JPH05252179A - Communication method and communication system - Google Patents

Abstract

PURPOSE:To simplify the circuit configuration of each communication node by sending out the same cell on two transmission lines, and transferring the cell by a reception selection system. CONSTITUTION:A communication node 1 sends out user information received from a terminal 10 to the transmission line 9. In such a case, the reception selection system in which the sending side of the communication node always sends out the cell to both transmission lines 9, and a reception side selects data convenient for the reception side is employed. At the reception side, a cell disassembling part 5 checks the continuity of the SR number of the cell arriving at its own node, and deletes the cell provided with the SN number other than the SN number scheduled to receive at the next time. When a certain cell to be deleted on the middle way of transmission exists, no serial number can be obtained in the SR number to be received, and also, the inversion of sequence when the cell arrives can be recognized by observing the passing of the SN number. When the SN number is continuous, the cell disassembling part 5 judges that no deletion of the cell is performed, and writes the user information on a reception buffer 6.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention shares a transmission line with a plurality of communication nodes and sends cells on the transmission line.
The present invention relates to a communication method and a communication system for transmitting information between arbitrary communication nodes.

[0002]

2. Description of the Related Art In a network in which a transmission line is shared and used, an access method is defined so that communication nodes connected to the transmission line do not randomly send cells. This access method includes a token passing method and an AT.
There is an MR method and the like. The token passing method is a method in which the token representing the transmission right is circulated on the transmission path, only the communication node that received the token obtains the right to transmit the data, and after the transmission is completed, the token is passed to the next communication node. Is. The ATMR system has been devised so that one communication node does not occupy a transmission line for a long time and each communication node can perform equal communication (for example, the Institute of Electronics, Information and Communication Engineers Exchange System Research Group). (See “SESE 90-41”, “Consideration on the construction method of subscriber access high speed ring network (ATMR)”).
That is, in the ATMR method, a communication section is provided in time,
Window control is performed to limit the transmission capacity in this communication section. In the window control, the number of cells that can be transmitted per fixed time is given as the band permitted to the communication node.

FIG. 8A shows a ring network having the above ring access protocol. The ring network is composed of a plurality of communication nodes and two ring-shaped transmission lines that connect the communication nodes in a ring shape. The communication node can transmit information between arbitrary communication nodes having different addresses by sending a cell including control information and user information onto the transmission path. For example, when the right system transmission line is used as the transmission line, when the cell is transferred from the communication node A to the communication node X, the communication node A writes the address of the communication node X in the control information of the cell and sets the cell. It is sent to the right transmission line α. The communication node X monitors the control information of the cell input via the right transmission path α, and determines whether or not it is addressed to the own node. The cell not addressed to the own node is relayed and reaches the adjacent communication node Y. When the cell is addressed to the own node, the cell is dropped to the own node without being relayed to the right transmission path α.

By the way, in order to improve the reliability of the network, there is a technique in which two ring-shaped transmission lines are used to perform active standby switching and loop back when a failure occurs. That is, in the ring network, the transmission lines are duplicated, and normally only one transmission line is used. Then, when a failure occurs in the transmission path being used, switching to the other transmission path prevents interruption of network operation. The normally used transmission line is called the active system, and the standby transmission line is called the standby system.

First, the active standby switching method will be described with reference to FIG. As shown in (a), the right transmission line α
When the left transmission path β is operated as the standby system, the communication node B and the communication node C are operated as shown in (b).
It is assumed that a failure γ has occurred in the right transmission path α that connects between and.
Then, if the system is switched, the network can be operated using the left system transmission line β which was the standby system as shown in the figure.

However, if a failure occurs in both the right transmission line α and the left transmission line β at the same time, the ring network is not restored even if the active system is switched to the standby system. In this case, if the transmission lines are folded back at the communication nodes at both ends of the faulty transmission line, all communication nodes can communicate. Such a loopback method will be described with reference to FIG. When both the right system transmission line α and the left system transmission line β between the communication node D and the communication node E have a fault δ, the communication node D and the communication node E loop back as shown in the figure. do. It can be seen that loopback allows all communication nodes to maintain communication. Even in the case of the failure γ as shown in FIG. 8B, the communication node B and the communication node C perform the loopback control, so that the network can be recovered from the failure.

[0007]

As described above, in the active standby switching system, only one transmission line is used.
On the other hand, in the loopback method, if the transmission capacities of both transmission lines are used during normal operation, many cells will be discarded during loopback. Therefore, when operating the ring network using both transmission paths, it is necessary to use it on the assumption that all the data being transferred may be discarded at the time of loopback. Alternatively, it is necessary to prioritize cells that are discarded and cells that are not discarded during loopback, and allocate cells that have a priority that is not discarded and that is okay to loopback. .. In either case, the loopback method can only use the capacity of one transmission line.

