JPH09284324A - Atm communication system using loop-shaped bus and its change-over method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To restrict the deterioration of transmission quality by providing a means for setting and controlling a start point and an end point in the respective plural nodes, setting and controlling the start point and the end point of a bus by means of transmission/reception of a control cell and re-constituting a system. SOLUTION: A cell transmitting part 5 receives a cell and, then, an RTG extracting part 15 extracts position information of the node in the transmission destination of the cell. A cell output direction selecting part 18 calculates the direction of a multiplex bus for outputting the cell based on mounting position information of a self node which is previously set in a self node mounting position information storing part 20 and a bus opening part information storing part 21 and extracted position information. A cell output direction selecting selector 19 uses information calculated in the selecting part 18 so as to write the cell in distributed queues 13 and 14 corresponding to the multiplex bus A2 or B3. A bus access part 8 access-controls the buses A2 and B3 and transmits the cell stored in the queues 13 and 14 to the bus A2 and B3 while adjusting traffic between the respective nodes.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of an ATM communication system for transmitting / receiving cells using a loop-shaped bidirectional bus.

[0002]

2. Description of the Related Art In an ATM communication system for transmitting and receiving cells by a plurality of communication nodes, various switches such as a space switch, a time switch and a bus switch are used for switching cells. Among these, the standardization of the configuration of the ATM communication system using the bus switch is in progress, and the Recommendation of the Institute of Electrical and Electronics Engineers (IEEE) 802.
The distributed matrix type dual bus (DQDB) system described in No. 6 is known. This system consists of two unidirectional buses having different transmission directions and a plurality of communication nodes, and a cell is connected from a certain communication node to an adjacent communication node and then to an adjacent communication node. Is transmitted by a unidirectional bus. Each communication node transmits by multiplexing cells on the bus when there is no cell transmitted by another communication node on this dual bus, and the cell addressed to the own communication node is transmitted from the bus. Separate reception is possible, and data transmission / reception between communication nodes can be performed at high speed. In addition, A using DQDB
In a TM communication system, two buses are physically connected in a loop shape, but each bus is provided with a logical bus start point (hereinafter referred to as a slot generator) and an end point to perform routing control. As a result, the cell is not discarded at the end of each bus and it does not return to the start. The start point and the end point can be set to arbitrary nodes.

As a loop network configuration in which DQDB is improved, the same applicant has proposed a configuration of a loop type communication network capable of easily executing network control, expansion and fault countermeasures in Japanese Patent Laid-Open No. 6-303248. This is to prepare an unused part of the bus (hereinafter referred to as a bus opening) by providing the start point and the end point of the looped bus to different nodes, and to make it possible to operate with the same network configuration at the time of failure and at the time of normal operation. is there. In addition, it is possible to add a node in an operating state by moving the opening of the bus with the configuration that always includes the bus opening.

Generally, when switching (system switching or network configuration switching) is performed in a communication network, instantaneous data interruption occurs at the time of switching and communication quality deteriorates. DQDB (including the improved loop network described above) Is no exception. In DQDB, when a node in the middle of a loop fails, it is necessary to reconfigure the position of the slot generator and reconfigure the bus so that it does not pass through the failed node. May not reach the target node and the cell is discarded. This cell discard is DQ
It occurs in all nodes in the DB whose use bus direction changes. Also, in IEEE Recommendation 802.6, D
As a method of sending cells from one node to another node using QDB, a method of sending cells in both directions and setting a sending direction for each connection in advance in order to reduce traffic and referencing the table Therefore, a method of transmitting cells to only one bus in the necessary direction is disclosed. With this method of sending cells to one bus,
From the two buses, select the bus that is not interrupted by the slot generator and the end point. However, since the position of the slot generator changes due to a failure or the like, it is necessary to reselect the direction of the bus to be used. Due to this reselection and switching, a large number of cells are discarded and the communication quality deteriorates. As a communication system for improving cell discard, there is a communication system described in Japanese Patent Application Laid-Open No. 7-107104 by the same applicant. This is because the cell output direction is logically calculated from the logical position of the bus opening (the position of the slot generator), its own node on the loop, and the logical position of the cell destination node at each node. The configuration is such that the cell output direction is conventionally determined by the processor and software, but the cell loss is not completely prevented.

Regarding the hitless switching of the ATM network, there is a configuration described in "Instantaneous path switching method in ATM network" (June 1993) on page 421 of the IEICE Transactions BI. . This shows a configuration in which a buffer that absorbs a transmission delay difference is provided in switching between the active system and the standby system and switching is performed without interruption for various networks such as ring networks and mesh networks. It is desirable to realize non-instantaneous switching of a network that is configured with only the active system as described above and has no backup system.

[0006]

SUMMARY OF THE INVENTION The problem to be solved by the present invention is that a failure or maintenance occurs in a communication system or communication network in which a plurality of communication nodes are connected to a loop-shaped bidirectional bus as described above. It is an object of the present invention to provide a communication system and a switching method capable of performing switching at high speed and preventing deterioration of transmission quality when switching networks or systems due to the above circumstances. Furthermore, in communication networks such as DQDB,
It is an object of the present invention to provide a communication system and a switching method suitable for reconfiguring a communication network by disconnecting a faulty node or a designated node at high speed without affecting other nodes.

Specifically, when the faulty node or the designated node is disconnected from the communication network and the communication network is reconfigured, the switching of the non-instantaneous interruption without the error of data or the discarding is performed at high speed. It is to provide a communication system to be executed and a hitless switching method with a simple configuration and procedure. Moreover,
Along with the above-mentioned switching, information about the network configuration such as the start and end points of the communication network of each node can be changed at high speed, and the communication network can be reconfigured without interruption to perform communication between nodes. It is to provide a method with a simple configuration and procedure.

Further, even when the non-instantaneous switching or the network reconfiguration is not possible, when the faulty node or transmission line is disconnected from the communication network and the communication network reconfiguration is executed,
It is an object of the present invention to provide a communication system and a high-speed switching method that perform high-speed switching to suppress data error and discard with a simple configuration and procedure. Moreover, in addition to the above switching, a communication system and a switching method which can change the information about the network configuration such as the start point and the end point of the communication network of each node at high speed to reconfigure the communication network and perform the communication between the nodes are simple. It is to be provided according to various configurations and procedures.

Further, even if the communication system or the communication network is in a state close to congestion, it does not depend on the traffic condition of the communication network. It is an object to provide a communication system capable of executing switching and network reconfiguration and a switching method with a simple configuration and procedure.

More specifically, in a communication system or communication network in which a plurality of communication nodes are connected to a loop-shaped bidirectional bus, non-interruptible switching, high-speed switching, and network or system reconstruction can be reliably executed. It is to provide a communication node with a simple configuration.

Further, it provides means for generating and transmitting information for performing switching and network or system reconfiguration at high speed and reliably, and further provides a communication node equipped with these means with a simple configuration. It is to be.

It is another object of the present invention to provide a procedure for transmitting the above information between the nodes and a procedure for controlling the communication node so that the switching without interruption and the high speed switching and the reconstruction of the network or the system can be surely executed.

