JP2000069067A - Control method for ring network system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To instantaneously control a network into normal state in the case of a simultaneous recovery event. SOLUTION: When the simultaneous recovery event occurs, a switching node under switching receives and discriminates a ring switching request signal addressed to the other node in clockwise or counter-clockwise direction, and when the ring switching request signal addressed to the present node is received from that discriminated direction, the state of switching of this node is returned into initial state. By performing control for sending a cutback request signal for requesting the return of switching state to the initial state to the other node, the network is controlled into normal state.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control method for a ring network system in which a transmission line has a ring configuration, and more particularly to a control method when a simultaneous recovery event of ring switching performed from outside control or failure occurs. .

[0002]

2. Description of the Related Art A plurality of nodes are connected by two fibers or four fibers.
A ring network system connected by a fiber line has a ring switching function of switching a transmission path of a communication path set between each node and performing control to continue communication. Such a ring network system has a control function of automatically switching the ring when a failure is detected and forcibly switching the ring according to an instruction from an external control device or the like.

This ring switching function is described in ITU-T Recommendation G. 841 (07/95), and in the ring switching based on the above recommendation, a node that starts switching performs ring switching with respect to another node that needs a switching operation to perform ring switching. For this purpose, a K-byte request signal using the K-byte of the SDH frame is transmitted to each node, and the other nodes switch communication paths based on this control signal.

[0004] In addition, the above recommendation proposes a switchback control in which a ring-switched communication path is returned to the original state when the failure is cleared or by an operation of restoring the communication path switched from the external control device. It is also regulated. In the case of performing the switchback of the ring switching, similarly to the case of performing the ring switch, the node that starts the switchback transmits a K-byte request signal, and each node that has received the K-byte request signal disconnects the communication path. It can be returned to the normal state (normal state).

In such a ring configuration network,
A failure may occur simultaneously in a plurality of transmission sections (segments). In this case, each node that has detected the failure transmits a K-byte request signal, and attempts to switch the communication path of each node. Here, in the specified ring switching function, according to the K byte request signal, from the network control state in which the ring switching control is performed on two or more non-adjacent segments, all the switching nodes are in other segments. Before recognizing the start of the switching control of the ring switching by the K byte control signal (specified in the above recommendation), each starts the switching control of the ring switching of its own node. For this reason, when controlling the ring network to the normal state, the entire ring network enters the pass-through state, and it takes time to complete the control.

[0006]

As described above, in the conventional ring network system, the ring switch release control is simultaneously performed from the state of the network in which the ring switch control is executed in at least two or more non-adjacent segments. When performing, ITU-T recommendation G. 841 (07
In accordance with / 95), each node performing the release process must perform a process for a switching factor of another section recognized by the K byte control signal. At this time, even though all switching factors are canceled in the network, each node executes processing for a switching factor that does not exist, and it takes time to control the network to the normal state. .

[0007] The present invention solves the above-mentioned problem, and performs control to quickly return the network to a normal state without causing erroneous traffic connection (misconnect) in response to a simultaneous recovery event of the ring network system. The aim is to provide a method.

[0008]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a switching control in which a plurality of nodes are connected to each other in a ring via a plurality of transmission paths to change a switching state in each node. Is applied to a ring network system capable of performing ring switching in which the transmission path of the set communication path is switched to a different transmission path and continuing communication, and the node that starts the ring switching performs the ring switching. A ring switching request signal for transmitting a ring switching request signal for another node to perform a switching control to change the switching state in the node according to the ring switching request signal, thereby controlling the ring network system to perform ring switching, The switching state of each node on the ring network is switched over a plurality of sections. As a control when returning from the state in which the ring switching is performed to the normal state in which the ring switching is not performed, a simultaneous recovery that detects that a simultaneous recovery event that attempts to recover the ring switching in the plurality of sections at the same time occurs. An event detecting step, a switching state initializing step of returning a switching state of the own node to an initial state when occurrence of a simultaneous recovery event is detected in this step, and returning a switching state of another node to an initial state. And a switchback request signal transmitting step of transmitting a switchback request signal requesting the request.

Here, the ring switching is a process of switching a transmission path to a route that avoids a section designated by an operation from an external control device connected to each node, or a node detecting a failure in the transmission path. Then, it is considered that the process is a process of switching the transmission path to a route that avoids the failure section.