As described above, in the conventional communication system, even if the active standby switching system and the loopback system use two transmission lines, the capacity that can be used for transmission is about the capacity of one transmission line. However, in order to detect the timing to perform the active standby switching operation and the loopback operation, and to implement the active standby switching function and the loopback function, an extra circuit is required, and the circuit configuration of each communication node is complicated. There was a problem of becoming.

The present invention has been made in view of the above circumstances, and provides a communication method and a communication system in which the circuit configuration of a communication node can be simplified while communication can be continued even when a failure occurs in a transmission path. The purpose is to

[0010]

According to a first aspect of the present invention, a plurality of communication nodes and two transmission lines for mutually connecting these communication nodes and having different physical routes are used.
In a communication method for transmitting information between arbitrary communication nodes by transmitting a cell consisting of control information and user information on a transmission line, the transmission side of each communication node sends a cell if there is information to be transmitted. A cell is composed of control information including information indicating the order and user information to be transmitted,
The cell is sent to two transmission lines, and the receiving side of each communication node arrives at its own node from the two transmission lines based on the information indicating the cell transmission order contained in the cell control information. It is characterized in that only the necessary cells are selected from the cells to be processed.

According to a second aspect of the present invention, a ring-shaped transmission line is provided,
Communication for transmitting information between arbitrary communication nodes by sending a cell consisting of control information and user information to the transmission path using a plurality of communication nodes having different addresses connected to this transmission path The method uses two ring-shaped transmission lines in which cells are transmitted in opposite directions,
On the sending side of each communication node, if there is information to be sent,
A cell is composed of control information including information indicating the cell transmission order and user information to be transmitted, and the cell is transmitted to both of the two transmission lines, and the cell is controlled on the reception side of each communication node. It is characterized in that only the necessary cells are selected from the cells arriving at the own node from the two transmission paths based on the information indicating the cell transmission order included in the information.

According to a third aspect of the present invention, in addition to the first or second aspect of the invention, based on the information indicating the cell transmission order included in the cell control information on the receiving side of the communication node, When only necessary cells are selected from the cells arriving at the own node from the book transmission path, cells are selected in the order of cell transmission order, and cells that do not have the transmission order information that should arrive next are discarded. It is characterized by

According to a fourth aspect of the present invention, in addition to the first or second aspect of the invention, based on the information indicating the cell transmission order included in the cell control information on the receiving side of the communication node, When only necessary cells are selected from the cells arriving at the own node from the book transmission line, the arriving cell is 1
Only in the case of cell loss, store that cell and wait for the arrival of the next cell.If the next arrival cell is a cell that has left out, select that cell and then select the stored cell If it does not exist, it is characterized in that the sequence information of the next arrival cell is set as the head and the subsequent operation is performed.

The invention of claim 5 is characterized in that, in addition to the invention of any one of claims 1 to 4, the SN bit of the ATM adaptation layer header is used as the information indicating the cell transmission order. According to the invention of claim 6, in addition to the invention of any one of claims 1 to 5, there is a bit for identifying a use state, an idle state and a waiver state in the cell control information. , If the user information to be sent is less than or equal to a predetermined band on the transmission side of each communication node, the information is sent to two transmission lines using the idle cell, and the idle corresponding to the surplus band is sent. If there is information to change the status cell to the right abandonment status and send it to its own node and send it over the specified band, the idle state cell corresponding to the band and the other node abandoned the right status And send information using
The feature is that the cell in the renounced state sent to the own node is changed to the idle state.

The invention of claim 7 includes a plurality of communication nodes,
Information transmission between arbitrary communication nodes is provided by providing two transmission paths that connect these communication nodes to each other and have different physical routes, and send out cells consisting of control information and user information onto the transmission paths. In the communication system configured to perform the above, a cell is configured for each communication node from control information including information indicating a cell transmission order and user information to be transmitted, and the cell is transmitted to two transmission lines. Based on a cell transmission unit, a cell reception unit that receives cells arriving at its own node from two transmission paths, and information indicating the cell transmission order included in the cell control information received by the cell reception unit. And a cell disassembling unit that selects only necessary cells.

The invention of claim 8 is a ring-shaped transmission line,
A configuration is provided in which a plurality of communication nodes with mutually different addresses connected to this transmission line are provided, and information is transmitted between arbitrary communication nodes by sending out cells consisting of control information and user information to the transmission line. In this communication system, two ring-shaped transmission lines for transmitting cells in opposite directions are provided, and control information including information indicating the cell transmission order and user information to be transmitted are provided to each communication node. It is received by the cell sending unit that configures a cell and sends the cell to both of the two transmission lines, the cell receiving unit that receives the cell arriving from the two transmission lines to the own node, and the cell receiving unit. And a cell disassembling unit that selects only necessary cells based on the information indicating the cell transmission order included in the cell control information.

