JP2000083042A - Part time traffic connection control method and transmitting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a part time traffic connection control method without causing any misconnection. SOLUTION: First, span switching is carried out in the nodes 2 and 3 of both ends of a fault section when a fault takes places and the completion is waited for. When the span switching is completed at the point of time T1, a part time traffic connection request 61 is transmitted from the both nodes 2 and 3 to the other node at the next point of time T2. The respective nodes 2 and 3 execute switching connection of part time traffic after the point of time T3 when they mutually receive the part time traffic connection request 61 from the other node.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an SDH (Synchronous
ous Digital Hierarchy) or SONET (Sync
The present invention relates to a connection control method for part-time traffic in a duplex ring network conforming to hronous Optical NETwork) and a transmission device used in the duplex ring network.

[0002]

2. Description of the Related Art In recent years, there has been a demand for the development of a broadband ISDN based on a globally unified user network interface.
SDH (Synchronous Digital Hierarchy) that can multiplex various high-speed services and existing low-speed services in a unified manner
Has been standardized. Under such a trend, a technology for a network in which a large-capacity optical submarine cable is laid internationally and communication devices conforming to the SDH standard are connected in a ring shape is being actively developed.

[0003] SDH is based on an optical transmission system, and is provided with various characteristic functions in order to make use of its enormous bandwidth. For example, in a large-capacity optical submarine cable system to which SDH is applied, a system in which transmission cables are laid in a ring shape to avoid signal interruption due to the occurrence of a failure has been considered. In this type of system, Some have a function called APS (Auto Protection Switch). This is defined in ITU-T Recommendation G. 84
It is specified in 1 and realizes system switching between transmission terminal equipments in response to a failure of a repeater or a transmission medium of a transmission system.

In the SDH transmission system, in order to improve the operation efficiency when there is no failure in the transmission path, relatively low-priority traffic such as information that does not require real-time characteristics is transmitted to the protection transmission path. It may flow to an empty channel. This traffic is called part-time traffic.

However, the above recommendation does not specify a connection control method for part-time traffic after completion of switching / switchback. For this reason, there is a risk of erroneous connection when switching part-time traffic,
There is a need to provide a connection control method for part-time traffic in a manner compliant with this recommendation.

[0006]

SUMMARY OF THE INVENTION As described above, I
TU-T Recommendation G. There is a need to provide a connection control method for part-time traffic that conforms to 841. SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a connection control method and a transmission apparatus for part-time traffic that does not cause erroneous connection.

[0007]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a plurality of transmission devices, and a ring network formed by connecting the plurality of transmission devices in a ring to a working system and a protection system in a ring shape. Part-time traffic connection control method in a ring network system, wherein each of the plurality of transmission devices has a function of switching between the active and the standby of the transmission line when a failure occurs in the ring network. In the case where it is necessary to switch the working / standby of the transmission line, after the working / standby switching of the transmission line is completed, the transmission devices adjacent to each other across the section where the transmission line switching factor exists are interposed. A first step of sending a part-time traffic connection request to a transmission device of each other between
In each of the adjacent transmission devices, a second step of receiving the part-time traffic connection request sent from the other transmission device, and after the completion of the second step, the adjacent transmission devices Third to perform reconnection of part-time traffic between
And the following steps.

The present invention also includes a plurality of transmission devices and a transmission line which is duplexed into an active system and a standby system and connects the plurality of transmission devices in a ring to form a ring network. Each of the transmission lines of the system includes a line in both directions consisting of a clockwise direction and a counterclockwise direction,
In the part-time traffic connection control method in a ring network system having a function of performing active / standby switching of the transmission line when a failure occurs in the ring network, each of the plurality of transmission devices includes When it is necessary to switch the working / protection of the transmission line, after the completion of the working / protection switching of the transmission line, the transmission device serving as a switching node taking the initiative of the transmission line switching enters the ring network system. A first step of transmitting a part-time traffic connection request via the line in a direction opposite to the section in which the transmission path switching factor exists, and a transmission device other than the switching node via the line. Receives the incoming part-time traffic connection request from both directions A second step, in the transmission device as the switching node, a third step of receiving the part-time traffic connection request arriving via the line, and in each of the transmission devices other than the switching node, After the completion of the second step, the transmission device serving as the switching node performs a reconnection of part-time traffic after completion of the third step, respectively.
And the following steps.

By taking such means, when reconnecting the part-time traffic that has been disconnected when the transmission line is switched between working and protection, each of the transmission devices that performs the reconnection control performs a retransmission control on the transmission line. The fact that the working / standby switching has been completed is reliably recognized. Then, reconnection of the part-time traffic will be performed. For this reason, each transmission device does not connect the part-time traffic without permission, and erroneous connection of the part-time traffic can be avoided.

[0010] Factors that require the switching between the working and the protection of the transmission path include not only the occurrence of a fault but also a failback due to the recovery of the fault and a fault of a higher priority among faults that have occurred repeatedly. There is a transmission line switch for the suspended failure accompanying the recovery. In such a case, even when reconnection control of part-time traffic is performed, the above-described method can reliably avoid erroneous connection.

The part-time traffic connection request includes information indicating a type of transmission line switching, information indicating a transmission device to which the part-time traffic connection request is transmitted, and a transmission source of the part-time traffic connection request. , And information indicating a direction in which the part-time traffic connection request is transmitted.

[0012] The part-time traffic connection request is transmitted and received between the opposite transmission devices using the surviving transmission line in the faulty section when the surviving transmission line survives. Is transmitted in the opposite direction via all transmission devices constituting the ring network. At this time, the part-time traffic connection request is transmitted, for example, according to ITU-T Recommendation G. D specified in 709
The data is exchanged between the transmission devices via the CC.

