JP3301565B2 - Ring transmission equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used for ultra-high capacity optical digital transmission. In particular, it relates to communication between nodes connected by a bidirectional ring transmission path.

[0002]

2. Description of the Related Art With the rapid development of optical technology, ultra-large capacity 10
Gbit / s optical transmission systems are becoming possible.
A large-capacity transmission system is economical with a small number of fiber cores, and realizes a simple communication network.

A digital network based on SDH (Synchronous Digital Hierarchy) defined in CCITT (International Telegraph and Telephone Consultative Committee) recommendations G707, 708, 709, 781, 783 uses abundant overhead information and digital switching technology. As a result, high reliability and excellent operability can be realized. Therefore, it is considered that an economical, simple, and highly reliable and operable communication network is realized by constructing a large-capacity transmission system compatible with SDH.

[0004] By the way, at present, the capacity required for the service to the subscriber is not wide band, so that the large-capacity optical transmission system is limited to use for a long-distance trunk transmission line. However, if a high-speed broadband service is provided by the introduction of B-ISDN (Broadband Service Integrated Digital Network), the capacity required by the subscriber is expected to increase dramatically. Therefore, the capacity processed by each node in the network naturally increases. For this reason, it is considered that an ultra-large capacity optical transmission system will be required for medium-distance networks and urban networks in the future. At this time, the network configuration must satisfy various connectivity required by the service.

As a conventional network configuration, 622 Mbit / s
Up to 2.5 Gbit / s SDH large capacity optical transmission network, physical mesh network, SONET one-way ring network, and SON
The ET bidirectional ring network will be described.

FIG. 34 shows an example of a block configuration of a conventional SDH large-capacity optical transmission line network. With the introduction of the optical fiber transmission method, the cost of the transmission line has been significantly reduced. As a result, it is more economical to house the lines together in a large-capacity optical transmission line even if it is a little detour, and to distribute each line at an appropriate location in units of line bundles (hereinafter referred to as "paths"). Become Therefore, the digital multiplexer MUX (Digi
156Mbit / multiplexed by tal Multiplexer)
s signal, the digital cross-connect device DC
S (Digital Cross-Connect System) is used to sort and multiplex paths, and 622 Mbit / s to 2.5
Transmit at Gbit / s. As the size of the network increases, it is economical to define a bundle of paths as a higher-order path, and furthermore, a higher-order digital cross-connect device DC that distributes paths between the digital cross-connect devices DCS.
It is more economical to provide S.

In such a network configuration, the fiber and the terminal equipment have a one-to-one redundant configuration for transmission and reception in preparation for a node failure, and a failure recovery function for recovering the failure by a DCS network switch is provided. However, with such a network configuration, it is not possible to recover from a failure when the entire cable is disconnected. Current large-capacity transmission networks have a point-to-point transmission network configuration.

FIG. 35 shows a configuration example of a physical mesh network.
In this network configuration, a plurality of nodes (the number of nodes is 1 in this example)
0) are connected to each other by an optical transmission line. The current medium-distance transmission line infrastructure network in Japan is being constructed with multi-core optical fiber cables based on loops between medium-distance transmission nodes. Although it is based on a loop, since it is spatially multiplexed by increasing the number of fibers, it is physically equivalent to the physical mesh network shown in FIG. Since such a physical mesh network is basically a point-to-point transmission system, it is similar to the SDH long-distance transmission line network in terms of the failure recovery function, has a one-to-one redundancy configuration, and uses a DCS network switch. Perform recovery.

FIGS. 36 and 37 show SONETs respectively.
1 shows a configuration example of a unidirectional ring network and a SONET bidirectional ring network. In North America and other countries, research on future network architecture is being actively conducted. Discussions are being conducted from the viewpoint of improving reliability, flexibility, and economic efficiency, and are being actively discussed. A common ideal network in these discussions is that one infrastructure network is composed of many logical sub-networks. As a result, costs can be shared, management is easy, and connectivity specific to the service can be satisfied. The requirements for such a network include allowing different types of connectivity, and that the infrastructure network is available to all nodes. One solution to these requirements is a ring architecture. The SDH-based ring architecture not only satisfies these requirements, but also maximizes the self-healing function using abundant overhead information. Above all, SONET one-way ring network and SONET
Two-way ring networks are superior in terms of reliability and economy (TH. Wu et al., GLOBECOM., 1991, 403.2, 44
Four).

[0010] The SONET one-way ring network has a network configuration that carries services in one direction on the ring. In FIG. 36, the service from node A to node E is carried clockwise, and the service from node E to node A is carried clockwise. The number of fibers required in the SONET one-way ring network is a total of two, working and spare.

In the case of a SONET bidirectional ring network, services are carried bidirectionally on the ring. For example, in FIG. 37, the service from node A to node E is carried counterclockwise.
Conversely, the service from node E to node A is carried clockwise. Therefore, only two fibers are required for the working ring alone, and four fibers are required including the spare ring.

FIGS. 38 and 39 are diagrams for explaining a method of restoring a failure in the SONET one-way ring network. FIG. 38 shows path switching on the receiving side, and FIG. 39 shows transmission path switching.

In a SONET one-way ring network, a spare ring (spare fiber) carries information in a direction opposite to the working ring. The transmitting node always sends signals to both working and protection fibers, and the receiving node switches between them. Here, for example, if a fiber break or a complete cable break occurs between the node C and the node D,
The node that detects the path alarm switches. In the figure, the switched paths are indicated by thick lines.

In the case of transmission line switching, if a fiber break or a cable break occurs between the node C and the node D, the ring is looped back at the faulty end, that is, the nodes C and D to recover from the fault. Fulfill. At the time of failure recovery, the working ring and the protection ring are linked to form a new loop.

FIGS. 40 and 41 are diagrams for explaining a method of restoring a failure in the SONET bidirectional ring network. FIG. 40 shows path switching on the receiving side, and FIG. 41 shows transmission path switching.

In the case of path switching, as in the case of the SONET one-way ring network, the node detecting the path alarm switches the path to the protection system on the receiving side to recover from the failure. In the case of transmission line switching, two working fibers are connected to the corresponding spare fibers, respectively, and loopback is performed to recover from the failure.

[0017]

Existing networks are completely separately configured and managed by the services they provide. The cost of configuring, managing, and repairing these disjointed networks is expected to increase year by year as new services are introduced. If these separate networks are integrated under one infrastructure network, an economical and intelligent communication network can be constructed by sharing costs.

Incidentally, the conventional ultra-large capacity optical transmission system is a point-to-point signal transmission system as a network configuration.
Such an architecture is suitable for a long-distance trunk line network. However, it is not suitable for use in which different types of services are transmitted using one infrastructure network as a medium and transmitted and received by a large number of nodes. This is because different services require different connectivity such as point-to-point for telephone, one-to-many for broadcasting, and many-to-many for videoconferencing. For this reason, the point-to-point ultra-large capacity transmission system cannot completely satisfy the other requirements for connectivity. Also, when a new high-speed broadband service is introduced, the point-to-point ultra-large capacity transmission system is not considered to completely meet the connectivity requirements of this new service. To cope with this, it is necessary to lay a new transmission line. Therefore, a point-to-point ultra-large capacity optical transmission system is inflexible and uneconomical. Furthermore, from the viewpoint of reliability, the point-to-point large-capacity optical transmission system has no way to recover from a failure when the cable is completely disconnected.

One solution of the network that satisfies the connectivity condition is a physical mesh network in which an optical fiber runs over all pairs of nodes. However, since the physical mesh network is not multiplexed and transmitted efficiently, the cost required for the transmission path and the transmission device becomes enormous. In this mesh architecture, the number of transmission / reception fibers is n (n-1) / 2 pairs, where n is the number of nodes, and n (n-1) terminal devices are required for transmission / reception. Therefore, if the number of nodes is 10, the transmission / reception fiber pair is 90
Ninety terminal equipment are required. FIG. 42 shows an example of a node configuration in a physical mesh network when the number of nodes is 10. Even in the case where the number of nodes is 10, each of the nodes terminates 36 fibers in total for transmission / reception for each partner node and four for backup, and 36 transmission line terminators L
Requires T.