According to a ninth aspect of the present invention, in addition to the seventh or eighth aspect of the invention, the cell disassembling unit determines whether two cells are transmitted based on the information indicating the cell transmission order included in the cell control information. When only necessary cells are selected from the cells arriving at the own node from the transmission line, the cells are selected in the order of cell transmission order, and the cells that do not have the transmission order information that should arrive next are discarded. It is characterized by doing.

In addition to the invention of claim 7 or claim 8, the invention of claim 10 is characterized in that the cell disassembling unit determines that two cells are transmitted based on the information indicating the cell transmission order included in the control information of the cell. When only the necessary cells are selected from the cells arriving at the own node from the transmission line, the cells are stored only when one cell is missing, and the next cell is waited for until the next cell arrives. If it is a missing cell, the cell that has been stored is selected after selecting that cell, and if it is not a missing cell, the sequence information of the next arriving cell is set as the head and the subsequent operation is performed. There is.

According to the invention of claim 11, in addition to the invention of any one of claims 7 to 10, the S of the ATM adaptation layer header is used as information indicating the cell transmission order.
The feature is that the configuration uses N bits. According to the invention of claim 12, in addition to the invention of any one of claims 7 to 11, there is a bit for identifying a use state, an idle state, and a waiver state in the cell control information. When the cell transmission unit is controlled by the transmission management unit and the user information to be transmitted is less than or equal to a predetermined band, the cell in the idle state is used to transmit the information to the two transmission lines, and there is a surplus. If there is information to change the idle cell corresponding to the band to the abandoned state and send it to its own node and send it over the specified band, the idle cell corresponding to the band and other nodes It is characterized in that information is transmitted using the abandoned cell in the abandoned state, and the cell in the abandoned state transmitted to the own node is changed to the idle state.

[0020]

According to the invention of claim 1, on the transmission side of each communication node, if there is information to be transmitted, a cell is constructed from control information including information indicating the cell transmission order and user information to be transmitted. Then, the cell is transmitted to the two transmission lines, and the receiving side of each communication node transmits the cells from the two transmission lines to the own node based on the information indicating the cell transmission order included in the cell control information. Only the required cells are selected from the cells arriving at.

According to the second aspect of the present invention, two ring-shaped transmission lines in which cells are transmitted in opposite directions are used, and the transmission side of each communication node determines the cell transmission order if there is information to be transmitted. A cell is composed of control information including information indicating that the cell and user information to be transmitted, and the cell is transmitted to both of the two transmission paths. The receiving side of each communication node includes the cell in the control information of the cell. Based on the information indicating the cell transmission order that has been set, only the necessary cell is selected from the cells arriving at the own node from the two transmission paths.

According to the third aspect of the invention, on the receiving side of the communication node, the cell arriving from the two transmission lines to the own node based on the information indicating the cell transmission order contained in the cell control information. When only the necessary cells are selected, the cells are selected in the order of cell transmission order, and the cells that do not have the transmission order information that should arrive next are discarded. In the invention of claim 4, on the receiving side of the communication node, among the cells arriving from the two transmission lines to the own node, it is necessary based on the information indicating the cell transmission order included in the cell control information. When selecting only the best cell, the arriving cell is 1
Only in the case of cell loss, store that cell and wait for the arrival of the next cell.If the next arrival cell is a cell that has left out, select that cell and then select the stored cell If not, the sequence information of the next arriving cell is set as the head and the subsequent operation is performed.

In the invention of claim 5, the SN bit of the ATM adaptation layer header is used as the information indicating the cell transmission order. In the invention of claim 6,
In the cell control information, there are bits for identifying the usage status, the idle status, and the waiver status, and if the user information to be transmitted at the transmission side of each communication node is below a predetermined band, 2 information using idle cells
Sent to the book transmission line, change the idle cells corresponding to the surplus band to the right abandoned state and send to the own node. Information is transmitted using the cell in the idle state and the cell in the abandoned right in which another node has abandoned the right, and the cell in the abandoned state sent to the own node is changed to the idle state.

In the invention of claim 7, the cell transmission section is
A cell is composed of control information including information indicating the cell transmission order and user information to be transmitted, and the cell is transmitted to two transmission lines. The cell receiving unit receives cells arriving at its own node from the two transmission paths. The cell disassembling unit selects only necessary cells based on the information indicating the cell transmission order included in the cell control information received by the cell receiving unit.

In the invention of claim 8, the cell transmission section is
A cell is composed of control information including information indicating the cell transmission order and user information to be transmitted, and the cell is transmitted to both of the two transmission paths. The cell receiving unit receives cells arriving at its own node from the two transmission paths. The cell disassembling unit selects only necessary cells based on the information indicating the cell transmission order included in the cell control information received by the cell receiving unit.