Further, in order to realize the above-mentioned part-time traffic connection control method, the present invention provides a plurality of transmission devices,
A transmission line that is duplexed into an active system and a standby system and that includes a transmission path that connects the plurality of transmission devices in a ring to form a ring network. Transmission signal rescue control means for relieving a transmission signal by performing active / standby switching of the transmission path when the transmission path has occurred; Transmission means for transmitting a part-time traffic connection request to a transmission device opposing the transmission line switching factor after the completion of the current / standby switching, and a period in which the transmission channel switching factor exists Receiving means for receiving the part-time traffic connection request transmitted to itself from a transmission device opposed to the part-time traffic connection device Reconnection means for executing reconnection of part-time traffic with a transmission device which is opposed to the section where the transmission path switching factor is present after receiving the part-time traffic connection request by the reception means. It is characterized by having.

Further, the present invention comprises a plurality of transmission devices and a transmission line which is duplexed into an active system and a standby system and connects the plurality of transmission devices in a ring to form a ring network. Each of the transmission lines of the system is in the transmission device used in a ring network system having a circuit in both directions consisting of clockwise and counterclockwise directions, and when a failure occurs in the ring network, the transmission is performed. Transmission signal rescue control means for relieving a transmission signal by performing active / backup switching of a path;
When it is necessary to switch the transmission line between working and protection, and when the transmission device is in charge of the initiative of switching the transmission line, if the switching between the working and protection of the transmission line is completed, the ring Transmitting means for transmitting a part-time traffic connection request via the line in the direction opposite to the section in which the transmission path switching factor exists in the network system, and a transmission unit other than the transmission apparatus which is in charge of switching the transmission path. In the case of a transmission device, the transmission device performs reconnection of part-time traffic after receiving the part-time traffic connection request arriving via the line from both directions, and is itself in charge of switching the transmission path. The part-time traffic after receiving the part-time traffic connection request arriving via the line. Characterized by comprising a reconnection means for performing a reconnection click.

[0015]

Embodiments of the present invention will be described below in detail with reference to the drawings. (First Embodiment) FIG. 1 shows the configuration of an information communication system according to a first embodiment of the present invention. In this information communication system, a plurality of nodes 1 to 6 are connected in a ring by a high-speed line L. Each node 1 to 6 is connected to a high-speed line L
Of the information transmitted via the low-speed line M, and drop it to each of the lower-level communication devices such as the exchanges S1 to S6.
The information sent from 1 to S6 is added to the high-speed line L. Here, each of the exchanges S1 to S6 is connected to equipment (not denoted by reference numerals) such as a lower-level subscriber line exchange.

The high-speed line L is connected to the active transmission line 1
1 and a backup transmission line 12, the information communication system has a so-called duplex ring network configuration.
The working transmission line 11 is mainly used when performing information communication in the present information communication system.
Is used as a backup when a failure occurs in the active transmission line 11.

Here, the high-speed line L is a multiplex line such as STM-16 standardized in SDH, for example, in which signals transmitted through communication paths set between the nodes 1 to 6 are time-division multiplexed. I have.

For example, the node 1 receives a high-speed time-division multiplexed signal transmitted from another node via the adjacent node 6, and changes the channel addressed to the own node to the high-speed line L.
From the low-speed line M. Then, the signal transmitted from the low-speed line M of the own node is multiplexed (added) with the time-division multiplexed signal of another channel not addressed to the own node, and the time-division multiplexing is performed on the adjacent node 2. Output a signal. Similarly, the high-speed multiplexed time-division signal transmitted from the node 2, which is a transmission signal in the reverse direction, is similarly multiplexed / separated (add / demultiplex) to the low-speed line M of the own node.
Drop) and outputs the result to the node 6.

FIG. 2 shows a main configuration of each of the transmission devices N1 to Nm. That is, each of the transmission devices N1 to Nm
A synchronous transmission data transmitted via the high-speed line L is provided to the add / drop multiplexer (ADM) 100 via the interface units (I / F) 201 to 204. The data is dropped to the low-speed line M via the interface (I / F) 205. The synchronous transmission data input from the low-speed line M is introduced into an add / drop multiplexer (ADM) 100 via the interface unit 205 and multiplexed on the high-speed line L.

An add-drop multiplexer (AD)
The operation control for the M) 100 is performed by the control unit 300 based on information provided from each of the interface units (I / F) 201 to 204. This control unit 300
Data relating to various controls is stored in the storage unit 400.

Here, the control unit 300 is realized as, for example, a microcomputer or the like, and includes, in addition to known control means relating to information communication with another node,
Switching control means 300a and connection request transmission / reception control means 30
0b and the part-time traffic connection control means 300
c.

When a failure occurs on the ring network, the switching control means 300a operates according to ITU-T Recommendation G. 8
The transmission / reception control function (so-called APS function) for transmitting / receiving the APS byte based on the procedure defined in 41 and relieving the service traffic by performing the active / standby switching of the transmission path is executed. The connection request transmission / reception control means 300b controls a function of transmitting / receiving a connection request for part-time traffic with another node on the network. The part-time traffic connection control means 300c controls connection of part-time traffic to a transmission channel of a standby transmission line that is not used for switching service traffic.

Next, the operation of the information communication system having the above configuration will be described. In the following description, each node 1 to 1
6 will be described with identification numbers (ID) 0 to 5 respectively. Here, as an example, as shown in FIG. 3, service traffic 21 is transmitted from node 1 to node 2, node 3,
The packet is dropped by the node 5 via the node 4, and the part-time traffic 2 is further reduced by using the protection transmission line 12 of the node 2 (ID = 1) to the node 3 (ID = 2).
2 is transmitted. In the figure,
The active transmission line 11 is indicated by a solid line, the protection transmission line 12 is indicated by a dotted line, and the transmission line on which traffic is flowing is indicated by bold lines.

Here, the part-time traffic 22
Shows a case where data is transmitted between adjacent nodes. However, the present invention is not limited to this, and a communication path is set so that transmission can be performed between the non-adjacent nodes via the respective backup transmission lines 12. No problem.

