JPH08181697A - Uninterruptible transmitter - Google Patents

Abstract

PURPOSE: To prevent interruption of transmission by receiving a cell frame and identifying cell frames having the same information, sending a cell in one cell frame of them to a post-stage and aborting the other cell frame. CONSTITUTION: Each uninterruptible transmitter arranged opposite to each other via plural transmission units 10 sending cells in an ATM network is made up of a transmission section 20 and a reception section 30. Cell frames 11 having the same information are sent in parallel via the plural transmission units between the transmission section 20 and the reception section 30. Even when part of the transmission unit is interrupted, the frame 11 is surely sent via other transmission units. A cell frame discrimination means 31 identifies cell frames having the same information arrived sequentially from the plural transmission units 10 and sends a cell of one cell frame among them to the post-stage. Thus, even when part of the transmission units is interrupted, so long as normal transmission units remain, the reception section 30 prevents loss of the cell attended with the interruption to send the cell to the post stage.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an uninterrupted transmission apparatus for preventing transmission interruption and cell loss when disconnecting a transmission unit caused by a failure or a factor in network operation in an ATM (Asynchronous Transfer Mode) network. Regarding The transmission unit means a transmission line, a section, an SDH path, a virtual path, and a virtual channel.

[0002]

2. Description of the Related Art As a system for switching a transmission unit in response to a failure in a network, for example, there is a system described in Japanese Patent Application No. 2-136814. The outline is shown in FIG. In the figure, reference numeral 91 is a transmission node, and reference numeral 92 is a transmission unit. When a failure occurs in the network, the failure point is detected, and the transmission unit is switched to a preset detour path or a detour path formed after the failure occurs to recover the failure.

Further, as a switching system without loss of transmission information, there is, for example, the non-instantaneous switching system of Japanese Patent Application No. 4-56915. The outline is shown in FIG. In the figure, a transmission unit 93 duplicates a cell and transmits the same information to each transmission unit 92 of 0 system / 1 system. The switching unit 95 of the receiving unit 94 normally selects one system, and when a switching command is input, switches to the other system and sends a cell that arrives to the subsequent stage. At this time, the delay adjusting unit 96 gives a constant delay to cells arriving from a system having a short transmission delay time so that the transmission delay time of each system becomes the same. That is,
It is possible to switch without interruption by making the transmission delay time of each system the same.

[0004]

By the way, in the conventional switching method for a failure, disconnection of a transmission unit is detected by detecting a signal disconnection, and the transmission unit is switched to another transmission unit formed in a route bypassing the disconnection point to eliminate the failure. Had been restored. Therefore, it takes time from the occurrence of a failure to the completion of switching, and the signal disconnection state continues during that time. That is, the loss of transmission information was unavoidable.

Further, the conventional hitless switching method is applied when switching is performed according to the operator's intention, such as construction or testing of a transmission node or a transmission line. Therefore, when the transmission unit is disconnected due to a failure or the like, it is impossible to switch to another transmission unit without loss of transmission information. SUMMARY OF THE INVENTION It is an object of the present invention to provide an uninterrupted transmission device capable of preventing cell loss in a cell flow even when a transmission unit is disconnected due to a failure or other factors in an ATM network.

[0006]

FIG. 1 is a block diagram showing the basic configuration of an uninterrupted transmission device according to a first aspect of the present invention.
In the figure, an uninterruptible transmission device arranged oppositely via a plurality of transmission units 10 for transmitting cells in an ATM network is composed of a transmitter 20 and a receiver 30.

The transmission unit 20 arranged at one end of the plurality of transmission units 10 is a cell frame 1 composed of a plurality of cells.
1 and a cell frame duplicating unit 21 that duplicates a cell frame having the same information and sends the cell frame to a plurality of transmission units 10 in parallel. The receiving unit 30 arranged at the other end of the plurality of transmission units 10 receives the cell frames 11 arriving from the plurality of transmission units 10, identifies the cell frames having the same information, and identifies the cell frames in one of the cell frames. The cell frame determining means 31 for sending out the cells of the above to the latter stage and discarding other cell frames is provided.