A further problem to be solved by the present invention is to provide a concrete configuration and switching method of a communication system for surely realizing hitless switching and high-speed switching in a conventional communication system using DQDB. However, it is another object of the present invention to provide an improved DQDB system that prevents deterioration of transmission quality during switching or network reconfiguration. That is, a DQDB system that can perform switching and network / system reconfiguration without generating cell discard, or a DQDB system that can perform switching and network / system reconfiguration while suppressing cell discard, and the influence of traffic conditions Highly reliable DQD system that can perform switching and reconfiguration of network and system without receiving
It is to provide a device and a switching method for constructing a B system.

[0014]

In order to solve the above-mentioned problems, a communication system using a loop bus of the present invention includes:
The configuration is as follows. First, in an ATM communication system in which a plurality of communication nodes are connected in a loop by a plurality of buses each having a start point and an end point and cells are transmitted and received between communication nodes, each of the plurality of loop-shaped buses is connected. AT that can change system configuration by switching start point and end point
In the M communication system, a control cell for switching the system is defined, and switching is performed by transmitting and receiving this control cell between communication nodes. Specifically, I
The reserved bits of the access control field of the cell defined in EEE Recommendation 802.6 are used as the identifier of the control cell, and the information section indicating the type of the switching control operation in each communication node in the cell and the type are supported. A control information unit capable of storing information on the start point and the end point,
When the information about the system configuration is transmitted between the nodes, each node performs a switching operation so that the system configuration can be changed.

The ATM communication system includes, for each of a plurality of communication nodes, control cell generation means for generating a control cell for notifying switching, communication means for transmitting / receiving the control cell, and control means for setting and controlling the start point and end point of the bus. The ATM communication system is configured to reconfigure the system by controlling the start and end points of the bus by transmitting and receiving control cells.

Further, each of the plurality of communication nodes is also provided with storage means for storing normal cells transmitted / received between the communication nodes, and the transmission / reception of control cells controls the storage means and the start and end points of the bus to perform switching. The ATM communication system is configured to prevent cell loss and reconfigure the system. Specifically, each communication node is provided with a means for generating and transmitting a switching control cell and a storage means for temporarily storing a normal cell at the time of switching, and when switching the communication system, transmitting and receiving the switching control cell between a plurality of communication nodes. Then, failure notification, switching preparation instruction and communication restart instruction are given, and each communication node controls the storage means and reconfigures the communication system so as to prevent cell loss at the time of switching based on the switching control cell. More specifically, each of the plurality of communication nodes stores a plurality of queuing means that waits for cell transmission in correspondence with a plurality of buses, a position information of its own node on the bus, and a position information of start and end points. Information accumulating means, deciding means for deciding whether to transmit a cell to be transmitted to any of a plurality of buses, accumulating means for accumulating cells to be input to a plurality of queue means, and a plurality of queue means A plurality of cell number detecting means for detecting the number of cells waiting in each, a control cell generating means for generating a control cell for notifying switching, a communication means for transmitting / receiving the control cells, and a control for setting and controlling the start point / end point of the bus Means for controlling the setting of the start and end points of the bus by transmitting and receiving control cells, the accumulating means, the plurality of queuing means, and the plurality of cell number detecting means.

Further, in each of the plurality of communication nodes,
A means for generating empty cells at a predetermined interval and transmitting the empty cells to the bus and a changing means for rewriting the empty cells into control cells are also provided, and the empty cells are transmitted on the bus, and the empty cells are transmitted when switching is necessary. An ATM communication system for reconfiguring the above-mentioned system by rewriting it into a control cell is also possible.

It should be noted that A for preventing cell loss during the above switching
Each of the TM communication systems is an ATM communication for stopping cell transmission / reception between a plurality of communication nodes being switched by accumulating cells to be transmitted by the accumulating means during transmission / reception of control cells and until completion of control for setting start and end points of the bus. The system.

Then, the ATM communication system controls the setting of the start point and the end point of the bus based on the steps of generating a control cell notifying the switching, transmitting the control cell, receiving the control cell, and receiving the control cell. The switching method consists of steps to perform. Further, if a step of controlling transmission / reception of cells during the switching operation is added to this method, a switching method of an ATM communication system capable of preventing cell loss at the time of switching is provided.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION In a communication network using a loop bidirectional bus, there is provided a communication system according to the present invention, which is suitable for realizing non-interruptible system switching, switching capable of suppressing cell loss, and high-speed switching. For some embodiments,
This will be described in detail with reference to the drawings. <Embodiment 1: Uninterrupted Reconfiguration of Multiple Buses> FIG. 1 is a network configuration diagram showing a configuration of a communication network including a communication system and a transmission line for implementing uninterruptible switching according to the present invention. The communication network is
It is composed of a plurality of communication nodes 1 to 7, and each node is connected by two bidirectional buses, a multiplex bus A2 and a multiplex bus B3. Each bus has a start point (hereinafter referred to as a slot generator (SG)) 2s and 3 on each bus.
There are s and end points 2e and 3e. FIG. 2 shows FIG.
4 is a network configuration diagram showing a configuration of a communication network reconfigured when a node 4 fails in the communication network shown in FIG. In this communication network, when a failure occurs in the node 4, the node 4 is disconnected from the multiplex bus and the slot generator (S
G) and change the position of the end point. Specifically, for the multiplex bus A2, the slot generator is changed from node 1 to node 5 and the end point is changed from node 7 to node 3, and for the multiplex bus B3, the slot generator is changed from node 7 to node 3 and the end point is node 1. From the node 5 to the node 5, the bus is connected so as not to pass through the faulty node 4, and the communication network is reconfigured.

FIG. 3 is a block diagram showing the configuration of a node using the multiplex bus according to the present invention. The communication node 1 according to the present invention comprises a cell transmitter 5 for transmitting cells from the user interface 4 to the multiplex buses A2 and B3, and a cell receiver 6 for receiving cells from the multiplex buses A2 and B3 and transmitting them to the user interface 4. A fault detecting unit 7 for detecting a fault in the node, and an SG flag 9 for setting a slot generator (SG).
2 or B3, a bus access unit 8 and a network management system (NMS) 10 that performs maintenance management of this node or the entire communication network request a bus reconfiguration, or a fault detection unit in the node. A bus configuration control unit 11 that controls the configuration between the nodes when 7 detects a failure, and a processor CP1 that controls the nodes.
Composed of 2 and.

Then, the cell transmission section 5 distributes the cells from the user interface 4 to the distributed queues 13 (corresponding to the multiplex bus A2) and 14 (corresponding to the multiplex bus B3) for waiting the cell output to the multiplex buses A2 and B3. , An RTG extraction section 15 for extracting information (RTG) regarding the destination of a cell transmitted from the node 1 and a cell number detection circuit 16 for detecting the number of cells in the distributed queues 13 and 14 (corresponding to the multiplex bus A2).
And 17 (corresponding to the multiplex bus B3), a cell output direction selection unit 18 that determines the direction of the multiplex bus that outputs cells, and a cell output direction selection selector that performs switching in the direction determined by the cell output direction selection unit 18. 19, a self-node mounting position information storage unit 20 that recognizes and holds the position of the self-node on the network, a bus opening position information storage unit 21 that recognizes and holds the position of the bus opening, and a multiplex bus. It is composed of a waiting buffer 22 for switching without interruption, which waits for cell transmission when switching between A2 and B3. When the multiplex buses A2 and B3 are in the state of being interrupted during reconfiguration due to a node failure or an instruction from the NMS 10, the non-interruptible switching buffer 22 does not send a cell to the multiplex buses A2 and B3 and sends a cell between them. This is a buffer for temporary storage.