In the SONET one-way ring network, the service is transmitted in one direction in a normal state, so that the transmission capacity is not effectively used. FIG. 43 shows the relationship between the number of nodes in the ring network and the transmission capacity of the active system in comparison between a unidirectional ring and a bidirectional ring. Here, it is assumed that each node needs a capacity of 622 Mbit / s as an example.
As shown in this figure, in the SONET one-way ring network, the maximum number of nodes that can be tolerated even when the transmission capacity is 10 Gbit / s is six. If all nodes are to be rescued when the cable is completely cut, the spare ring requires the same transmission capacity.

In the case of the SONET bidirectional ring network, there is a problem of the number of optical fibers. Considering a large-capacity network, it is difficult to construct a basement or the like in an area where there is such a demand at present, so it is desirable to effectively use the pipeline. If four optical fibers must be newly laid in order to introduce the SONET bidirectional ring network, enormous costs are required. Furthermore, if all the nodes are to be rescued when the cable is completely cut, the information must be carried on the spare ring in the backup ring by a distant route that is all in the opposite direction to the working route.
Therefore, the spare ring requires more transmission capacity than the working ring. In addition, in the switching of the transmission path, loopback is performed only at the failure end, so that the transmission distance at the time of restoration is wasted. Therefore, it is considered that the problem of transmission delay increases.

The present invention solves such problems, satisfies different connectivity for each service, can recover from a failure when the cable is completely disconnected, can be economically configured, and has a simple terminal configuration. It is another object of the present invention to provide a ring transmission device that can effectively utilize the transmission capacity and can reduce the number of fiber cores.

[0023]

A ring transmission apparatus according to the present invention includes a plurality of nodes for transmitting and receiving data, and a bidirectional ring transmission line for connecting the plurality of nodes in a ring. Respectively, a working path setting means for setting a working path, which is a line bundle unit for performing communication with each other node, on one of the two-way ring transmission paths, and Failure path identification means for detecting a working path that has been disconnected due to the failure when a failure has occurred, and setting a protection path in the opposite direction to the working path to a bidirectional ring transmission line according to the output of the failure path identification means. to look contains a backup path setting means, the working path setting means, a logical mesh network between each set each working path on the side path length is short of the two directions of a bidirectional ring transmission path node Formation Ring transmission apparatus der including means that
You .

Here, the feature of the present invention is that it comprises means for inserting control data indicating the connection state of each path into each frame transmitted to the bidirectional ring transmission line, and the faulty path identification means transmits from its own node. comprises means for detecting failure information of the working path to, the backup path setting means is to include a means for setting a reverse backup path relative to the working path for transmission of its own node.

Each of the plurality of nodes has means for arranging signals destined for each node propagating through the bidirectional ring transmission line in a time-series order in the spatial arrangement of the respective nodes, A means for branching and receiving a signal at a time series position addressed to the own node from the signal sequence, and a transmission destination node assigned so that each node on the bidirectional ring transmission path can perform reception processing in the same time series. A means for inserting a transmission signal destined for each node at a time series position, and a time series position occupied by a signal passing through the own node so that each node on the bidirectional ring transmission path can perform reception processing in the same time series And time-series conversion means for reusing the time-series positions to which signals between the nodes are allocated.

The protection path setting means switches the signal to be branched and the signal to be inserted at the own node from the working path to the protection path, and passes through the own node so that each node can perform processing in the same time series. Means for switching the order of the signal of the protection path and the signal inserted into the protection path by the own node, and storage means for accumulating operation information of the switching means and the switching means in accordance with the failure state of the path.

[0027]

By setting the working path to the side having the shorter path length in the two directions of the bidirectional ring transmission line, a logical mesh network is formed between the nodes, and signals between the nodes are multiplexed to achieve a very large capacity. To be transmitted. This makes it possible to adapt to high-speed broadband services.

Further, in order to rescue all the paths in the event of a complete disconnection of the cable, the transmitting node reverses the direction of the paths, ie, clockwise and counterclockwise. In this case, since a backup path is set to a new route in the direction opposite to the working side for the path in which communication is disabled, it is not necessary to send a signal to the backup side in normal times. Therefore,
All nodes can be rescued without limiting the number of nodes or transmission capacity. Further, the transmission path can be used effectively.

The signals destined for each node are arranged in time series in the order of spatial arrangement of the nodes, and each node performs signal reception, transmission, and conversion of the time series position at the same time series position. Is independent of the position in the ring, and the transmission capacity can be effectively used. Further, also for the protection path, the order of the signal to be passed and the signal to be inserted can be changed so that each node performs processing in the same time series, and the transmission capacity can be used effectively.

The two-way ring transmission line may be composed of two working and standby optical fibers, and two-way wavelength multiplexing may be used for bidirectional communication with each optical fiber. In this case, the number of necessary fibers is two including the spare fiber, and a more economical network can be constructed.

[0031]

Embodiments of the present invention will be described below with reference to the drawings.

1. 1 and 2 are diagrams showing a ring transmission apparatus according to a first embodiment of the present invention. FIG. 1 shows its configuration, and FIG. 2 shows its traffic pattern.

The ring transmission device includes a plurality of nodes 10 to 14 for transmitting and receiving data, and a plurality of nodes 10 to 14 for transmitting and receiving data.
To 14 in a ring shape. Multiple nodes 10-14
Respectively, a working path setting means for setting a working path, which is a line bundle unit for performing communication with each other node, on one of the two-way ring transmission paths, and Failure path identification means for detecting a working path that has been disconnected due to the failure when a failure has occurred, and setting a protection path in the opposite direction to the working path to a bidirectional ring transmission line according to the output of the failure path identification means. Backup path setting means for performing the setting. This configuration will be described later.

A feature of this embodiment is that the working path setting means sets each working path to the shorter path length of the two directions (clockwise and counterclockwise) of the optical fiber 16. Means for forming a logical mesh network between nodes as shown in FIG.

In this embodiment, the logical mesh has a ring configuration and can be implemented, for example, in a 10 Gbit / s ultra-large capacity optical transmission system. The path unit defines a high-speed path. With current technology, the path units are 1.5 Mbit / s and 52 Mbit / s.
Mbit / s, which simplifies network and intra-station configurations. This unit is useful as a line operation unit in a network based on telephone services. However, in the case of ultra-large capacity, when transmitting a high-speed signal from a multimedia terminal or the like, there is a possibility that the efficiency becomes low in this path unit. Further, the transmission network is operated on a path-by-path basis, but in a very large-capacity communication network, these path units are relatively slow. Therefore, the multiplexing device and the cross-connect device are complicated and expensive. Therefore, it is considered that a very high-capacity communication network requires a higher-speed path unit. In an ATM (Asynchronous Transfer Mode) network which is said to be a fundamental technology in the future B-ISDN era, a VP (Virtual Path) having a variable capacity is used.
Thus, more flexible path operation can be performed. Even in ATM networks, failure recovery and switching for high reliability are required.
STM (Synchronous Transfer Mode)
) The use of a format SOH (Section Over Head) has been studied. In this case, ATM cells are VC-4 (156 Mbit / s) and VC-4-4c of the SDH interface.
(622 Mbit / s) or VC-4-16c
(2.4 Gbit / s).

As a path unit which satisfies the demands of various signal forms including the increase in capacity and ATM, 62 units are used.
A path unit of 2 Mbit / s or 2.4 Gbit / s is a strong candidate. Although the present invention does not limit the number of nodes or the path capacity, here, for example, each node is assumed to be able to transmit and receive with a path capacity of 622 Mbit / s.

The upper limit of the transmission capacity of the bidirectional ring transmission line constituted by the optical fiber 16 is estimated based on the traffic pattern requiring the most capacity. The traffic patterns that require the most capacity are nodes 10-14.
Are 622 Mbit / s for all other nodes, respectively.
, Ie, a logical mesh traffic pattern. Future services are expected to require any connectivity. Therefore, the transmission capacity is set so as to cover the traffic pattern requiring the highest connectivity. Therefore, the transmission capacity is set so as to cover the traffic pattern requiring the highest connectivity.

In the configuration shown in FIG.
The paths emanating from each of 14 are clockwise and counterclockwise distributed. The required transmission capacity is indicated by the number of paths 17 in the optical fiber 16. If the number of nodes is 5, 3
A path, that is, a capacity of 1.8 Gbit / s is required.

FIGS. 3 and 4 are diagrams showing a ring transmission apparatus according to a second embodiment of the present invention. FIG. 3 shows its configuration and FIG. 4 shows its traffic pattern. In this embodiment, the number of nodes is 10, and the nodes 20 to 29 are connected in a ring shape by an optical fiber 31.

