KR0136071B1 - Atm communication system - Google Patents

Abstract

An ATM communication system, comprising a plurality of communication nodes connected to each other in a loop shape by a bus to provide a digital communication network using a loop-shaped multiple bus that realizes high-speed communication by simple device configuration and processing. According to the buffer provided, a synchronous pulse generating circuit for performing cell multiple separation of all communication nodes at the same timing, the storage device of the mounting position information and the slot generator position information of each communication node, and the respective communication information according to their position information. The node has a circuit for automatically transmitting and receiving cells.

This eliminates the necessity of providing a complicated circuit to realize the loopback function as in the prior art, and achieves the effect of miniaturization and low cost.

Description

ATM communication system

1 is a schematic configuration diagram of a communication node of an ATM communication system according to the present invention.

2 is a configuration diagram of an ATM communication system in which a communication node according to the present invention is connected in a loop by multiple buses.

3 is a diagram showing the timing of cell multiplexing processing for each communication node according to the present invention.

4 is a block diagram of a cell transmitter and a cell receiver of a communication node according to the present invention.

5 is a table showing the routing information inside the cell transmitter of the communication node according to the present invention.

6 is a diagram illustrating a configuration to which an ATM communication system according to the present invention is connected and a method of providing mounting information to each communication node.

7 is a flowchart showing a procedure for the communication node to determine the transmission direction of the multiple bus according to the present invention.

8 is a block diagram (normally) of an ATM communication system that duplicates a communication node according to the present invention.

9 is a block diagram (at the time of failure) of an ATM communication system which duplicates the communication node according to the present invention.

10 is a block diagram of a cell transmitter and a cell receiver of a communication node performing point-multipoint communication according to the present invention.

11 is a table showing a table of routing information inside a cell transmitter that performs point-multipoint communication according to the present invention.

12 is a flowchart showing a procedure for determining a transmission direction in the case of performing point-multipoint communication according to the present invention.

13 is a block diagram of a cell transmitter and a cell receiver having a loopback function in a communication node according to the present invention.

14 is a flowchart showing a procedure for determining a transmission direction when loopback is performed in a communication node according to the present invention.

In a communication network in which each communication node is not connected in a loop, a method of synchronizing operation by sending a common synchronization pulse to each communication node is known in the art. However, it has not yet existed that the synchronous method is taken in a communication network in which each communication node is connected in a loop shape.

On the other hand, in an ATM communication system in which several communication nodes transmit and receive cells, various switches such as a space switch, a time switch, and a bus switch are used for cell switching.

International standardization of ATM communication system using bus switch is progressing, for example, “Distributed Queue Dual Bus Subnetwork of a Metropolitan Area Network”, IEEE802.6 ( 12. There is a distributed matrix dual bus (DQDB) scheme described in 1990).

The ATM communication system transmits a cell by connecting a unidirectional bus from one communication node to an adjacent communication node, and transmits a cell by connecting a unidirectional bus from the communication node receiving the cell to another adjacent communication node. As described above, a plurality of communication nodes and adjacent communication nodes are connected by a unidirectional bus. It is also characterized by having the same bus in the opposite direction, and each communication node multiplexes the cells input from the input line onto the bus when there are no cells transmitted from other communication nodes on the bus. Transmission and transmission of data between the communication nodes at high speed by carrying out cell reception by separating the cell from the bus to its own communication node.

In this ATM communication system, the cell synchronization method described in page 120 of "Introduction to B-ISDN" (Omsa) is used as a synchronization method for finding the head of a cell when performing multiple separation of cells.

In the ATM communication system using the distributed matrix dual bus system, a bus in which two buses with different communication directions are physically looped is configured, and even in this case, a logical bus is used to equalize the bus frequency of each communication node. The start point and the end point of X are provided to perform the traffic control. That is, cells flowing on the bus are discarded at the end of each bus. In other words, the contents of the cell are not transmitted beyond the end point. In addition, the start point and the end point of this bus can be set and changed at arbitrary positions on each bus. The logical point of time of this bus, that is, the point of time of the loop, is called the slot generator.