The operation of the communication node 1 will be described below. First, the transmission operation for transmitting cells from the user interface 4 to the multiplex buses A2 and B3 will be described. (A) When the cell transmission unit 5 receives a cell from the user interface 4, the RTG extraction unit 15 causes the cell destination node to transmit the cell. The position information of is extracted.

(B) Mounting position information and bus opening position information of the own node preset in the mounting position information storage unit 20 of the own node and the bus opening position information storage unit 21 and the destination extracted in (a). The cell output direction selection unit 18 calculates the direction of the multiplex bus for outputting the cells based on the position information of the above. This output bus direction can be easily determined by using the method disclosed in JP-A-7-107104 by the same applicant.

(C) The cell output direction selection selector 19 uses the information calculated by the cell output direction selection unit 18 to send the cell from the user interface 4 to the distributed queue 13 or 14 corresponding to the multiplex bus A2 or multiplex bus B3. Write in. The waiting buffer 22 for switching without interruption will be described in detail later in the description of the communication network switching operation together with the operations of the cell number detection circuits 16 and 17.

(D) The bus access unit 8 uses the multiplex bus A2
A bus access unit 23 that accesses the multiplex bus B3, and a B bus access unit 24 that accesses the multiplex bus B3. The access control of the multiplex buses A2 and B3 is performed, and the distributed queue 13 is adjusted while adjusting the traffic between the nodes. The cells stored in and 14 are transmitted to multiplex buses 2 and 3, respectively. Specifically, the control of this multiplex bus is performed by transmitting cells using the control method disclosed in IEEE Recommendation 802.6.

Next, the cell receiving operation from the multiplex buses A2 and B3 will be described.
The cell receiving unit 6 determines whether or not the cell transmitted from the cell 2 or B3) can be received by the node. Specifically, the reception cell analysis units 25 and 26 transmit only the cells to be received from the cells transmitted from the multiplex buses A2 and B3 to the multiplexer 27, and the multiplexor 27 causes the multiplex bus A2 to transmit.
The contention control is performed so as to avoid the collision with respect to the cells transmitted from each of 2 and B3, and the cells are transmitted to the user interface 4.

Further, the bus configuration control section 11 transmits / receives control cells to / from another node at the time of failure according to the present invention, controls the buffer 22 for switching without interruption, and distributes cells using the cell number detection circuits 16 and 17. The number of cells stored in the Ted queues 13 and 14 is monitored, and the SG flag 9 and the opening position information storage unit 21 are rewritten.

The present invention controls cell transmission / reception between nodes using a control cell dedicated to the reconfiguration operation (switching operation) at the time of reconfiguration of the bus, and thereby cell loss due to a momentary interruption occurring at the time of reconfiguration of the bus. To prevent the deterioration of the transmission path quality. Hereinafter, the control cell defined by the present invention will be described with reference to the drawings. Figure 4 shows IEEE Recommendation 80
It is a format diagram which shows the format of the cell prescribed | regulated by 2.6. In a normal cell (cell transmitted / received for communication between nodes) 28, as shown in the figure, the 4th and 5th bits of the access control field are reserved areas (indicated as Res in the figure). There is). FIG. 5 is a format diagram showing the format of the control cell 29 according to the present invention. In the embodiment of the present invention, the CNT for identifying whether it is a normal user cell or a control cell used in the present invention at the 4th bit of the access control field which is a reserved area of a normal cell.
If a bit is newly defined and this bit is "0", it is a normal cell (user cell) 28, and if it is "1", it is a control cell 2
It was set to 9.

More specifically, the control cell 29 uses the segment header area of the normal user cell 28 (second byte and third byte) as an area for transferring the node configuration switching information. Then, the type of the control cell 29 is classified by the bit string with the second byte as the command type area, and in the present embodiment, the switching request cell 29-1, the SG switching preparation cell 29-2, and the switching preparation completion cell 29-3. The following three types of control cells were defined. The third byte is a field for storing control information added to various control cells defined by the second byte.

Explaining the function of each control cell concretely, the switching request cell 29-1 is from the node to be disconnected from the network to each node adjacent to the bidirectional multiplex bus (to one downstream node). , A cell that signals that this node needs to be disconnected from the network. The SG switching preparation cell 29-2 is a cell that requests the downstream nodes to prepare for changing the opening position of the network from the node that has received the switching request cell 29-1. This SG switching preparation cell 29-2
In the control information area of the 3rd byte, position information of a new opening set on each bus after switching the node configuration of the multiplex bus is included. Further, the switching ready cell is 29-3,
It is a cell in which each node notifies other nodes that the preparation for switching the node configuration has been completed.

The format of the cell shown in FIG.
There is an example adopted in this embodiment, and other formats may be used. That is, even if the other bits and bytes of the normal cell shown in FIG. 4 are used, it is a control cell according to the present invention, and the type of the control cell and the additional control information are connected between the nodes connected to the multiplex bus. Anything can be used as long as it can be transmitted / received and identified.

Now, the non-interruption switching operation of the communication system according to the present invention will be described in detail with reference to the drawings. 6 to 13 are operation explanatory diagrams for explaining the switching operation of the communication system according to the present invention, and are diagrams in which FIG. 1 is expanded. Further, FIG. 14 is an operation flow chart showing the operation of each node of the communication system. In the communication system described in this embodiment, the nodes 1 to 7 are multiplexed buses A2 and B3.
6 to FIG. 13 is a network connected with the network configuration shown in FIG. 2 by switching loops without interruption when a failure in the node of the node 4 occurs in this network. The operation for rebuilding will be described. 6 to 13, the lines connecting the nodes (1 to 7) and the multiplex bus are omitted for simplification. Less than,
The switching operation of the communication system of the present invention will be described with reference to FIGS. 3 and 6 to 14.

(1) In the network before switching, as shown in FIG. 1, the slot generator 2s of the bus A2 is at the node 1 and the end point 2e is at the node 7. The slot generator 3s of the bus B3 is at the node 7 and the end point 3e is at the node 1.

(2) When the network management system (NMS) 10 issues an instruction to disconnect from the multiple bus to the node 4 for maintenance reasons such as addition of nodes or construction, or when the node 4 is in the bus state. When the fault detection unit 7 detects a fault other than the access unit 8, the node 4
The CP 12 therein sends a bus switching command to the bus configuration control unit 11 in the node 4. When the bus configuration control unit 11 receives the bus switching command from the CP 12, the bus access unit 8
To adjacent nodes (nodes 1 downstream from the respective buses of the multiplexed buses A2 and B3), that is, nodes 3 and 5
The switch request cell 29-1 is transmitted to each of the switch request cell 29-1 (FIG. 6).
1 is received via the multiplex bus B3 or the multiplex bus A2, respectively. Here, it is known that one upstream node on the bus (node 5 for node 5 and node 4 for node 3) is a node to be disconnected, and the own node becomes a new slot generator. Specifically, each node (node 3, node 5) receives the received cell analysis units 25 and 26.
When the received cell is the switching request cell 29-1, the bus configuration control unit 11 determines that the SG switching preparation cell including the position information of the new slot generator is analyzed (FIG. 14-1). 29-2 is further transmitted to the downstream node (node 2 for node 3, node 6 for node 5) (FIG. 7).