In the invention of claim 9, the cell disassembly unit is
Based on the information indicating the cell transmission order included in the cell control information, when selecting only the necessary cells from the cells arriving at the own node from the two transmission paths, the cells are transmitted in the order of the cell transmission order. , And discards cells that do not have the transmission order information that should arrive next. In the invention of claim 10, the cell disassembling unit determines, based on the information indicating the cell transmission order included in the cell control information, only the necessary cell among the cells arriving from the two transmission paths to the own node. When selecting, the cell that arrived is stored only when one cell is missing and waits for the arrival of the next cell, and if the next arrival cell is missing, it is stored after selecting that cell. The selected cell is selected, and if it is not a missing cell, the sequence information of the next arriving cell is set as the head and the subsequent operation is performed.

In the eleventh aspect of the invention, the SN bit of the ATM adaptation layer header is used as the information indicating the cell transmission order. According to the twelfth aspect of the invention, the cell control information includes a bit for identifying a use state, an idle state, and a waiver state, and the cell transmission unit is controlled by the transmission management unit and transmitted. If the user information to be sent is less than the predetermined band, the information is sent to the two transmission lines by using the idle cell, and the idle cell corresponding to the surplus band is changed to the waiver state. If there is information to be sent to its own node and sent over a predetermined band, the information is sent using the idle cell corresponding to the band and the cell in the abandoned right in which another node has abandoned the right. , Change the cell in the waived state sent to its own node to the idle state.

[0028]

Embodiments of the present invention will be described in detail below with reference to the drawings. (Embodiment 1) FIG. 1 is a circuit block diagram of a communication node of a communication system in Embodiment 1 of the present invention.
Is a cell reception unit 2, a cell transmission unit 3, and a transmission management unit 4
The cell disassembly unit 5, the reception buffer 6, the transmission buffer 7, and the terminal interface unit 8 are provided. The cell reception unit 2 and the cell transmission unit 3 are each connected to a transmission line 9, and the terminal interface unit 8 is connected to a large number of terminals 10. The cell receiving unit 2 receives cells from the transmission line 9. The cell sending unit 3 sends cells to the transmission line 9. The transmission management unit 4 manages cell transmission. The cell disassembling unit 5 composes user information from the received cells. The reception buffer 6 buffers the user information reconstructed from the received cell. The transmission buffer 7 buffers the user information to be transmitted. Although not clear in FIG. 1, the transmission line 9 constitutes two ring-shaped transmission lines as described later, and the cell reception unit 2 receives cells from the two ring-shaped transmission lines, The sending unit 3 sends cells to the two ring-shaped transmission lines.

Next, the operation of the communication node 1 will be described. The cell receiving unit 2 of the communication node 1 receives a cell addressed to its own node among the cells passing through the transmission path 9, supplies the cell to the cell disassembling unit 5, and sends the control information in the cell to the transmission managing unit. Supply to 4. As a result, the cell disassembling unit 5 reconstructs the user information disassembled from the supplied cells into cells at the sending node, and supplies the user information to the reception buffer 6.
The user information in the reception buffer 6 is transmitted to the target terminal 10 through the terminal interface unit 8. On the other hand, the user information from the terminal 10 is temporarily stored in the sending buffer 7. When the user information in the transmission buffer 7 is in the state where it can be converted into cells, the transmission buffer 7 notifies the transmission management unit 4 of the cell transmission request. Upon receiving the cell transmission request, the transmission management unit 4 supplies the control information to the cell transmission unit 3. As a result, the cell sending unit 3 reads the user information from the sending buffer 7 and sends it to the transmission path 9 as a cell together with the control information received from the sending management unit 4.

As described above, each communication node 1 is connected to the terminal 10
It suffices if the user information received from the transmission line 9 can be transmitted to the transmission line 9. However, since the transmission line 9 is shared by a large number of communication nodes 1, transmission of cells from all the communication nodes 1 on the transmission line 9 is performed somehow. Must be managed in a way.
This is transmission line access control. The transmission management unit 4 performs this control in each communication node 1. Examples of the ring access control method in the communication method in which the cell is circulated on the ring-shaped transmission path 9 include the token passing method and the ATMR method. In this embodiment, the following access protocol is used. This access protocol is described in more detail in, for example, Japanese Patent Application No. 3-107802.

Regarding the access protocol of this embodiment,
This will be described below. The cells transmitted on the transmission line 9 are
It is classified into the following three states. (1) State of use: Cell being used. (2) Idle state: A cell that has a usage right and is not used. (3) Abandoned state: A cell whose usage right has been abandoned and has not been used.

The case where the user information is transferred is expressed as "used". These states are included in the cell control information. A window timer value is assigned to each communication node 1, and the following operation is repeated with the time indicated by the window timer value as a cycle. That is, in each communication node 1, if there is a cell transmission request from the transmission buffer 7 within the time of the window timer value, the cell transmission unit 3 and the transmission management unit 4 use the idle cell to transfer the cell to the transmission line 9. To send to. If there is a further cell transmission request within the window timer time, the cell transmission unit 3 and the transmission management unit 4 transmit the cell to the transmission line 9 by using the cell in the renounced state. In the above two cases, the cell used in each communication node 1 transits to the use state. On the other hand, when there is no cell transmission request from the transmission buffer 7 within the time of the window timer value, one cell in the idle state is put into the right abandoned state. At this time, the transfer destination of the cell in the renounced state is its own node. On the receiving side of the node, the used cell addressed to the own node and the cell in the waived state addressed to the own node transit to the idle state.