In addition, since two buses with different communication directions each have a start point and an end point for a bus, when transmitting a cell from one communication node to another communication node, which bus to transmit is multiplied to which bus? You need to judge. Conventionally, this transmission direction has been selected by providing a table in each communication node and setting the transmission direction in the table.

In this ATM communication system, since the multiple separation processing of cells is performed at each node, cells transmitted to adjacent nodes are delayed by the processing time. In addition, transmission delay to adjacent nodes also occurs. That is, the phase of the head of the cell received at the adjacent node is out of phase with the cell of the transmitting node. For this reason, in the receiving node, in order to find the head of the cell in the out-of-phase phase and perform the multiple separation processing of the cells, the reception data in each communication node as described in "Introduction to B-ISDN" (Omsa) on page 120 is given. The cell is synchronized by extracting the synchronization signal from the subfield and finding the head of the cell.

In other words, the digital communication network using the conventional loop-shaped multiple bus can realize high-speed communication, but requires the following complicated apparatus and processing for this realization.

[1] Since the head position of the packet is shifted by the cell processing time between adjacent communication nodes, a complicated synchronization method is required to synchronize each communication interface unit. In addition, when the position of the slot generator is changed, the phase of the cell changes before and after the change of the position of the slot generator, so that there is a drawback that the synchronization of all the communication nodes is once displaced.

[2] In order to determine the data transmission direction, the relationship between the communication bus and the transmission direction for each communication node is integrated with a dedicated table or another table, and the central processing unit updates the contents of this table every time it is called. It was necessary to determine the transmission direction. Therefore, when the position of the slot generator is changed, the transmission direction for each call changes, so it is necessary to rewrite the table of each communication node.

[3] In order to improve the reliability, when the communication node was duplicated, two systems were separately recognized and transmitted when the cell was transmitted. In other words, the central processing unit needed to execute the transmission processing at each call and every system.

[4] When transmitting information from one communication node to several communication nodes between multiple communication nodes, that is, when performing point-multipoint communication, it is necessary to transmit cells on both buses. However, the above-mentioned documents do not disclose a specific method.

SUMMARY OF THE INVENTION An object of the present invention is to provide a digital communication network using a loop-shaped multiple bus which realizes high-speed communication by simple device configuration and processing.

That is, a first object of the present invention is to provide an economical method of performing synchronization between communication nodes connected in a loop without depending on a complicated synchronization method.

A second purpose is to provide a simple and fast routing method (also called a route selection method) that does not use a table for determining the direction of data transmission, that is, the direction of transmission can be determined immediately even if the position of the slot generator is changed. To provide.

A third object is to provide a simple and high speed routing method even when duplexing a communication node.

A fourth object is to provide the manner necessary to realize point-multipoint communication.

Further, a fifth object is to provide an apparatus and a communication network which are easy to maintain and operate such as a fault diagnosis by providing a method of easily implementing a loop back function in a communication node.

In order to achieve the above object, an ATM communication system according to the present invention has the following configuration.

[1] Adjacent communication nodes among multiple communication nodes are connected by a transmission / reception bus to form a loop configuration. A buffer that absorbs timing deviations of multiple separations of cells between communication nodes adjacent to each communication node, that is, corrects the timing deviations, is set up so that the total delay time of the cell processing time and transmission delay time is adjusted. The phase of the timing of multiple separation of cells in each communication node is made the same for all communication nodes by reading the buffer at a constant period or an integer multiple of the periods that can be absorbed.

[2] In each communication node, routing is executed according to the mounting position information on the bus. To implement this method, a memory node and a slot generator for storing the position where the node is mounted on the bus are set up. A memory for storing a position is provided, and a transmission direction determining section for automatically determining a transmission direction of a cell from each communication node according to the position information where the communication node is mounted and the position information of the communication node where the slot generator is set. .

[3] In order to improve reliability, when duplexing communication nodes, redundant communication nodes are provided in adjacent mounting positions on multiple buses, and the same mounting position information is given to these two communication nodes. In addition, a setting position changing section for changing the slot generator setting position in accordance with the state of normality and failure is provided.