(4) Further, the nodes 3 and 5 which have received the switching request cell 29-1 accumulate the user cells 28 from the user interface 4 in the waiting buffer 22 for switching without interruption and form the distributed queue 13. When the writing of the user cell 28 to the memory cell 14 is stopped (see FIG.
4-2) SG for transmitting all the user cells 28 already stored in the distributed queues 13 and 14 (cells whose transmission directions have already been determined) before bus switching
Start switching preparations.

(5) The node that has received the SG switching preparation cell 29-2 (node 2 and node 6) transmits the SG switching preparation cell 29-2 to a further downstream node. And
The SG switching preparation similar to that when the node 3 and the node 5 receive the switching request cell 29-1 is started. Hereinafter, the core node connected downstream on the bus performs the same process (SG switching preparation cell 29-2
And the SG switching preparation) are repeated, and the process ends at the end point of the bus (SG node before switching of the bus in the opposite direction) (FIG. 7).

(6) The bus configuration control unit 11 of each node (nodes 1 to 3, 5 to 7) that has started SG switching preparation is accumulated in the distributed queues 13 and 14 by the cell number detection circuits 16 and 17. The accumulated user cells 28 are transmitted while monitoring the number of stored cells (FIG. 8), and when the accumulated user cells 28 are completely transmitted (FIG. 14-3), the SG switching preparation is considered to be completed. Judge (FIG. 14-4).

(7) At the node at the end of the bus (node 7 and node 1), when the SG switching preparation is completed, the bus configuration control unit 11 sends the SG switching preparation cell 2 via the bus access unit 8.
The switch preparation completion cell 29-3 is transmitted to the node (node 6 and node 2) located one downstream using the bus in the opposite direction to the multiplex bus that received 9-2 (FIG. 9).

(8) In the node (node 6 and node 2) located one downstream, the switching preparation completion cell 29-3 sent.
When the self node receives the SG switching preparation, it also transmits the switching preparation completion 29-3 cell to the further downstream nodes (node 5 and node 3). If the SG switching preparation is not completed at the time of receiving the switching preparation completion cell 29-3, waiting is performed until the SG preparation is completed (until the distributed queues 13 and 14 become empty), and when the SG preparation is completed, the switching preparation is made one downstream. The completed cell 29-3 is transferred (FIG. 9).

(9) After that, the switching ready cell 29-3 is sequentially transferred to each node by the same process, and the switching ready cell 29-3 is set to the node (node 3 and In node 5), multiple bus A2
And B3 are discarded when the switching ready cell 29-3 arrives. Each of the communication nodes 1 to 7 can judge whether or not another node has completed the switching preparation by receiving the switching preparation completion cell 29-3. Specifically, each node sets the switching ready cell 29-3 to A
It is recognized that all the other nodes have completed the preparation for switching when the data is received twice regardless of the bus 2 and the B bus 3 (Fig. 14-
5).

Each switching preparation completion cell 29-3
Are nodes at the end points of the multiplexed buses A2 and B3 (node 1 in the case of the switching ready cell transmitted from the node 7,
In the case of the switching ready cell transmitted from node 1, when the node is ready for switching when it reaches node 7), the cell is further transferred in that direction (through the slot generator). (FIG. 10: Only operation on one bus (B bus 3) is shown). With this configuration, the node that was the slot generator before the switching (node 7 and node 1 in FIG. 10) becomes the node that first transmits the switching ready cell 29-3, so that the switching ready cell 29 once It is possible to recognize that all the other nodes have completed the switching preparation by receiving -3.

(10) Each node, which has recognized that all the other nodes have completed the switching preparations, the SG switching preparation cell 29-
The bus opening position information storage unit 21 is rewritten according to the new opening information obtained in 2.
According to the method disclosed in Japanese Patent Publication No. 107104, the direction of the bus that newly outputs the user cell 28 is determined, and the user cell 28 is autonomously distributed to the distributed queues 13 and 14 (without interruption for switching without interruption). Writing is resumed in the switching queuing buffer 22 (including cells temporarily stored) to shift to the normal state (Fig. 14-
6). As a result, the node 4 is disconnected from the multiplex buses A2 and B3, the nodes 1 and 7 that were set to the slot generator before the switching release the slot generator, and the nodes 3 and 5 to be the slot generators after the switching are switched to the slot generator. Are set, and the network having the configuration shown in FIG. 2 is reconfigured (FIG. 13).

(11) More specifically, since the node (node 7 and node 1 in FIG. 10) that was the slot generator before the switching can recognize that the other node has completed the switching preparation first, At the time of recovery, the slot generators of both buses are first released (FIG. 11), and then each node shifts to the normal state (FIG. 12-
(Fig. 13). At this time, a state in which there is no slot generator occurs momentarily, but the nodes that should become SG in a form preceding the user cell 28 in which the switching ready cell 29-3 starts to flow again (node 3 and node 5 in FIG. 12). , And those nodes are set to SG at that time, so that the user cell 28 is not flowed twice (double) on the bus. With the above, the reconfiguration of the bus is completed, the network is configured without the faulty node, and the normal operation state is set.

According to this embodiment, each node transmits / receives the waiting buffer 22 for non-instantaneous switching and the control cell 29 so that there is no cell flowing on the multiplex buses 2 and 3 at the switching timing of the entire network. Since time can be created and the network configuration can be changed during that time, there is no interruption during that time and cell loss can be prevented. Also, regarding the cells whose bus directions used before and after the reconfiguration are different due to the reconfiguration of the buses that move the slot generators, the cell number detection circuits 16 and 17 are used to switch them to the respective buses 2 and 3 before switching. Since all the cells accumulated in the corresponding distributed queues 13 and 14 are transmitted and then switched, switching without interruption is realized and cell loss can be prevented.

<Embodiment 2: Immediate Reconfiguration of Multiplexed Bus> In the above embodiment, the operation of the communication system for performing the non-interruptible switching by the operation of combining the transmission / reception of the control cell 29 and the non-interruptive switching waiting buffer 22. However, depending on the environment in which the communication system is used, quick switching and network reconfiguration may be required even if some cell loss occurs. Of course, even in such a case, it is desirable to suppress cell loss due to switching as much as possible. According to the communication system and the switching method of the present invention, high-speed switching and network reconfiguration can be performed while suppressing cell loss. Therefore, an embodiment thereof will be described below with reference to the drawings.

FIG. 15 is a block diagram showing another structure of the node using the multiplex bus according to the present invention. The communication node 1'used in the present embodiment has substantially the same configuration and operation as the communication node 1 used in the first embodiment described above, and the cells from the user interface 4 are transferred to the multiple bus A2.
Cell transmitting unit 5 for transmitting to B3 and B3, and multiplex buses A2 and B3
A cell receiving unit 6 for receiving cells from the cell and sending them to the user interface 4, and a fault detecting unit 7 for detecting a fault in the node.
And a bus access unit 8 having an SG flag 9 for setting a slot generator to access the multiplex buses A2 and B3 from the cell transmission unit 5, and a network management system (NMS) for maintaining and managing this node and the entire communication network. ) When a bus reconfiguration request is issued from 10 or a fault detection unit 7 detects a fault in a node, a bus configuration control unit 11 that controls the configuration between the nodes and a control in the node are performed. Multiple bus A with processor CP12
2 and B3 upstream bus failure detection units 30 (corresponding to the multiplex bus A2) and 31 (multiplexed bus B) for detecting a failure occurring upstream.
3) was added.