By the above control, the communication node 1 sends the user information received from the terminal 10 to the transmission line 9.
The communication system of the present embodiment employs a reception selection method in which the transmission side of the communication node 1 always transmits cells to both transmission lines 9 and selects data that is convenient for the reception side. The communication by the reception selection method and the operation when the cell does not arrive due to a transmission line failure will be described below.

The cell transmitted to the transmission line 9 is, for example, as shown in FIG.
The AAL header has an SN bit for detecting cell discard. In FIG. 2, SN is a sequence number, S
NP is a sequence number protection, IT is an information type, LI is a valid information length, ST is a segment type, CRC is an error detection code, MID is a message ID, and RES is a spare.

First, the operation of the transmission side of the communication node 1 will be described with reference to FIG. Based on the ring access protocol, the cell sending unit 3 sends the same cell to the ring-shaped right transmission line α and the ring-shaped left transmission line β that form the transmission line 9 as shown in FIG. Sent to both. Then, the transmission management unit 4 increments the number indicated by the SN bit, that is, the SN number by 1, every time a cell is transmitted. Since the SN bit is 4 bits, the transmission management unit 4 sets a number from 0 to 15. 1
Next to 5, 0 is set. Now, as shown in (b) of FIG.
If a failure γ occurs in both the right system transmission line α and the left system transmission line β between the communication node B and the communication node C, the communication node C selects the cell from the right system transmission line α as a communication node. B
Then, the cells from the left transmission path β cannot be received. Here, for example, if the communication node C sends random information to the right system transmission line α, the operation of the communication nodes D, A, and B connected to the downstream side of the communication node C of the right system transmission line α is performed. Abnormality occurs. Therefore, the communication node C generates an idle cell in place of the cell originally supposed to be relayed and sends it to the right transmission line α.
This function guarantees the cell transfer function of the downstream node. Communication node B also executes similar processing.

On the receiving side, the cell disassembling unit 5 checks the continuity of the SN numbers of the cells arriving at the own node. Then, a cell having an SN number other than the SN number to be received next is discarded. If some cells are discarded during transmission, the received SN numbers will not be consecutive. Also, the order reversal at the time of cell arrival can be known by observing the passing of the SN number. If the SN numbers are consecutive, the cell disassembling unit 5 determines that there is no cell discard and writes the user information in the reception buffer 6.

FIG. 4 shows the arrival of cells and the operation of the cell disassembly unit 5. In FIG. 4, cells arriving from the right system transmission line α are shown in the upper stage, and cells arriving from the left system transmission line β are shown in the lower stage. The numbers in the figure indicate SN numbers. The cells having the same SN number are cells having the same user information transmitted to both the right system transmission line α and the left system transmission line β. Further, the meanings of the symbols ◯ △ × in the figure are as follows.

O mark: A cell using user information. △: A cell that arrived but was discarded by the communication node 1 without using the user information. X: A cell that should have arrived, that is, a cell that was discarded during transmission. FIG. 4A shows a case where there is no cell discard in both the right system transmission line α and the left system transmission line β, and the cell disassembling unit 5 sets the same cell (same SN number and information) to 2 Receive the pieces. Since the cell from the right system transmission line α arrives early, the cell disassembling unit 5 adopts the cell information received from the right system transmission line α. The cell arriving from the left transmission path β is not used.

FIG. 4B shows a case where the arrival time difference is larger than that in FIG. 4A. Also in this case, since the cell having the SN number that should come next does not come from the left system transmission line β, the cell from the left system transmission line β that arrived later is discarded, and the information from the right system transmission line α is discarded. Just choose. Next, consider the case where a cell is discarded during transmission. FIG. 4C shows FIG.
Although the arrival time difference is the same as that of (a), it is a case where a part of the cells from the right transmission path α are discarded during the transmission. Even if some of the cells from the right transmission path α are discarded, the cells can be restored as shown in the figure. (Second Embodiment) In the first embodiment, as shown in (d) of FIG. 4, when the arrival time difference is the same as that of (b) of FIG. 4, a part of the cells from the right transmission path α is discarded during transmission. If so, the above-mentioned function of the cell disassembling unit 5 cannot be applied. That is, the cell is selected as shown in the figure, the cell having the SN number 2 cannot be obtained, and the user information is interrupted. As described above, the cell discard can be detected only by observing the continuity of the SN numbers, but the recovery at the time when the arrival of the cell is reversed cannot be recovered.