In this case, the required transmission capacity is 13 paths, that is, 8.1 Gbit / s. Therefore,
For a bidirectional ring with 10 nodes, at least 8.1 Gbit
/ S is required. In general, the transmission capacity of the working system required when the number of nodes n is by recursive considerations, n is n ^2/8 times the respective node receiving volume when the even, when n is an odd number (n ² -1) / 8 times is required. This is similar to a conventional SONET bidirectional ring network. S
In the ONET unidirectional ring network, the capacity when the number of nodes is n is n (n-1) / 2 times the node transmission / reception capacity. If the number of nodes increases, the transmission capacity increases by the square of the number of nodes, and it is considered that further increase in capacity is required in the future.

FIG. 5 is a block diagram showing an example of a signal insertion / branch circuit for performing multiplexing and transmission / reception at each node. This signal drop and add circuit (ADM, add / dr
Op multiplexers) multiplex and transmit / receive by inserting or dropping necessary signals at each node. That is, the path switching circuit 501 and the path setting circuit 5
02, and light receiving elements 512 and 522 for respectively receiving signal lights from the input side working fibers 511 and 521 in the opposite directions to each other; a demultiplexing device 513 for demultiplexing the light receiving output and supplying the light receiving output to the path switching circuit 501; 52
3. Multiplexers 514 and 524 for multiplexing the transmission signal output from the path switching circuit 501, and a laser 515 for converting the output of the multiplexers 514 and 524 into an electric-optical signal and sending out the output optical fibers 516 and 526. , 525, and the input side spare fibers 531, 5
41, for the outgoing side spare fibers 536 and 546, the light receiving elements 532 and 532, the demultiplexers 533 and 543, the multiplexers 534 and 544, and the lasers 535 and 545.
Is provided.

FIG. 6 is a diagram showing in detail the configuration of the signal insertion / branching circuit shown in FIG. The path switching circuit 502 is controlled by the path setting circuit 502 and the failed path identification circuit 604 and the signal terminating device 605 for detecting a working path that has been disconnected due to the failure when a failure occurs in the bidirectional ring transmission path. A working path, which is a unit of line bundle, for performing communication with each of the other nodes is set on one of the transmission ring transmission paths, and a protection path in the direction opposite to the working path is set in accordance with the output of the failed path identification. A path protection switch 601 for setting a path to a bidirectional ring transmission path is provided. The demultiplexer 513 includes demultiplexers 611 and 612.
And the multiplexer 514 includes two multiplexers 6
13, 614. Similarly, the demultiplexers 523, 533, and 543 each include two demultiplexers 6
21 and 622, 631 and 632, 641 and 642, and multiplexers 524, 534, 5
44 denotes two multiplexing units 623 and 624, 6 respectively.
33 and 634, 643 and 644. Between these two stages, the high-speed signal termination device 602,
603 is arranged.

In normal times, it is assumed that the spare side of the bidirectional ring transmission line is empty. When the cable is disconnected, the path on the transmitting side where communication becomes impossible is identified, and the path is switched to the standby system so that the path is established by a new reverse route. In this way, it is not necessary to reduce the number of nodes in preparation for rescue of all nodes when the cable is completely disconnected. Because 1
This is because, even when one cable is completely disconnected, the transmission capacity required for the spare ring is only the transmission capacity required for the part where the full ring is disconnected.

FIG. 7 shows the transmission capacity required for a spare ring when a cable break occurs at one location in a network with n = 5 nodes. When a cable disconnection FP occurs between nodes C and D among nodes A to E arranged in a ring shape, node A
To E require the transmission capacity indicated by the lines connecting the nodes in (a) to (e). The path indicated by a bold line indicates a backup path set for a cable break. In this case, for both transmission and reception, three paths, that is, 1.8 Gbit /
Only s is the transmission capacity required for the standby system and is equal to the transmission capacity of the working system. This equivalence is expressed by the general node number n
Holds for.

Therefore, by implementing a 10 Gbit / s large-capacity optical transmission system on a ring network and using a transmission-side switch for reversing the direction of the path, the number of nodes is 10, and each node has a transmission / reception capacity of 622 Mbit / s. Mesh communication becomes possible, and all nodes can be rescued even when the cable is completely disconnected.

FIG. 8 shows the capacity required for the spare ring when all nodes are rescued when one cable is completely disconnected. Here, the transmission / reception capacity of each node is 622 Mbi.
t / s. In the SONET one-way ring, the working system needs only n (n-1) / 2 times the transmission / reception capacity of each node, and the standby system needs the same. SONET
In the bidirectional ring, the working system has n
Fold ^2/8 (n is an even number), (n ² -1) / 8 times (n is an odd number) is required, the standby system n (3n-4) / 8 times (n is an even number), (3n ² -4n + 1) / 8 times is required. In contrast, in the bidirectional ring according to the present embodiment,
Working system, both the protection system n ^2/8 of each node transmission capacity (the n even), is required by (n ² -1) / 8 times (n is an odd number). Therefore, in this embodiment, mesh communication can be performed between all nodes without limiting the node transmission / reception capacity or the number of nodes in preparation for the complete disconnection of the cable.

2. Path setting and path switching Next, a path setting algorithm and a path switching algorithm required in this embodiment, and a transmission capacity that can be effectively used by this algorithm will be described.

2.1 Path Setting Assuming that the spare ring is empty in normal times, in the bidirectional ring, a path is transmitted to the transmitting side in order to determine one of the two transmission directions depending on the path. A setting circuit is required. Here, in order to distinguish the paths, the numbers of the destinations of the paths are given as path numbers.

In this algorithm, the own number is set to "1" at any node, and processing is performed in a relative number layer that performs processing based on this number. This allows one algorithm to be used for all nodes.

The path setting in the normal state is performed as follows.

(1) Setting of longest path A path farthest from the transmitting node is set. Assuming that the total number of nodes in the ring is n, the longest path is a path to a node having a relative number of n being an odd number (n + 1) / 2 (n + 3) / 2 and n being an even number n / 2 + 1. However, the node numbers are numbered in a clockwise direction on the drawing, and this direction is hereinafter referred to as “clockwise”. However,
This direction is a direction between the node “1” and another node, and does not mean a direction in which a signal is transmitted. For example, even in a clockwise path, the direction of the transmission signal is certainly clockwise, but the direction of the reception signal is counterclockwise.

(2) Setting the path around the left and right FIGS. 9 and 10 show examples of setting the path. FIG. 9 shows an example where n = 5 as an example when n is an odd number, and FIG. 10 shows an example where n = 6 as an example when n is an even number.

When n is an odd number, there are two longest paths. Of these, the path to the node with the relative number (n + 1) / 2 is CP1, and the path to the node with the relative number (n + 3) / 2 is CP2. The path to the node whose relative number is (n + 1) / 2 or less is clockwise including CP1. The path to the node whose relative number is (n + 3) / 2 or more is CP2
And counterclockwise.

When n is an even number, the relative number is n / 2 + 1
Is the longest path to the node having the relative number n / 2 + 1. When this CP is clockwise (FIG. 10A), the path to the node whose relative number is n / 2 + 1 or less is clockwise, Path is counterclockwise. When the CP is clockwise (FIG. 10B), the path to the node whose relative number is smaller than n / 2 + 1 is clockwise, and the relative number n / 2 + 1
Let the path to the above node be counterclockwise. In addition, although the number of CPs is set to n / 2 in total, the CP of a certain node and the CP of an adjacent node are set to be opposite left and right so that the total number of left and right paths is as equal as possible. I do.

FIG. 11 shows a method of setting the path to the left and right.
Are shown together.

2.2 Path Switching FIG. 12 is a diagram showing the relationship between signal disconnection detection and path switching.

When a cable break or the like occurs, nodes on both sides of the faulty cable are LOS (Loss Of Signal), LOF
(Loss Of Frame), loss of signal such as LOP (Loss Of Pointer) is detected. The node at the failed end switches all add / drop paths passing through the failed cable to the standby system. In other words, all the right and left paths of the faulty path to be dropped and inserted at the own node are switched to the standby path in the opposite direction. Referring to FIG. 12, at the faulty end node “1”, the paths through the disconnected cables are “9” and “10”.
At the failed end node “5”, the paths passing through the disconnected cable are “3” and “10”. At the failure end node “1”, the counterclockwise paths “9” and “10” are switched clockwise on the transmission side. At the fault end node “5”, the clockwise paths “3” and “10” are switched to the counterclockwise on the transmitting side.