[0010] Further, the ring switching request signal is an ITU signal.
-T Recommendation G. 841 (07/95), S
It may be a switching request signal transmitted using the K byte signal of the DH frame.

[0011] Further, as a specific example, the simultaneous recovery event detecting step is performed when a ring switching request signal addressed to the own node is received after transmitting a request signal for switching back the ring switching. There is a method of determining that a simultaneous recovery event of ring switching has occurred.

An example of the switching control performed by each node in response to the ring switching request signal is as follows. A path in a direction from the node is transmitted by a ring switching with a working path which has been performing transmission. Bridge control to connect to both the standby path of the new transmission path and the path in the direction to be received by the node is separated from the active path that has been transmitting until now, and ring switching is performed. Switch control for switching connection to a standby route of a route that is newly set as a transmission route may be adopted.

When the ring network is returned to the normal state from a state in which ring switching has been performed in a plurality of sections, the switchback request signal sending step in the switching node that is switching among the plurality of nodes includes: Returning the switching state of the node to the bridge state by releasing the switch control; transmitting a request signal requesting the other node to return the switching state to the bridge state; and After confirming that the node has entered the bridge state, the step of releasing the switching state of the switching node to the initial state by releasing the bridge control, and returning the switching state to the initial state for the other nodes. Sending a request signal to make a request.

Further, it is conceivable that each of the ring-shaped transmission paths connecting the plurality of nodes includes a working line and a protection line. In this case, the ring network system may be a ring network system for transmitting part-time traffic, wherein transmission is performed using a free channel of the protection line.

Further, when transmitting part-time traffic, when the ring network is returned to the normal state from a state in which ring switching has been performed in a plurality of sections, switching among the plurality of nodes is performed. In the switching node, the switching request signal transmission step includes a step of releasing the switching state of the node to return to a bridge state by releasing switch control, and a request of another node to return the switching state to the bridge state. Sending a request signal to perform switching, and after confirming that all other nodes have entered the bridge state, returning the switching state of the switching node to the initial state by releasing the bridge control. Sends a request signal requesting that the switching state be returned to the initial state. Steps and may be provided with a step of connecting temporarily again the part-time traffic that has been dropped.

According to the above-described control, when a simultaneous recovery event switching factor in which a plurality of ring switchings are simultaneously switched back occurs in the ring network, the node that has determined this transitions to the idle state, thereby promptly switching to the idle state. It is possible to control the control state of the network appropriately and in a state where the ring switching is not performed, and it is also possible to prevent erroneous connection of the communication path.

[0017]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 shows a configuration of a ring network system to which a control method according to the present invention is applied.

In this system, nodes A, B, C,
Between each of D, E, and F, four fibers (hereinafter, referred to as four fibers) including service traffic fibers in the CW direction (clockwise) and CCW direction (counterclockwise) and protection fibers in the CW direction and CCW direction. ), The whole is connected in a ring shape.
Here, the service traffic cable and the protection cable do not necessarily need to be separate fibers, but they are the same cable, and each node is connected by two cables (hereinafter referred to as two fibers), and the transmission bandwidth is set. May be used separately.

Here, between AB, between BC, and between CD
The segments A, B, C, D, E, and F are defined as segments A, B, C, D, E, and F, respectively. Here, the service traffic fiber and the protection fiber are time-division multiplexed digital signal transmission high-speed lines each having a frame structure standardized by SDH, for example, STM-16 standardized by SDH. It is configured.

Each node has a low-speed line (for example, S which is standardized by SDH) having a lower speed than a service traffic fiber or a protection fiber.
TM-1).

In the ring network system having such a configuration, when no failure is detected or switching by an external command is performed at all (hereinafter, referred to as a normal state), a transmission signal between the nodes is transmitted via the service traffic fiber. Transmitted. Each node constantly monitors the transmission status of both the service traffic fiber and the protection fiber. If a failure occurs in the transmission system for service traffic in a certain segment, the transmission path between the segments is switched to a protection fiber, and communication is continued (span switching). Of course, this span switching can be forcibly switched by an external command from a control device (not shown) or the like.