In the state shown in FIG. 3, when a failure 31 occurs in the active transmission line 11 between the nodes 2 and 3, the nodes 2 and 3 at both ends of the failure section are connected to the ITU-T.
Recommendation G. According to 841, it operates as a switching node that performs span switching. Thereby, node 2 (ID =
1) and the node 3 (ID = 2) first temporarily disconnect the part-time traffic 22 (thick dotted line in the figure) to empty the protection transmission line 12, and then, as shown in FIG.
From the transmission channel of the active transmission line 11 in the section where the failure 31 occurs, the protection transmission line 12 prepared in the failure section is changed.
The service traffic 21 is switched to the transmission channel of.

After the completion of the span switching shown in FIG. 4, the nodes 2 and 3 as the switching nodes next perform a transmission / reception sequence of the part-time traffic connection request 61 shown in FIG. After the span switching is completed at the time T1, each of the nodes 2 and 3 sends a part-time traffic connection request 61 to the other node at the time T2. Thereafter, the part-time traffic connection request 61 transmitted from the partner node is received at time T3.

Each of the nodes 2 and 3 confirms that the span switching between the nodes 2 and 3 has been completed by receiving the part-time traffic connection request 61 and controls the connection of the part-time traffic 22 that is being disconnected. Execute. Here, after the span switching in FIG. 4, if the transmission channel of the protection transmission line 12 in which the part-time traffic 22 was set before the switching is already used for transmitting the service traffic 21, The actual connection of the time traffic 22 is not performed, and after the completion of the span switching, the traffic flows as shown in FIG.

On the other hand, when a channel that is not used for transmitting the service traffic 21 is generated among all the channels of the protection transmission line 12, the transmission of the part-time traffic 22 is restarted by using the channel. Will be.

This is made possible by the STM
This is because the high-speed line L as a -16 line is multiplexed. That is, the STM-16 line is, for example, 155.
It can be expressed as a bundle of 16 STM-1 lines having a transmission speed of 52 Mb / s. Usually,
Not all of these lines are used, and there may be a vacancy in one of the channels, so that the part-time traffic 22 can be transmitted using this vacant channel.

Now, when the failure 31 is recovered from such a state, the nodes 2 and 3 perform the switching back operation of the span switching. As shown in FIG. 6, the service traffic 21 is switched back from the transmission channel of the protection transmission line 12 in the faulty section to the transmission channel of the working transmission line 11 originally set.

After the completion of the span reverting of FIG. 6, each node 2, 3 receives the suspended part-time traffic 2
In order to restart the transmission of No. 2, the transmission / reception sequence of the part-time traffic connection request 61 shown in FIG. 5 is performed again. That is, at time T2 when span switching / switchback is completed in nodes 2 and 3, a part-time traffic connection request 61 is sent from each of node 2 and node 3 to the other node. Then, at time T3, the part-time traffic connection request 61 is received by each of the nodes 2 and 3.

The nodes 2 and 3 confirm that the switching back of the span switching in the section between the nodes 2 and 3 is completed at the time T3, and the connection control of the part-time traffic is performed at the nodes 2 and 3 respectively. Be executed. Thus, the normal traffic flow shown in FIG. 1 is restored again.

Here, an example of the message content of the part-time traffic connection request 61 is shown in FIG. The part-time traffic connection request 61 is exchanged via, for example, DCC in the SDH transmission frame. The part-time traffic connection request 61 is a message including four types of information defined by a predetermined bit string: a switching type, a source and destination switching node ID, and a message path. Here, there are three types of information after the span switching, after the ring switching, and after the reversion as information indicating the switching type, and indicates a faulty section side and a path on the opposite side of the faulty section as information indicating a message path. There are two types of information.

In the above control process, in the sequence of FIG. 5 after the span switching, the node 2 sends the message of FIG. 7A and the node 3 sends the message of FIG. 7B. On the other hand, in the sequence of FIG. 5 after the span switchback, the node 2 sends the message of FIG. 7C and the node 3 sends the message of FIG. 7D.

As described above, in the present embodiment, when a failure occurs, span switching is first executed in the nodes 2 and 3 at both ends of the failure section, and the completion thereof is waited. When the span switching is completed at the time point T1, at the next time point T2, both nodes 2, 3 transmit a part-time traffic connection request 61 to each other node. Then, the nodes 2 and 3 execute the switching connection of the part-time traffic after the time point T3 when the part-time traffic connection request 61 is received from the other party.

With this configuration, it is possible to reliably recognize that the span switching has been completed between the nodes, and there is no possibility of erroneous connection of part-time traffic. The same applies to the case of span return.

(Second Embodiment) Next, a second embodiment of the present invention will be described. In the drawings, the same parts as those in the first embodiment are denoted by the same reference numerals and described. In the present embodiment, as described above with reference to FIG. 3, when the service traffic 21 is transmitted between the node 1 and the node 5 via the nodes 2, 3, and 4,
As shown in (1), it is assumed that a failure (denoted by reference numerals 31 and 32) occurs in both the working transmission line 11 and the protection transmission line 12 between the nodes 3 and 4.

In such a case, since information cannot be transmitted between the node 3 and the node 4, the failure is avoided in the span switching in which the switching is performed only in the failure section as described in the first embodiment. Can not. For this reason, so-called ring switching in which switching is performed jointly by each of the nodes 1 to 6 in the entire system is performed. That is, the nodes 3 and 4 at both ends of the failure section are in accordance with ITU-T Recommendation G. According to 841, the device operates as a switching node that performs ring switching. Here, the Tr specified in the above recommendation
It is assumed that ring switching of the ansoceanic method is executed.

In performing such ring switching, first, transmission of the part-time traffic 22 between the node 3 as a switching node and the node 2 as an adjacent node is interrupted. Then, the transmission route of the service traffic 21 is changed as shown in FIG. 8, and the nodes 1 and 5 where the service traffic 21 is added / dropped have the working transmission line 11 passing through the nodes 2, 3 and 4. From the transmission channel, node 6
Is switched to the transmission channel of the backup transmission line 12 passing through.