[4] Routing markers according to the mounting position are assigned to point-to-point communications, while a routing marker-character granting section is provided for assigning routing markers exclusively for multi-point communications for point-multipoint communications. Specifically, a unique routing marker is defined for a combination of several output destination communication nodes, thereby routing the cells. In addition, a receiving unit of each communication node is provided with a table for performing the determination of cell reception and a decision receiving unit for receiving the multiplexed cells on the bus in accordance with the contents of the table.

[5] In order to realize the loopback function of outputting the cell inputted from the input line to its own output line via the bus, the cell receiver from the bus of each communication node is located on the end side of the bus, that is, the output side, rather than the cell transmitter to the bus. Let's make arrangement.

As a result, the present invention has the following advantages.

[1] Since all the communication nodes have determined that the time required for the transfer of cells between adjacently connected communication nodes is determined by the time that each communication node processes the cell, i.e., the same as the period of the cell or an integer multiple of the period of the cell, It is possible to uniquely determine the timing of the processing operation, thereby eliminating the need for a complicated synchronization method as in the prior art. Also, in an ATM communication system in which communication nodes are connected by multiple buses, when the multiple buses are formed in a loop shape, the position of the slot generator can be changed without causing synchronization misalignment.

[2] Configure multiple buses in a loop shape, assign mounting position information and slot generator position information to each communication node, and perform routing between communication nodes with mounting position information of each communication node, and transmit cells at that time. Since the algorithm for determining the direction has been determined, it is not necessary to always transmit the cell in both directions or to set the cell transmission direction on the table as in the prior art, which is effective in reducing communication traffic and simplifying management of routing information.

[3] The same routing information for duplicated communication nodes by constructing multiple buses in a loop, mounting redundant communication nodes at adjacent locations, and assigning the same mounting location information to these two communication nodes. This makes it possible to perform routing of cells and to configure a highly serviceable communication system that does not require changing routing information even in the event of a failure.

[4] Point-multipoint communication can be supported by defining a connection number for a combination of several communication nodes and performing routing of cells.

[5] Since the cell receiver in the communication node is installed behind the cell transmitter and the algorithm for loopback is decided, the loopback of the cell can be easily carried out via the bus, and a complicated circuit is implemented to realize the loopback function as in the prior art. This eliminates the need for provisioning, which is effective in miniaturization and cost reduction.

EMBODIMENT OF THE INVENTION Hereinafter, one Example of the ATM communication system which concerns on this invention is described in detail using drawing.

Example 1 Synchronization Method

1 is a diagram showing a schematic configuration of each communication node of the ATM communication system according to the present invention. FIG. 2 is a diagram showing the network configuration of an ATM communication system in which several communication nodes are connected. FIG. 3 is a diagram showing the transmission / reception timing of cells in each communication node in the network.

As shown in FIG. 1, the communication node 1 is connected to the multiple buses B opposite to the multiple buses A and B, and absorbs the phase difference of the transmission data for each of the buses A and B. The control circuit performs control to multiplex and communicate the cells input on the elastic buffer 4 (hereinafter referred to as ES) and the input line 17 on bus A and bus B to output the output data to A multiple access control section 5 which controls the lead timing of the ES by the synchronous pulses from (26). In addition, the communication terminal 20 as shown in FIG. 2 is connected to the output line 16 and the input line 17, for example.

2 shows a case where a communication network is formed by connecting the communication nodes 1 in a loop form and connecting the communication terminals 20 to each communication node. Bus A and bus B of adjacent communication node 1 are connected, and the whole is formed in a loop shape. At this time, it is assumed that the bus start point (slot generator) and the bus end point ⓔ exist in each of bus A and bus B, and data flowing between the bus start point and the bus end point is discarded at the bus start point.

At this time, as shown in FIG. 3, a cell transmitted to an adjacent communication node is out of phase by the sum of the processing time of the cell and the transmission delay time of the data in the multiple access control section. This phase shift is absorbed to match the phases of the cells flowing through the bus A and bus B phases, and the lead timing from the ES 4 at each node (the leading phase of the receiving cell after the phase shift absorption by the ES 4) is To be the same.

That is, the timing of the multi-processing of the cells for the bus A and the bus B of each communication node becomes as shown in FIG. 3, and the communication node can read from the ES 4 at the same timing to both the bus A and the bus B. FIG. .