Further, in order to implement the instant switching, in the present embodiment, in addition to the three types of control cells shown in the above-mentioned embodiment, the instant switching as shown in the format diagram of the control cell of FIG. Cell 29-4 was provided. This immediate switching cell 29-4 has the information of the slot generator corresponding to both directions of the multiplex buses A2 and B3 as the control information of the third byte of the control cell 29, and in order to achieve the hitless switching in the above-described embodiment. While the network was reconfigured by transmitting and receiving the SG switching preparation cell 29-2 and the switching preparation completion cell 29-3, each node receiving this cell immediately rewrites the opening position information storage unit 21. It is a cell that executes network reconfiguration.

The immediate switching operation of the communication system according to the present invention will be described in detail below with reference to the drawings. FIG.
6 to 19 are operation explanatory views each illustrating another switching operation of the communication system according to the present invention, which is an expanded view of FIG. 1. The communication system described in this embodiment is the node 1
16 is a network in which nodes 7 to 7 are connected by multiplex buses A2 and B3, and the operation explanatory diagrams of FIGS. 16 to 19 show, for example, when a failure occurs upstream of the node 3 of multiplex bus B3 in this network. When the node 3 of 16 detects an HEC (Header Error Code) error, which is an error in the ATM data from the upstream, in the upstream bus failure detection unit 31, the loop is immediately switched to the network configuration shown in FIG. To explain. still,
Also in FIGS. 16 to 19, the line connecting each node and the multiplex bus is omitted for simplification. The switching operation of the communication system of the present invention will be described below with reference to FIGS.

(1) In the network before switching, as shown in FIG. 1, the slot generator 2s of the bus A2 is at the node 1 and the end point 2e is at the node 7. The slot generator 3s of the bus B3 is at the node 7 and the end point 3e is at the node 1.

(2) When the node 3 detects an HEC error in the upstream bus failure detection unit 31 corresponding to the multiplex bus B3 on the network forming the multiplex bus, the CP of the node 3
Recognizes that the multiplex bus A2 from the upstream node or the bus access unit 8 of the upstream node 4 is in trouble (FIG. 16).

(3) CP12 of node 3 which has detected a failure
Sends a bus configuration immediate switching command to the bus configuration control unit 11. Upon receiving the bus configuration immediate switching command from the CP 12, the configuration control unit 11 receives the position information of the new slot generator from the bus access unit 8 in the control information portion of the third byte of the control cell (in the present embodiment, the multiplexed bus A2 is the node 5).
Then, the immediate switching cell 29-4 to which the multiplex bus B3 becomes the node 3) is transmitted in both directions of the multiplex buses A2 and B3 (FIG. 17).

(4) The nodes (nodes 2 and 4) that have received the immediate switching cell 29-4 are the immediate switching cells 29-
Based on the control information of 4, the opening position information storage unit 2 immediately
Switching is performed by rewriting 1 and the immediate switching cell 29-4 is transferred to the downstream nodes (node 1 and node 5) (FIG. 18).

(5) Time when all nodes have completed switching (time when the immediate switching cell 29-4 returns to the node that newly becomes the slot generator and the node that becomes the end point)
In the node which becomes the slot generator and the node which becomes the end point, the lot generator and the end point are set respectively, and when the immediate switching cell 29-4 is discarded, a faulty node and a multiplex bus in which a faulty part of the multiplex bus is separated are constructed,
The network as shown in FIG. 2 is reconfigured. Therefore, after that, the user cell 28 can be normally transmitted and received between the nodes (FIG. 19).

Immediate switching cell 29-4 as in this embodiment
In the switching using, the switching is performed immediately in response to the failure of the bus access unit 8 without performing the processing of the user cell 28 at the time of switching, and the switching can be performed without any interruption as in the previous embodiment. However, each node has an immediate switching cell 29-
When 4 is received, the switching is immediately performed by the autonomous switching operation of the hardware, so that the bus can be reconfigured quickly with a minimum cell loss.

<Third Embodiment: Reconfiguration of Multiplexed Bus by Empty Control Cell> FIG. 20 is a block diagram showing another configuration of a node using the multiplex bus according to the present invention. The communication node 1 ″ used in this embodiment is the communication node 1 or the communication node 1 used in the above-described Embodiment 1 or Embodiment 2.
The configuration is almost the same as that of the communication node 1 or the communication node 1 ', and an empty control cell 29-5, which is one of the control cells 29 according to the present invention to be described later, is provided in the multiplex bus A2 at predetermined fixed intervals.
And a control cell generation timer 32 for outputting to B3. Specifically, on the multiplex buses A2 and B3 of the communication system using the communication node 1 ″, in addition to the user cell 28 transmitted / received between the nodes, an empty control cell 29 is provided.
-5 is transmitted and received at regular intervals. Then, when the switching as shown in the first and second embodiments is required, the empty control cell 29-5 is a control cell which is the control cell described in the first and second embodiments according to the switching situation. Cell 29-1
Or SG switching preparation cell 29-2 or switching preparation completed cell 29-
After rewriting to either 3 or the immediate switching cell 29-4,
The configuration is such that the non-instantaneous switching or the immediate switching shown in the first and second embodiments is performed.

FIG. 5 shows an empty control cell 29-5 used in the present invention.
Format is shown. This empty control cell 29-5
In the above configuration, only the various control cells described above can be overwritten and the normal user cell 28 cannot be written.

In this embodiment, the configuration control unit 11 of the node having the slot generator uses the multiplex bus A2 or B3.
Even if all the throughputs are used by the user cell 28, a minimum area necessary for transmission of the empty control cell 29-5 is secured and the empty control cell 29-5 is transmitted to the multiplex bus A2 or B3. Control so that you can. Specifically, the configuration control unit 11 of the node in which the slot generator is set in each of the multiplex bus A2 and the multiplex bus B3 uses the empty control cell generation timer 32 at a predetermined constant interval set in the NMS 10, for example. , The access control unit 8 so as to transmit the empty control cell 29-5 to each multiplex bus.
Give instructions to The access control unit 8 outputs the empty control cell 29-5 in the downstream direction of the bus. Of course, the empty control cell 29-5 has a configuration in which overwriting of the user cell 28 is prohibited as described above. In such a state, when the switching situation described in the first or second embodiment occurs, the configuration control unit 11 of the node designated by the NMS 10 or the node that has detected the failure causes an instruction from the NMS 10 or a communication system. The empty control cell 29-5 is rewritten into each of the control cells 29-1 to 29-4 in accordance with the failure situation that occurred in (1). After that, the switching described in the first or second embodiment is performed, and the network in a state in which the designated node, the faulty node, or the faulty part of the multiplex bus is disconnected is reconfigured and Communication continues.