The path switching circuit 502 shown in FIG.
Then, these path alarms are constantly monitored, and when an alarm is detected, a P-AIS signal (all mark signals) is written to the passing fault path. In the failed node, the P-AI
The S path and the normal path are multiplexed and transmitted. FIG.
In the example shown in FIG. 5, the path “3” is the P-AIS path for the node “1”, the path “9” is the P-AIS path for the node “5”, and the paths “1” and “2” for the node “1”. , Paths “7” and “8” are normal paths.

FIG. 6 shows whether or not a path to be dropped and inserted at another node other than the failed end is an alarm or not.
, The alarm path (path “3” at node “2”, path “9” at node “4”) is switched to the standby system on the transmission side, and the normal path is normally To process.

For the faulty path passing through the path other than the faulty end node, the path alarm of all mark signals written first at the faulty end node is monitored, and the P-AIS is written again. This notifies the node that adds and drops the faulty path. This is performed by the path switching circuit 502 shown in FIG.

2.3 Switching Method FIG. 13 shows a path switching method using a path switching circuit when a cable is disconnected. Here, a switching method in a node having the node number n and the node number p is generally described.

This method is slightly different depending on whether n is an even number or an odd number. What is different is the number of longest paths, the method of setting left and right rotations of the associated faulty path, and the method of setting the path to be switched. However, they are basically equivalent,
Only the range of the inequalities is different.

Here, in order to distinguish a path, a destination number is given to the path, and this is set as the number of the path.

In this method, an absolute number layer and a relative number layer are provided. By processing path switching in the relative number layer, one algorithm can be used for all nodes. This method is illustrated in FIG.
Shown in

The method shown in FIG. 14 will be described with reference to FIG. 6. The signal terminating device 605 detects a path alarm such as a path AIS or a path BIP described in a path overhead or the like. The failure path identification circuit 604 identifies a communication disabled path in the relative number layer based on the detection of the path alarm of the signal terminating device 605, and drives the path protection switch 601. In the path protection switch 601, the fault path identification circuit 60
4 actually drives the switch.

FIG. 15 shows a specific operation when n = 5. Here, to avoid confusion, the physical numbers of the nodes are A to
Expressed by E. It is assumed that nodes A to E are arranged clockwise, and the operation at node D will be described. Here, the relative numbers of the nodes A to E viewed from the node D are “3”, “4”, “5”, “1”, and “2”, respectively.

First, it is assumed that the cable is disconnected between the nodes C and D as shown in FIG. At this time, the signal termination device of the node D detects a path alarm for the path (path “3”) extending to the node C and the path extending to the node B (path “2”). This unreachable path is
Looking at the relative number layer, the path is “4” and the path is “5”. This identification is performed by a fault path identification circuit. Since these paths are both clockwise, the path protection switch switches clockwise. As a result, the fault is recovered.

Next, it is assumed that the cable between nodes B and C is disconnected as shown in FIG. At this time, the signal termination device of the node D detects a path alarm for the path (path “2”) extending to the node B. This incommunicable path is path “4” in the relative number layer. Since this path is counterclockwise, the path protection switch switches clockwise and the fault is recovered.

As shown in FIG. 15C, when the cable between the nodes A and B is disconnected, the path alarm is not detected by the signal termination device of the node D. Therefore, there is no path to be repaired as the node D.

Next, it is assumed that the cable between nodes A and D is disconnected as shown in FIG. At this time, the signal termination device of the node D detects a path alarm for the path (path “1”) extending to the node A. This uncommunicable path is path “3” when viewed from the relative number layer. Since this path is clockwise, the path protection switch is turned counterclockwise, and the fault is recovered.

Next, it is assumed that the cable between the nodes D and E is disconnected as shown in FIG. At this time, in the signal termination device of the node D, a path alarm is detected for the path (path "1") extending to the node A and the path (path "5") extending to the node E. The incommunicable paths are the path “3” and the path “2” in the relative number layer. Since these paths are clockwise, the path protection switch switches them counterclockwise, and the fault is recovered.

Here, in the case where n = 5, it has been described that all paths can be rescued for all cable breaks. This method can also relieve a path in the event of a node failure.

2.4 Transmission Capacity Reusable by This Path Switching Next, the transmission capacity reusable by this method will be described. According to the path setting described above, the standby system is normally empty. Therefore, in normal times, 10G
There will be a spare with a bit / s transmission capacity. By utilizing this, it is also possible to provide a low priority service. However, this service is stopped when the cable is disconnected.

By such path switching, the conventional S
The transmission path can be used more effectively than the transmission path switching method in which the ONET bidirectional ring switches between working and standby at the failure end when a failure occurs. FIG. 16 shows the difference between the reusable transmission capacity according to the present invention and the reusable transmission capacity when the SONET bidirectional ring switches the transmission path at the failure end. It can be seen that the difference increases as the number of nodes increases.

3. Time Slot The relationship between a frame and a time slot multiplexed by bytes will be described with reference to FIG. 17 and FIG. 18 using STM-4 as an example. n ^2/8 sheets when n is an even number, if n is an odd number (n ²
-1) Byte-multiplex / 8 STM-4 frames.
When this is read out temporally in byte units as indicated by arrows in FIG. 17, a signal as shown in FIG. 18 is obtained. FIG. 18 shows the case where n is an even number. The assignment of time slots for this signal will be described below.

In the present invention, it is assumed that the transmission capacity of the bidirectional ring transmission line is minimized. Therefore, the time slot allocation of the working ring network is considered as follows. In other words, the time slot occupied by a signal from one node to another node is not fixed. Assignment is made to be the same. In this way, transmission capacity is greatly saved. For example, a fixed time slot requires a capacity for all paths in any part of the ring transmission network. That is, assuming that the number of nodes is n, the transmission capacity is required to be n (n-1) / 2. This is because a band is secured for a signal that does not pass, and the fixed time slot method is wasteful. On the other hand, in the present embodiment, when the transmission capacity is n is an odd number, (n ² −1)
/ 8, n it may be n ^2/8 in the case of an even number.

As a simple example, FIG. 19 shows a case where the number of nodes is n = 5. In this example, the signals received at each node are the first two in the time series, and the passing signal is the last one. At the time of insertion, among signals to be inserted, a signal addressed to an adjacent node is placed at the top, and a signal addressed to two adjacent nodes is placed at the end. As illustrated, at the node A, the signal from the immediately preceding node E to the node A is the head, the signal from the immediately preceding node D to the node A is the middle, and the signal from the immediately preceding node E to the immediately preceding node E is one. The passing signal to the node B is the last.
The signal processing of the node A receives the signals of the first two time-series positions, and inserts the signal to the next node, the node B, and the signal to the next node D at the beginning and the end, respectively. I do. The time slot of the signal passing through node A is converted from the third to the second. The signal generated by the node A is transmitted to the node B. Node B
, The first two signals (AB, EB) are received, the passing signal (AC) is shifted from the third time slot to the second time slot, and the signal destined for node C is The signal going to the node D is inserted at the beginning and at the end.
In this way, the time slot allocation seen from each node on the ring transmission network becomes general in the ring, and the transmission capacity is the minimum of three paths ((n ² -1) /
8). As shown, the first time slot is reused between nodes E and A and between nodes A and B. Similarly, the second timeslots are nodes D and A
The third time slot is reused between the nodes E and B and between the nodes A and C.

This will be described more generally. In order to be able to cope with any kind of cable break, a time slot switching device (TSI, ti
me slot interchanger) is required. In the following, a description will be given of a method of allocating a time slot to the active system (this is unchanged even when the cable is disconnected) and a method of replacing the arbitrary cable by the spare time slot switching device. Here, it is assumed that a multiplexing method for performing time division multiplexing in byte units is used. The time slot allocation method described here is based on a distributed rearrangement scheme (T-
H Wu et al., IEEE J. Select.Areas Comm., Vol. 10, N
o.9, 1459, 1992).

3.1 Allocation of Working Time Slot 3.1.1 When Number of Nodes is Odd N is the number of nodes. The paths inserted and branched by each node are (n-1) / 2 paths in each of the left and right directions. Since the transmission capacity is (n ² -1) / 8, the number of paths passing through the node is (n-1) (n-3) / 8.