This makes it possible to determine the timing of multiplexing the cells of each communication node without being aware of cell synchronization. Moreover, even if the position of the slot generator is changed, the timing of the multi-processing of the cells does not change. Therefore, a complicated cell synchronization circuit as in the prior art is not necessary, and synchronization shift does not occur even when the slot generator is changed in position.

Example 2 cell transmission and reception method

In the following description, in the ATM communication system formed by connecting several communication nodes shown in FIG. 2, the positions of the slot generators defining the heads of the multiple buses are arranged in node A on bus A and node F in bus B, respectively. As an example, an embodiment of a cell transmission / reception method will be described.

[1] transmission methods

4 is a diagram showing the detailed configuration of each communication node 1 (the cell transmitting unit and the cell receiving unit). The communication node 1 receives and outputs a cell from the cell transmitter 6 and a bus A or bus B, which transmits the cell inputted from the input line 17 to the bus A or the bus B through the cell multiprocessor 5. It consists of the cell receiver 7 which outputs on the line 16. FIG. The common synchronization pulses are transmitted from the synchronization circuit 26 to each communication node 1 and used for the control of the lead timing of the ES 4.

Here, the cell transmitter 6 includes a routing information granter 8 for giving routing information indicating a relationship between an input and a destination to an input cell, and a transmission direction selector 9 for distributing cells to bus A or bus B. A mounting direction on the bus of the communication node 1, a transmission direction indicating section 10 for indicating a cell transmission direction to the transmission direction selecting section 9, a routing information storage section 11 for storing routing information for each cell, and a communication node 1; And a slot generator position memory section 13 for storing the position information on the bus of the communication node to which the slot generator is set, and the cell receiver section 7 includes a cell transmitter section 6 ), The reception judging section 15 for determining whether or not the cells received in each of the bus A and bus B are received, and the cells received in the bus A and bus B are output lines 16, respectively. It consists of a cell output unit 14 to multiplex and output. In addition, in this embodiment, although the mounting position information storage part 12 was provided in both the cell transmitter 6 and the cell receiver 7, since the information stored is the same, one is provided in the common part of the communication node 1; It is good also as a structure to make. Numeral 25 designates the data of the mounting position information storage unit 12 and the slot generator position storage unit 13 as a processor.

5 is a diagram showing the configuration of a table 50 for storing routing information provided in the routing information granting unit 8 in the cell transmitter 6, wherein the input cell is input VPI / VCI as header information by this table. Is converted to output VPI / VCI, and routing information RTG is assigned and transmitted on the bus.

FIG. 6 shows an example of values set in the mounting position information storage unit 12 and the slot generator position storage unit 13 provided in each communication node in the configuration of the system (same as FIG. 2) when a plurality of communication nodes are connected. As shown in Fig. 7, the transmission direction indicating section 10 determines whether to transmit the cell to either bus A or bus B according to the procedure shown in Fig. 7 according to this value.

Hereinafter, one detailed operation example of the cell transmission direction determination method according to the present invention will be described.

First, the mounting position T, which is information indicating the physical arrangement and the order of F in each communication node A, is assigned to the bus A phase along the direction in which the cell flows, and set by the processor 25 in the mounting position storage unit 12. do. In this embodiment, as shown in FIG. 6, T = 0, 1, 2, 3, 4, and 5 are mounted positions of each communication node 1 with respect to nodes A, B, C, D, E, and F. It sets in the memory | storage part 12.

Next, the position of the slot generator is defined according to the mounting position of the communication node on which the slot generator is set on the bus A, and set by the processor 25 in the slot generator position storage section 13. The value set in the slot generator position memory 13 is set to SG. In the present embodiment, since the slot generator Ð of bus A is set to communication node A, SG = 0 is set to the slot generator position memory 13 of each communication node 1 as shown in FIG. .

Next, in the routing information assigning section 8, routing information (hereinafter referred to as R) defined by the mounting position of the receiving node is provided for each cell and stored in the routing information storing section 11.