According to the communication system of the present embodiment, the empty control cells 29-5 exist on the bus at regular intervals even when the throughputs of the multiplex buses A2 and B3 are all used by the user cells 28. When switching is required, this empty control cell 29-5 is replaced with a predetermined control cell 29-1.
Switching is executed by rewriting to any of cells 29 to 29-4. That is, even though the switching is necessary, the situation in which the control cell 29 cannot transmit / receive due to the traffic does not occur, so that the switching can be performed quickly and the occurrence of the cell loss due to the switching can be suppressed. The reliability of the system can be improved.

[0060]

According to the present invention, a control is provided in a communication system having a structure in which a communication node is connected in a loop by a bidirectional bus and the start and end points of the bus on the loop are switched to disconnect the faulty communication node. By using a cell and transmitting / receiving this between each node, it becomes possible to control so that there is no cell on the multiplex bus during the time when the configuration of the multiplex bus is switched, and to switch by hardware autonomously. Therefore, when a failure occurs in a part other than the access part of the multiplex bus, it is possible to switch the multiplex bus without cell loss and reconfigure the network by disconnecting the failed node.

Further, in the above communication system, even if a failure occurs in the bus access unit, the downstream node detects the failure and transmits control cells to all the nodes, and the control cells received by each node. Since the configuration is such that the multiple buses are switched and the faulty node is separated by the autonomous operation of the hardware without the intervention of the processor, the network can be reconfigured with a minimum cell loss.

Further, since the control cell is transmitted and received regardless of the traffic condition of the multiplex bus, it is possible to surely reconfigure the network at high speed. With the above, it is possible to realize a highly reliable communication network.

[Brief description of drawings]

FIG. 1 is a network configuration diagram showing a configuration of a communication network according to the present invention.

FIG. 2 is a network configuration diagram showing a configuration of a reconfigured communication network.

FIG. 3 is a block configuration diagram showing a configuration of a communication node according to the present invention.

FIG. 4 is a format diagram showing a format of a cell transmitted on a multiplex bus.

FIG. 5 is a format diagram showing a format of a control cell according to the present invention.

FIG. 6 is an operation explanatory view explaining a switching operation of the communication system of the present invention.

FIG. 7 is an operation explanatory diagram explaining a switching operation of the communication system.

FIG. 8 is likewise an operation explanatory diagram illustrating a switching operation of the communication system.

FIG. 9 is likewise an operation explanatory diagram illustrating a switching operation of the communication system.

FIG. 10 is also an operation explanatory diagram explaining a switching operation of the communication system.

FIG. 11 is also an operation explanatory diagram explaining a switching operation of the communication system.

FIG. 12 is also an operation explanatory diagram explaining the switching operation of the communication system.

FIG. 13 is also an operation explanatory diagram explaining a switching operation of the communication system.

FIG. 14 is a flowchart showing a switching operation of communication nodes according to the present invention.

FIG. 15 is a block diagram showing another configuration of the communication node according to the present invention.

FIG. 16 is an operation explanatory view explaining another switching operation of the communication system of the present invention.

FIG. 17 is an operation explanatory diagram explaining a switching operation of the communication system.

FIG. 18 is an operation explanatory diagram explaining a switching operation of the communication system.

FIG. 19 is also an operation explanatory view explaining the switching operation of the communication system.

FIG. 20 is a block diagram showing another configuration of the communication node according to the present invention.

[Explanation of symbols]

1 ... Communication node, 2 ... Multiplex bus (bus A), 3 ... Multiplex bus (bus B), 2s, 3s ... Slot generator, 2e, 3e ... Bus end point,
4 ... User interface, 5 ... Cell transmission unit,
6 ... Cell reception unit, 7 ... Failure detection unit,
8 ... bus access unit, 9 ... SG flag,
10 ... Network management system, 11.
..Bus configuration control unit, 12 ... CP, 13 ... A bus distributed queue, 14 ... B bus distributed queue, 15 ... RTG extraction unit,
16 ... Cell number detection circuit A, 17 ... Cell number detection circuit B, 18 ... Cell output direction selection unit, 19 ... Cell output direction selection selector, 20 ... Self node mounting position information storage 21 ... Bus opening position information storage section, 22 ... Waiting buffer for switching without interruption, 23 ... A bus access section,
24 ... B bus access unit, 25 ... A bus reception cell analysis unit, 26 ... B bus reception cell analysis unit, 27 ... Multiplexer, 28 ... User cell, 29 ... Control cell , 30 ... A bus upstream failure detection unit,
31 ... B bus upstream failure detection unit, 32 ... Control cell generation timer.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Junichiro Yanagi 216 Totsuka-cho, Totsuka-ku, Yokohama-shi, Kanagawa Stock company Hitachi Information & Communication Division

Claims (30)