On the receiving side, (n-1) /
The signals included in up to two paths are branched one byte at a time. This is common to the clockwise receiving system and the counterclockwise receiving system.
Thus, the time slot allocation on the receiving side is simple. This is shown in FIG. Here, one slot is in units of bytes. When the time slot on the receiving side is clockwise (reception from the node with the relative number “n”), the byte group to the node “1” including (n−1) / 2 slots at the beginning, and the next ( A byte group for node “2” consisting of (n−1) / 2−1 pieces and a byte group for node “k” are made up of (n + 1) / 2-k slots. The last byte group is (n-1) / 2, and is composed of one slot. When counterclockwise, the beginning is (n-
1) Byte group to node "1" consisting of / 2 slots, next byte group to node "n" consisting of (n-1) / 2-1, and byte group to node "k" Is k-
It consists of (n + 3) / 2 slots. The last byte group is for the node “(n + 5) / 2” and is composed of one slot.

In the clockwise transmission system (transmission in the direction of node “2”), the path farthest from the end of the frame received by the node having the relative number “1” is (n + 1) /
Insert a two-way byte. 2 counting from this insertion position
Insert the byte of the next (n-1) / 2 bound path before this one. Similarly, the bytes of the path for the node “k” are counted from the insertion position at the back (n + 3) / 2−2.
Insert at the kth previous position. The byte of the path to the node “2”, which is the closest path, is inserted (n−1) / 2 before the byte inserted to the node “3”, that is, at the beginning. The clockwise transmission system time slot is composed of a (n-1) / 2 headed byte group for node "2" (at the head of which a byte of the path from node "1" is transmitted), Is a byte group for node “3” consisting of (n−3) / 2 (the head of which transmits the byte of the path from node “1”), and the byte group for node “k” is (n + 1) ) / 2-k bytes. The last byte group is a byte group for the node "(n + 1) / 2", and is composed of one slot.

In the counterclockwise transmission system (transmission in the direction of the node “n”), the byte of the path to the node “(n + 3) / 2” which is the farthest path from the end of the frame passing through the node “1” Insert The byte of the path to the next farthest node “(n + 5) / 2” is inserted second before counting from this insertion position. In this way, the byte of the path to the node "k" is inserted at the k- (n + 1) / 2-th previous position counted from the later insertion position. The byte of the path to the node “n” that is the closest path is counted from the insertion position of the byte to the node “n−1” (n
-1) Insert at the 2nd, that is, at the beginning. The time slot of the counterclockwise transmission system is composed of (n-1) / number of bytes heading to node "n" (the first byte transmits the bytes of the path from node "1"), followed by ( n-
3) A byte group destined for node "n-1" consisting of / 2 (the head of which transmits the byte of the path from node "1"), and the byte group destined for node "k" is (n-
1) It becomes a byte group consisting of / 2-n + k bytes. The tail is a byte group for the node "(n + 3) / 2", which is composed of one byte.

3.1.2 When Node Number n is Even Here, it is assumed that CP is clockwise. Let n be the number of nodes. It is assumed that n is an even number and n / 2 is an odd number. n
Depending on whether // 2 is an even number or an odd number, there is a difference as to whether or not the longest path CP passes through the same route for sending and receiving, and thus needs to be distinguished.
The number of paths at which the node with the right-handed CP branches is n / 2−1 in the clockwise receiving system and n / 2 in the counterclockwise receiving system. The number of paths to be inserted is n / 2 in the clockwise transmission system, and n / 2-1 in the counterclockwise transmission system. The number of paths (n / 2) branching from the total number of paths arriving (n ² / 2−1 / 2) in the clockwise system is the number of paths that pass through the node that is clockwise in the CP.
−1 is subtracted, which is (n ² −2) / 8.
^2/2 + 1/2 Pull n / 2 from the (n ² -2) / 8.

FIG. 21 shows the assignment of the working time slot clockwise to the CP when the number of nodes n is even and n / 2 is odd.

The clockwise receiving system branches the first n / 2-1 slots. The time slot for clockwise reception is n /
2-1 byte group for node "1", next is n / 2-
One byte group for node "2", the next byte group for n / 2-3 node "3", the next byte group for n / 2-3 node "4", and so on. In addition, the number of time slots in which two adjacent byte groups are paid out is equal to or different from each other. The byte group for node "k (odd)" is composed of n / 2-k time slots. The byte group for node "m (even number)" is n / 2
-M + 1 slots.

The clockwise transmission system is somewhat more complicated than the reception system. Node “n / 2” which is the path farthest from node “1”
The n bytes of the path going to “+1” are inserted at the end of the time slot. A byte for the node “n / 2” is inserted at the position immediately before that. A byte for the node "n / 2-1" is inserted three times before this insertion position. In this way, the path for the node “k (odd number)” is inserted at the position n / 2−k + 1 before the counting from the rear insertion position. The byte for the node “m (even number)” is inserted at a position n / 2−m + 2 before the byte insertion position at the rear. Therefore, the byte bound for node “2” is inserted n / 2 before the byte insertion position bound for node “3”, that is, inserted at the beginning. The clockwise transmission system time slot is headed by a byte group consisting of n / 2 time slots destined for node "2", followed by a byte group destined for node "3" consisting of n / 2-2 slots. Become. The byte group for node “k (odd)” is composed of n / 2−k + 1 time slots. The byte group for the node “m (even number)” is n / 2−
It consists of m + 2 time slots. The byte group destined for the node “n / 2 + 1”, which is the longest path, consists of one last time slot.

FIG. 22 shows the time slot assignment of the working system in the counterclockwise direction of the CP when the number of nodes n is even and n / 2 is odd.

The counterclockwise receiving system branches the first n / 2 slots. The time slot of the counterclockwise receiving system is a byte group for n / 2 nodes “1”, a byte group for n / 2−2 nodes “n” next, and a next n / 2-2 node “n”. Byte group for node "n-1", next is n / 2-4
For example, the number of time slots in which two adjacent byte groups are paid out is equal to or different from each other, such as a byte group directed to a plurality of nodes “n−2”. The byte group for the node “k (odd number)” is composed of −n / 2 + k−1 slots. The byte group for the node “m (even number)” is composed of −n / 2 + m−2 slots. The last byte group is for the node “n / 2 + 2”, and is composed of one slot.

In the case of the counterclockwise transmission system, the byte of the path to the node “n / 2 + 2”, which is the farthest path from the node “1”, is inserted second from the end of the time slot.
A byte for the node “n / 2 + 3” is inserted at a position two places before that. Four nodes before this insertion position, the node "n / 2
Insert a byte bound for "+4". In this way, the byte for the node "k (odd number)" is inserted at a position -n / 2 + k before counting from the later insertion position. Node "m
(Even number) ”bytes-
Insert at n / 2-m-1 previous position. Therefore, the byte destined for node “n” is inserted n / 2-1 before the position where the byte destined for node “3” is inserted, that is, inserted at the head. The time slot of the counterclockwise transmission system is a byte group consisting of n / 2−1 slots toward the node “n” at the beginning, and a node “n” consisting of n / 2 slots after the byte group.
-1 ". The byte group for node "k (odd)" is composed of -n / 2 + k time slots. The byte group for node “m (even number)” is −n / 2 +
It consists of m-1 time slots. The byte group for the node “n / 2 + 2”, which is the farthest path, includes the last two time slots.

As described above, even when n is an even number and n / 2 is an odd number, the working time slot can be determined in both the case of clockwise rotation of the CP and the case of clockwise rotation of the CP. This is shown in FIG. Similarly, when n is an even number and n / 2 is an even number, the time slot of the active system can be set in both the clockwise direction and the counterclockwise direction of the CP. These are summarized in Table 1.

[0091]

[Table 1]

3.2 Reserve Time Slot Assignment Next, reserve time slot assignment will be described. As described above, the standby system is empty in normal times, and is switched to the standby system by the path switching circuit when any cable is disconnected. In the following, a method of allocating a spare time slot when one of the cables is disconnected, that is, a method of replacing the time slot by a time slot switching device (TSI) will be described. In the following description, the smallest one among the path numbers identified by the failure identification circuit is S, the largest one is L, and the number of failed paths is F.

3.2.1 When the Number of Nodes is Odd Number FIG. 23 is a diagram showing the time slot allocation of the standby system when the number of nodes n is odd, and (a) is set to the node "2" side. If the cable breaks for the path,
(B) shows a case where the cable is disconnected for the path set on the node “n” side.