More specifically, VPI / VCI, which is header information of the cell input on the input line 17, is converted from Hin0 51 to Hout0 52 by the routing information granting table 50 shown in FIG. Further, the mounting position information R0 53 of the communication node of the transmission destination is provided as the routing information.

The transmission direction indicating unit 10 determines the transmission direction in accordance with the procedure shown in FIG. 7 in accordance with the values of T, SG, and R. FIG. That is, first and foremost, the magnitudes of the values of T and SG and R and SG are compared. Where T and R are both less than SG (Yes in both (701) and (702)) and T and R are both equal to or greater than SG (all in (701) and (703) are no). Compare R and transmit the cell to bus A if T is less than R (YES at 704), otherwise transmit the cell to bus B (No at 704) (706). . On the other hand, when T is smaller than SG and R is equal to or larger than SG, the cell is transmitted to bus B (YES at 701, NO at 702). If T is equal to or larger than SG and R is smaller than SG (NO in 701, YES in 703), the cell is transmitted to bus A. This procedure can be easily realized by the control of firmware or software by a logic circuit or a processor.

By the above configuration and operation, when the routing information providing unit 8 determines the cell transmission direction, there is no need to provide a table of communication paths and data transmission directions as in the prior art. In addition, even when the position of the slot generator is changed, the contents of the slot generator position storage section 13 need only be rewritten, so that it is not necessary to update the data transmission direction for each communication path as in the prior art. The time required can be shortened.

[2] receiving methods

For example, in FIG. 6, when the cell is to be transmitted from the communication node B to the communication node E, the communication node B gives the transmitting cell mounting location information “T = 4” as the routing information R. FIG. . That is, the cell is sent out with R = 4. In addition, since the mounting position information T = 1 and the slot generator position information SG = 0 are stored in the communication node B, the transmission cell is sent to the bus A according to the procedure shown in FIG. In the communication node E, the routing information R of the cells received by the bus A and the bus B in the reception determining unit 15 is compared with the mounting position information T = 4 set in the mounting position information storage unit 12, and the cell is received. Determine. As a result of the determination, when the mounting position information T and the routing information R of the received cell coincide, the cell received as the cell to the own node is output to the output line 16 via the cell output unit 14. In the present embodiment, since the mounting position information T = 4 of the communication node E, the cell having the routing information R = 4 is received. In addition, communication nodes C, D, and F do not receive cells with routing information R = 4.

As a result, communication node E can receive the cell transmitted from communication node B.

Example 3 Communication Node Duplication

FIG. 8 is a diagram showing the configuration of the system in the case where the communication node 1 is duplexed to improve the reliability (setting of mounting position information outside the arrangement of the communication node). In this embodiment, a configuration in which the communication node F and the communication node G are duplicated is shown.

In the case of duplexing a communication node, the redundant nodes F and G must be connected so as to be seen in the same direction of the bus as seen from other communication nodes. In order to do so, the redundant communication node F and the communication node G are mounted in adjacent positions. Also, in bus A, the slot generator 2s is prohibited from being set in the communication node G, and in the bus B, the slot generator 3s is set in the communication node F. It is forbidden. In addition, for the mounting position information "T", the same value is set to the communication node F and the communication node G. In this embodiment, T = 5 is set for both the communication node F and the communication node G. As a result, the same routing information is given to the duplicated communication node as in the case of singlet without being aware of the duplication of other communication nodes. You can send and receive.

If a failure occurs in communication node F, the central processing unit releases the prohibition in normal operation. As shown in FIG. 9, slot generators 2s and 3s are positioned at communication node G at bus A, and at bus B. By setting the communication node E, the communication node F having the trouble is separated from the bus A and the bus B. At this time, it is not necessary to change the routing information grant method and the transmission direction determination method in each communication node, and even in the case of failure by simply rewriting the contents of the slot generator position memory unit 13 of each communication node to SG = 5. As in the second embodiment, the cell transmission direction can be determined and the cell can be transmitted and received.

The present invention is not limited to duplication of communication nodes, but can be applied to a plurality of redundant configurations more than two.

Example 4 Multipoint Communication

The operation of one embodiment of point-multipoint communication will be described below using FIGS. 10 to 12. FIG.