The cell frame creation section 24 of the transmission section 20 creates a cell frame by inserting a special cell (synchronous cell) as defined in claim 4, for example. Further, the cell frame determining means 31 of the receiving unit 30 needs to identify cell frames having the same information from a plurality of transmission units 10 one after another, and to select one of them. Becomes Various cell frame determination means are configured depending on the selection method.

The cell frame determination means according to claim 2 determines whether or not there is a reception history of a cell frame having the same information for a received cell frame from each transmission unit,
If there is no reception history, the cell in the cell frame is sent to the subsequent stage and the reception history is recorded, and if there is a reception history, the cell frame is discarded. The cell frame determination means according to claim 3 accumulates the received cell frames from each transmission unit, and has the same information at every predetermined time when all the cell frames having the same information transmitted in parallel can be expected to arrive. Is identified, a cell in one cell frame among them is transmitted to the subsequent stage, and another cell frame is discarded.

The uninterrupted transmission apparatus according to the fourth aspect uses the synchronous cell to facilitate the cell frame identification when the transmission delay time difference between the transmission units is large. That is, the transmission unit includes a synchronization cell insertion unit that inserts synchronization cells at a predetermined cycle in the cell frame creation unit. The cell frame determining means of the receiving unit is configured to determine a cell frame boundary and identify a cell frame by using synchronous cells that arrive from a plurality of transmission units in a predetermined cycle.

According to the fifth aspect of the present invention, in the non-interruptible transmission apparatus, an error detection / correction code of each cell frame transmitted in parallel in a plurality of transmission units is created in a transmission unit, and the error detection / correction code is used as a synchronization cell or An error detection / correction code creation unit for sending to the reception unit using another cell is provided. Further, the receiving section is provided with an error detection / correction section that detects whether or not there is a transmission error in the received cell frame based on the received error detection / correction code, and corrects the transmission error, and the cell frame determination means A cell in a cell frame having no error or a cell in a cell frame in which a transmission error is corrected is transmitted to the subsequent stage.

[0012]

In the uninterruptible transmission device according to the first aspect, the cell frame 11 having the same information is transmitted in parallel between the transmission unit 20 and the reception unit 30 via the plurality of transmission units 10. As a result, even if some transmission units are disconnected, the cell frame 11 can be reliably transmitted via the other transmission units. Cell frame determination means 31 of the receiving unit 30
Identifies a cell frame having the same information, which arrives from a plurality of transmission units 10 one after another, and sends a cell in one cell frame among them to the subsequent stage. In this way, as long as normal transmission units remain even if some transmission units are disconnected,
The receiving unit 30 can prevent the cell loss due to disconnection and send the cell to the subsequent stage.

The cell frame determination means according to the second aspect of the present invention is a reception history indicating that a cell frame having the same information has already been received through another transmission unit for the reception cell frame from each transmission unit. Determine the presence or absence. If there is no reception history, this cell frame is the earliest received cell frame, so the cells in the cell frame are sent to the subsequent stage and the reception history is recorded.
On the other hand, if there is a reception history, a cell frame having the same information has already been received via another transmission unit and is sent to the subsequent stage, so that cell frame is discarded.

Therefore, a received cell frame from a transmission unit that minimizes the transmission delay time is usually selected, and the cell therein is sent to the subsequent stage. Further, when this transmission unit is disconnected, thereafter, the received cell frame from the transmission unit with the next shortest transmission delay time is selected, and the cell in it is sent to the subsequent stage. On the other hand, even if the transmission unit whose transmission delay time is not the minimum is disconnected, there is no change because the received cell frame is normally discarded. Thus, as long as a normal transmission unit remains even if some transmission units are disconnected, no cell loss occurs in the cell stream sent from the cell frame determination means.

The cell frame determination means according to a third aspect of the present invention accumulates cell frames arriving one after another from a plurality of transmission units, and identifies a cell frame having the same information transmitted in parallel from among the cell frames. Further, since one cell frame among them is selected and the cells therein are transmitted to the subsequent stage, as long as a normal transmission unit remains even if some transmission units are disconnected, the cell frame determination means No cell loss occurs in the delivered cell stream.

Even if some transmission units are cut off and not all cell frames having the same information are prepared, the identification processing is performed every predetermined time when all the cell frames having the same information can be expected to arrive. There is no. In the uninterruptible transmission device according to the fourth aspect, the synchronization cell is inserted from the transmission unit to the reception unit at a predetermined cycle, and the cell frame boundary is defined by the synchronization cell. On the other hand, the cell frame determining means of the receiving unit determines the cell frame boundary by the synchronization cell and identifies the cell frame having the same information based on the synchronization cell. This defines the cell frame structure, and regardless of the difference in transmission delay time between transmission units,
It is possible to facilitate the identification process of the cell frame having the same information.

In the uninterruptible transmission device according to the fifth aspect of the present invention, the transmission section creates the error detection and correction code and sends it to the reception section. On the other hand, the error detection / correction unit of the reception unit detects whether or not there is a transmission error in the received cell frame based on the received error detection / correction code, and corrects the transmission error. Thereby, the cell frame determination means can send the cells in the cell frame having no transmission error or the cell frame in which the transmission error is corrected to the subsequent stage in the identification processing of the cell frame having the same information.

[0018]

FIG. 2 is a block diagram showing the construction of an embodiment of the non-interruptive transmission apparatus according to the second aspect of the present invention. In the figure, AT
The uninterruptible transmission device, which is arranged opposite to each other via a plurality of transmission units 10 that transmit cells in the M network, includes a transmission unit 20a and a reception unit 30a. A plurality of transmission units 10
Are set to independent paths to avoid disconnecting all transmission units at the same time. The transmission unit 20a includes a cell frame creation unit 24 and a cell frame duplication unit 21. The reception unit 30a includes a cell frame determination unit 32a as a cell frame determination unit, a cell transmission unit 33, and a reception history holding unit 34.

The cell frame creating section 24 of the transmitting section 20a
Composes a cell frame with a plurality of cells input from the previous stage. The cell frame duplication unit 21 duplicates a cell frame having the same information as the input cell frame and sends the cell frame to a plurality of transmission units 10 in parallel. The cell frame determination unit 32a of the reception unit 30a receives the cell frames arriving from the plurality of transmission units 10 and refers to the reception history holding unit 34 to determine the presence or absence of the reception history. If there is no reception history, among the cell frames having the same information transmitted in parallel,
Since this is the earliest received cell frame, the cell frame is sent to the cell sending unit 33. Further, the reception history is written in the reception history holding unit 34. The reception history is information for identifying whether or not a cell frame having the same information as the received cell frame has already been received via another transmission unit, and for example, the synchronous cell information that defines the cell frame is Used. Therefore, if the cell frame determination unit 32a refers to the reception history holding unit 34 and determines that there is a reception history for the received cell frame,
Since it is known that the cell frame having the same information has already been received via another transmission unit, the cell frame is discarded. The cell transmission unit 33 transmits the cells in the cell frame transmitted by the cell frame determination unit 32a to the subsequent stage.

Now, the uninterrupted transmission operation of this embodiment will be specifically described with reference to FIG. In this description, it is assumed that the number of transmission units is 2, and the transmission delay time of the transmission unit A is smaller than the transmission delay time of the transmission unit B. FIG.
(a) shows the operation when both transmission units are normal. The cell frame streams (1) and (2) sent from the transmitter 20a normally reach the receiver 30a via the transmission units A and B. The receiving unit 30a sends the received cell frame from the transmission unit A to the subsequent stage based on the rule of sending the cell in the first arrived cell frame to the latter stage, and receives the received cell frame from the transmission unit B that arrives later. Discard.

In FIG. 3B, a disconnection occurs in the transmission unit A,
The operation when the cell frame (2) and the subsequent frames do not arrive from the transmission unit A is shown. As shown in (a), the cell frame (1) is transmitted from the transmission unit A to the subsequent stage, and is discarded from the transmission unit B arriving later. However, the disconnection occurs in the transmission unit A, and the cell frame (2) and thereafter do not arrive. Therefore, the receiving unit 30a uses the cell frame
After (2), the cell arriving from the transmission unit B is determined to be the earliest, and the reception cell is transmitted to the subsequent stage. At this time, no cell loss occurs in the cell flow sent from the receiving unit 30a to the subsequent stage.

In FIG. 3 (c), a disconnection occurs in the transmission unit B,
The operation when the cell frame (2) and subsequent cells do not arrive from the transmission unit B is shown. The reception unit 30a selects the reception cell frame from the transmission unit A before and after the transmission unit B is disconnected, and discards the reception cell frame from the transmission unit B. Therefore, the reception unit 30a transmits the reception cell frame to the subsequent stage. There is no change in the cell flow.

FIG. 4 is a block diagram showing the configuration of an embodiment of the uninterrupted transmission apparatus according to the third aspect. In the figure, the feature of this embodiment is the configuration of the receiving unit 30b. The reception unit 30b includes a reception cell frame accumulation unit 36, a cell frame determination unit 32b, and a cell transmission unit 33 as cell frame determination means.

Received cell frame accumulator 3 of receiver 30b
6 stores the cell frames that arrive from each transmission unit 10. The cell frame determination unit 32b identifies, from among the received cell frames stored in the received cell frame storage unit 36, a cell frame having the same information transmitted in parallel via each transmission unit 10, and selects 1 from among them. One cell frame is selected, the cells in it are sent to the cell sending unit 33, and the other cell frames are discarded. The cell sending unit 33
The cells in the cell frame transmitted by the cell frame determination unit 32b are transmitted to the subsequent stage.

The identification process of the cell frame having the same information in the cell frame determination unit 32b is performed as follows, for example. When one of the cell frames having the same information transmitted in parallel arrives, it waits for the arrival of another cell frame having the same information, and when all the cell frames having the same information are available, that one cell frame is selected. To the cell transmission unit 33. Further, even if some transmission units are disconnected and not all cell frames having the same information are prepared, one cell frame is transmitted after a predetermined time that all cell frames having the same information transmitted in parallel can be expected to arrive. Is selected and the cell frame therein is transmitted to the cell transmission unit 33.

As described above, normally, the cell frame having the same information is identified after the arrival of the cell frame from the transmission unit having the maximum transmission delay time. However, some transmission units are disconnected and the same. Even if all the cell frames having information are not prepared, the identification process is not hindered, and the cell transmission unit 3
No cell loss occurs in the cell stream sent out from 3. Here, the uninterrupted transmission operation of the present embodiment will be specifically described with reference to FIG. In this description, it is assumed that the number of transmission units is 2, and the transmission delay time of the transmission unit A is smaller than the transmission delay time of the transmission unit B.

In FIG. 5A, both transmission units are normal, and the cell frames (1) to (3) arriving from the transmission unit A have already been accumulated in the reception cell frame accumulating section 36, and the cell unit from the transmission unit B to the cells has been already accumulated. This shows the operation when frame (1) arrives. In this state, the cell frame determination unit 32b is configured to transmit both transmission units A and B
It is determined that the cell frame (1) has arrived, the cell frame (1) is read from the received cell frame accumulating unit 36, and the cell therein is transmitted to the subsequent stage via the cell transmitting unit 33. The same applies to the cell frame (2) and subsequent ones, and each time a cell frame arrives from the transmission unit B, it is sent to the subsequent stage.

In FIG. 5B, a disconnection occurs in the transmission unit A,
The operation when the cell frame (4) and subsequent ones do not arrive from the transmission unit A is shown. For cell frames (1) to (3),
As shown in (a), from transmission unit B to cell frame (1)
When (3) arrives, the cell frame determining unit 32b receives the cell frames (1) to (3) from the received cell frame accumulating unit 36.
Are sequentially read out, and the cells therein are sent to the subsequent stage via the cell sending section 33. On the other hand, the cell frame determination unit 32b determines that the transmission unit A is disconnected when the cell frame (4) arrives from the transmission unit B. Therefore, for the cell frame (4) and thereafter, the cell frame determination unit 32b immediately reads the cell frame arriving from the transmission unit B from the received cell frame storage unit 36, and the cells in the cell frame determination unit 32b via the cell transmission unit 33 to the subsequent stage. Send to. At this time, no cell loss occurs in the cell flow sent from the cell sending unit 33 to the subsequent stage.

In FIG. 5C, a disconnection occurs in the transmission unit B,
The operation when the cell frame (2) and subsequent cells do not arrive from the transmission unit B is shown. The cell frame determination unit 32b determines that the cell frame having the same information from the transmission unit B has passed for a predetermined time after the cell frame (2) has arrived from the transmission unit A.
When (2) does not arrive, it is determined that the transmission unit B is disconnected. Therefore, after that, the cell frame arriving from the transmission unit A is read and sent to the subsequent stage. At this time, no cell loss occurs in the cell flow sent from the cell sending unit 33 to the subsequent stage.

When the transmission delay time difference between the transmission units becomes large, the cell frame determination units 32a and 32b of the reception units 30a and 30b identify the cell frames having the same information that arrive from the transmission units 10 one after another. It can be difficult. In order to solve this problem, it is preferable that the transmitting unit transmits a synchronous cell at a predetermined cycle, and the receiving unit performs identification processing of a cell frame having the same information based on the synchronous cell. This can be applied to each of the embodiments shown above, but FIG. 6 shows the one applied to the embodiment shown in FIG. 4 here.

In FIG. 6, the feature of the present embodiment is that the transmission section 20b includes a cell frame creation section 24a including a synchronization cell insertion section 22a, and the reception section 30c uses a synchronization cell for cell identification. Cell frame determination unit 32c to perform
It is configured to include. The synchronous cell inserting unit 22a creates a cell frame by inserting a synchronous cell into the input cell stream in a predetermined time period or a predetermined number of cells cycle in the cell frame creating unit 24a. Since it is necessary to identify that the synchronization cell is a cell different from the normal cell in the receiving unit 30c, an OAM cell or the like in the ATM network is used. The cell frame duplication unit 21 duplicates a cell frame including a synchronous cell and sends the cell frame to each transmission unit 10 in parallel.

Cell frame determining section 32c of receiving section 30c
Identifies a synchronization cell arriving from a plurality of transmission units 10 in a predetermined cycle, and identifies a cell frame based on this synchronization cell. Other functions are the same as those of the cell frame determination unit 32b of the reception unit 30b. As a result, even if the transmission delay time difference between the transmission units 10 is large, the normal cells arriving from the transmission units 10 can be easily identified. The synchronous cell is discarded after the cell frame is selected.

Next, a method of coping with bit errors in cell frame information, cell loss, cell mixture, and other transmission errors that occur in the traffic between the transmitter and the receiver will be described. This can be applied to each of the above-described embodiments, but FIG. 7 shows one applied to the embodiment shown in FIG. 6 here. In FIG. 7, the feature of the present embodiment is that the transmission unit 20c includes a cell frame creation unit 24b including the error detection and correction code creation unit 23, and the reception unit 30d includes an error detection and correction unit 37. is there.

The error detection / correction code creation unit 23 is connected to the synchronization cell insertion unit 22b and creates an error detection / correction code for each cell frame created by the synchronization cell insertion unit 22b. As the error detection / correction code, a CRC code or the like is used which is capable of detecting a transmission error by decoding in the receiving unit 30d and correcting the transmission error. The synchronization cell insertion unit 22b describes the error detection and correction code of the cell frame in the synchronization cell and sends it to the cell frame duplication unit 21.

The error detection / correction unit 37 is connected to the cell frame determination unit 32d and receives a cell frame from each transmission unit 10 based on the error detection / correction code transmitted via the synchronization cell for each transmission unit 10. Whether or not there is a transmission error, and corrects the compensable transmission error. Based on the result of the error detection / correction unit 37, the cell frame determination unit 32d corrects a cell frame having no transmission error or a transmission error among the cell frames having the same information stored in the reception cell frame storage unit 36. The selected cell frame is selected, and the cell in the selected cell frame is transmitted via the cell transmission unit 33. The other functions of the receiving unit 30d are the receiving unit 30d.
Similar to c.

[0036]

As described above, the uninterruptible transmission apparatus of the present invention transmits the cell frame having the same information between the transmission unit and the reception unit in parallel via a plurality of transmission units, and the reception unit normally operates. The cell is taken out from one of the cell frames having the same information that has arrived at and is sent to the subsequent stage. Therefore, as long as a normal transmission unit remains even if some of the transmission units that perform parallel transmission are disconnected, there is no cell loss in the cell flow sent to the subsequent stage from the receiving unit. Can be realized.

[Brief description of drawings]

FIG. 1 is a block diagram showing a basic configuration of an uninterrupted transmission device according to claim 1.

FIG. 2 is a block diagram showing the configuration of an embodiment of the uninterruptible transmission device according to claim 2;

FIG. 3 is a diagram for explaining an operation example of the uninterruptible transmission device according to claim 2;

FIG. 4 is a block diagram showing the configuration of an embodiment of the uninterruptible transmission device according to claim 3;

FIG. 5 is a diagram illustrating an operation example of the uninterruptible transmission device according to claim 3;

FIG. 6 is a block diagram showing the configuration of an embodiment of the uninterruptible transmission device according to claim 4;

FIG. 7 is a block diagram showing the configuration of an embodiment of the uninterruptible transmission device according to claim 5;

FIG. 8 is a diagram illustrating a conventional switching method for a failure.

FIG. 9 is a diagram illustrating a conventional hitless switching method.

[Explanation of symbols]

 10 Transmission Units 11 Cell Frames 20, 20a, 20b, 20c Transmission Units 21 Cell Frame Duplication Units 22a, 22b Synchronous Cell Insertion Units 23 Error Detection and Correction Code Creation Units 24, 24a, 24b Cell Frame Creation Units 30, 30a, 30b, 30c , 30d reception unit 31 cell frame determination means 32a, 32b, 32c, 32d cell frame determination unit 33 cell transmission unit 34 reception history holding unit 36 reception cell frame accumulation unit 37 error detection and correction unit

Claims (5)

[Claims] 1. In an uninterruptible transmission apparatus, which is arranged opposite to each other via a plurality of transmission units for transmitting cells in an ATM network, a transmission unit arranged at one end of the plurality of transmission units is composed of a plurality of cells. The cell frame creation unit that creates the cell frame that duplicates the cell frame that has the same information,
A cell frame duplicating unit for transmitting in parallel to the plurality of transmission units, the receiving unit arranged at the other end of the plurality of transmission units receives cell frames arriving from the plurality of transmission units, and receives the same information. An uninterruptible transmission apparatus comprising: a cell frame determining means for identifying a cell frame having the above, transmitting a cell in one of the cell frames to the subsequent stage, and discarding another cell frame. 2. The uninterruptible transmission device according to claim 1, wherein the cell frame determination means of the reception unit determines whether or not there is a reception history of cell frames having the same information for the received cell frames from each transmission unit. , If the cell frame with the same information transmitted in parallel arrives earliest and has no reception history, the cell in the cell frame is sent to the subsequent stage and the reception history is recorded, and if there is a reception history, that cell An uninterruptible transmission device having a configuration in which a frame is discarded. 3. The uninterrupted transmission apparatus according to claim 1, wherein the cell frame determination means of the reception unit accumulates the received cell frames from each transmission unit and transmits all the cell frames having the same information transmitted in parallel. The cell frame having the same information is identified at every predetermined time when the arrival of the cell is expected, the cell in one of the cell frames is transmitted to the subsequent stage, and the other cell frame is discarded. Transmission equipment. 4. The uninterruptible transmission device according to claim 1, wherein the cell frame creation unit of the transmission unit creates a cell frame by inserting a synchronous cell at a predetermined cycle. The cell frame determination means of the receiving unit is configured to identify a cell frame having the same information based on the synchronous cell with respect to a cell frame received from the plurality of transmission units. Transmission equipment. 5. The uninterruptible transmission device according to claim 4, wherein the transmission unit creates an error detection and correction code for each cell frame transmitted in parallel in a plurality of transmission units, and synchronizes the error detection and correction code. An error detection / correction code creation unit for sending to the reception unit using a cell or another cell is provided, and the reception unit detects whether there is a transmission error in the received cell frame based on the received error detection / correction code, and It is characterized in that it is provided with an error detection / correction unit for correcting a transmission error, and the cell determination means is configured to send a cell in a cell frame having no transmission error or a cell in a cell frame in which a transmission error has been corrected to a subsequent stage. Uninterrupted transmission equipment.