timer 12 is a timer for measuring the time for detecting the recovery of the connection in the alarm state to the normal state. That is, when the alarm cell detection notification of a connection is received, the time measurement timer 12 starts counting the timer for that connection, and after counting a predetermined time (3 seconds), times out and stops. , The timer count value is reset and the timer count is started from 0 second. Therefore, when the time measurement timer 12 times out, it is detected that the connection has recovered from the alarm state to the normal state. However, the time measurement timer 12
When the occurrence of a physical layer failure is notified, the timer count is temporarily stopped for all the connections included on the physical layer, and when the recovery of the physical layer failure is notified, the timer count is restarted.

Upon receiving the alarm cell detection notification of the connection that was in the normal state, the state management unit 13 determines that the connection has transitioned to the alarm state, and sends a state change to the network maintainer, the host processor, and the like. When the time measurement timer 12 times out for the connection, or when the arrival of the user cell from the connection is notified,
It determines that the connection has returned to a normal state, and sends a state change notification signal.

As described above, when the time measurement timer 12 temporarily stops the timer count when a physical layer failure occurs and restarts the timer count when the failure is recovered, the timer counts from the stopped timer count value, A method of counting again from 0 seconds is possible.

FIG. 3 is a diagram showing an operation example in the case where the time measurement timer 12 restarts from the timer count value at the time of stop in the apparatus of the present embodiment. When an alarm cell arrives from a certain connection when the connection is in a normal state, the connection failure detecting unit 10
To the status management unit 13. As a result, the state management unit 13 determines that the connection has transitioned from the normal state to the alarm state and notifies the maintenance person or the like of the state change, and the time measurement timer 12 resets the timer count value and then starts counting the timer count. Start. One second later, the alarm cell arrives again from the connection, so the connection failure detection unit 10 notifies the time measurement timer 12 of the alarm cell, and the time measurement timer 12 resets the timer count value and starts the timer count from 0 seconds. . Since a physical layer failure has occurred before 3 seconds have elapsed, the physical layer failure detection unit 11 detects this and
2 and the time measurement timer 12 temporarily stops counting the timer. Thereafter, the state management unit 13 determines that this connection is in the alarm state regardless of the lapse of time. Eventually, when the physical layer failure is recovered, the physical layer failure detection unit 11 detects this and notifies the time measurement timer 12,
The time measurement timer 12 restarts the timer count from the timer count value at the time of stop.

FIG. 4 is a diagram showing an operation example in the case where the time measurement timer 12 counts time from 0 second at the time of restart in the apparatus of this embodiment. It is the same as FIG. 3 up to the point where the physical layer failure occurs after the connection transitions from the normal state to the alarm state due to the arrival of the alarm cell. When the physical layer failure detection unit 11 detects this failure and notifies the time measurement timer 12, the time measurement timer 12 stops the timer count and resets the timer count value to 0 seconds. Thereafter, the state management unit 13 determines that this connection is in the alarm state regardless of the lapse of time. When the physical layer failure is recovered, the physical layer failure detecting unit 11
Detects this and notifies the time measurement timer 12, and the time measurement timer 12 restarts the timer counting from 0 seconds.

FIG. 5 is a diagram showing a configuration of an alarm cell processing device as another embodiment of the present invention. Alarm cell processing device 1
Is provided, for example, in an ATM exchange, and comprises a connection failure detecting unit 10, a time measuring timer 12, a state managing unit 13, and an alarm cell counting unit 14.

The functions of the connection failure detecting unit 10 and the time measuring timer 12 are the same as those of the embodiment shown in FIG. The alarm cell counting unit 14 counts the number of alarm cells arriving in response to the connection based on the alarm cell detection notification from the connection failure detection unit 10 and notifies the state management unit 13 of the count value. Although the function of the state management unit 13 is almost the same as that of the embodiment of FIG. 2, even if it is determined that a certain connection has transitioned from the normal state to the alarm state, a notification signal is not immediately sent to the maintenance person, etc. The difference is that when the counting unit 14 counts a plurality of cells (for example, three cells) in succession in the alarm cells of the connection, a notification signal is transmitted. With such a configuration, one or two alarm cells are set to A due to a cause other than the occurrence of a connection failure (for example, due to automatic transmission path switching in the VP relay device).
Unnecessary notification signals can be prevented from being sent out when arriving at the TM exchange or the like.

FIG. 6 is a diagram showing an operation example when the transmission line automatic switching occurs on the upstream side in the apparatus of this embodiment.
When a certain connection is in a normal state and an alarm cell arrives from the connection due to automatic transmission path switching on the upstream side, the connection failure detection unit 10
Detects this, the time measurement timer 12 and the state management unit 13
To the alarm cell counting unit 14. As a result, the state management unit 13 determines that the connection has transitioned from the normal state to the alarm state. However, since the alarm cell count number notified from the alarm cell count unit 14 is “1”, the state change is notified to the maintenance person or the like. Is not performed. After that, the alarm cell does not arrive and the user cell arrives from the connection before three seconds elapse.
2 stops the operation, and the state management unit 13 determines that the connection has transitioned from the alarm state to the normal state, but does not notify the state change.

Thereafter, when a failure occurs in the connection, an alarm cell arrives at an interval of one second from the upstream side. 1
When the cell of the number arrives, the state management unit 13 determines that the connection has transitioned from the normal state to the alarm state. However, since the alarm cell count notified from the alarm cell count unit 14 is “1”, the notification is made. Not performed. Even when the second cell arrives, no notification is made because the alarm cell count is "2". When the third cell arrives, the alarm cell count becomes “3”, and the state management unit 13 notifies the state change. Thereafter, alarm cells continue to arrive at one-second intervals. When the connection failure is recovered and the user cell arrives, the connection failure detection unit 10 detects it and the time measurement timer 12 stops operating, and the state management is stopped. The unit 13 determines that the connection has transitioned from the alarm state to the normal state, and issues a notification. As described above, the present embodiment apparatus can distinguish between the arrival of an alarm cell due to the occurrence of a connection failure and the arrival of an alarm cell due to automatic switching of the transmission line on the upstream side. Can be avoided.