10 is a diagram showing the configuration of a communication node 1a for performing point-multipoint communication. 11 is a diagram showing the configuration of a table in the routing information providing unit 8-1 in the communication node 1a, and FIG. 12 is a transmission direction indicating unit 10-1 in the communication node 1a. Fig. 1 shows the transmission direction determination procedure in "

In the routing information providing unit 8-1, the routing information R defined by the mounting position of the receiving node is given to the cells of the point-point communication in the same manner as in Embodiments 1 to 3, and the point-multipoint communication For the cell, a connection number (hereinafter referred to as MC) for each combination of receiving nodes that are the target of point-multipoint communication, which is routing information dedicated to multipoint communication, is defined and assigned thereto.

Specifically, in the routing information granting table 110 shown in FIG. 11, the header information VPI / VCI is converted from Hin1 1101 to Hout1 1102 for the cell of point-to-point communication, and as routing information. R1 1103, which is mounting position information of the communication node of the destination of point-point communication, is given. For the cell of point-multipoint communication, the header information VPI / VCI is converted from Hin2 (1104) to Hout2 (1105), and MC0, which is information of a combination of communication nodes of the source of point-multipoint communication as the ruty information, is used. (1106).

In the transmission direction indicating unit 10-1, the transmission direction is determined in accordance with the procedure shown in FIG. 12 by the routing information R or MC, T, and SG stored in the routing information storage unit 11-1. If the cell to be transmitted is a cell of point-multipoint communication, it is transmitted in both directions of buses A and B (Yes at 1201). If it is a cell of point-point communication (No at 1201), the procedure of FIG. In the same manner, the transmission direction is determined. In this case, in the case of a cell of point-multipoint communication, the cell is transmitted in both directions of buses A and B in order to omit the process of determining the transmission direction for each transmission destination.

On the receiving side, similarly to Embodiments 1 to 3, the reception determination table 18, which determines whether the cell is received or not based on the routing information of the received cell, has the routing information R and MC of the cell to be received by the communication node in the form of a table. Receive the cell when the routing information of the received cell matches the value kept in the table.

For example, in the configuration of FIG. 6, when node B performs point-multipoint communication with node E and node A, the central processing unit defines connection number MC in which node E and node A are a combination of destinations. And set it in the routing information grant table of NodeB. The connection numbers MC defined in the acceptance judgment tables 18 of the nodes A and E are also set. In the example, if MC = 6 is defined as the connection number, the routing numbers used for point-point communication are 1 to 5, so that routing information dedicated to point-multipoint communication can be used. The node B transmits this cell in both directions of bus A and bus B in accordance with the procedure shown in FIG. Node A receives this cell on bus B, and since MC = 6 is set in the acceptance determination table 18, it receives the cell. The node E receives the cell on the bus A, and receives the cell because MC = 6 is set in the reception determination table 18. As a result, point-to-multipoint communication can be realized. Here, since the connection number is defined by the combination of the communication nodes of the source, if the combination of communication nodes of the destination is the same, the same connection number can be used even if the communication nodes of the source are different.

Example 5 Loopback Method

13 and 14, the operation of one embodiment of the loopback method according to the present invention will be described.

FIG. 13 is a diagram showing the configuration of the communication node 1b when the loopback function is provided from the input line 17 to the output line 16. As shown in FIG. At this time, since the cell receiving unit 7 from the bus in the communication node is provided after the cell transmitting unit 6 to the bus, the loopback gives the routing information granting unit 8 with the routing information for setting its own communication node as the destination. good.

In addition, the transmission direction indicating unit 10-2 determines the transmission direction in accordance with the procedure shown in FIG. Specifically, first of all, one of bus A and bus B is set as the loopback route in the loopback route selector 19 in the central processing unit. The cell is transmitted on the bus A or the bus B in accordance with the loopback route set in the unit 19. The reception judging unit 15 of the bus A and the bus B is connected to the multiple buses at the output side of the cell multiplexing section 5, respectively, to determine receipt of the cell. If bus A or bus B is fixedly used as the loop back route, the loop back route selector 19 may not be provided.