On the other hand, if a fault occurs in both the service traffic fiber and the protection fiber in a certain segment, the transmission path is switched to a protection fiber on a transmission path different from the conventional communication path to continue transmission. Ring switching is performed. As with the span switching, the ring switching can be forcibly switched by an external command from a controller (not shown) or the like.

The control method according to the present invention in the ring network system having the above configuration will be described below with reference to FIGS. FIG. 2 shows a state in which FS-R (Forced Switch Ring) switching is performed in two sections of segment C and segment F in the ring network system having the above configuration, and the FS-R of two sections is controlled by the control method according to the present invention. R switching request is released at the same time (F
S-R Release), showing a sequence until the network is controlled to a normal state.

As shown in FIG. 2, the control signal indicating the request output content for performing the ring switching exchanged between the nodes is a section overhead (SOO) of the SDH frame.
H), a K-byte request signal (IT) transmitted using 8-bit K1 byte and K2 byte respectively.
U.T. Recommendation G. 841 (07/95).

Here, as shown in FIGS. 3 to 5, the K-byte request signal is composed of the first to fourth bits of the K1 byte and is used to request a switch to another node (Forced Switch Ring: Ring forced switch request, Reverse switch request). Request Ring: A response to a ring switching request (hereinafter, referred to as a "ring switching response"),
No Request: no request), and the request destination is indicated by the fifth to eighth bits. Further, the first to fourth bits of the K2 byte are the request source, and the fifth bit is the direction to the switching section (failure section) (Short: Direct transmission direction of the switching section (hereinafter, referred to as Short direction), Long: Switching. The direction of transmission via a section other than the section (hereinafter referred to as Long direction),
Bit 6 to bit 8 indicate the switch state of the requesting node (Bridge: a state in which the transmission side is connected to both service and protection, Switch: a state in which the reception side is switched from service to protection, Idle: Bridge control When
Switch control is not performed).

In FIGS. 3 to 5, as an example of actual transmission using K bytes, No Request is “0000”, Short is “1”, Long is “0”,
"010" for Bridge & Switch, "001" for Bridge, Id
Although le is transmitted using “000”, another code may be used.

First, an example of a normal control state of the network based on the network configuration of FIG. 1 is shown in FIG. Each node performs communication by setting a communication path between the nodes in response to a communication request from the low-speed side communication line.

In FIG. 6, a communication path for two-way service traffic 57, 58 is set between node A and node C, and a two-way part-time traffic 59 is provided between node D and node F. , 60, and a communication path for bidirectional part-time traffic 61, 62 is set between node A and node B.

The setting of the communication path of the service traffic 57 is performed in the node C by setting all or a part of the signal input from the low-speed side to a certain time slot of the multiplexed signal transmitted from the node B. ) Suppose that switching control for multiplexing (adding) is performed, and switching control for separating (dropping) signals of time slots multiplexed at node C is performed at node A. By performing such control, a communication path in which a signal input from the low-speed side of the node C is transmitted to the node A via the nodes D, E, and F is set as the service traffic 57. Become. Similarly, the service traffic 58 in the reverse direction is set as a communication path which is multiplexed by the node A on the high-speed line and separated by the node C by controlling the switching of the nodes A and D.

In an actual operation mode, a plurality of communication paths are simultaneously set for service traffic communication paths and part-time traffic between various nodes. When receiving a request signal relating to span switching and ring switching, each node determines only the communication paths that need to be switched, based on the communication path setting status at that time.
Here, for the sake of simplicity, a description will be given below assuming that communication paths are set in the form of FIG.

First, it is assumed that the network shown in FIG. 6 is in a normal control state in which ring switching is not performed at all. From this state, it is assumed that, at time T1 in FIG. 2, the node C is performing ring switching on the segment C, and the node F is also performing ring switching control on the segment F.

In this state, node C becomes node D
On the other hand, in the Short direction (here, segment C), a K-byte request signal (1a in FIG. 2) of a ring compulsory switching request indicating that the requesting node C controls Bridge & Switch to the requesting node D. Hereinafter, a “request signal (ring switching: C → D, Short, Bridge & Switch)” is transmitted. Also, in the Long direction,
The requesting node C sends a Bridge & Swit to the requested node D
A K-byte request signal (1b in FIG. 2; hereinafter, referred to as "request signal (ring switching: C → D, Long, Bridge &Switch)") of a ring forced switching request indicating that the channel is being controlled. ).