Therefore, in the second embodiment, the cell disassembling unit 5 is constructed as shown in FIG. 5 so that the cell can be recovered even when the arrival of the cell is reversed. That is, the cell disassembling unit 5 includes the control information extracting circuit 12, the switch 13, the memory 14, and the switch 15
And a switch control circuit 16. The configuration other than the cell disassembly unit 5 is the same as that of the first embodiment. The control information extracting circuit 12 divides the cell into control information and user information, and extracts the SN number from the control information. Switch 13
Is controlled by the switch control circuit 16 and the control information extracting circuit 1
The state of supplying the user information from the memory 2 to the memory 14,
The state of supplying to the switch 15 and the state of supplying nowhere can be switched. The memory 14 stores the user information from the switch 13. The switch 15 causes the switch control circuit 16 to supply the user information from the memory 14 to the receiving buffer 6, the state of supplying the user information from the switch 13 to the receiving buffer 6, and the supplying to the receiving buffer 6. You can switch to the state that you do not. The switch control circuit 16 uses the S from the control information extracting circuit 12.
The switches 13 and 15 are controlled based on the N number.

The cell disassembly unit 5 has the following functions. Function 1: 1 Wait for the arrival of the next cell only when the cell is missing. At this time, the arrived cell is stored. Function 2: If the next cell is a missing cell, use that cell. After that, the stored cell is used.

Function 3: If the next cell is not the missing cell, the SN number of the cell is set as the head and the operation is continued thereafter. Next, the operation of the cell disassembly unit 5 will be described. 1, 2, 3 and SN
When the cells having the numbers arrive, since these are consecutive numbers, the switch control circuit 16 connects the switch 13 to the terminal 13b and the switch 15 to the terminal 15b.
As a result, the user information is sent to the reception buffer 6.
However, the S of the cell that arrived after the cell with SN number 3
If the N number is 5, there is one cell missing,
The user information carried by the cell having the SN number 5 is temporarily stored in the memory 14 without being discarded as it is. That is, the switch control circuit 16 connects the switch 13 to the terminal 13a. As a result, the user information is input to the memory 14.
If the SN number of the next arrival cell is 4, the switch control circuit 16 switches the switches 13 and 15 to the terminals 13b and 15
Connect to b. As a result, the user information is sent to the reception buffer 6. After that, the switch control circuit 16 connects the switch 15 to the terminal 15a. As a result, the user information stored in the memory 14 is transferred to the reception buffer 6
Sent to. On the other hand, the SN number of the next cell to arrive is 4
If not, it is determined that the cell having the SN number 4 is discarded during the transmission.

Therefore, as shown in (e) of FIG. 4, due to the function of the cell disassembling unit 5 corresponding to the one-cell omission, an arrival cell from the right transmission line α and an arrival cell from the left transmission line β are formed. User information can be transferred even if there is a delay difference. By the way, when the cell generation interval of the communication node 1 is small, it is considered that the SN number of the cell input from the right transmission line α and the SN number of the cell input from the left transmission line β are largely deviated. In this case, the cell disassembling unit 5 must be able to control the number reversal to a large extent in response to this.
The reception selection method does not work properly when cell discard occurs. The relationship between the cell generation interval and the arrival time difference will be described below.

First, when the data is transmitted from the communication node 1 to the right system transmission line α and the left system transmission line β at the same timing, the cell is transmitted from the communication node A to the communication node B in the ring network shown in FIG. 6, for example. Consider the difference in cell arrival times. The transmission path distance between adjacent communication nodes is L ₁ [km], the propagation speed on the right transmission path α and the left transmission path β is V ₁ [μsec / km], and the transmission path speed is Sr.
[Mbit / s], and the cell length is Lc [bit]. If the cell time Tc is defined as the time required to send one cell, the cell time Tc is expressed by the following mathematical expression 1.

[0045]

[Equation 1]

When the time required for a cell to travel between the communication node A and the communication node B is T ₁ , the time T ₁ is expressed by the following equation 2.

[0047]

[Equation 2]

The number N ₁ of cells existing between the communication node A and the communication node B is expressed by the following expression 3.

[0049]

[Equation 3]

On the other hand, in order to relay each communication node 1,
If N ₂ times the cell time Tc is required, the time required for transmission from the communication node A to the communication node B (calculated by the cell time) is represented by the following formula 4.

[0051]

[Equation 4]

Therefore, the right system transmission line α and the left system transmission line β
The time difference from

[0053]

[Equation 5]

Now, consider a ring network under the following conditions. Transmission path distance L 1 between adjacent communication nodes 1 and ₁ : 1 [km] Propagation speed V ₁ on the transmission path 9: 5 [μsec / km] Transmission path speed Sr: 622 [Mbit / s] Cell length Lc: 53 × 8 [bit] In this case, the number N ₁ of cells existing between the communication node A and the communication node B is 7.3 cell time. That is,
There are 7.3 cells on the right transmission line α between the communication node A and the communication node B. On the other hand, if the time N ₂ required for relaying a cell at each of the communication nodes J to C is 5 cell times, the arrival time difference is 8 × (7.3+).
5) = 98.4. That is, under the above conditions, the cell arrival time difference TD between the adjacent communication nodes 1 and 1 becomes about 100 cell time.