The path to be rescued when the cable is disconnected on the node "2" side is the clockwise path of the active system.
The “clockwise path” is clockwise on the transmitting side, but counterclockwise on the receiving side. Therefore, in the standby system, the receiving side is clockwise and the transmitting side is counterclockwise. In the standby system, these paths are not received counterclockwise or transmitted clockwise. Such signals are passing signals and do not perform any processing. Here, the path to be rescued is the path identified by the failed path identification circuit.

The standby system is a counterclockwise receiving system, and the number of fault paths F must be dropped and inserted. The method of branching is the same as in the case of the active system, and a byte group having F slots counted from the head is branched. Of the F bytes to the node "1", the leading byte is the path from the node "(n + 1) / 2" which is the closest path on the spare route to the node "1" among the paths to be rescued. Bytes. The last byte is a byte of a path from the node “S”, which is the farthest path on the backup route among the paths to be relieved, to the node “1”.

The processing of the transmission time slot is performed as follows. Of the paths to be rescued, the bytes of the path from node “1”, which is the farthest path on the backup route, to node “S” are inserted into the (S−1) -th slot from the end. The byte of the next distant path to the node “S + 1” is inserted into the (S−1) th slot counted from the insertion position. In the standby system, the interval from the rear insertion position to the new insertion position is constant regardless of the destination. Therefore, the byte of the path to the node “(n + 1) / 2” which is the closest path on the backup route is:
It is also inserted into the S-1 slot from the rear insertion position.

The path to be rescued when the cable is disconnected on the node "n" side is the path that was counterclockwise in the active system, the transmission side is counterclockwise, and the reception side is clockwise. Therefore, in the standby system, the receiving side is counterclockwise and the transmitting side is clockwise. The standby system does not receive these paths clockwise or transmit them counterclockwise. Such signals are passing signals and do not perform any processing.

The number of paths to be relieved is F, and branching is performed up to F from the top. The head of the branched byte group is the byte of the path from the nearest node on the spare route in the path to be rescued, and the node “(n + 3) /
2 "to the node" 1 ". The last byte is the byte of the path from the node farthest on the backup route, and is the byte of the path from node “L” to node “1”.

The time slot on the transmitting side is processed as follows. Of the paths to be rescued, the bytes of the path from node “1”, which is the farthest path on the backup route, to node “L” are inserted into the (n−L + 1) th slot from the end. The byte of the path to the node “L−1”, which is the next distant path, is inserted into the (n−L + 1) th slot similarly counted from the insertion position. In the standby system, the interval from the rear insertion position to the new insertion position is constant regardless of the destination. Therefore, the byte of the path to the node “(n + 3) / 2”, which is the closest path on the backup route, is also inserted into the (n−L + 1) th slot from the subsequent insertion position.

3.2.2 When Number of Nodes is Even FIG. 24 is a diagram showing the time slot allocation of the standby system when the number of nodes n is even. FIG. , (B) shows a case where the cable is disconnected on the node “n” side. Here, the case of clockwise rotation of the CP will be described as an example. However, in the case of clockwise rotation of the CP, the left and right sides may be reversed.

When the cable on the node "2" side is disconnected, the receiving side turns clockwise and the transmitting side turns counterclockwise in the standby system to rescue the clockwise path of the active system. The number of paths that must be dropped and inserted is F.

The method of branching in the receiving system is the same as in the case of the working system, and a byte group having F slots counted from the head is branched. Of the F bytes to the node "1", the leading byte is the path from the node "(n + 1) / 2" which is the closest path on the spare route to the node "1" among the paths to be rescued. Bytes. The last byte is a byte of a path from the node “S”, which is the farthest path on the backup route among the paths to be relieved, to the node “1”.

The time slot of the transmission system is processed as follows. Of the paths to be rescued, the bytes of the path from node “1”, which is the farthest path on the backup route, to node “S” are inserted into the (S−1) -th slot from the end. The byte of the next distant path to the node “S + 1” is inserted into the (S−1) th slot counted from the insertion position. In the standby system, the interval from the rear insertion position to the new insertion position is constant regardless of the destination. Therefore, the byte of the path to the node “n / 2 + 1”, which is the closest path on the backup route, is also inserted into the (S−1) th slot from the later insertion position.

When the cable is cut off at the node "n", the receiving side turns left and the transmitting side turns right in the standby system. The number of passes to be relieved is F.

On the receiving side, up to F branches are counted from the head. The head of the split byte group is the byte of the path from the nearest node on the spare route in the path to be rescued, and is from node “n / 2 + 2” to node “1”.
The path to the byte. The tail is the byte of the path from the farthest node on the backup route, that is, the byte of the path from node "L" to node "1".

The time slot on the transmitting side is processed as follows. Of the paths to be rescued, the bytes of the path from node “1”, which is the farthest path on the backup route, to node “L” are inserted into the (n−L + 1) th slot from the end. The byte of the path to the node “L−1”, which is the next distant path, is inserted into the (n−L + 1) th slot similarly counted from the insertion position. The byte of the path to node “n / 2 + 2”, which is the closest path on the backup route, is
It is also inserted into the (n−L + 1) th slot from the rear insertion position.

The assignment of the working and protection time slots in the event of a cable break on any of the rings has been described above. Although such time slot assignment is performed by the time slot exchange device, this may be realized by hardware or software.

4 Path Protection Switch Next, the configuration of the path protection switch will be described. FIG. 25 shows a configuration example of a path protection switch when the number of nodes n = 5.

The path protection switch includes switches SWW1 to SWW4 for inserting signals from the own node to nodes "2" to "5" into the working path, and switches for signals from nodes "2" to "5" to work. Switches SWW5 to SWW8 for branching off the path, switches SWP1 to SWP4 for inserting signals from the own node to nodes “2” to “5” into the backup path, and nodes “2” to
SW for splitting the signal from "5" through the backup path
P5 to SWP8 and time slot exchange devices SWT1 to SWT for exchanging time slots in the standby system
4 is provided.

The time slot exchange devices SWT1 to SWT5 are
In this example, it is constituted by a space switch that does not include a buffer. An external buffer may be provided.

In this example, the working time slot is assigned by wiring between ports. Multiplexing / demultiplexing devices are arranged on the input side and the output side of the path protection switch. In the drawing, each port is shown as being multiplexed in time series from the lower port.

When the number of nodes is n = 5, the number of paths passing through each node is one for transmission and reception, and the number of paths to be inserted and branched is two. Therefore, the working system needs a transmission capacity that is three times the transmission / reception capacity of itself.

In this configuration example, the time slot switching device SWT2,
SWT3 is provided. This is to ensure that the backup traffic passing through the own node and the backup traffic branching off at the time of the failure are effectively reduced to the required minimum capacity in preparation for any cable disconnection. If n = 5, the spare time slots can be replaced by four 2 × 2 space switches.

FIG. 25 shows a state where all the switches are off, that is, a case where no cable break has occurred. Table 2 shows the switches SWW in this configuration example.
1 shows logical value matrices of 1 to SWW8, SWP1 to SWP8, and time slot exchange devices SWT1 to SWT4. This matrix is stored as a table in the fault path identification circuit. Although there are 20 switches including the time slot switching devices SWT1 to SWT4, some of these switches are interlocked with each other, and the number of independent switches is 8.

[0115]

[Table 2] The self-healing function when the cable is disconnected will be described based on the logical value matrix shown in Table 2. The following description is based on the relative number layer. Here, the switch SWW
1, SWP1, SWW5 and SWP5 operate in conjunction with each other, and are hereinafter referred to as "first switch group". Similarly, switches SWW2, SWP2, SWW6 and S
WP6 is “second switch group”, switches SWW3, S
WP3, SWW7 and SWP7 are referred to as “third switch group”, switches SWW4, SWP4, SWW8 and S
WP8 is referred to as a “fourth switch group”.

The paths “2” and “3” (node “2”,
When an alarm occurs on the path between "3"), the first switch group and the second switch group are turned on. Therefore, the paths to the nodes “2” and “3” are switched to the left in FIG. 25, and the nodes “2” and “3” are switched.
The path coming from you to yourself will also come from the left. Here, the spare time slot is shown in FIG.
5, the receiving system from the left and the transmitting system to the left become active. The time slots received from the left are sequentially (FIG. 25).
, No signal, a signal from node “3” to “1”, and a signal from node “2” to “1”.