On the other hand, at the opposing node D, a request signal (ring switching: D → C, Short, Bridge & Switch) (2b in FIG. 2) and a request signal (ring switching: D → C, Long, Bridge)
& Switch) (2a in FIG. 2). Similarly, the node F sends a request signal (ring switching: F → A, Shor
t, Bridge & Switch) (3b in FIG. 2) and request signal (ring switching: F → A, Long, Bridge & Switch) (3 in FIG. 2)
a), the node A sends a request signal (ring switching: A
→ F, Short, Bridge & Switch) (4b in FIG. 2) and request signal (ring switching: A → F, Long, Bridge & Switch)
(4a in FIG. 2).

Here, in the nodes B and E which are intermediate nodes, the received request signal in the Long direction (ring switching:
Long, Bridge & Switch) (1b, 2a, 3b, 4 in Fig. 2)
a) is passed through and transmitted to an adjacent node.

In the switching nodes C and D, a request signal in the Long direction for ring switching of the segment F (ring switching: Long, Bridge & Switch) (4a in FIG. 2,
3b), but also receives a request signal (ring switching: Short, Bridge & Switch) (1a, 2b in FIG. 2) in segment C in the short direction, so that a request signal in the long direction (ring switching: long). , Bridge & Switch) (4 in Fig. 2)
a, 3a) are held without passing through. Similarly, the switching nodes A and F provide a request signal in the Long direction (for ring switching:
Long, Bridge & Switch) (1b, 2a in FIG. 2) are received, but are retained without passing through.

As a result, the network control is in a state where the ring switching control for the two segments is performed. FIG. 7 shows the control state of the network at this time. As a control result, the service traffic (57, 58 in FIG. 6) is restored (switching the service to protection) to (65, 66 in FIG. 7). Part-time traffic (59, 60 in FIG. 6)
Is controlled by restoring (restoring the device that has been dropped once) to control part-time traffic (FIG. 7).
63, 64).

Next, it is assumed that, at time T2 in FIG. 2, in the control state of FIG. 7, a release event occurs simultaneously at the switching nodes C and F. The nodes C and F execute the maintenance (maintenance) controls 14 and 15 for maintaining the control state of the nodes, and request signals for performing the held link switching F (ring switching: A → F, Long, Bridge & Switc)
h) (4a in FIG. 2), request signal (ring switching: D → C, L
ong, Bridge & Switch) (2a in FIG. 2) are respectively passed through and transferred to the next nodes, nodes D and A (5a and 6a in FIG. 2). At this stage, the control state of the network is the same as the control state of FIG.

At time T3 in FIG.
Is a request signal from the node C regarding the ring switching F (ring switching: A → F, Long, Bridge & Switch) (5 in FIG. 3).
By receiving a), it recognizes that the switching request in the segment C has been released, and performs the ring bridge & switch control 16 necessary for the ring switching F (in the communication path setting state of FIG. The switching operation is not performed because there is no path required for switching.) Then, a request signal (ring switching: A → F, Long, Bridge & Switch) (FIG. 3
5a) is passed through and transferred to the node E, and the request signal (ring switching: F → A, Long, Bridge & Sw) related to the ring switching F received and held in the reverse direction
itch) (3b in FIG. 3) is transmitted to the node C.

On the other hand, the node C sends a request signal from the node D (ring switching: F → A, Long, Bridge & Switch).
(3b in FIG. 3), when it is confirmed that the opposite node D has recognized the release of the switching request of the segment C, the control 18 of the ring bridge & switch for performing the ring switching F is executed (FIG. 7). In the communication path setting state,
The bridge control 70 and the switch control 69 remain unchanged. ) And request signal (ring switching: F → A, Long, Br)
idge & Switch) (3b in FIG. 3), and transmits to the node B.

On the other hand, the intermediate node E sends a request signal from the node D (ring switching: A → F, Long, Bridge & Switch).
When (5a in FIG. 3) is received, the ring bridge & switch control 21 for performing the ring switching F (the switching operation is not performed in the communication path setting state in FIG. 7 because there is no path required for switching), and The received request signal (ring switching: A → F, Long, Bridge & Switch) (5a in FIG. 3) is passed through and transmitted to the node F.

Similarly, at time T3, node A
Request signal from node F (ring switching: D → C, Long, Br
idge & Switch) (6a in FIG. 2), detects that the switching request of the segment F has been released, and performs the ring bridge & switch control 17 for ring switching C (the communication path of FIG. 7). In the setting state, the bridge control 68
And the switch control 67 remain unchanged. ). And a request signal (ring switching: D → C, Long, Bridge & Switch)
(6a in FIG. 2) to the node B and the held request signal (ring switching: C → D, Long, Bridge &
Switch) (1b in FIG. 3) is transmitted to the node F.

On the other hand, the node F receives the request signal (1b in FIG. 3) from the node A, and can confirm that the opposite node A has recognized that the switching request of the segment F has been canceled.
The control 19 of the ring bridge and the ring switch based on the ring switching request for the segment C is executed (the switching operation is not performed in the communication path setting state in FIG. 7 because there is no switching required path), and a request signal (ring switching). : C →
D, Long, Bridge & Switch) (1b in FIG. 3), and transmits to the node E.

Similarly, the intermediate node B sends a request signal from the node A (ring switching: D → C, Long, Bridge & Switch).
(6a in FIG. 2) is received, the ring bridge & switch control 20 is performed (in the communication path setting state in FIG. 7, the switching operation is not performed because there is no switching required path), and the received request signal (FIG. 2) 6a) is passed through,
Send to node C. The control state of the network is the same as the control state of FIG.

At time T4 in FIG. 2, the node B and the node E perform the ring bridge & switch control 2 respectively.
2 and 23, the received request signal (ring switching: Brid
ge & Switch), and transmits to node A and node D, respectively.

However, although the node C controls the ring switch release of the segment C,
A request signal (ring switching: D → C, Long, Bridge & Switch) (6a in FIG. 2) indicating that a ring switching related to the segment C destined to the own node is being performed from the CW direction is newly received. It is determined that a simultaneous recovery event has occurred for the ring switching factor of the segment (here, segment F and segment C). At this time, in the node F, similarly to the node C, the segment F
It is determined that a simultaneous recovery event has occurred for the ring switching factor of the segment C.

For this reason, the nodes C and F recognize that it is necessary to perform control for transitioning their nodes to the idle state and the network to the normal state.
As a result, the nodes C and F drop switch all nodes of the network (return switch control).
In order to set the state, the own node
And 25, the control state of the own node is set as a ring bridge, and a request signal (no request: Bridge) whose transmission source and request destination are not specified is transmitted in the CW direction (7a in FIG. 4) and the CCW direction (7a in FIG. 4). 7b).

At this time, in the request signal in which the transmission source and the request destination are not specified, 5-8 bits of the K1 byte and 1-4 bits of the K2 byte indicating the transmission source and the transmission destination are numerical values not set as node names. Any value may be used, and as an example, “0” is set in the present embodiment.

The nodes A, B, D, and E, which have received the request signal (Bridge) (7a in FIG. 4) or (7b in FIG. 4) for which the transmission source and the request destination are not specified, respectively, are dropped. The switch control 27, 29, 26, 28 is performed, and the control state of the node is set to the ring bridge state.
Then, the nodes E and B further pass through the received request signal (no request: Bridge).

The control state of the network up to this point is shown in FIG.
Shown in FIG. 8 shows drop switch control states 73 and 75 and bridge control states 74 and 76 of nodes A and C. Reference numerals 77 and 78 denote the bidirectional flow of service traffic.

At time T5 in FIG. 2, nodes A and D
In this example, since the request signals (no request: Bridge) 7b and 7a are received from both directions of the CW direction and the CCW direction, at this time, all the nodes (nodes A, B, C, D, E, In F), the drop switch control ends, and it can be determined that the state is the bridge control state. Then, the own node performs the drop bridge control 30 and 31 respectively. Then, the nodes A and D send a request signal (no request: Idle) indicating that the own node is not controlling the bridge and the switch in the CW direction (9a, 8 in FIG. 2).
a) and in the CCW direction (9b, 8b in FIG. 5). FIG. 9 shows the drop switch control 79 and the drop bridge control 80 of the node A.

Next, the nodes C and F receive a request signal (no request: Idle) (8b, 9b in FIG. 5) from the CCW direction, and a request signal passed through the node B or the node E (no request). : Idle) 7b and 7a are received. Since the nodes F and C have received the K byte request signals 7a and 7b from both directions of the nodes, all the nodes (nodes A, B, C, D,
Regarding F), it is determined that the drop switch control ends and the bridge control state is established. Then, the own node performs the drop bridge control 32 and 33 respectively, and the node F transmits a request signal (no request: Idle) in the CW direction (11a in FIG. 5) and the CCW direction (11b in FIG. 5). .
The node C transmits a request signal (no request: Idle) in the CW direction (10a in FIG. 5) and the CCW direction (10b in FIG. 5). FIG. 9 shows the drop bridge control 81 of the node C.
And the drop switch control 82.

The nodes E and B respectively receive request signals 11b and 10b addressed to the own node from the adjacent nodes (no request: Idle), and perform drop bridge control 3 of the own node.
5 and 34, and the node E sends a request signal (no request: Idl).
e) in the CW direction (13a in FIG. 2) and in the CCW direction (FIG.
13b) is transmitted. The node B sends a request signal (no request: Idle) in the CW direction (12a in FIG. 2) and the CCW
Transmit in the direction (12b in FIG. 2).

At this point, in all the nodes, the communication path of the service traffic is in an idle state, but the part-time traffic remains dropped. Therefore, the reestablishment control of the part-time traffic is started next.

The part-time traffic (61, 62 in FIG. 6) dropped for service traffic restoration control is transferred to the DCC (Data Communication Channel) after the control of the drop bridge and drop switch for the service traffic shown in FIG. Using the message signal, information indicating that each node can be reestablished is transmitted to adjacent nodes.

As shown in FIG. 2, nodes D are 45, 46,
Node A 47, 48, node C 49, 50, node F 51, 52, node B 53, 54, node E 5
5 and 56 are transmitted as DCC signals. At this point, each node can process another switching factor and reprocess the switching factor that is pending (waiting for execution).

At time T6 in FIG. 2, the reestablishment of part-time traffic is performed. The description will focus on node D. At node D, CW, CCW
In both directions, the own node receives the DCC message signal 4
4, DCC message signals 50 and 55 transmitted from the destination nodes C and E to the own node.
Is received, the reestablishment control 40 of the part-time traffic on both sides of the own node is performed, and the node enters the initial control state (no switching factor). Similarly, when the reestablishment control 37, 41, 38, 36, and 39 of the part-time traffic for the nodes E, F, A, B, and C ends, the network enters the normal control state shown in FIG. .

Here, in the sequence of FIG. 2, the reestablishment of the part-time traffic is performed after receiving the DCC message signals 50 and 55 from both sides of the own node. However, the present invention is not limited to this, and part-time traffic may be re-established for each segment from the side receiving the DCC message signal.

Therefore, according to the above control method, the entire network is in a pass-through control state in response to a simultaneous recovery event, and despite the fact that there is no switching factor,
In a state where protection switching cannot be performed, the above-mentioned method is newly used to quickly stabilize the network state without affecting service traffic and without causing traffic misconnection (misconnect). It is possible to control to the normal state.

[0059]

As described above, according to the present invention, erroneous connection of traffic (misconnect) can be prevented in response to a simultaneous recovery event of the ring network system.
It is possible to provide a control method of a ring network system that can quickly control a network to a normal state.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a ring network system to which a control method according to an embodiment of the present invention is applied.

FIG. 2 is a state transition diagram showing a state in which the network is controlled to a normal state from a point in time when the FS-R switching request in two sections is simultaneously released by the control method of the present invention in the embodiment.

FIG. 3 is a diagram showing request output contents of each node shown in FIG. 2;

FIG. 4 is a diagram showing request output contents of each node shown in FIG. 2;

FIG. 5 is a diagram showing request output contents of each node shown in FIG. 2;

FIG. 6 is a block diagram showing a normal control state of the network based on the network configuration of FIG. 1;

FIG. 7 is a block diagram showing a control state of the network at times T1, T2, and T3 in FIG. 2;

FIG. 8 is a block diagram showing a control state of the network at time T4 in FIG. 2;

FIG. 9 is a block diagram showing a control state of the network at time T5 in FIG. 2;

[Explanation of symbols]

A, B, C, D, E, F ... nodes (segments) 45-56 ... DCC signals 57, 58, 65, 66, 77, 78 ... bidirectional flow of service traffic 59, 60, 61, 62, 63 , 64 ... bidirectional flow of part-time traffic 67, 69 ... switch control 68, 70, 74, 76 ... bridge control 71, 72 ... pass-through control 24, 25, 28, 29, 73, 75, 79, 82 ... drop Switch control 30, 31, 32, 33, 80, 81 ... drop bridge control

Claims (10)

[Claims] A plurality of nodes are connected to each other in a ring via a plurality of transmission paths, and perform switching control for changing a switching state in each node, thereby transmitting different transmission paths of a set communication path. The present invention is applied to a ring network system capable of performing ring switching in which communication is continued by switching to a path, wherein a node that starts ring switching sends a ring switching request signal for performing ring switching, and another node transmits the ring switching request signal. A control method for a ring network system that performs ring switching by performing switching control for changing a switching state in a node according to a switching request signal, wherein the switching state of each node on the ring network is changed in a plurality of sections. Ring switching is not being performed from the state where ring switching is being performed As a control for returning to the normal state, a simultaneous recovery event detecting step of detecting that a simultaneous recovery event that is about to simultaneously recover the ring switching of the plurality of sections has occurred, and the occurrence of a simultaneous recovery event in this step. Is detected, a switching state initializing step of returning the switching state of the own node to the initial state, and a switchback request for sending a switchback request signal requesting another node to return the switching state to the initial state. A method for controlling a ring network system, comprising: a signal transmitting step. 2. The ring according to claim 1, wherein the ring switching is a process of switching a transmission path to a route that avoids a section designated by an operation from an external control device connected to each node. Network system control method. 3. The method according to claim 1, wherein the ring switching is a process of, when a node detects a failure in the transmission path, switching the transmission path to a route that avoids the failure section.
The control method of the ring network system described in the above. 4. The ring switching request signal according to ITU-T Recommendation G. 2. The control method for a ring network system according to claim 1, wherein the signal is a signal transmitted using a K-byte signal of an SDH frame based on the specification of 841 (07/95). 5. The simultaneous recovery event detecting step comprises: transmitting a request signal for switching back the ring switching, and receiving a ring switching request signal addressed to the own node.
2. The control method for a ring network system according to claim 1, wherein it is determined that a simultaneous recovery event of a plurality of ring switchings has occurred. 6. The switching control performed at each node in response to the ring switching request signal is performed by switching the path in the direction transmitted from the node with the working path which has been performing transmission so far. Bridge control to connect to both the standby path of the new transmission path and the path in the direction to be received by the node is separated from the active path that has been transmitting until now, and ring switching is performed. 2. The control method for a ring network system according to claim 1, wherein a switch control for switching connection to a standby system of a route to be a new transmission path is performed. 7. A return request signal transmission step in a switching node that is switching among the plurality of nodes when returning the ring network from the state in which ring switching has been performed in a plurality of sections to the normal state. Resetting the switching state of the node to the bridge state by releasing the switch control; transmitting a request signal requesting the other nodes to return the switching state to the bridge state; After confirming that the other node has entered the bridge state, resetting the switching state of the switching node to the initial state by releasing the bridge control, and returning the switching state of the other node to the initial state. Transmitting a request signal requesting that the request be made. Method of controlling a ring network system. 8. The control of the ring network system according to claim 1, wherein the ring-shaped transmission path connecting the plurality of nodes is applied to a ring network system including a working line and a protection line. Method. 9. The control method for a ring network system according to claim 8, wherein the method is applied to a ring network system for transmitting part-time traffic using an available channel of the protection line. 10. A return request signal transmission step in a switching node that is performing switching among the plurality of nodes when returning the ring network from the state in which ring switching has been performed in a plurality of sections to the normal state. Resetting the switching state of the node to the bridge state by releasing the switch control; sending a request signal requesting another node to return the switching state to the bridge state; After confirming that the node has entered the bridge state, the step of releasing the switching state of the node to the initial state by releasing the bridge control, and the step of returning the switching state to the initial state for the other nodes. Sending a request signal to request, and the part-time traffic dropped temporarily. The method of claim 9, wherein the ring network system, characterized in that it comprises a step of again connected.