Next, considering the cell transmission interval at each communication node 1, for example, when data of a constant speed Sc [Mbit / s] is converted into cells and transferred, the cells are (Sr / S
c) The right system transmission line α and the left system transmission line β once per time
(However, the overhead such as the cell header is not included). That is, the average cell transmission interval TI is (Sr / Sc). If the ISDN primary group velocity of 1.5 Mbit / s is selected as the constant velocity Sc, the cell transmission interval TI becomes about 400.

If the cell arrival time difference TD is smaller than the cell transmission interval TI, the relationship shown in FIG. However, when the cell arrival time difference TD becomes a size that cannot be ignored as compared with the cell transmission interval TI (TD> TI),
As shown in (b). According to the function of the cell disassembling unit 5 in this embodiment, the cell arrival time difference TD up to twice the cell transmission interval TI is allowed. Under the above conditions, the cell arrival time difference TD is about 100 cell time, so if the cell transmission interval TI is 50 cells or more, the user information is re-created even if there is a cell discard as shown in (d) and (e) of FIG. Can be configured. That is, if the constant speed Sc is about 12 Mbit / s, the cell transmission interval TI is 50 cells, and the reliability can be improved by the reception selection method in the ring transmission line under the above conditions.

As described above, in the reception selection method adopting the above protocol, the same cell is transmitted to both the right system transmission line α and the left system transmission line β, so that the right system transmission line α and the left system transmission line α are transmitted. Even if a failure occurs in one or both of the paths β, it is possible to receive the cells from either the right transmission path α or the left transmission path β and restore the original data. Further, a circuit for detecting the timing of performing the active standby switching operation or the loopback operation, and a circuit for realizing the active standby switching function, the loopback function, or the like is unnecessary, and the circuit configuration of each communication node 1 can be simplified. For example, since the loopback function is unnecessary, it is not necessary to provide a switch for loopback in each communication node 1. Further, if the cell disassembling unit 5 having the function of permitting the reversal of the transmission order is employed as in the present embodiment, the cells are discarded due to cell discard due to a bit error in the right transmission path α or the left transmission path β. Even if the arrival reverse occurs, the original data can be restored well.

It should be noted that how much the cell disassembling unit 5 that allows the reversal of cell arrival is used is appropriately determined based on the actual size of the transmission path 9, the time of passing through the communication node 1, the interval of cells to be transmitted, and the like. do it. Although the two ring-shaped transmission lines 9 are used in the above embodiment, the present invention is not necessarily limited to such a configuration, and two bus-type transmission lines may be used, for example. .. Also in this case, the original data can be properly restored even if a failure occurs in one transmission path.

[0059]

As described above, according to the present invention, 2
Since the same cell is sent to the transmission line of the book and the cell is transferred by the reception selection method, communication can be continued even when the transmission line fails, and detection of the timing for performing the active standby switching operation or the loopback operation can be performed. A circuit for realizing the active standby switching function and the loopback function is unnecessary, and the circuit configuration of each communication node can be simplified.

Further, if a cell disassembling section having a function of permitting the reverse of the transmission order is adopted in each communication node, even if the cell arrival reverse occurs due to the cell discard due to the bit error in the transmission path, The original data can be restored well.

[Brief description of drawings]

FIG. 1 is a circuit block diagram of a communication node of a communication system according to a first embodiment of the present invention.

FIG. 2 is an explanatory diagram of a cell format.

FIG. 3 is an explanatory diagram of a transmission operation of a communication node.

FIG. 4 is an explanatory diagram of cell arrival by two transmission paths.

FIG. 5 is a configuration diagram of a cell disassembly unit of a communication system according to a second embodiment of the present invention.

FIG. 6 is an explanatory diagram of two ring-shaped transmission lines.

FIG. 7 is an explanatory diagram of a cell arrival time difference.

FIG. 8 is an explanatory diagram of a conventional network failure recovery method.

[Explanation of symbols]

 1 communication node 2 cell receiving unit 3 cell transmitting unit 4 transmission managing unit 5 cell disassembling unit 9 transmission path

Claims (12)

[Claims] 1. A cell comprising control information and user information is transmitted to a transmission line by using a plurality of communication nodes and two transmission lines which mutually connect these communication nodes and which have different physical routes. By doing so, in the communication method for transmitting information between arbitrary communication nodes, if there is information to be transmitted on the transmission side of each communication node,
A cell is composed of control information including information indicating the cell transmission order and user information to be transmitted, and the cell is transmitted to two transmission lines. The receiving side of each communication node uses the cell control information as the cell control information. A communication method characterized in that only a necessary cell is selected from cells arriving at its own node from two transmission paths based on the included information indicating the cell transmission order. 2. A ring-shaped transmission line and a plurality of communication nodes connected to the transmission line and having mutually different addresses are used to send a cell including control information and user information to the transmission line. , In a communication method in which information is transmitted between arbitrary communication nodes, two ring-shaped transmission lines in which cells are transmitted in opposite directions are used, and at the transmission side of each communication node, if there is information to be transmitted, ,
A cell is composed of control information including information indicating the cell transmission order and user information to be transmitted, and the cell is transmitted to both of the two transmission lines, and the cell is controlled on the reception side of each communication node. A communication method characterized in that only a necessary cell is selected from cells arriving at its own node from two transmission paths based on information indicating a cell transmission order included in the information. 3. The receiving side of the communication node, based on the information indicating the cell transmission order included in the cell control information, 2
When selecting only the necessary cells that arrive at the node from the book transmission line, select the cells in the order of cell transmission order, and discard the cells that do not have the transmission order information that should arrive next. The communication system according to claim 1 or 2, characterized in that. 4. Based on the information indicating the cell transmission order included in the cell control information, the receiving side of the communication node performs 2
When selecting only the necessary cells among the cells arriving at the own node from the book transmission path, only when the arriving cell is missing one cell, store that cell and wait for the arrival of the next cell, then the next arrival If the cell is a missing cell, the stored cell is selected after selecting the cell, and if it is not the missing cell, the sequence information of the next arrival cell is set as the head and the subsequent operation is performed. The communication method according to claim 1. 5. ATM as information indicating a cell transmission order
The communication method according to claim 1, wherein the SN bit of the adaptation layer header is used. 6. The cell control information includes a bit for identifying a use state, an idle state, and a waiver state, and at the transmission side of each communication node, user information to be transmitted has a predetermined band. In the following cases, the cells in the idle state are used to send the information to the two transmission lines, the idle cells corresponding to the surplus bandwidth are changed to the right relinquished state, and are sent to the own node. If there is information to be sent over the specified band, the information is sent using the idle cell corresponding to the band and the cell in the abandoned right in which another node has abandoned the right, and is sent to the own node. The communication method according to any one of claims 1 to 5, wherein the cell in the abandoned right state is changed to an idle state. 7. A plurality of communication nodes and two transmission lines which mutually connect these communication nodes and whose physical routes are different from each other are provided, and a cell consisting of control information and user information is transmitted to the transmission line. As a result, in a communication system configured to transmit information between arbitrary communication nodes, each communication node forms a cell from control information including information indicating the cell transmission order and user information to be transmitted, Included in cell control information received by the cell receiving unit, and a cell sending unit that sends the cell to the two transmission lines, a cell receiving unit that receives cells arriving at the own node from the two transmission lines, And a cell disassembling unit that selects only necessary cells based on the information indicating the cell transmission order. 8. A ring-shaped transmission path and a plurality of communication nodes connected to the transmission path, the communication nodes having different addresses from each other, and by transmitting a cell including control information and user information to the transmission path, In a communication system configured to transmit information between arbitrary communication nodes, two ring-shaped transmission lines for transmitting cells in opposite directions are provided, and each communication node includes information indicating the cell transmission order. A cell transmitting unit that forms a cell from the control information and the user information to be transmitted, and transmits the cell to both of the two transmission lines, and a cell that arrives at its own node from the two transmission lines. And a cell disassembling unit that selects only necessary cells based on information indicating the cell transmission order included in the control information of the cells received by the cell receiving unit. Communication Temu. 9. A cell disassembling unit selects only a necessary cell from cells arriving at its own node from two transmission paths, based on information indicating a cell transmission order included in cell control information. 9. The communication system according to claim 7 or 8, wherein the cells are selected in the order of cell transmission order, and the cells that do not have the transmission order information that should arrive next are discarded. .. 10. A cell disassembling unit selects only a necessary cell from cells arriving at its own node from two transmission paths, based on information indicating a cell transmission order included in cell control information. When arriving, the cell is stored only when one cell is missing and waits for the next cell to arrive. If the next arriving cell is the missing cell, the cell stored after selecting that cell 9. The communication system according to claim 7 or 8, wherein if the selected cell is not a dropped cell, the sequence information held by the next arrival cell is set as a head and the subsequent operation is performed. 11. The AT is used as information indicating a cell transmission order.
11. The configuration using the SN bit of the M adaptation layer header is used.
The communication system according to any one of 1. 12. The cell control information includes a usage status,
There is a bit to identify the idle state and the waiver state, and when the cell transmission unit is controlled by the transmission management unit and the user information to be transmitted is below a predetermined band, the cell in the idle state is used. Then, the information is sent to two transmission lines, the idle cells corresponding to the surplus band are changed to the abandoned state and sent to the own node, and when there is information to be sent over a predetermined band or more. Sends information by using the idle cell corresponding to the band and the cell in the abandoned state in which the other node has abandoned the right, and changes the cell in the abandoned state sent to the own node to the idle state. The communication system according to any one of claims 7 to 11, which has a configuration.