When only the path "3" is an alarm, the second switch group and the time slot switching device SWT1,
Switch between SWT2 and SWT3. Only "3" can be switched. At this time, the time slots received from the left side of FIG.
A signal from node “3” to “1”, a signal from node “4” to “2”, and a signal from node “3” to “2”. The time slot to be transmitted in the right direction in FIG. 25 is only a passing signal. FIG.
The time slots received from the right side of 5 are only pass-through signals, in that order: none, signal from node "2" to "4", signal from node "2" to "3". The time slots transmitted in the left direction in FIG. 25 are, in order, a signal from node “2” to “4”, a signal from node “1” to “3”, and a signal from node “2” to “3”. is there.

When the cable is disconnected between the nodes "3" and "4", there is no path alarm and no switching is performed. Therefore, all the standby systems are passed signals. FIG.
The time slots from the left side to the right side of 5 are the signals from node “4” to “3” and the nodes “5” to “3”, respectively.
, And the signal from node “4” to “3”. The time slots from the right to the left are, in order, a signal from node “3” to “5”, a signal from node “2” to “4”, and a signal from node “3” to “4”.

When only the path "4" is an alarm, the third switch group and the time slot switching device SWT2,
Switch between SWT3 and SWT4. This allows
In the current use, the path “4” output to the left in FIG.
Is output to the right. In the standby system,
The time slots received from the left side of No. 5 are only passing signals, which are in turn, none, a signal from node “5” to “3”, and a signal from node “5” to “4”. The time slots transmitted to the right in FIG. 25 are, in order, a signal from node “5” to “3”, a signal from node “1” to “4”, and a signal from node “5” to “4”. is there. FIG.
The time slots received from the right side of No. 5 are, in order, a signal from node “4” to “1”, and a signal from node “3” to “5”.
, And the signal from node “4” to “5”. The time slot to be transmitted in the left direction in FIG. 25 is only a passing signal, none, a signal from node “3” to “5”, and a signal from node “4” to “5”.

When the paths "4" and "5" are alarms, the third and fourth switch groups are switched. As a result, the directions of the paths “4” and “5” are switched. Time slots transmitted to the right in FIG. 25 in the standby system are, in order, a signal from node “1” to “4” and a signal from node “1” to “5”. The time slots received from the right side of FIG. 25 are, in order, none, a signal from node “4” to “1”, and a signal from node “5” to “1”.

FIGS. 26 and 27 show examples of the configuration of the path protection switch when the number of nodes n = 5. When n is an even number, the configuration is slightly different depending on whether the longest path CP is clockwise or counterclockwise. FIG. 26 shows the clockwise direction of the CP (the path to the node “6” passes through the nodes “2” to “5”), and FIG. 27 shows the counterclockwise direction of the CP (the path to the node “6” turns the nodes “10” to “7”). Via). In any case, the switches SWW1 to SWW for inserting signals from the own node to the nodes “2” to “10” into the working path
W9 and switches SWW10 to SWW15 for branching signals from nodes “2” to “10” from the working path
Switches SWP1 to SWP9 for inserting signals from the own node to nodes “2” to “10” into the backup path
And SWP10 to SWP15 for branching signals from the nodes “2” to “10” from the backup path. Although the spare time slot switching device is omitted here, an external buffer may be used as in the case where the number of nodes is n = 5, or a space switch may be used. .

Tables 3 and 4 show logical value matrices for driving the path protection switches shown in FIGS. 26 and 27, that is, tables stored in the faulty path identification circuit.

[0123]

[Table 3]

[0124]

[Table 4]

FIG. 28 shows a configuration example of a general path protection switch when the number of nodes is an odd number n. Also,
Table 5 shows the logical value matrix. When the number of nodes is odd,
The total number of required switches is 4n-4, but the number of independent switches is n-1. In Table 5, the column “0” in the column of the path alarm is the node “(n + 1) / 2”,
This includes the case where the cable between “(n + 3) / 2” is disconnected, and even in this case, it is not necessary to switch the path at the node “1”.

[0126]

[Table 5]

[0127] 5. Wavelength multiplexing bidirectional transmission FIGS. 29 and 30 show an example of a node configuration for performing bidirectional communication with one fiber by wavelength multiplexing of two waves. FIG. 29 shows a transmitting unit, and FIG. 30 shows a receiving unit.

In this case, the ring transmission line is composed of two working and protection fibers, and each node has four lasers 291 to 293 and a path setting circuit 29 in the transmitting section.
5 and the receiver includes light receivers 301 to 304 and a signal processing circuit 305.

The transmitting section sends signals in mutually opposite directions to the working fiber using the wavelengths λ1 and λ2. Further, the two wavelengths are respectively transmitted to the protection fiber in a direction opposite to that of the working fiber. That is, the laser 291 sends out the signal light of the wavelength λ1 in the first direction of the working fiber. The laser 292 sends out the signal light having the wavelength λ2 in a second direction opposite to the first direction of the working fiber. In addition, the laser 293 sends out the signal light having the wavelength λ1 in the second direction of the standby fiber. The laser 294 sends out the signal light of the wavelength λ2 in the first direction of the standby fiber.

In the receiving section, the light receiving device 301 receives the wavelength λ1 transmitted through the working fiber in the first direction, and the light receiving device 302 receives the wavelength λ2 transmitted through the working fiber in the second direction. The light receiver 303 receives the wavelength λ1 transmitted through the spare fiber in the second direction, and the light receiver 304 receives the wavelength λ2 transmitted through the working fiber in the second direction. Therefore, the receiving unit always receives both the working and protection signals. However,
In normal times, no signal flows through the spare ring.

In this configuration example, the number of fibers is two including the spare fiber. The wavelength is set for each of the left and right directions of the path. That is, in order to perform bidirectional transmission in the left and right directions, the left and right rotation directions are sorted according to the path. At this time, an effective path of the fiber is realized by selecting a path closer to the target node from the two paths extending left and right.

The setting of the wavelength for each path is performed as follows. That is, in the working ring, the wavelength λ1 is used for the signal transmitted in the first direction, and the wavelength λ2 is used for the signal transmitted in the second direction opposite to this direction. Conversely, the spare ring uses the wavelength λ2 for the signal transmitted in the first direction and the wavelength λ1 for the signal transmitted in the second direction.

FIG. 31 shows an example of a configuration using a circulator for two-way communication. Circulators 311-
314 propagates the signal light in only one direction, and FIG.
The transmitter and the receiver shown at 30 can be combined. FIG. 31 further includes a path switching circuit 501,
10Gbit / with multiplexing device or demultiplexing device
The s transmission line terminating device 311, the path setting circuit 502, and the 600 Mbit / s transmission line terminating device 312 for terminating the transmission line between the outside of the ring are shown.

FIG. 32 shows the relationship between the transmission delay and the recovery rate when a single cable is disconnected, and FIG. 33 shows the relationship between the transmission delay and the recovery rate when a composite cable is disconnected. Here, the horizontal axis is the transmission delay time in units of the time when each node branches and inserts.
Here, the number of nodes n = 51. The processing time up to switching can be reduced by storing a matrix table in advance and automatically performing path switching using hardware.

Table 6 shows the comparison results of the spare transmission capacity due to path switching on the transmitting side, the transmission delay at the time of restoration, and the restoration rate in the case of a complex failure, as compared with the case where the conventional self-healing is used. . The method of the present invention is generally superior to conventional transmission line switching at the failure end and path switching at the receiving side.

[0136]

[Table 6]

[0137]

As described above, the ring transmission apparatus of the present invention can form a logical mesh network while being a physical ring transmission path, and can be adapted to future high-speed and broadband services. Can be. Also, the present invention relates to SD
H and has high reliability and operability. The node configuration at this time may be a device configuration for dropping and inserting an arbitrary signal, and the number of required signal termination devices may be small.

Further, when the cable is disconnected, the path is switched on the transmitting side, and only the path that cannot communicate is identified, the direction of the path is reversed, and a path is established with a new backup route.
As a result, mesh communication between all nodes can be performed without all nodes being restricted by overflow calls due to congestion. Therefore, all nodes can be rescued without restricting the number of nodes or the current transmission / reception capacity of each node in preparation for cable disconnection.

The time required for path switching is the same as that of the conventional SO.
It is comparable to a NET bidirectional ring network and is sufficiently fast.