As a result, loopback of the cell from the input line 17 to the output line 16 can be easily realized without providing a complicated circuit for implementing the loopback function. You can choose whether to loop back through B. That is, since loopback using the bus in operation is possible, it is easy to carry out maintenance operation operations such as failure analysis of the communication node.

Claims (21)

A plurality of communication nodes connected in a physical loop shape by two transmission means in which cell transmission directions are opposite to each other, the two transmission means each having a logical start point and an end point, Buffer means provided in each communication node and executing cell transmission and reception and connected to the two transmission means; Synchronizing pulse generating means connected to each communication node and generating a timing pulse for reading a cell from the buffer means; Cell multiple means provided in each communication node and having an input / output unit connected to the two transmission means and multiplexing a cell by the two transmission means; Cell transmission means provided in each communication node and transmitting a cell to the cell multiple means on an input line and connected to the cell multiple means; Cell reception means provided in each communication node and receiving a cell from the two transmission means, supplying the cell to an output line, and connected to the cell multiple means at the output part; First storage means provided in each of the communication nodes and storing information identifying each of the communication nodes connected by the transmission means; Second storage means provided in each of the communication nodes and storing information for identifying a communication node serving as a logical time point in a physical loop; And direction selection means for selecting a cell transmission direction from among transmission directions of the cells opposite to each other in accordance with the information stored in each of the communication nodes and stored in the first and second storage means. The method of claim 1, And said identification information of the communication node stored in said first storage means includes information indicating a mounting position of each communication node on a loop. The method of claim 1, The identification information of the communication node functioning as a logical time point in the physical loop stored in the second storage means includes ATM indicating information indicating a mounting position of the communication node functioning as a slot generator indicating a logical time point. Communication system. The method of claim 1, Among the communication nodes, a plurality of communication nodes having a redundant configuration are arranged adjacent to each other, The first and second storage means each include a memory for storing the same information, and when a failure occurs in one of the communication nodes having the redundant configuration, the logical position of the loop is cut to a position where the failure occurs. Means for changing information stored in said second storage means and changing information stored in said second storage means. The method of claim 1, Wherein each communication node further comprises means for assigning information to a cell indicative of a plurality of source communication nodes. A plurality of communication nodes connected in a physical loop shape by two transmission means in which cell transmission directions are opposite to each other, each of which has a logical start point and an end point; Buffer means provided in each communication node and executing cell transmission and reception and connected to the two transmission means; Synchronizing pulse generating means connected to each communication node and generating a timing pulse for reading a cell from the buffer means; A cell multiple means provided at each communication node and multiplexing a cell to any one of the two transmission means and having an input / output unit connected to the two transmission means, Cell transmission means provided at each communication node and transmitting a cell to the cell multiple means on an input line and connected to the cell multiple means; Provided at each communication node and connected to both of the two transmission means at a position in front of the cell transmission means, receiving a cell from any one of the two transmission means and supplying the cell to an output line; An ATM communication system comprising cell receiving means connected to multiple means. The method of claim 6, Wherein each communication node comprises means for designating the communication node as a destination communication node. The method of claim 6, And each communication node further comprises means for selecting any one of the two transmission means. A plurality of communication nodes connected in a physical loop shape by two transmission means in which cell transmission directions are opposite to each other, each of which has a logical start point and an end point; First storage means provided in each communication node and storing information for identifying each communication node connected by said transmission means; Second storage means provided in each of the communication nodes and storing information for identifying a communication node serving as a logical time point in a physical loop; And direction selection means for selecting a cell transmission direction from among transmission directions of the cells opposite to each other in accordance with information stored in each communication node and stored in the first and second storage means. The method of claim 9, And the identification information of each communication node stored in the first storage means includes information indicating a mounting position of each communication node on a loop. The method of claim 9, The identification information of the communication node functioning as a logical time point in the physical loop stored in the second storage means includes information indicating a mounting position of the communication node functioning as a slot generator indicating a logical time point. ATM communication system. The method of claim 9, Among the communication nodes, a plurality of communication nodes having a redundant configuration are arranged adjacent to each other, The first and second ginger means each include a memory for storing the same information, and when a failure occurs in one of the communication nodes having the redundant configuration, the failure occurs when the communication node is disconnected from the loop. And means for changing information stored in said second storage means while changing a logical viewpoint. The method of claim 9, Wherein each communication node further comprises means for assigning information to a cell indicative of a plurality of source communication nodes. A plurality of communication nodes connected in a physical loop shape by two transmission means in which cell transmission directions are opposite to each other, each of which has logical start and end points; Buffer means provided in each communication node and executing cell transmission and reception and connected to the two transmission means; Synchronizing pulse generating means connected to each communication node and generating a timing pulse for reading a cell from the buffer means; Cell multiple means provided in each communication node and having an input / output unit connected to the two transmission means and multiplexing a cell by the two transmission means; Cell transmission means provided in each communication node and transmitting a cell to the cell multiple means on an input line and connected to the cell multiple means; Cell reception means provided in each communication node and receiving a cell from the two transmission means, supplying the cell to an output line, and connected to the cell multiple means at the output part; First storage means provided in each of the communication nodes and storing information identifying each of the communication nodes connected by the two transmission means; Second storage means provided in each of the communication nodes and storing information for identifying a communication node serving as a logical time point in a physical loop; And direction selection means for selecting a cell transmission direction from among transmission directions of the cells opposite to each other in accordance with the information stored in each of the communication nodes and stored in the first and second storage means. The method of claim 14, And said identification information of each communication node stored in said first storage means includes information representing said each communication node on a loop. The method of claim 14, The identification information of the communication node serving as the logical time point in the physical loop stored in the second storage means includes information indicating the mounting position of the communication node functioning as the slot generator indicating the logical time point. Communication system. The method of claim 14, Among the communication nodes, a plurality of communication nodes having a redundant configuration are arranged adjacent to each other, The first and second storage means each include a memory for storing the same information, and when a failure occurs in one of the communication nodes having the redundant configuration, the failure-producing communication node is cut off from the loop. And means for changing information stored in said second storage means while changing a logical viewpoint. The method of claim 14, Wherein each communication node further comprises means for assigning information to a cell indicative of a plurality of source communication nodes. Two transmission paths of reverse cell transmission directions are connected to at least three communication devices so as to form a first loop and a second loop, each loop having a logical starting point and an end point of cell transmission of the ATM communication device. As an ATM communication device used in a shape communication network, First and second cell multiple circuits for multiplexing cells to be transmitted in each of the first and second loops and outputting the multiplexed cells; A routing information granting circuit for assigning routing information identifying an ATM communication apparatus to which a cell to be transmitted is to be received; A selection circuit for allocating cells transmitted to any one of the first cell multiple circuit or the second cell multiple circuit; A first memory corresponding to each ATM communication device and storing first position information of said ATM communication device, A second memory corresponding to each ATM communication device and storing second position information of said ATM communication device; and a direction indicating circuit for controlling said selection circuit in accordance with said information stored in said first and second memories and said routing information; Including, The first location information indicates a location of the ATM device on the loop, the second location information indicates a logical time point on the loop, By selecting any one of the first loop or the second loop in accordance with the first location information, the second location information and the routing information, the cell to be transmitted is received by the ATM communication apparatus. This ATM communication device is transmitted. The method of claim 19, First and second receiving circuits for determining a cell to be received by comparing the first location information with routing information included in each cell received through the first and second loops, And a cell transmitted through the first or second loop with respect to the ATM communication device. Two transmission paths of reverse cell transmission directions are connected to at least three communication devices so as to form first and second loops, each loop having a logical start point and an end point of cell transmission of the ATM communication device, A loop selection method of an ATM communication apparatus in a loop communication network in which one of the first and second loops is selected and a cell is transmitted. Determining routing information identifying an ATM communication device to which a cell to be transmitted is to be received; The first loop or the second loop according to first position information indicating a position of an ATM communication device in the network, second position information indicating a logical time point in the first and second loops, and the routing information. Includes a step of selecting one in the loop, The step to select A first step of comparing the first positional information indicating the position of the ATM communication device in the network with the second positional information indicating the logical viewpoint in the loop; A second step of comparing the routing information with the second positional information indicating the logical viewpoint in the loop; and And a third step of comparing the routing information with the first location information indicating the location of the ATM communication device in the network.