[0027]

As described above, in the ATM layer,
Alarm cell monitoring is performed for each ATM connection.
Is set to the alarm state, and the alarm cell
The non-wearing state is determined to be a normal state.
ATM alarm cell at ATM layer when failure occurs
Monitoring, the occurrence of a physical layer failure
The ATM alarm cell has not arrived, and
It will be judged as a state. This is the ATM alarm
Alarm state transition using an ATM alarm cell
Transition to the normal state if the state continues
This is due to a certain phenomenon. According to the present invention, the AT
In the failure monitoring of the M connection, even if an alarm cell does not arrive from the alarmed ATM connection due to the occurrence of a physical layer failure, it is no longer erroneously determined that the ATM connection has recovered to a normal state. Coordination between ATM layer and physical layer fault monitoring
This makes it possible to prevent erroneous determinations as described above.

Further, according to the present invention, when a transmission path failure that immediately recovers even if it occurs, it is possible to avoid a notification of a change in the state of the ATM connection accompanying the failure, thereby suppressing an increase in the load on network processing.

[Brief description of the drawings]

FIG. 1 is an explanatory view of the principle according to the present invention.

FIG. 2 is a diagram showing a configuration of an alarm cell processing device as one embodiment of the present invention.

FIG. 3 is a diagram illustrating an operation example of the embodiment device when the timer count is restarted from the time count value at the time of stop.

FIG. 4 is a diagram illustrating an operation example of the embodiment device when the timer count value is reset and the timer count is restarted.

FIG. 5 is a diagram showing a configuration of an alarm cell processing device as another embodiment of the present invention.

FIG. 6 is a diagram illustrating an operation example of the embodiment device when transmission line automatic switching occurs on the upstream side.

FIG. 7 is a diagram for explaining an example of alarm cell transmission due to a transmission path failure.

FIG. 8 is a diagram showing conditions for connection state transition.

FIG. 9 is a diagram illustrating an example of a case where a connection is restored to a normal state due to non-arrival of an alarm cell for 3 seconds.

FIG. 10 is a diagram illustrating an example of a case where a connection is restored to a normal state by the arrival of a user cell.

FIG. 11 is a diagram illustrating an example of a case where recovery of a connection to a normal state is erroneously determined;

FIG. 12 is a diagram illustrating an example of alarm cell transmission accompanying automatic switching of a transmission path by a VP relay device.

FIG. 13 is a diagram illustrating an example of connection state transition during automatic transmission path switching.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 alarm cell processing device 10 connection failure detection unit 11 physical layer failure detection unit 12 time measurement timer 13 state management unit 14 alarm cell count unit 100, 200 alarm cell processing device 101, 201 alarm cell monitoring unit 102, 202 state management unit 103 Physical layer failure detector

──────────────────────────────────────────────────続 き Continuing from the front page (73) Patent holder 000005108 Hitachi, Ltd. 4-6-6 Kanda Surugadai, Chiyoda-ku, Tokyo (72) Inventor Hideaki Ono 1015 Uedanaka, Nakahara-ku, Kawasaki-shi, Kanagawa Prefecture 72) Inventor Yasushi Takagi Inside Nippon Telegraph and Telephone 3-2-1, Nishi-Shinjuku, Shinjuku-ku, Tokyo (72) Inventor Jun Itoda 3-2-1, Nishi-Shinjuku, Shinjuku-ku, Tokyo Nippon Telegraph and Telephone Corporation (72) Inventor Tomoyuki Mitseki 1-7-12 Toranomon, Minato-ku, Tokyo Oki Electric Industry Co., Ltd. (72) Inventor Shigeki Morisaki 5-7-1 Shiba, Minato-ku, Tokyo NEC Corporation (72) Inventor Ichiro Kobashi 216 Totsuka-cho, Totsuka-ku, Yokohama-shi, Kanagawa Prefecture, Hitachi, Ltd. Information and Communication Division (56) References JP-A-6-326754 ( JP, A) JP-A-5-191408 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H04L 12/28 H04L 12/24 H04L 12/26

Claims (2)

(57) [Claims] 1. A user cell for each ATM connection
Faults that notify the arrival of alarm cells and alarm cells, respectively
Detector and object to detect and notify occurrence and recovery of physical layer failure
Between the physical layer failure detector and the reception of the alarm cell from the connection failure detector.
When the interval exceeds a predetermined time, the A
When it is determined that the TM connection is in a normal state,
The ATM connection is sent from the physical layer fault detector to the ATM connection.
When a physical layer failure related to the
The timeout does not occur until the ear failure is restored
Timer for suspending the operation and an alarm cell detection notification from the connection failure detector
The ATM connection has transitioned to the alert state.
After that, the time measurement timer sets the ATM connection.
Time out for the AT or its AT
Notification of user cell arrival from M connection
The ATM connection has returned to a normal state.
And a status management unit that sends out a status change notification signal.
Alarm cell processing apparatus characterized by obtaining. 2. An alarm cell monitoring unit for monitoring the arrival state of alarm cells for each ATM connection and counting the number of alarm cells arriving, and alarm cells have arrived based on the monitoring result of the alarm cell monitoring unit. A status management unit for determining that the ATM connection is in the alarm state; and after the ATM connection transitions from the normal state to the alarm state, until the predetermined plurality of alarm cells are counted for the ATM connection, the alarm is generated for the ATM connection. An alarm cell processing device that prevents notification.