[Claims] 1. A plurality of communication nodes are connected by a plurality of buses.
Connected in a loop and transmitting / receiving cells between the communication nodes A
In an ATM communication system in which the configuration of the system is changed by switching the start point and the end point of each of the plurality of loop-shaped buses, the switching is performed in each of the plurality of communication nodes. A control cell generation means for generating a control cell for notifying the control cell, a communication means for transmitting / receiving the control cell, and a control means for setting and controlling the start point and the end point of the bus, and the start point and the end point of the bus by transmitting / receiving the control cell. An ATM communication system characterized in that the system is reconfigured by performing the setting control of the above. 2. A plurality of communication nodes are routed by a plurality of buses.
Connected in a loop and transmitting / receiving cells between the communication nodes A
A TM communication system, wherein the configuration of the communication system is changed by switching the start point and the end point of each of the plurality of loop-shaped buses,
In each of the plurality of communication nodes, a storage unit that stores the cell, a control cell generation unit that generates a control cell that notifies the switching, a communication unit that transmits and receives the control cell, and a start point and an end point of the bus are set and controlled. And a control means for
An ATM communication system characterized in that the system is reconfigured by controlling the start and end points of the storage means and the bus by transmitting and receiving the control cell. 3. An ATM communication system in which a plurality of communication nodes are connected in a loop form by a plurality of buses each having a start point and an end point of each bus to transmit and receive cells, wherein
In an ATM communication system in which the configuration of the system is changed by switching the start point and the end point of each of a plurality of bus-like buses, each of the plurality of communication nodes transmits a cell corresponding to the plurality of buses. A plurality of queue means to wait, position information storage means for storing position information of own node on the bus and position information of start and end points of the bus, destination information of the cell to be transmitted, and information of the position information storage means. Detecting means for deciding whether to transmit the cell to any of a plurality of buses, accumulating means for accumulating the cells to be input to the plurality of queue means, and detecting the number of cells waiting in each of the plurality of queue means A plurality of cell number detecting means, a control cell generating means for generating a control cell notifying the switching, and a communication means for transmitting / receiving the control cell A control means for setting and controlling a start point and an end point of the bus, and setting control of the start point and the end point of the bus by transmission and reception of the control cell, control of the accumulating means, a plurality of queuing means, and a plurality of cell number detecting means. An ATM communication system characterized in that the communication system is reconfigured. 4. A plurality of communication nodes are connected by a plurality of buses.
Connected in a loop and transmitting / receiving cells between the communication nodes A
In an ATM communication system in which the configuration of the system is changed by switching the start point and the end point of each of the plurality of loop-shaped buses, a predetermined number is assigned to each of the plurality of communication nodes. Means for generating empty cells at intervals and transmitting them to the bus, control cell generating means for generating control cells notifying the switching, changing means for rewriting the empty cells to the control cells, and communication means for transmitting and receiving the control cells An ATM communication system comprising: a control means for setting and controlling a starting point and an ending point of the bus; and controlling the setting of the starting point and the ending point of the bus by transmitting and receiving the control cell to reconfigure the system. 5. The communication node stores cells to be transmitted during transmission / reception of the control cell and until completion of setting control of start and end points of the bus by the storage means, and a cell between a plurality of communication nodes being switched. 5. The ATM communication system according to claim 2, wherein transmission / reception is stopped. 6. The control cell comprises a first control cell for instructing each of the nodes to perform the switching preparation, and a second control cell for notifying completion of the switching preparation, and each node has the first control cell. 6. The ATM communication system according to claim 1, wherein when the second control cell is received after the cell is transmitted, the start point and the end point of the bus are set and the communication system is reconfigured. 7. The control cell includes a first control cell for notifying that its own communication node is a node disconnected from the plurality of buses, and a second control cell for instructing each of the nodes to perform the switching. , A third control cell notifying that switching preparation is completed, and when each node receives the third control cell after transmitting the first or second control cell, it performs setting control of the start point and end point of the bus, and the communication described above. The AT according to any one of claims 1 to 5, wherein the system is reconfigured.
M communication system. 8. The control cell is a fourth control cell for notifying that when the control node receives the control cell at a node which is disconnected from the plurality of buses, the start point and the end point of the bus are controlled. 5. The ATM communication system according to claim 1, wherein each node reconfigures the communication system by controlling the start point and the end point of the bus upon receiving the fourth control cell. 9. The ATM communication system according to claim 4, wherein the empty cell is a fifth control cell. 10. An ATM communication system in which a plurality of communication nodes are connected in a loop by a plurality of buses and cells are transmitted and received between the communication nodes, and a starting point of each of the plurality of the loop-shaped buses is provided. A method for switching an ATM communication system in which the configuration of the system is changed by switching the end point,
A first step of generating a control cell notifying the switching, a second step of transmitting the control cell, a third step of receiving the control cell, and a start point of the bus based on the received control cell And a fourth step of controlling the setting of the end point. 11. An ATM communication system in which a plurality of communication nodes are connected in a loop by a plurality of buses and cells are transmitted and received between the communication nodes, and a starting point of each of the plurality of loop-shaped buses is provided. A method for switching an ATM communication system in which the configuration of the system is changed by switching the end point,
A first step of generating a control cell notifying the switching, a second step of transmitting the control cell, a third step of receiving the control cell, and a start point of the bus based on the received control cell And a fourth step of controlling the setting of the end point, and a fifth step of controlling the transmission and reception of the cell during the switching operation of the first to fourth steps. 12. An ATM communication system in which a plurality of communication nodes are connected in a loop by a plurality of buses and cells are transmitted and received between the communication nodes, and a starting point of each of the plurality of the loop-shaped buses is provided. A method for switching an ATM communication system in which the configuration of the system is changed by switching the end point,
A first step of generating an empty cell and transmitting the empty cell to the bus; a second step of generating a control cell notifying the switching; and a third step of rewriting the empty cell into the control cell and transmitting it. An ATM comprising a fourth step of receiving the control cell and a fifth step of setting and controlling the start point and the end point of the bus based on the received control cell.
Communication system switching method. 13. An ATM communication system in which a plurality of communication nodes are connected in a loop form by a plurality of buses and cells are transmitted and received between the communication nodes. A method for switching an ATM communication system in which the configuration of the system is changed by switching the end point,
A first step of generating an empty cell and transmitting the empty cell to the bus; a second step of generating a control cell notifying the switching; and a third step of rewriting the empty cell into the control cell and transmitting it. A fourth step of receiving the control cell, a fifth step of setting and controlling the start point and the end point of the bus based on the received control cell, and a switching operation of the second step to the fifth step. A method of switching an ATM communication system, comprising a sixth step of controlling transmission and reception of the cell. 14. An ATM communication system in which a plurality of communication nodes are connected in a loop by a plurality of buses and cells are transmitted and received between the communication nodes, and a starting point of each of the plurality of loop-shaped buses is provided. A method for switching an ATM communication system in which the configuration of the system is changed by switching the end point,
First to generate a first control cell for instructing the switching preparation
The second step of transmitting the first control cell, the third step of receiving the first control cell, and the first control cell transmission / reception waiting for transmission to the bus. A fourth step of transmitting a cell, a fifth step of accumulating a cell to be newly transmitted, and a sixth step of transmitting a second control cell notifying completion of switching preparation after the fourth step is completed. A seventh step of receiving the second control cell, an eighth step of setting and controlling a start point and an end point of the bus based on the received second control cell, and a fifth step after the end of the eighth step. 9. A method for switching an ATM communication system, which comprises the ninth step of transmitting the cells accumulated in step 1 to the bus. 15. An ATM communication system in which a plurality of communication nodes are connected in a loop shape by a plurality of buses each having a start point and an end point of each bus to transmit / receive cells, wherein the loop type In an ATM communication system in which the configuration of the system is changed by switching the start point and the end point of each of a plurality of buses, each of the plurality of communication nodes waits for a cell transmission in correspondence with the plurality of buses. Position information storage means for storing position information of the queue means and own node on the bus and position information of start and end points of the bus, destination information of the cell to be transmitted, and information of the position information storage means Of the queuing means and the deciding means for deciding whether to transmit the cell to any of the A plurality of cell number detecting means for detecting the number of waiting cells respectively, a first control cell for instructing switching preparation for notifying the switching, and a second control cell for notifying completion of switching are generated. A control cell generation means, a communication means for transmitting / receiving the control cell, a control means for setting a start point and an end point of the bus, and controlling transmission / reception of the cell, wherein the control means transmits / receives the first control cell. When the cells waiting in the plurality of queuing means are transmitted to the plurality of buses, new cells are accumulated in the accumulating means, and when the vacancy of the queuing means is notified from the plurality of cell number detecting means, When the second control cell is transmitted and the second control cell is received from another communication node, the contents of the position information accumulating means are rewritten and the cell accumulated in the accumulating means is transmitted. ATM communication system, characterized in that reconfiguring the communication system Ri. 16. An ATM communication system in which a plurality of communication nodes are connected in a loop shape by a plurality of buses each having a start point and an end point of each bus to transmit / receive cells, wherein the loop type In an ATM communication system in which the configuration of the system is changed by switching the start point and the end point of each of a plurality of buses, when a communication node disconnected from the bus transmits a first control cell notifying the disconnection, the first