Further, regarding the number assigned to the node and the processing based on the number, an absolute number layer that assigns a serial number over the entire network and performs based on the number, and each node always sets its own node number to “1” It is divided into a relative number layer that performs processing based on the number, and path switching in the event of cable disconnection or node failure is processed in the relative number layer. Thus, the processing algorithm is unified in each node. Further, a new reusable transmission capacity is provided for the working system and the standby system.

By arranging the time slots of the working system and the protection system of the signal add / drop circuit of each node in a time-series order in the spatial arrangement of the nodes, mesh communication between all nodes can be performed without overflowing calls. In the event of any cable break or node failure, all nodes can be made rescuable.

As described above, according to the present invention, the problems that occur when the conventional network is used for the ring network, namely, the demand for connectivity that differs for each service, the problem of recovery from a failure when the cable is completely cut off, the economy, The problem of the number of terminal systems, the problem of the effective transmission capacity, and the problem of the number of fiber cores can be solved.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a ring transmission device according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a traffic pattern according to the first embodiment.

FIG. 3 is a diagram showing a configuration of a ring transmission device according to a second embodiment of the present invention.

FIG. 4 is a diagram showing a traffic pattern according to the second embodiment.

FIG. 5 is a block diagram showing an example of a signal insertion / branch circuit for performing multiplexing and transmission / reception at each node.

FIG. 6 is a diagram showing a more detailed configuration of a signal insertion / branching circuit.

FIG. 7 is a diagram illustrating a transmission capacity required for a spare ring when a cable break occurs at one location in a network having n = 5 nodes.

FIG. 8 is a diagram showing a capacity required for a spare ring when all nodes are rescued when one cable is completely disconnected.

FIG. 9 is a diagram showing an example of setting a path when the number n of nodes is an odd number;

FIG. 10 is a diagram showing an example of setting a path when the number n of nodes is an even number;

FIG. 11 is a diagram showing a method for setting the path to the left and right.

FIG. 12 is a diagram illustrating a relationship between detection of signal interruption and path switching.

FIG. 13 is a diagram showing a path switching method when a cable is disconnected.

FIG. 14 is a diagram showing a relationship between an absolute number layer and a relative number layer.

FIG. 15 is a diagram showing a specific path switching operation when the number of nodes is n = 5.

FIG. 16 is a diagram showing a difference between a reusable transmission capacity due to the path switching and a reusable transmission capacity when the SONET bidirectional ring performs transmission path switching at a failure end.

FIG. 17 is a diagram illustrating a relationship between a frame and a time slot multiplexed by bytes, and is a diagram illustrating a frame configuration.

FIG. 18 is a diagram illustrating a relationship between a frame and byte-multiplexed time slots, and a diagram illustrating a time slot arrangement.

FIG. 19 is a diagram showing time slot allocation when the number of nodes is n = 5.

FIG. 20 is a diagram showing time slot allocation on the receiving side.

FIG. 21 is a diagram illustrating the assignment of a working time slot clockwise to the CP when the number of nodes n is even and n / 2 is odd;

FIG. 22 is a diagram showing the time slot allocation of the working system in the counterclockwise direction of the CP when the number of nodes n is an even number and n / 2 is an odd number.

FIG. 23 is a diagram showing a time slot allocation of a standby system when the number of nodes n is an odd number.

FIG. 24 is a diagram showing a time slot allocation of a standby system when the number of nodes n is an even number.

FIG. 25 is a diagram illustrating a configuration example of a path protection switch when the number of nodes is n = 5.

FIG. 26 is a configuration example of a path protection switch when the number of nodes is n = 5, showing a configuration in a case where a path to a node “6” passes through nodes “2” to “5”.

FIG. 27 is a configuration example of a path protection switch when the number of nodes is n = 5, and shows a configuration in a case where a path to a node “6” passes through nodes “10” to “7”.

FIG. 28 is a diagram illustrating a configuration example of a general path protection switch when the number of nodes is an odd number n.

FIG. 29 is a diagram illustrating an example of a node configuration for performing bidirectional communication using one fiber by two-wavelength wavelength multiplexing, and is a diagram illustrating a configuration of a transmission unit.

FIG. 30 is a diagram illustrating an example of a node configuration for performing bidirectional communication using one fiber by two-wavelength wavelength multiplexing, and is a diagram illustrating a configuration of a receiving unit.

FIG. 31 is a diagram showing a configuration example using a circulator for bidirectional transmission and reception.

FIG. 32 is a diagram illustrating a relationship between a transmission delay and a recovery rate when a single cable is disconnected.

FIG. 33 is a diagram showing a relationship between a transmission delay and a recovery rate when the composite cable is disconnected.

FIG. 34 is a diagram showing an example of a block configuration of a conventional SDH large-capacity optical transmission network.

FIG. 35 is a diagram showing a configuration example of a conventional physical mesh network.

FIG. 36 is a diagram showing a configuration example of a SONET one-way ring network.

FIG. 37 is a diagram showing a configuration example of a SONET bidirectional ring network.

FIG. 38 is a diagram for explaining a failure recovery method for the SONET one-way ring network, and showing path switching on the receiving side.

FIG. 39 is a diagram for explaining a failure recovery method for the SONET one-way ring network, and is a diagram showing transmission path switching.

FIG. 40 is a diagram for explaining a failure recovery method for the SONET bidirectional ring network, and showing path switching on the receiving side.

FIG. 41 is a diagram for explaining a failure recovery method for the SONET bidirectional ring network, and is a diagram showing transmission path switching.

FIG. 42 is a diagram showing an example of a node configuration in a physical mesh network when the number of nodes is 10.

FIG. 43 is a diagram showing the relationship between the number of nodes in the ring network and the transmission capacity of the working system in comparison between a unidirectional ring and a bidirectional ring.

[Explanation of symbols]

 10-14, 20-29 Node 16, 31 Optical fiber 17, 32 paths

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yukio Kobayashi 1-6-6 Uchisaiwaicho, Chiyoda-ku, Tokyo Nippon Telegraph and Telephone Corporation (72) Kiyoshi Nakagawa 1-1-6 Uchisaiwaicho, Chiyoda-ku, Tokyo Japan (56) References JP-A-62-214748 (JP, A) JP-A-5-63698 (JP, A) JP-A-6-164615 (JP, A) JP-A-61-127247 ( JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) H04L 12/42-12/437

Claims (3)

(57) [Claims] 1. A plurality of nodes for transmitting and receiving data,
A bidirectional ring transmission that connects these nodes in a ring
And a plurality of nodes each connected to one of the two-way ring transmission lines.
Working packet, which is a unit of line bundle for communicating with
Working path setting means for setting a path, and when a failure occurs in the bidirectional ring transmission path,
A failed path identification device that detects a working path that has been disconnected due to harm
And the working path according to the output of the failed path identifying means.
Set a backup path in the opposite direction to the bidirectional ring transmission path.
Backup path setting meansSee  The working path setting means sets each working path to the bidirectional path.
Set the shorter path length of the two directions of the ring transmission line
Means to form a logical mesh network between nodes
MIn a ring transmission device, Each path to each frame transmitted to the bidirectional ring transmission path
Means for inserting control data indicating the connection state of the The failed path identification means is a working path transmitted from its own node.
Means for detecting failure information of The backup path setting means is used for the working path transmitted by the own node.
Including means for setting a backup path in the opposite direction Specially
Sign Ring transmission device. 2. The plurality of nodes respectively: means for arranging a signal destined for each node propagating through the bidirectional ring transmission line in a time-series order in a spatial arrangement order of the respective nodes; Means for branching and receiving a signal at a time-series position addressed to the own node from a signal sequence destined for each node; and assigned so that each node on the bidirectional ring transmission path can perform reception processing in the same time-series. Means for inserting a transmission signal destined for each node at the time series position of the destination node, and a signal passing through the own node so that each node on the bidirectional ring transmission path can perform reception processing in the same time series. ring transmission system according to claim 1, further comprising a stream conversion means when reusing sequence position when the time signal between the converted series location nodes are assigned to occupy the. 3. The protection path setting means includes means for switching a signal to be branched and a signal to be inserted at the own node from a working path to a protection path, and a protection path setting means for enabling each node to perform processing in the same time series. Means for switching the order of the signal of the backup path passing through and the signal inserted by the own node into the backup path, and storage means for accumulating operation information of the switching means and the switching means in accordance with the failure state of the path. 3. The ring transmission device according to claim 1, further comprising: