JPH08125679A - Ring network reception status determination method and transmission device - Google Patents

Abstract

(57) [Summary] [Object] The present invention relates to a ring type network transmission device and the like, and an object thereof is to prevent duplicate reception of data. A transmitting node includes a sequence number adding means 101 for adding a sequence number indicating a transmission sequence to each of the data units to be sequentially transmitted to the receiving node, and the receiving node sets the received data unit to the previous one. The previous sequence number of the received data unit and the current sequence number of the data unit currently undergoing the reception process are compared, and the comparison result shows that the sequence indicated by the current sequence number is the same as or smaller than the sequence indicated by the previous sequence number. If it is, the comparison unit 102 that determines that the data unit currently undergoing the reception process is the duplicate reception, and the comparison unit 102.
Discarding means 103 for discarding the data unit determined to be redundantly received in step 104, and means 104 for stopping the updating of the previous sequence number when the comparing means 102 determines that there is duplicated reception.
With.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for determining a data reception state of a ring network, a ring network transmission device, and a node device of the ring network.

In a ring LAN, there may be a case in which received data is lost or duplicate reception of the same data occurs due to a failure of a transmitting / receiving node or switching of routes of a dual transmission path. Currently, software measures are taken to deal with the loss of received data, but effective measures have not been taken to duplicate data reception, so measures against such duplicate data reception are required.

[0003]

2. Description of the Related Art FIG. 7 shows a ring-type LAN in which a ring-type transmission line is duplicated in order to improve reliability. Hereinafter, this conventional example will be described. In FIG. 6, nodes # 1 to # 4
Are connected in a ring form to form a ring type transmission line, and the nodes are connected by double ring type transmission lines I and II in which transmission directions are opposite to each other. The source node sends the same data clockwise and counterclockwise to this duplicated ring type transmission line. Therefore, even if a failure occurs in one transmission line, data communication is performed by the other transmission line. Can continue. In this way, by making the transmission line redundant, high reliability is achieved.

FIG. 8 shows a format of a signal transmitted through the ring type transmission line. As shown in the figure, one frame is divided into a plurality of time slots TS-1, TS-2, ..., Each time slot is assigned to each node on the transmission path, and each node is assigned its own time slot. Use to communicate. Each time slot consists of data and a parity bit for detecting a bit error of the data.

Transmission and reception of a transmission frame between nodes in this ring LAN are performed as follows. A transmission frame transmitted from a transmission source node (hereinafter referred to as a transmission node) is received by a node adjacent to a transmission path downstream, and the node extracts data from a time slot assigned to itself in the transmission frame, If there is transmission data, the transmission data is inserted in the time slot and sent to the node further downstream. By repeating this in sequence by each node, the transmission frame goes around the ring type transmission path. At that time, the time slot data (hereinafter, abbreviated as TS data) transmitted by the transmitting node to the data destination node (hereinafter, referred to as a receiving node) is received by the receiving node and erased. Become.

Since each node normally uses a frame aligner to absorb the reception phase and the transmission phase of the transmission frame, the relay delay time required for the transmission frame to pass through one node is one frame cycle. Since it is longer than the time, the total relay delay time required for a transmission frame to go around the ring type transmission line is (number of nodes on the transmission line x
1 frame period) or more.

On the other hand, in the case of the broadcast communication in which the same data is simultaneously delivered from one transmitting node to a plurality of receiving nodes, it is performed as follows. That is, the transmitting node inserts the TS data for broadcast communication into a predetermined time slot of the transmission frame and sends it out to the transmission line. The transmitted transmission frame is sequentially received by each receiving node on the ring type transmission line as described above. However, even if each receiving node receives the broadcast TS data, it does not erase the same time slot. It is sent to the downstream node while being put in.
Therefore, the broadcast TS data goes around the ring type transmission path and returns to the original transmitting node, and the transmitting node itself erases the broadcast TS data.

Next, which route of the duplicated ring type transmission line is selected is performed as follows. Each node performs a parity check on the TS data received from both the clockwise and counterclockwise paths, and adopts the TS data on the normal path as the received data. As an algorithm for this selection, if both routes are normal, if the currently selected route is normal and the unselected route is abnormal, or if both routes are abnormal, The currently selected route is continuously selected, and when the currently selected route is abnormal and the unselected route is normal, the normal route is selected.

[0009]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
Then, there is a problem that the same data is received in duplicate at the receiving node for the following reasons.

Each node on the transmission line is provided with a bypass function. This bypass function allows a transmission frame received from an upstream transmission line to be bypassed through the bypass route as it is when a failure occurs in the local station or at the time of maintenance. Relay to the downstream transmission line. As a result, even when a node failure occurs, the failure can be prevented from spreading to other nodes.

However, when the receiving node enters a bypass state due to a failure or the like, the TS data sent from the transmitting node simply bypasses the receiving node.
Not erased by the receiving node. As a result, the TS data makes a round around the ring type transmission line and returns to the transmitting node. However, if the transmitting node performs bit error detection and the like on the TS data, and if there is no abnormality, it is addressed to itself. It is determined that the TS data is different, and the data is taken in and processed.

As a countermeasure against this, a 1-bit control bit is added to TS data as a directional bit at the time of time slot transmission, and as a value of this directional bit, "1" is added to one node between nodes facing transmission and reception. , "0" is fixedly assigned to the other node so that it is possible to determine whether the received TS data is the TS data from the partner node or the own TS data that has gone around the transmission path, the latter. In this case, the returned TS data is discarded.

Further, when the transmitting node is in a bypass state due to a failure or the like, the following inconvenience occurs during the broadcast communication. That is, when the transmitting node enters a bypass state due to a failure or the like immediately after transmitting the broadcast TS data, even if the broadcast TS data goes around the transmission line and returns to the transmitting node, the transmitting node is bypassed. Therefore, the broadcast TS data cannot be erased. As a result, the broadcast TS data continuously circulates on the ring type transmission line many times. Therefore, the receiving node targeted for the broadcast communication receives the same TS data repeatedly, but even in that case, if the result of the bit error detection is normal, it is treated as normal received TS data.

Furthermore, double reception of the same data or loss of data may occur even if the route of the duplex transmission line is switched. That is, as shown in FIG. 7A, it is assumed that the transmitting node # 1 now transmits the sequence of TS data, ... To the receiving node # 4. At this time, if the TS data, ... Are sequentially transmitted to the counterclockwise (clockwise) route I for each frame period, the TS data ',', ',' ...・ Send to the right (counterclockwise) direction II.

On the other hand, both paths I in the receiving node # 4,
Regarding the reception timing of the TS data from II, since the transmission path length between the nodes # 1 and # 4 is different on both paths, there is a time difference as shown in FIG. The reception timing of the TS data, ... Is delayed compared to the TS data ',', ',' ... received from the near route II, and in this example, a delay of three frame periods occurs.

Now, the receiving node # 4 has selected the clockwise route II as a normal route, and when TS data ',', 'is received in this state, the right route between the nodes # 1 and # 4 is received. It is assumed that there is a failure in the route II. When receiving node # 4 detects a failure, it switches the route from the clockwise route II to the counterclockwise route I. As a result, the TS data is received from the counterclockwise route I thereafter, but the received data of the counterclockwise route I is delayed by three frame periods from the received data of the clockwise route, After switching the route, the data will be received from the TS data. Therefore, the TS data received by the receiving node is ',',
, And so on, and the TS data is received in duplicate, but these data are handled as being judged as normal data by the bit error check or the like.

On the other hand, when the receiving node # 4 selects and switches the counterclockwise route I as the normal route to the clockwise route at the time of receiving TS data, the TS data string received by the receiving node is received. Is ... ',' ...
Therefore, TS data will be lost.

Conventionally, such a data reception error has been dealt with by the higher-order application software on the node terminal side for the latter data loss. If no measures were taken, and if it was done, the system would be temporarily stopped at the time of such route switching.

The present invention has been made in view of the technical problems described above, and it is an object of the present invention to prevent erroneous reception of data, particularly duplicate reception of data.

[0020]

FIG. 1 is an explanatory view of the principle according to the present invention. In order to solve the above-mentioned problems, in the present invention, a ring type network transmission device in which a plurality of nodes are connected in a ring shape, wherein a transmitting node is provided for each data unit to be sequentially transmitted toward a receiving node. The reception node includes a sequence number adding unit 101 for adding a sequence number indicating a transmission sequence, and the receiving node has a previous sequence number of a data unit received last time and a current sequence number of a data unit currently undergoing reception processing with respect to the received data unit. When the order indicated by the current sequence number is the same as or smaller than the sequence indicated by the previous sequence number,
A comparing unit 102 that determines that the data unit currently undergoing the reception process is duplicate reception; a discarding unit 103 that discards the data unit that the comparing unit 102 has determined to be duplicate reception;
There is provided a ring type network transmission device including a means 104 for stopping the update of the previous sequence number when the comparison means 102 determines that there is duplicate reception.

In this ring type network transmission device,
The sending node adds the order number indicating the sending order to each of the data units to be sequentially sent to the receiving node by the order number adding means and sends the data unit. In the receiving node, the comparing means 102 compares the previous sequence number of the data unit received last time with the current sequence number of the data unit currently undergoing the reception process with respect to the received data unit. The result of this comparison is
If the sequence indicated by the current sequence number is the same as or smaller than the sequence indicated by the previous sequence number, it is determined that the data unit currently undergoing the reception process is duplicate reception. At this time, the discarding unit 103 performs processing such as discarding the data unit determined to be the duplicate reception. At this time, the update of the previous sequence number is stopped.

In the ring-type network transmission device described above, when the comparison result indicates that the sequence indicated by the current sequence number is larger than the sequence indicated by the previous sequence number by two or more, the data unit of the previous sequence number and the current sequence number are compared. It may be configured to determine that there is a data unit reception loss between the data units.

Further, in the above ring type network transmission device, when the comparison result by the comparing means 102 that the order indicated by the current sequence number is the same as the order indicated by the previous sequence number is repeated two or more times, the transmitting node An abnormality detecting unit that determines that there is an abnormality in the sequence number addition function or the receiving node comparison function, and an invalidating unit that invalidates the discarding function of the discarding unit 103 when the abnormality detecting unit detects an abnormality. You may comprise further.

Further, in the above ring-type network transmission device, when the comparison result that the order indicated by the current order number by the comparing means 102 is larger than the order indicated by the previous order number by two or more times consecutively, two or more times. Second abnormality detecting means for determining that there is an abnormality in the sequence number adding function at the transmitting node or the comparing function at the receiving node;
When the abnormality is detected by the abnormality detecting means, the discarding means 10
It may be configured to further include a second invalidating unit that invalidates the discarding function of No. 3.

Further, in the above ring type network transmission device, the ring transmission lines connecting the nodes may be duplicated.

Further, in the present invention, the transmitting side circuit is
A sequence number adding means for adding a sequence number indicating the transmission sequence to each of the data units sequentially transmitted to the receiving node is provided, and the sequence number of the data unit previously received from the network is set as the previous sequence number in the receiving side circuit. The sequence number storage means to hold and the sequence number of the data unit currently undergoing the reception process are compared as the current sequence number with the previous sequence number in the sequence number storage unit, and the comparison result indicates that the sequence indicated by the current sequence number is If it is the largest than the order indicated by the previous order number,
When the sequence indicated by the current sequence number is greater than the sequence indicated by the previous sequence number by 2 or more, and when the sequence indicated by the current sequence number is the same as or smaller than the sequence indicated by the previous sequence number, Sequence number comparing means for detecting,
When the comparison result of the comparison means is that the order indicated by the current order number is larger than the order indicated by the previous order number by one or more, the previous order number of the order number storage means is updated by the current order number. When the comparison result of the update means and the comparison means is that the order indicated by the current sequence number is the same as or smaller than the order indicated by the previous sequence number, the data unit currently undergoing the reception process is regarded as the duplicate reception data. Provided is a ring-type network node device having a discarding means for discarding.

In this node device, when the comparison result that the order indicated by the current sequence number by the comparing means is the same as the sequence indicated by the previous sequence number is consecutive two or more times, or the current sequence number by the comparing means. When the comparison result that the order indicated by is greater than the order indicated by the previous order number is two or more times consecutively, the order number addition function at the sending node or the order number comparison function at the receiving node is abnormal. It may be configured to further include an abnormality detection unit that determines that there is an abnormality, and an invalidation unit that invalidates the discarding function of the discarding unit when the abnormality detection unit detects an abnormality.

[0028]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 2 shows an embodiment of the present invention. For simplification of description, this embodiment is a case where a ring LAN in which transmission lines are duplicated by nodes of four stations is configured.
In an actual system, nodes are composed of about 64 stations, for example. Although only the internal configuration of the node # 3 is shown in the figure, the other nodes # 1, # 2, and # 4 have the same configuration.

In FIG. 2, the transmission frame received from the upstream transmission line is sent to the terminal via the transmission line interface 1, the circuit switching unit (TSW) 2 and the signal processing unit 9, and the transmission data from the terminal is reversed. And is sent to the downstream transmission line. Even in this node, each circuit 1,
2 and 9 are duplicated for high reliability,
The transmission TS data from the parity adding circuit 3 of the signal processing unit 9 is input to both of the duplicated circuit switching units 2, and the TS data received by both of the circuit switching units 2 are received by the signal processing unit 9. It is input to each of the route selection circuits 4.

The circuit switching unit 2 extracts time slot data addressed to the own station from the received transmission frame and inserts the transmission data of the own station into the time slot assigned to the own station in the transmission frame. In the case of an optical network, the transmission line interface 1 is a circuit that performs a signal interface between the transmission line and the node, such as performing mutual conversion between an optical signal on the transmission line and an electric signal inside the node.

FIG. 5 shows a structural example of a frame transmitted on the transmission line by the apparatus of this embodiment. As shown, one frame has a plurality of time slots TS-1, TS-2 ...
Each node on the transmission line is assigned a different time slot for communication. One frame period is set to 125 μs, for example. As shown in the figure, the data of each time slot has a total of 2 bits including an 8-bit data area, a 7-bit sequence number area, and a parity bit.
It consists of bytes.

In the signal processing unit 9, the transmitting side circuit has a terminal interface 7, a sequence number adding circuit 5, and a parity adding circuit 3.
Further, the receiving side circuit includes the receiving route selection circuit 4, the order violation determination circuit 6, and the terminal interface 8.

The sequence number adding circuit 5 is a circuit for adding the sequence number S to the transmission data from the own station. This sequence number S
Is the sequence number area S0 to S6 of the time slot configuration of FIG.
This sequence number S is a value that circulates between 0 and S _max due to a monotonic increase, that is, S = 0, 1,
It is a cyclic sequence such as 2, 3, ..., S _max , 0, 1, 2, ..., and the number is sequentially increased for each data (8-bit unit) of the transmission data sequence. And add.

As a method of determining the maximum value S _max of the sequence number S, if the maximum relay delay time of the ring type transmission line is M frame periods, S _max = 2 ⁿ -1 ≧ 2M-1 To decide. For example, if the maximum relay delay time M is 64 (= 2 ⁶ ) frame periods or less, the information added as a sequence number is n = 7 bits, and the sequence number is a sequence of numbers S = 0 to 127.

FIG. 3 shows a configuration example of the sequence number adding circuit 5. A counter (modulo S _max counter) 31 for counting circulating the sequence number S = 0~S _{ma x,} consists selector 32 for switching between data from the sequence number S and the terminal interface 7 of the counter 31 alternately outputs The counter 31 monotonically increases the count value for each frame pulse of the transmission frame (that is, for each frame period) and outputs it as the sequence number S. The selector 32 switches so as to add this sequence number after the data from the terminal (8-bit unit in this example), and outputs the output signal to the parity adding circuit 3.

The parity addition circuit 3 is a sequence number addition circuit 5
Is a circuit for calculating a parity with respect to the output signal from, and adding a parity bit to the end of the TS data as shown in FIG.

The receiving route selection circuit 4 includes two circuit switching units 2
Received TS for left-handed route I and right-handed route II received from
A circuit for selecting the received data of the normal path from the data, performing bit error detection of the received TS data and selecting the TS data of the path determined to be normal according to the algorithm described in the prior art. And sends it to the order violation judgment circuit 6.

The order violation judgment circuit 6 checks the order numbers of the sequentially received TS data to detect whether there is a order number violation, that is, whether there is duplicate reception or loss of data, and the duplication. The received data is discarded, and the processed signal is sent to the terminal via the terminal interface 8.

FIG. 4 shows a detailed configuration example of the order violation determination circuit 6. In FIG. 4, the sequence number storage circuit 12
Is a register for storing the previous sequence number Sp of the TS data received last time. The sequence number comparison circuit 10 compares the current sequence number Sr of the TS data received this time from the reception route selection circuit 4 with the previous sequence number Sp stored in the sequence number storage circuit 12 to determine whether there is a sequence violation. If there is a violation, it is a circuit that detects what kind of violation (duplicate reception, missing, etc.).

The sequence number comparison circuit 10 comprises a sequence number extraction circuit 11, an unsigned binary number subtraction circuit 13, and a sign bit check circuit 14. Sequence number extraction circuit 11
Extracts the sequence number S and the parity bit from the received TS data, sends the remaining data D1 to D8 to the 0-system input terminal of the selector 21, and stores the extracted sequence number S as the current sequence number Sr and the subtraction circuit 13 and the sequence number. Circuit 1
It is a circuit to send to 2.

The subtraction circuit 13 performs an arithmetic operation of Sa = Sr-Sp with an unsigned binary number for the current sequence number Sr from the sequence number extraction circuit 11 and the previous sequence number Sp from the sequence number storage circuit 12, This is a circuit that outputs the calculation result Sa. By this processing, 0-127 = 1 can be obtained even in the operation of Sa at the turnaround point of the sequence number.

The sign bit check circuit 14 handles the operation result Sa from the subtraction circuit 13 as a signed binary number (that is, handles the most significant bit MSB of the operation result Sa as a sign bit), and the operation result Sa is Sa> 1. , S
It is a circuit that detects which of the four modes a = 1, Sa = 0, Sa <0. Here, Sa> 1 is a case where the current sequence number Sr is 1 or more away from the previous sequence number Sp, which means that, for example, the duplex transmission line is changed from the long distance route to the short distance route from the transmitting node. It corresponds to the state where data loss occurs due to switching. Sa = 1 indicates that the current sequence number Sr monotonically increases by one with respect to the previous sequence number Sp, and corresponds to the state in which the data is normally received. Sa = 0 is the previous sequence number S
If p and the current sequence number Sr are the same, Sa
<0 is the sequence number Sr of this time, contrary to the sequence number Sp of the previous time.
Indicates that there is a decrease in the transmission rate. In this case, there is TS data that repeatedly circulates on the transmission path or the double transmission path is switched from the short-distance route to the long-distance route, resulting in duplicate reception of data. Corresponding to the state.

Here, the calculation result Sa makes it possible to discriminate TS data that has returned around the transmission path as Sa <0, and is the highest in the whole system from the path with the longest relay delay time. It is necessary to make Sa> 1 even when switching to a smaller route, and in order to correctly calculate whether the calculation result Sa is positive or negative when calculating the calculation result Sa in unsigned binary number calculation. In addition, the maximum value S _max of the sequence number S is such that S _max = 2 ⁿ −1 ≧ 2M−1 if the maximum relay delay time is M frame periods as described above, and the number of bits of the sequence number S Determine n.

In the sequence number storage circuit 12, the judgment of the sign bit inspection circuit 14 is Sr> Sp (that is, Sa = 1 and S).
When a> 1), the current sequence number Sr from the sequence number extraction circuit 11 is fetched and held as the previous sequence number Sp for comparison with the sequence number of the next TS data. On the other hand, Sr ≤ Sp (that is, Sa = 0 and Sa <
In the case of 0), the previous sequence number Sp stored in the sequence number storage circuit 12 is not updated. In order to perform this operation, the output signal of Sa = 1 and Sa> 1 of the sign bit inspection circuit 14 passes through the OR circuit 15, and further passes through the AND circuit 16 which is opened / closed by the frame pulse and the sequence number storage circuit 1
It is input to the second clock terminal CLK. As described above, the circuit of the present embodiment considers not only the normal reception of Sa = 1 but also the normal reception of Sa ≧ 1, that is, the data loss. As described in the technology, higher-level application software is used in the post-processing process.

The abnormality detection circuit 18 is the sign bit inspection circuit 1.
This is a circuit for detecting an abnormal operation of the sequence number comparison circuit 10 itself based on the value of 4. The abnormality detection circuit 18 has its Fd input connected to the output of the sign bit check circuit 14 indicating Sa> 1, and its Fe input is Sa = 0 of the bit check circuit 14.
Connected to the output indicating. That is, the Sa> 1 output of the sign bit check circuit 14 indicates that the sequence number has increased discontinuously, but this state indicates that the data when the duplex transmission path is switched from the long-distance path to the short-distance path. It represents a lack. Therefore, the fact that the Fd input of the abnormality detection circuit 18 is continuously input twice or more means that the switching from the long-distance route to the short-distance route is continuously performed twice or more,
That is impossible in theory. Further, the Sa = 0 output of the sign bit check circuit 14 indicates that the same sequence number as that of the previous frame has been received. In this state, the delay amount of the long-distance route corresponds to one frame for the short-distance route. When the number is large, it means that the short-distance route is switched to the long-distance route. Therefore, the fact that the Fe input of the abnormality detection circuit 18 is continuously input twice or more means that the switching from the short-distance route to the long-distance route is continuously performed twice or more, and theoretically. Is impossible.

That is, when these Fd inputs or Fe inputs continue twice or more, there is an operation abnormality in the sequence number addition circuit on the transmitting node side or an operation abnormality in the order violation judging circuit itself on the receiving node side. It can be estimated that there is. Therefore, the abnormality detection circuit 18 detects that the Fd input or the Fe input is continuously set for two cycles or more, and in that case, an alarm signal ALM ("1" at the time of abnormality is detected as an abnormality of the order violation determination circuit or the like). )) Is output. This alarm signal AL
M is input to the inverting input terminal of the AND circuit 19, so that the AND circuit 19 is activated when the order violation determination circuit or the like is abnormal.
Is designed to be closed.

FIG. 6 shows an example of the configuration of the abnormality detecting circuit 18. The Fe input is held in the previous state by the D flip-flop 41. This D flip-flop 4
By logically ANDing the output signal of No. 1 and the Fe input by the AND circuit 45, when the Fe input is set twice in the last time and this time, the D-type flip-flop 42
The output signal of is set to "1". If the previous or current Fe input was reset, D
The output signal of the flip-flop 42 is reset to "0". The Fd input, the D-type flip-flops 43 and 44, and the AND circuit 46 are also configured in the same manner, and when the Fd input is set twice in succession, the previous time and this time,
If the output signal of the D-type flip-flop 44 is set to "1" and the Fd input of either the previous time or this time is reset, the output signal of the D-type flip-flop 44 is reset to "0". . The OR circuit 27 ORs the output signal of the D-type flip-flop 42 and the output signal of 44 to generate an alarm output signal ALM.
By configuring the abnormality detection circuit 18 in this way,
It is detected that the Fe input has been set continuously more than once or the Fd input has been set more than once consecutively.

The selector 21 receives the received data from the sequence number extraction circuit 11 at its 0-system input terminal, the dummy TS data from the dummy TS generation circuit 22 at its 1-system input terminal and its selection terminal SEL. According to the selection signal, when the selection signal is “0”, the input signal on the 0-system input terminal side is selected, and when it is “1”, the input signal on the 1-system input terminal side is selected and sent to the terminal interface 8. Select terminal SEL
The selection signal to be input to is generated by passing the output signals of Sa = 0 and Sa <0 from the sign bit check circuit 14 through the OR circuit 20 and the AND circuit 19.

Therefore, the selector 21 receives the sequence number normally (Sa = 1), receives the missing data (Sa> 1), and detects the operation abnormality of the order violation judgment circuit (alarm). = 1), the received data is sent to the terminal interface side as it is, and when data duplication reception is performed (Sa = 0, Sa <0), the duplication TS generation circuit 22 generates the duplication reception data instead of the duplication reception data. The dummy TS data is selected to be sent to the terminal interface side. The dummy TS data is T
Data in which the S data area is all "1" can be used.

The operation of the apparatus of this embodiment will be described below.
First, while the ring LAN is operating normally, the sequence number S added to the TS data monotonically increases by one every frame period, so that the previous sequence number Sp and the current sequence number Sr in the sequence number comparison circuit 10 are increased. The comparison result is always Sa = S
r −Sp = 1. In this case, the selector 21 selects the input signal of the 0-system input terminal, that is, the received data from the receiving route selection circuit 4, and outputs it to the terminal interface 8 side.

Next, a case will be described in which the same TS data is repeatedly circulated on the ring type transmission line without being erased because the transmission node is in a bypass state in the broadcast communication. As described above, when this TS data (herein referred to as “circulating TS data”) is received, the maximum value S _max of the sequence number is set so that the sequence number is smaller than the previous sequence number Sp. . Therefore, after a certain node receives the circulating TS data,
While the S data makes another round of the transmission line and returns (during the delay time of one round of the transmission line), the sequence number of the received data monotonically increases at the node, but the round TS data is received again. Sometimes the phenomenon that the sequence number Sr becomes smaller than the previous sequence number Sp is repeated. Since Sr ≤ Sp is always satisfied at the time of receiving the circulating TS data, the sequence number comparison circuit 10 detects this and determines that it is an order violation due to duplicate reception.
An output signal of = 0 or S <0 is output to switch the selector 21 to the 1-system input terminal side. Therefore, the dummy TS from the dummy TS generation circuit 22 is provided on the terminal interface 8 side.
The data is sent and the received circular TS data is discarded.

Next, a case where the receiving route is switched due to deterioration or failure of the transmission line will be described. First, when a long-distance route is switched from the transmission node to a short-distance route, double reception of data occurs at the time of switching. That is, the comparison result in the sequence number comparison circuit 10 shows that after switching, Sr≤Sp during the period corresponding to the difference in transmission delay time of both paths (duplex reception period).
Then (because the previous sequence number Sp stored in the sequence number storage circuit 12 is not updated during the synchronization), the selector 21 is set to 1 by the output signal S = 0 or S <0 output from the sign bit check circuit 14. Switching to the system input terminal side, the dummy TS data is sent to the terminal interface 8, and the received double received TS data is discarded. When the difference time of this transmission delay time passes, the sequence number storage circuit 1
Since the current sequence number Sr of the received TS data is larger than the previous sequence number Sp stored in 2, the sequence number storage circuit 1
The previous sequence number Sp of 2 is updated each time a time slot is received, and therefore Sr-Sp is always 1, so that the selector 21 selects the 0 system input terminal side and receives the received TS data from the terminal interface 8 Send to.

On the other hand, when the duplexed transmission path is switched from the short-distance path to the long-distance path, the received data will be lost. In this case, the comparison result in the sequence number comparison circuit 10 is Sa = Sr-Sp> 1. However, even in this case, the apparatus of the present embodiment considers this state as a normal state for the time being, and the select 21 selects the 0-system input terminal side, and sends the received TS data to the terminal interface 8. Then, the processing for the missing data is performed by the upper application software on the terminal side. In this case, when the difference period of the transmission path delay time has passed, Sa = Sr-Sp = 1 in the comparison result of the sequence number comparison circuit 10.
Then, normal operation is restored.

Further, when the transmission line distances from the transmission nodes of the duplicated transmission line are equal, the comparison result in the sequence number comparison circuit 10 is Sa = Sr -Sp = 1 even if the routes are switched.
Therefore, there is no influence of the route switching.

Next, a case will be described in which the order number adding circuit of the transmitting node or the order violation determining circuit of the receiving node itself is abnormal. In the device of the present embodiment, one or more transmission frames are stored for circuit switching in the circuit switching unit 2, so that any node has a transmission delay time of at least one frame period or more. Therefore, even if the transmitting node is in the bypass state, there are always two or more transmission frames (hence TS data) on the transmission path. As a result, even if there is revolving TS data left unerased by the transmitting node, only the revolving TS data does not circulate on the transmission path. Therefore, the sequence number comparison circuit 10 may determine that Sr = Sp in two frames. It is not detected continuously for more than the period (that is, more than 2 time slots). Therefore, in the sequence number comparison circuit 10, Sr = S
When the state of p is detected for two consecutive cycles, the anomaly detection circuit 18 detects it by two consecutive sets of Fe inputs, and determines that the sequence number assigning circuit or the order violation determining circuit is abnormal. Since it is unreasonable to discard the received data when the sequence number assigning circuit or the order violation determining circuit is abnormal, the abnormality detecting circuit 18 outputs the alarm signal ALM and closes the AND circuit 19, thereby causing the selector 21 to operate.
Always selects the 0-system input terminal side, that is, the received TS data and outputs it to the terminal interface 8.

When the Fd input of the abnormality detection circuit 18 is set twice in succession, it means that the switch from the long-distance route to the short-distance route is performed twice in succession. This means that this is theoretically impossible. Therefore, also in this case, the abnormality detection circuit 18 determines that the sequence number assignment circuit or the order violation determination circuit is abnormal, and at that time, the abnormality detection circuit 1
8 outputs the alarm signal ALM to close the AND circuit 19 so that the selector 21 always selects the received TS data. In this way, when an abnormality is detected in the order violation determination circuit or the like, the function of discarding the received TS data by the order violation determination circuit is invalidated.

[0057]

As described above, according to the present invention, it is possible to prevent duplicate reception of received data even when the transmitting node is bypassed or when the receiving node is switched to another route. Since it is not necessary to stop even temporarily, it greatly contributes to the improvement of system reliability. Further, it becomes possible to detect the abnormality in the order number addition circuit of the transmitting node and the order violation judging circuit of the receiving node to invalidate the function of discarding double received data, which also contributes to the improvement of reliability.

[Brief description of drawings]

FIG. 1 is a diagram illustrating the principle of the present invention.

FIG. 2 is a diagram showing an apparatus according to an embodiment of the present invention.

FIG. 3 is a diagram showing a configuration example of a sequence number adding circuit in the apparatus of the embodiment.

FIG. 4 is a diagram illustrating a configuration example of an order violation determination circuit in the device of the embodiment.

FIG. 5 is a diagram showing a configuration example of a transmission frame in the device of the embodiment.

FIG. 6 is a diagram showing a configuration example of an abnormality detection circuit in the apparatus of the embodiment.

FIG. 7 is a diagram illustrating a conventional ring-type LAN having a duplicated transmission path configuration.

FIG. 8 is a diagram showing a configuration example of a transmission frame in a conventional ring LAN.

[Explanation of symbols]

 1 Transmission Line Interface 2 Circuit Switching Unit 3 Parity Addition Circuit 4 Reception Route Selection Circuit 5 Sequence Number Addition Circuit 6 Sequence Violation Judgment Circuit 7, 8 Terminal Interface 10 Sequence Number Comparison Circuit 11 Sequence Number Extraction Circuit 12 Sequence Number Storage Circuit 13 Subtraction Circuit 14 Sign bit inspection circuit 15, 20, 47 OR circuit 16, 19, 45, 46 AND circuit 21 Selector 22 Dummy TS generation circuit 41, 42, 43, 44 D-type flip-flop

Claims (12)

[Claims] 1. A method for determining a reception state of a ring network in which a plurality of nodes are connected in a ring, wherein a transmitting node assigns a sequence number indicating a transmission sequence to each data unit to be sequentially transmitted to the receiving node. At the receiving node, the receiving node compares the previous sequence number of the previously received data unit with the current sequence number of the data unit currently undergoing reception processing, and the comparison result indicates that A ring configured to determine that the data unit currently undergoing the reception process is duplicate reception and stop updating the previous sequence number when the sequence indicated by the number is the same as or smaller than the sequence indicated by the previous sequence number. Method for determining reception status of type network. 2. If the comparison result shows that the sequence indicated by the current sequence number is greater than the sequence indicated by the previous sequence number by 2 or more, the data unit of the previous sequence number and the data unit of the current sequence number are The method according to claim 1, wherein it is determined that there is a reception loss of a data unit between them. 3. A sequence number addition function in the transmitting node or a receiving node in the receiving node when the result of comparison that the sequence indicated by the current sequence number is the same as the sequence indicated by the previous sequence number is repeated two or more times. The method for judging the reception state of a ring network according to claim 1, wherein it is judged that the comparison function is abnormal. 4. A sequence number addition function at the transmitting node or the sequence number addition function at the transmitting node when the result of comparison that the sequence indicated by the current sequence number is greater than the sequence indicated by the previous sequence number by two or more consecutive times 4. The reception status determination method for a ring network according to claim 1, wherein the comparison function of the reception node is determined to be abnormal. 5. The reception state determination method according to any one of claims 1 to 4, wherein the ring type transmission line connecting the nodes is duplicated in a ring network. 6. A ring-type network transmission device in which a plurality of nodes are connected in a ring shape, wherein a transmitting node adds a sequence number indicating a transmission sequence to each data unit to be sequentially transmitted to a receiving node. The receiving node is provided with a sequence number adding means, and the receiving node compares the previous sequence number of the previously received data unit with the current sequence number of the data unit currently undergoing the reception process for the received data unit, and the comparison result indicates that If the sequence indicated by the current sequence number is the same as or smaller than the sequence indicated by the previous sequence number, the comparison unit that determines that the data unit currently undergoing the reception process is the duplicate reception, and the comparison unit determines that the duplicate reception is performed. A ring type network having a discarding means for discarding the data unit determined to be present and a means for stopping the updating of the previous sequence number when the comparison means determines that there is duplicate reception. Work transmission equipment. 7. If the comparison result shows that the sequence indicated by the current sequence number is greater than the sequence indicated by the previous sequence number by two or more, the data unit of the previous sequence number and the data unit of the current sequence number are 7. The ring type network transmission device according to claim 6, wherein it is determined that there is a reception loss of a data unit between them. 8. The result of comparison by the comparing means in which the order indicated by the current sequence number is the same as the sequence indicated by the previous sequence number is 2
Abnormality detection means for determining that there is an abnormality in the sequence number addition function at the transmission node or the comparison function at the reception node when the abnormality detection means detects the abnormality when the abnormality detection means detects the abnormality. 8. The ring type network transmission device according to claim 6, further comprising invalidating means for invalidating the discarding function of the means. 9. The sequence number at the transmitting node when the comparison result by the comparing means that the sequence indicated by the current sequence number is greater than the sequence indicated by the previous sequence number by two or more consecutive times. Second abnormality detecting means for determining that the additional function or the comparing function at the receiving node has an abnormality, and invalidating the discarding function of the discarding means when the second abnormality detecting means detects an abnormality. 9. The ring network transmission device according to claim 6, further comprising invalidating means. 10. The ring-type network transmission device according to claim 6, wherein the ring-shaped transmission line connecting the nodes is duplicated. 11. The transmission side circuit is provided with a sequence number adding means for adding a sequence number indicating a transmission order to each of the data units to be sequentially transmitted to the reception node, and the reception side circuit previously received from the network. A sequence number storage means for holding the sequence number of the data unit as the previous sequence number, and the sequence number of the data unit currently undergoing the reception process as the current sequence number are compared with the previous sequence number in the sequence number storage section, and the comparison result is compared. , If the sequence indicated by the current sequence number is the largest than the sequence indicated by the previous sequence number, if the sequence indicated by the current sequence number is larger than the sequence indicated by the previous sequence number by 2 or more, and the current sequence is The sequence number comparing means for separately detecting when the sequence indicated by the number is the same as or smaller than the sequence indicated by the previous sequence number, and the comparison result of the comparing means is the current sequence number. When the order indicated by is larger than the order indicated by the previous sequence number by at least one, the updating means for updating the previous sequence number of the sequence number storage means by the current sequence number, and the comparison result of the comparing means. Is a ring having a discarding unit that discards the data unit currently undergoing reception processing as duplicate reception data when the sequence indicated by the current sequence number is the same as or smaller than the sequence indicated by the previous sequence number. Type node device. 12. When the comparison result that the order indicated by the current sequence number by the comparing means is the same as the sequence indicated by the previous sequence number is consecutive two or more times, or the sequence indicated by the current sequence number by the comparing means. Is larger than the sequence indicated by the previous sequence number by two or more consecutive times, and the sequence number adding function at the transmitting node or the sequence number comparing function at the receiving node is abnormal. 12. The node device of the ring network according to claim 11, further comprising: an abnormality detecting unit for determining; and an invalidating unit for invalidating the discarding function of the discarding unit when the abnormality detecting unit detects an abnormality.