5. An ATM communication system, wherein a communication node adjacent to a communication node that is disconnected from the bus that has received the control cell of (1) sets a start point or an end point of each of the plurality of buses to reconfigure the system. 17. An ATM communication system in which a plurality of communication nodes are connected in a loop shape by a plurality of buses each having a start point and an end point of each bus to transmit and receive cells, wherein the loop-shaped ATM communication system is provided. In an ATM communication system in which the configuration of the system is changed by switching the start point and the end point of each of a plurality of buses, a control cell generating unit that generates a control cell that notifies the switching to each of the plurality of communication nodes, and the control. The first control cell includes communication means for transmitting and receiving cells and control means for setting and controlling the start point and end point of the bus, and when a communication node disconnected from the bus transmits a first control cell notifying of disconnection. The communication node adjacent to the communication node that has been disconnected from the bus that has received the message sets the start point or end point of each of the plurality of buses and restarts the system. ATM communication system, characterized by forming. 18. A communication node adjacent to a communication node disconnected from the bus transmits a second control cell including new start point and end point information to a downstream communication node connected to the plurality of buses. The ATM communication system according to claim 16 or 17, wherein the system is reconfigured by reconfiguring the system. 19. Each of the communication nodes prepares to switch the communication system when receiving the second control cell, and transmits a third control cell for notifying preparation completion when the switch preparation is completed. 19. The ATM communication system according to claim 18, wherein each of the nodes reconfigures the system when receiving the third control cell. 20. An ATM communication system in which a plurality of communication nodes are connected in a loop by a plurality of buses each having a start point and an end point of each bus to transmit and receive cells, wherein the loop-shaped ATM communication system is provided. In an ATM communication system in which the configuration of the system is changed by switching the start point and the end point of each of a plurality of buses, when an arbitrary communication node on the bus transmits a control cell including information of a new bus start point and end point, An ATM communication system characterized in that a communication node on the bus corresponding to the new start point and end point receiving the control cell sets respective start points or end points of the plurality of buses to reconfigure the system. . 21. An ATM communication system in which a plurality of communication nodes are connected in a loop shape by a plurality of buses each having a start point and an end point of each bus to transmit and receive cells, wherein the loop type In a communication node of an ATM communication system that changes the configuration of the system by switching the start point and the end point of each of a plurality of buses, the communication node generates a control cell that notifies the switching, and the control cell. A communication of an ATM communication system, which comprises a communication means for transmitting and receiving data and a control means for setting and controlling the start point and the end point of the bus, and reconfiguring the system by transmitting and receiving the control cell and controlling the start point and the end point of the bus. node. 22. An ATM communication system in which a plurality of communication nodes are connected in a loop by a plurality of buses each having a start point and an end point of each bus to transmit and receive cells, wherein the loop-shaped ATM communication system is used. In a communication node of an ATM communication system that changes the configuration of the system by switching the start point and the end point of each of a plurality of buses, the communication node generates a storage unit that stores the cell and a control cell that notifies the switching. A control cell generating means, a communication means for transmitting and receiving the control cell, and a control means for setting and controlling the start point and the end point of the bus, and the storage means and the setting control of the start point and the end point of the bus by transmitting and receiving the control cell. A communication node of an ATM communication system for reconfiguring the system. 23. An ATM communication system in which a plurality of communication nodes are connected in a loop by a plurality of buses each having a start point and an end point of each bus to transmit / receive cells, wherein the loop-shaped ATM communication system In a communication node of an ATM communication system that changes the configuration of the system by switching the start point and the end point of each of a plurality of buses, the communication node has a plurality of queue means that waits for cell transmission in correspondence with the plurality of buses. Any one of the plurality of buses depending on position information storage means for storing position information of its own node on the bus and position information of start and end points of the bus, destination information of the cell to be transmitted, and information of the position information storage means. Each of the deciding means for deciding whether to transmit the cell, the accumulating means for accumulating the cells to be input to the plurality of queuing means, and the plurality of queuing means A plurality of cell number detecting means for detecting the number of waiting cells, a control cell generating means for generating a control cell for notifying the switching, a communication means for transmitting and receiving the control cell, and a start point and an end point of the bus are set and controlled. An ATM communication system comprising a control means, and reconfiguring the system by controlling the start and end points of the bus by transmitting and receiving the control cell, controlling the accumulating means, a plurality of queuing means, and a plurality of cell number detecting means. Communication node. 24. An ATM communication system in which a plurality of communication nodes are connected in a loop form by a plurality of buses each having a start point and an end point of each bus to transmit and receive cells, wherein the loop type In a communication node of an ATM communication system that changes the configuration of the system by switching the start point and the end point of each of a plurality of buses, the communication node generates means for transmitting empty cells at predetermined intervals, and the means for transmitting to the bus. The control cell generating means for generating a control cell notifying the switching, the changing means for rewriting the empty cell into the control cell, the communication means for transmitting / receiving the control cell, and the control means for setting and controlling the start point and the end point of the bus are provided. A communication node of an ATM communication system that reconfigures the system by transmitting the empty cell, transmitting and receiving the control cell, and controlling the start and end points of the bus. 25. An ATM communication system in which a plurality of communication nodes are connected in a loop by a plurality of buses to transmit and receive cells between the communication nodes, each of the plurality of loop-shaped buses Is an AT with a configuration including the start point and the end point of the bus
In the M communication system, a plurality of communication nodes transmit and receive a control cell including information about a start point and an end point of the bus to configure the system. 26. An ATM communication system in which a plurality of communication nodes are connected in a loop by a plurality of buses to transmit and receive cells between the communication nodes, each of the plurality of the loop-shaped buses In an ATM communication system in which the configuration of the system is changed by switching the start point and the end point, a plurality of communication nodes transmit and receive control cells for notifying the switching, and set and control the start point and the end point of the plurality of buses. The ATM is characterized by reconfiguring the above system.
Communications system. 27. An ATM communication system using a DQDB defined in IEEE Recommendation 802.6, wherein a plurality of communication nodes are connected in a loop by a plurality of buses and cells are transmitted and received between the communication nodes. An AT having a configuration in which each of the plurality of loop-shaped buses has a start point and an end point of the bus
In the M communication system, a plurality of communication nodes transmit and receive a control cell including information about a start point and an end point of the bus to configure the system.
ATM communication system using. 28. An ATM communication system using a DQDB defined in IEEE Recommendation 802.6, wherein a plurality of communication nodes are connected in a loop by a plurality of buses and cells are transmitted and received between the communication nodes. In an ATM communication system in which the configuration of the system is changed by switching the start point and the end point of each of the plurality of loop-shaped buses, a plurality of communication nodes send and receive control cells for notifying the switching. A DQD, wherein the system is reconfigured by setting and controlling start points and end points of the plurality of buses.
ATM communication system using B. 29. An ATM communication system using DQDB defined in IEEE Recommendation 802.6, wherein a plurality of communication nodes are connected in a loop by a plurality of buses and cells are transmitted and received between the communication nodes. A method for switching an ATM communication system, wherein the configuration of the system is changed by switching the start point and the end point of each of a plurality of bus-like buses,
A first step of generating a control cell notifying the switching, a second step of transmitting the control cell, a third step of receiving the control cell, and a start point of the bus based on the received control cell And a fourth step of controlling the setting of the end point. 30. In an ATM communication system in which a plurality of communication nodes are connected in a loop by a plurality of buses and cells are transmitted and received between the communication nodes, a starting point of each of the plurality of the loop-shaped buses and A control cell for transmitting and receiving information regarding the switching of an ATM communication system in which the configuration of the system is changed by switching an end point between a plurality of communication nodes, wherein the control cell is defined in IEEE Recommendation 802.6. A reserved bit of an access control field of a cell is used as an identifier of the control cell, and an information section indicating a type of switching control operation in at least each communication node and information about the start point and the end point corresponding to the type are stored in the cell. A control used in switching of the ATM communication system according to any one of claims 1 to 29, further comprising: cell.