After the completion of the ring switching of the service traffic 21 shown in FIG. 8, the nodes 3 and 4 transmit a part-time traffic connection request 62 toward the side opposite to the failure section. FIG. 9 shows a part-time traffic connection request 62.
FIG. 5 is a diagram showing a transmission / reception sequence of FIG. Each node 3, 4
Sends a part-time traffic connection request 62 to the other node at time T6, and sends the part-time traffic connection request 62
Is received via the intermediate nodes Node 1, Node 2, Node 5, and Node 6.

This part-time traffic connection request 6
At the time T9 (FIG. 9) when the node 2 is received, the nodes 3 and 4 confirm that the ring switching of the failed section is completed, and execute connection control of part-time traffic in each node. Here, each of the node 1, node 2, node 5, and node 6, which are intermediate nodes of the ring switching, transmits the part-time traffic connection request 6 transmitted from the node 3 and the node 4 which are the switching nodes of the ring switching.
At time T7 when one of the two is received, the part-time traffic connection request 62 is transferred to the other switching node via another intermediate node.

Further, at the time T8 when the part-time traffic connection request 62 sent from the other switching node is received, the nodes 1, 2, 5, and 6 complete the ring switching by all the nodes 1 to 6 on the ring network. Confirm that the connection has been made, and then execute connection control for part-time traffic.

Here, after the ring switching shown in FIG.
The transmission channel of the protection transmission line 12 to which the part-time traffic 22 has been set before the switching remains open. Therefore, the part-time traffic 22
Is performed, and the traffic flow shown in FIG. 10 is realized. That is, the connection control of the part-time traffic 22 is performed after the ring switching in FIG.
The part-time traffic 22 is transmitted on the standby transmission line 12 between them.

Now, from such a state, the failures 31, 32
Are recovered, the nodes 2 and 3 perform the ring switching reverting operation. As shown in FIG. 11, the service traffic 21 is a transmission channel of the working transmission line 11 originally set from the transmission channel of the protection transmission line 12 in the nodes 1 and 5 where the service traffic 21 is added / dropped. It is cut back to.

After the switching back of the ring switching shown in FIG. 11 is completed, each of the nodes 3 and 4 performs the transmission / reception sequence of the part-time traffic connection request 62 shown in FIG. 9 again. That is, at time T6, the part-time traffic connection request 6
2 and a part-time traffic connection request 62 is received at each node 3, 4 at time T9.

At the time T9, the nodes 3 and 4 confirm that the switching back of the span switching in the section from the node 3 to the node 4 is completed, and the connection control of the part-time traffic is performed at the nodes 3 and 4 respectively. Be executed. Thus, the traffic flow shown in FIG. 1 is restored again.

Here, an example of the message content of the part-time traffic connection request 62 is shown in FIG. 7, similarly to the first embodiment. Similarly, the part-time traffic connection request 62 is transmitted / received via the DCC in the SDH transmission frame. In the sequence of FIG. 9 after the ring switching, the node 3 sends the message of FIG. 7 (E) and the node 4 sends the message of FIG. 7 (F). On the other hand, in the sequence of FIG.
The node 4 sends out the message shown in FIG. 7H.

As described above, in the present embodiment, when a failure occurs, the nodes 3 and 4 at both ends of the failure section first execute the ring switching and wait for the completion. When the ring switching is completed at the time point T5, at the next time point T6, the two nodes 3 and 4 transmit the part-time traffic connection request 62 to the other nodes without passing through the failure section, that is, reverse the ring network. Send around. And
Each of the nodes 3 and 4 performs the switching connection of the part-time traffic after the time T9 when the part-time traffic connection request 62 is received from each other.

With this configuration, it is possible to reliably recognize that the ring switching has been completed between the nodes, and there is no possibility that erroneous connection of part-time traffic will be caused. The same applies to ring back.

(Third Embodiment) Next, FIGS.
A third embodiment of the present invention will be described with reference to FIG. In the present embodiment, a switching sequence when a node failure occurs will be described. In the drawings, the same parts as those in the first embodiment are denoted by the same reference numerals and described. In the present embodiment, in addition to the state shown in FIG. 3, the part-time traffic 23 is further transmitted using the protection transmission line 12 between the node 5 (ID = 4) and the node 6 (ID = 5). It is assumed that the data is being transmitted. FIG. 12 shows the flow of traffic in a normal state.

When the node failure 33 occurs in the node 4 from the state shown in FIG. 12, the nodes 3 (ID = 2) and 5 (ID = 4) adjacent to the failed node 4
Recommendation G. According to 841, it operates as a switching node that performs node failure switching. In this case as well, ring switching is performed. Here, it is also assumed that ring switching based on the Transoceanic method specified in the above recommendation is performed.

When performing such ring switching, first, transmission of the part-time traffics 22 and 23 is interrupted. Then, as shown in FIG. 13, the transmission route of the service traffic 21 is changed, and the nodes 1 and 5 where the service traffic 21 has been added / dropped have the working transmission line 11 passing through the nodes 2, 3 and 4. The transmission channel is switched to the transmission channel of the protection transmission line 12 via the node 6.

After the completion of the ring switching of the service traffic 21 shown in FIG. 13, the nodes 3 and 5 transmit a part-time traffic connection request 63 toward the side opposite to the failure section. FIG. 14 is a diagram showing a transmission / reception sequence of the part-time traffic connection request 63. Each node 3,
5 transmits a part-time traffic connection request 63 to the other node at time T11, and transmits a part-time traffic connection request 6 transmitted from the other node to the other node.
3 is received via nodes 1, 2, and 6 which are intermediate nodes.

This part time traffic connection request 6
At time T14 (FIG. 14) when node 3 is received, nodes 3 and 5 confirm that ring switching of the failed section is completed, and execute connection control of part-time traffic in each node. Here, each of the node 1, node 2, and node 6, which are intermediate nodes of the ring switching, receives one of the part-time traffic connection requests 63 sent from the nodes 3 and 5, which are the switching nodes of the ring switching. At T12, this part-time traffic connection request 63 is transferred to the other switching node via another intermediate node.

Further, at time T13 when the part-time traffic connection request 63 sent from the other switching node is received, the nodes 1, 2, 6 are connected to the nodes 1, 2, 3, 5, 6 on the ring network. After confirming that the switching has been completed, the connection control of the part-time traffic is executed.

Here, after the node failure switching in FIG. 13, the transmission channel of the protection transmission line 12, for which the part-time traffic 22 was set before the switching, remains open. Therefore, connection control of the part-time traffic 22 is executed, and the traffic flow shown in FIG. 15 is realized. That is, the connection control of the part-time traffic 22 is performed after the node failure switching in FIG. 13, and as shown by the thick dotted line in the figure, the part-time traffic 22 Is resumed.

When a channel that is not used for transmitting the service traffic 21 is generated among all the channels on the protection transmission line 12 between the nodes 5 and 6, the channel is used for part-time transmission. Transmission of the traffic 23 will be resumed.

Now, from such a state, the node failure 33
Is recovered, the nodes 3 and 5 perform a fail-over operation for node failure switching. The service traffic 21 is, as shown in FIG. 17, the transmission channel of the working transmission line 11 originally set from the transmission channel of the protection transmission line 12 at the nodes 1 and 5 where the service traffic 21 is added / dropped. It is cut back to.

When the switching back of the node failure switching in FIG. 17 is completed, the transmission / reception sequence of the part-time traffic connection request 64 shown in FIG. 18 is performed mainly by the node 4. That is, after the failback is completed at time T15, the node 4 sends the part-time traffic connection request 64 to the self at time T16, and sends it out on the ring network clockwise and counterclockwise. Then, the part-time traffic connection request 64 transferred via the nodes 1, 2, 3, 5, and 6 is received. At the time T19 when the part-time traffic connection request 64 is received from both paths, the node 4 confirms that the failback has been completed, and executes the part-time traffic connection control.

Node 1, which has been performing node failure switching,
At time T17 when one of the part-time traffic connection requests 64 (one from one direction) is received, 2, 3, 5, and 6 respectively transfer the connection request 64 along the clockwise or counterclockwise transfer direction. Forward to node. Further, at time T18 when the other (from the other direction) connection request 64 is received, it is confirmed that each node on the ring network has completed node failure switching, and connection control of part-time traffic is executed.

As described above, when the part-time traffic connection control is performed after the switching back of the node failure switching is completed, the result is as shown in FIG. Thus, the traffic flow shown in FIG. 12 is restored again.

Here, an example of the message contents of the part-time traffic connection requests 63 and 64 is shown in FIG.
The part-time traffic connection requests 63 and 64 are also SD
It is exchanged via the DCC in the H transmission frame. The part-time traffic connection requests 63 and 64 are messages composed of four pieces of information defined by a predetermined bit string: switching type, source and destination switching node ID, and message path. Here, as the information indicating the switching type, there are three types of information after node failure switching, after node failure switching back, and after span switching following ring switching and node failure switching back (first).
And 6 types when combined with the second embodiment). Also, there are four types of information on the message path: the side opposite to the failed node, clockwise, counterclockwise, and the opposite side of the span switching section (six types when combined with the first and second embodiments). ).

In the above control process, in the sequence of FIG. 14 after node failure switching, node 3 (ID = 2) receives the message of FIG. 16 (I), and node 5 (ID = 4) receives the message of FIG. 16 (J). Is sent out. On the other hand, in the sequence of FIG. 18 after the node failure switchback, the node 4 (ID = 3) sends the messages of FIGS. 16 (K) and (L).

As described above, in the present embodiment, when a node failure occurs, the nodes 3, 5 adjacent to the failed node
First, node failure switching is executed, and its completion is awaited. When the node failure switching is completed at the time point T10, at the next time point T11, both nodes 3 and 5 send a part-time traffic connection request 63 to each other node.
Is transmitted through the ring network in the reverse direction without passing through the failure section. Then, each of the nodes 3 and 5 executes the switching connection of the part-time traffic after the time T14 when the part-time traffic connection request 63 is received from the other party.

At the time of node failure recovery, the switching connection of the part-time traffic is executed under the initiative of the recovery node 4 from time T15 when the node failure recovery is completed. That is, the node 4 transmits the part-time traffic connection request 64 in both directions in the ring network after the node failure recovery is completed at the time T15.
Then, after receiving the part-time traffic connection request 64 from both directions, the node 4 executes the part-time traffic switching connection after time T19.

With this configuration, each node can reliably recognize that the node failure switching and failback has been completed, and there is no possibility that erroneous connection of part-time traffic is caused.

(Fourth Embodiment) Next, a fourth embodiment of the present invention will be described.
An embodiment will be described. In this embodiment, a description will be given of a sequence at the time of transmission line switching and switching back when a failure occurs simultaneously at a plurality of locations in a ring network (such a situation is hereinafter referred to as a duplicate failure). . That is, a part-time traffic connection sequence when one of the faults is recovered from the duplicate fault will be described. There are various forms of multiple disorders, and there are various patterns in how to recover. First, some examples will be described with reference to FIGS.

FIGS. 19A and 19B show a state in which a span failure (a failure that can be avoided by span switching) has occurred in a ring network, and a ring failure (a failure that cannot be avoided unless ring switching is performed). ) Has occurred. In FIG. 19 (a), the SD (Signal Degrade: a signal transmission is possible, but a transmission error is large and it is difficult to use) has occurred in the working transmission line in a certain section (indicated by a mark in the figure), and the other transmission path is changed. In this case, SF (Signal Fail: a failure in which a signal cannot be transmitted) occurs in both the working and protection transmission lines in the section (1) (indicated by X in the figure). FIG.
(B) shows a case where SF has occurred in an active transmission line in a certain section and further SF has occurred in another section. For convenience of explanation, the state in the left column (left from the arrow) in the figure is called (initial state), and the state in the right column (right from the arrow) is called (last state).

In the last state of FIG. 19A, ring switching is executed after span switching of the SD section is switched back. This is defined in ITU-T Recommendation G. According to the specification of 841, SF-R (SF-Ring) is better than SD-S (SD-Span).
Has higher priority. Then, if there is an empty channel in the protection transmission line, the part-time traffic is reconnected (restored).

In the last state of FIG. 19B, SF-R
Is not performed in response to the occurrence of. This is SF-
This is because SF-S (SF-Span) has a higher priority than R. Instead, the part-time traffic transmitted to the protection transmission line other than the span section is dropped.

FIGS. 19 (c) and 19 (d) show a case where a span failure has occurred from a state where a ring failure has occurred in the ring network. FIG.
In (c), the active and standby transmission lines in a certain section are S
From the state where D has occurred, S is added to the working transmission line in another section.
The case where F has occurred is shown. FIG. 19D shows a case where SF occurs in the active transmission line in a certain section and SD occurs in the active transmission line in another section.

In the last state of FIG. 19C, after the ring switching related to the SD section is switched back, the span switching is executed. This is more SF-SD than SD-R (SD-Ring).
This is because S has a higher priority. Then, if there is an empty channel on the spare transmission line in the span section, the part-time traffic is reconnected (restored). Here, all the part-time traffic other than the span section is dropped.

In the last state of FIG. 19D, the ring switching realized in the first state is continued as it is. This is because SF-R has a higher priority than SD-S. Also, the connection state of the part-time traffic remains in the initial state.

Here, the priorities of the respective fault states related to this description are described in ITU-T Recommendation G. Along the line 841 is shown in FIG. Each state in FIG. 21 is called a bridge request code (Bridge request code), and the state before the K1 byte is 4
Defined by bits. Of these, five states from SF-S to SD-R are related to this description, and SF-S, SF-R, SD-P, SD-S, S
DR.

FIG. 20 is a diagram showing a switching state when a failure has been recovered from the last state in FIG. 19 (indicated by a circle in the figure). 20 (a) and 20 (b) show a state in which the ring failure has been recovered from the duplicated failure (duplication of the span failure and the ring failure), and FIGS. 20 (c) and (d) show that the span failure has been recovered. Indicates the status.

Here, the first state in FIGS. 20A and 20C both correspond to the last state in FIGS. 19A and 19D, and the first state in FIGS. 20B and 20D. 19 are both shown in FIG.
This corresponds to the last state of (b).

In the last state of FIG. 20A, the SF-R
After the ring switching of the section is switched back, the span switching of the SD section is executed. After the completion of the reestablishment of part-time traffic in the span section,
Part-time traffic other than the span section is reestablished.

In the last state of FIG. 20B, the part time traffic other than the span section is reestablished while the span section is switched. FIG.
In the last state (c), the switching state in the ring network is kept the same as the first state. The same applies to part-time traffic.

In the last state of FIG. 20D, after the span switching is switched back, the ring switching related to the SF-R section is executed. After completing this ring switch,
The reestablishment of the part-time traffic related to all the protection transmission lines in the ring network is executed.

In the present embodiment, in the ring network, the nodes 3 (ID = 2) to 4
In the case where the active system and protection system transmission line failure (ring failure) in the section of (ID = 3) is recovered (FIG. 22), or when the node failure of the node 4 (ID = 3) is recovered (FIG. 2)
The reconnection sequence of the part-time traffic in 3) will be described. Further, in any state, before the recovery from the failure, the node 1 (ID = 0) to the node 2 (ID =
It is assumed that the SD-S switching in the active transmission line in the section 1) is suspended (according to the priority in FIG. 21).

In the state shown in FIG. 22 or FIG. 23, the service traffic 21 is transmitted between the nodes 1 to 5 via the transmission channel of the protection transmission line 12 passing through the node 6. Further, the part-time traffic 22 is transmitted via the backup transmission line of the nodes 2 and 3.

When the ring fault or the node fault is recovered from such a state, the nodes 1 at both ends of the SD reserved section are restored.
(ID = 0) and node 2 (ID = 1) are in accordance with ITU-T Recommendation G. According to 841, it operates as a switching node that performs span switching. This allows service traffic 2
As shown in FIG. 24, reference numeral 1 denotes the active transmission line 11 in the faulty section.
Is switched to the transmission channel of the protection transmission line 12 in the failure section. Also, all part-time traffic on the protection transmission line is dropped.

FIG. 24 After the completion of the span switching, the nodes 1 and 2, which are switching nodes, transmit a part-time traffic connection request 65 toward the side opposite to the SD section. FIG. 26 shows a part-time traffic connection request 65.
FIG. 5 is a diagram showing a transmission / reception sequence of FIG. After the span switching is completed at time T1, each of the nodes 1 and 2 sends a part-time traffic connection request 65 to the other node at time T21, and also transmits the part-time traffic connection request 65 sent from the other node. , Via the nodes 3, 4, 5, and 6, which are intermediate nodes.

This part-time traffic connection request 6
At the time T24 when the node 5 receives the node 5, the nodes 1 and 2 confirm that the span switching of the faulty section has been completed, and execute connection control of part-time traffic in each node. Here, each of the intermediate nodes 3, 4, 5, and 6 receives one of the part-time traffic connection requests 65 transmitted from the nodes 1 and 2 at time T22, and the part-time traffic connection request 65
To another switching node via another intermediate node.

Further, at time T23 when the part-time traffic connection request 65 sent from the other switching node is received, the nodes 3, 4, 5, and 6 confirm that the nodes 1 and 2 have completed the span switching. And perform connection control of part-time traffic on it.

Here, after the span failure switching in FIG. 24, the transmission channel of the protection transmission line 12 to which the part-time traffic 22 has been set before the switching remains open. Therefore, the connection control of the part-time traffics 22 and 23 is executed from this state, and the traffic flow shown in FIG. 25 is realized. That is, after the span failure switching, the part-time traffic 2
By executing the connection control of the nodes 2 and 23, the transmission of the part-time traffic 22 is restarted on the protection transmission line 12 between the node 2 and the node 3, as indicated by the thick dotted line in the figure. Further, the transmission of the part-time traffic 23 is resumed on the protection transmission line 12 between the nodes 5 and 6.

Here, an example of the message content of the part-time traffic connection request 65 is shown in FIG. The part time traffic connection request 65 is also exchanged via the DCC in the SDH transmission frame.

In the above control process, in the sequence of FIG. 26 after the span failure switching, the node 1 (ID = 0) receives the message of FIG. 16 (M), and the node 2 (ID = 1) receives the message of FIG. 16 (N). Is sent out.

As described above, in the present embodiment, when a ring failure or node switching is recovered from a ring switching with SD-S suspension or a node failure switching state,
SD-S by nodes 1 and 2 adjacent to the span failure section
Execute switching and wait for its completion. SD-S switching at time T
When the process is completed at 20, the node 1 and the node 2 transmit a part-time traffic connection request 65 to each other at the next time point T21 without passing through the failure section, that is, in the reverse direction around the ring network. . Then, in each of the nodes 1 to 6 in the ring network, the part-time traffic switching connection is executed after the point-in-time (T23 or T24) when the part-time traffic connection requests 65 from both directions are received.

With this configuration, each node can surely recognize that the span switching has been completed, and there is no risk of erroneous connection of part-time traffic. Note that the present invention is not limited to the above embodiments. For example, in each of the above embodiments, the description has been made in accordance with the SDH.
Application to T (Synchronous Optical NETwork) is also possible. Further, although the nodes 1 to 6 are connected by STM-16 lines, they may be connected by lines having other capacities such as STM-1 and STM-4. Further, the transmission channel of the part-time traffic is not limited to the DCC, and another available channel in the overhead of the SDH frame may be used. In addition, various modifications can be made without departing from the spirit of the present invention.

[0091]

As described above in detail, according to the present invention, it is possible to provide a connection control method and a transmission apparatus for part-time traffic that do not cause erroneous connection.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of an information communication system according to an embodiment of the present invention.

FIG. 2 shows each of nodes 1 to 6 according to the embodiment of the present invention.
FIG. 2 is a block diagram showing the configuration of FIG.

FIG. 3 is a diagram showing a flow of traffic in a normal state in the information communication system according to the first and second embodiments of the present invention.

FIG. 4 is a diagram showing a traffic flow after span switching in the information communication system according to the first embodiment of the present invention.

FIG. 5 is a diagram showing a transmission / reception sequence of a part-time traffic connection request 61.

FIG. 6 is a diagram showing a traffic flow after recovery from a failure in the information communication system according to the first embodiment of the present invention.

FIG. 7 is a diagram showing an example of message contents of part-time traffic connection requests 61 and 62 according to the first and second embodiments of the present invention.

FIG. 8 is a diagram showing a traffic flow after ring switching in the information communication system according to the second embodiment of the present invention.

FIG. 9 is a diagram showing a transmission / reception sequence of a part-time traffic connection request 62.

FIG. 10 is a block diagram illustrating a part-time traffic connection request 62 according to a second embodiment of the present invention;
The figure which shows the flow of traffic after performing the transmission / reception sequence of FIG.

FIG. 11 is a diagram showing a flow of traffic after recovery from a failure in the information communication system according to the second embodiment of the present invention.

FIG. 12 is a diagram showing a traffic flow in a normal state of the information communication system according to the third embodiment of the present invention.

FIG. 13 is a diagram showing a flow of traffic after node failure switching according to the third embodiment of the present invention.

FIG. 14 is a diagram showing a transmission / reception sequence of a part-time traffic connection request 63.

FIG. 15 is a diagram showing a traffic flow after restoring of part-time traffic is completed in the third embodiment of the present invention.

FIG. 16 is a diagram showing an example of message contents of part-time traffic connection requests 63, 64 and 65 according to the third and fourth embodiments of the present invention.

FIG. 17 is a diagram showing a traffic flow after recovery from a node failure in the information communication system according to the third embodiment of the present invention.

FIG. 18 is a diagram showing a transmission / reception sequence of a part-time traffic connection request 64.

FIG. 19 is a view showing various forms of occurrence of a double fault.

FIG. 20 is a diagram showing a form of recovery from a duplicate failure.

FIG. 21 shows ITU-T recommendation G. The figure which shows the priority of the switching state determined by 841.

FIG. 22 is a diagram showing a flow of traffic after executing a ring switch at the time of an overlapping failure in the information communication system according to the fourth embodiment of the present invention.

FIG. 23 is a diagram showing a flow of traffic after executing node failure switching at the time of a duplicate failure in the information communication system according to the fourth embodiment of the present invention.

FIG. 24 is a diagram showing a flow of traffic after a ring failure or a node failure has been recovered from the states shown in FIGS. 22 and 23;

FIG. 25 is a diagram showing a flow of traffic after restoring of part-time traffic has been performed from the state of FIG. 24;

FIG. 26 is a diagram showing a transmission / reception sequence of a part-time traffic connection request 65.

[Explanation of symbols]

 1 to 6: Node L: High-speed line 11: Working transmission line 12: Stand-by transmission line M: Low-speed line S1 to S6: Switch 100: Add-drop multiplexer (ADM) 201 to 205: Interface unit (I / F) 300: control unit 300a: switching control unit 300b: connection request transmission / reception control unit 300c: part-time traffic connection control unit 400: storage unit 21: service traffic 22, 23: part-time traffic 31: active transmission line failure 61-65 ... part-time traffic connection request 32 ... stand-by transmission line failure 33 ... node failure 34 ... recovery of active transmission line failure 35 ... recovery of standby transmission line failure 36 ... recovery of node failure 33 37 ... active transmission line Failure in a hospital

Claims (14)

[Claims] 1. A transmission system comprising: a plurality of transmission devices; and a transmission line which is duplexed into an active system and a standby system and connects the plurality of transmission devices in a ring to form a ring network, wherein each of the plurality of transmission devices is provided. A part-time traffic connection control method in a ring network system having a function of switching between working and protection of the transmission line when a failure occurs in the ring network, wherein it is necessary to switch between working and protection of the transmission line. When this occurs, after the current / preliminary switching of the transmission path is completed, the transmission apparatuses adjacent to each other across the section in which the transmission path switching factor exists are connected to the transmission apparatus of the other party in part-time traffic connection. A first step of sending a request, and in each of the adjacent transmission devices, A second step of receiving the transmitted part-time traffic connection request; and, after completion of the second step, performing a re-connection of the part-time traffic between the adjacent transmission devices. And a step of controlling a part-time traffic connection. 2. A transmission system comprising: a plurality of transmission apparatuses; and a transmission line which is duplexed into an active system and a standby system and connects the plurality of transmission apparatuses in a ring to form a ring network. Each of the paths has a line in both directions consisting of a clockwise direction and a counterclockwise direction, and each of the plurality of transmission devices switches the working / protection switching of the transmission path when a failure occurs in the ring network. A part-time traffic connection control method in a ring network system having a function of performing a function of performing transmission / reception switching of the transmission path when the current / preservation switching of the transmission path is completed. A transmission path switching factor is generated in the ring network system from the transmission device serving as a switching node in charge of switching. A first step of transmitting a part-time traffic connection request via the line in a direction opposite to the existing section, and the part-time traffic arriving via the line in each of the transmission devices other than the switching node. A second step of receiving a connection request from both directions; a third step of receiving, in the transmission device as the switching node, the part-time traffic connection request arriving via the line; A fourth step of executing reconnection of part-time traffic after completion of the second step in each of the transmission devices and in the transmission device as the switching node after completion of the third step, respectively; A partner comprising: Im traffic connection control method. 3. The part-time traffic connection control method according to claim 1, wherein the transmission path switching factor is occurrence of a failure. 4. The part-time traffic connection control method according to claim 1, wherein the transmission path switching factor is a transmission path switching back due to a recovery from a failure. 5. The transmission line switching factor is associated with recovery of a high-priority failure among failures that have occurred repeatedly.
3. The part-time traffic connection control method according to claim 1, wherein the transmission line switching is performed for a suspended failure. 6. The part-time traffic connection request includes information indicating a type of transmission path switching, information indicating a transmission device to which the part-time traffic connection request is transmitted, and a transmission source of the part-time traffic connection request. The part-time traffic connection control method according to any one of claims 1 to 5, further comprising information indicating the transmission device of (1) and information indicating a direction in which the part-time traffic connection request is transmitted. 7. The method according to ITU-T Recommendation G.7, wherein the part-time traffic connection request is transmitted. DCC specified in 709
The method according to claim 6, wherein the transmission is performed via a (Data Communication Channel). 8. The transmission used in a ring network system comprising: a plurality of transmission devices; and a transmission line that is duplexed into an active system and a standby system and connects the plurality of transmission devices in a ring to form a ring network. In the device, when a failure occurs in the ring network, transmission signal rescue control means for rescuing a transmission signal by performing active / spare switching of the transmission path, and necessity of active / spare switching of the transmission path Transmission means for transmitting a part-time traffic connection request to a transmission device that is opposite to the transmission device on the section where the transmission path switching factor exists, after the current / protection switching of the transmission channel is completed, The part-time trough transmitted to itself from an opposing transmission apparatus with a section in which the transmission path switching factor exists interposed therebetween. Receiving means for receiving a part-time traffic connection request by the receiving means, and receiving the part-time traffic connection request between the receiving apparatus and a transmission device facing the transmission apparatus with the transmission path switching factor interposed therebetween. A transmission device comprising: reconnection means for performing reconnection. 9. A transmission system comprising: a plurality of transmission devices; and a transmission line which is duplexed into an active system and a standby system and connects the plurality of transmission devices in a ring to form a ring network. In the transmission apparatus used in a ring network system in which each of the paths has a line in both directions including a clockwise direction and a counterclockwise direction, when a failure occurs in the ring network, the working / protection of the transmission path is used. A transmission signal rescue control means for relieving the transmission signal by performing the switching, and a transmission device which takes the initiative of the transmission path switching when the necessity of the active / backup switching of the transmission path arises. Is a section in which a transmission path switching factor exists in the ring network system after the current / standby switching of the transmission path is completed. A transmitting means for transmitting a part-time traffic connection request via the line in the opposite direction; and a transmission device other than the transmission device which takes the initiative of switching the transmission path, which arrives via the line. Performing a reconnection of the part-time traffic after receiving the part-time traffic connection request from both directions,
When the transmission device itself is the transmission device that takes the initiative of switching the transmission path, reconnection means for reconnecting the part time traffic after receiving the part time traffic connection request arriving via the line. A transmission device, comprising: 10. The transmission apparatus according to claim 8, wherein the transmission path switching factor is a failure occurrence. 11. The transmission line switching factor according to claim 8, wherein the transmission line switching factor is transmission line switching back due to recovery from a failure.
Or the transmission device according to 9. 12. The transmission line switching factor according to claim 1, wherein the transmission line switching factor is a transmission line switching for a suspended failure accompanying recovery of a high-priority failure among failures that have occurred repeatedly. 10. The transmission device according to 8 or 9. 13. The part-time traffic connection request, wherein the part-time traffic connection request includes: information indicating a type of transmission line switching; information indicating a transmission device to which the part-time traffic connection request is transmitted; 13. The transmission device according to claim 8, wherein the transmission device includes information indicating a transmission device of a request source and information indicating a direction in which the part-time traffic connection request is transmitted. 14. An SDH (Synchronous Digital Hierar)
chy) a transmission device, wherein the transmitting means transmits the part-time traffic connection request to an ITU-T recommendation 7
DCC (Data Communication Chann)
The transmission device according to claim 13, wherein the transmission is performed via el).