JP2000049796A - Communication system and oam cell transfer method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To confirm the continuity of a line by using OAM cells, regardless of ATM line and existing line by transferring the OAM cells to the existing line in the form of housing an existing terminal in an ATM network. SOLUTION: This system is provided with an OAM cell detection means 3 for detecting a maintenance operation management(OAM) cell from an ATM cell stream from the side of the ATM network 2, a mapping means 4 for mapping the detected OAM cell to an STM frame to be sent out to the side of an STM terminal 1 as the OAM information of an STM form, an OAM information detection means 5 for detecting the OAM information in the STM frame received from the side of the STM terminal 1, and an OAM cell reproduction/ transmission means 6 for reproducing the OAM cell from the detected OAM information and transmitting it. In the form for housing the existing line in the ATM network, the OAM cell can be transferred to the side of the existing line as well, and thus the continuity of line is confirmed by using the OAM cell, regardless of the ATM line and the existing line. Also, the continuity for respective connections is confirmed without affecting the other connections, even during communication in the plural connections.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a communication system in which an STM terminal communicating in a synchronous transfer mode (STM) is connected to an ATM network via an ATM (asynchronous transfer mode) switch. The present invention relates to an improvement in an OAM cell transfer method for accommodating OAM cells.

[0002]

2. Description of the Related Art Conventionally, this type of synchronous transfer mode (ST
M), the STM terminal communicating with the AT via the ATM exchange
FIG. 8 shows the configuration of a communication system connected to the M network.
In the example of FIG. 8, 1.5M is used as the STM terminal.
A multiplexing device (TDM) is used.

In this conventional system, when accommodating the existing terminal 80 'in the ATM exchange 100', it is necessary to confirm the continuity of the line, which is one of the line maintenance operations, using an OAM cell.

However, conventionally, when an OAM cell is inserted on the ATM line from the high-speed interface unit 120 'of the ATM switch 100' shown in FIG. 8 toward the existing terminal 80 ', in the conventional system, the low-speed interface unit 110'
In order to decelerate all the ATM cells from the ATM network 90 ', the OAM transfer route shown in FIG.
The continuity of the line could be confirmed using the OAM cell only between the TM exchange 100 ', the ATM network 90', and the opposite ATM exchange 100 '.

[0005] Therefore, in the conventional system, when checking the continuity of the line from the ATM switch 100 'accommodating the existing terminal 80' to the existing terminal 80 ', a test machine is prepared separately. Needed.

[0006]

As described above, in the conventional system, when the continuity of a line, which is one of the line maintenance operations, is checked using an OAM cell, the system shown in FIG. As described above, the OAM cell can be transferred only between the ATM exchange 100 ', the ATM network 90', and the opposite ATM exchange 100 '.
The OAM cell could not be transferred between the ATM switch 100 'accommodating 0' and the continuity of the line could not be confirmed.

Therefore, the present invention solves the above problem,
The existing network is accommodated in the ATM network.
An object of the present invention is to provide a communication system capable of confirming line continuity using OAM cells irrespective of an ATM line or an existing line by enabling transfer of M cells, and an OAM cell transfer method thereof.

[0008]

In order to achieve the above object, according to the present invention, an STM terminal communicating in a synchronous transfer mode (STM) is connected to an ATM network via an ATM (asynchronous transfer mode) switch. Communication system,
The ATM switch detects an OAM cell from an ATM cell stream from the ATM network.
M cell detecting means, and ST for transmitting the detected OAM cell to the STM terminal side as OAM information in STM format.
Mapping means for mapping to M frames;
The OAM in the STM frame received from the TM terminal side
OAM information detecting means for detecting information;
OAM cell reproducing and transmitting means for reproducing and transmitting an OAM cell from the AM information.

The invention of claim 2 is the invention of claim 1, further comprising OAM information storage means for storing OAM information of the OAM cell detected by the OAM cell detection means,
The OAM information detecting means detects an information part that matches the OAM information stored in the OAM information storing means from an STM frame received from the STM terminal side.

According to a third aspect of the present invention, there is provided an OAM cell transfer method for a communication system in which an STM terminal communicating in a synchronous transfer mode (STM) is connected to an ATM network via an ATM (asynchronous transfer mode) switch. The ATM switch detects a maintenance and operation management (OAM) cell from the ATM cell stream from the ATM network side, maps the detected OAM cell as STM format OAM information to an STM frame, and sends the OAM cell to the STM terminal side. The OAM information is detected in the STM frame received from the STM terminal, the OAM cell is reproduced from the detected OAM information and transmitted, and the OAM cell is transmitted along the transfer path to the STM terminal.
It is characterized by transmitting and receiving AM cells.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment according to the present invention will be described below in detail with reference to the accompanying drawings.

FIG. 1 is a diagram showing a configuration of a communication system according to the scope of the present invention. In the communication system, an STM terminal 1 communicating in a synchronous transfer mode (STM) is connected to an ATM network 2. 1 shows the configuration.

In this communication system, the ATM switch comprises:
OAM cell detecting means 3 for detecting an OAM cell from the ATM cell stream from the ATM network 2 side, and using the detected OAM cell as OAM information in STM format
A mapping means 4 for mapping an STM frame to be transmitted to the TM terminal 1;
OAM information detecting means 5 for detecting OAM information in a TM frame, and OAM cell reproducing / transmitting means 6 for reproducing and transmitting an OAM cell from the detected OAM information.

The OAM cell detecting means 3 detects the OAM
OAM information storage means 7 for storing OAM information of AM cells
The OAM information detecting means 5 detects an information part that matches the OAM information stored in the OAM information storing means 7 from the STM frame received from the STM terminal 1 side.

According to this configuration, the existing (S
TM) In a communication system in which the terminal 1 is accommodated,
Enables transfer of OAM cells to existing lines, thereby
Regardless of the TM line or the existing line, the continuity of the line can be confirmed using the OAM cell.

Next, a preferred embodiment for realizing the above communication system will be described.

FIG. 2 is an overall configuration diagram showing a specific embodiment of the communication system shown in FIG. 1. In this communication system, a 1.5M multiplexer (TDM) is accommodated in an ATM network. ing. In this communication system, as a method for accommodating existing terminals, a method for accommodating a TDM directly and a method for accommodating an existing terminal through an existing line, that is, 1.5M multiplexing in the ATM switch 100 on the left side of the ATM network 90 as shown in FIG. In the case where the device (TDM) 80 is directly accommodated, the above-mentioned 1.5M multiplexer (TDM) is connected to the ATM switch 100 on the right side of the ATM network 90 via the existing 1.5M line 81.
80 is shown.

Hereinafter, a data flow in the communication system will be described. The 1.5M data from the 1.5 multiplexer (TDM) 80 is transmitted to the 1.5M in the ATM switch 100.
M (low-speed) interface 110 is multiplexed with another low-speed interface and is multiplexed with another low-speed interface.
Sent to 30. The multiplexed cell stream is switched based on the cell header by the ATM switch section 140, and the ATM
It is sent to the 155M (high speed) interface unit 120 for output to the network 90. Next, the cells routed in the ATM network 90 are sent to the opposite ATM switch 100. The cells routed through the ATM network 90
It is sent to the TM exchange 100 and the opposite 1.5M existing line 8
1 to a 1.5M multiplexer (TDM) 80.

Next, the overall configuration of the 1.5M (low speed) interface section 110 will be described in detail with reference to FIG. FIG. 3 is a block diagram showing a detailed configuration of the 1.5M (low speed) interface unit 110 shown in FIG.
The 1.5M (low speed) interface unit 110 includes:
It comprises a 5M frame generation / separation unit 111, a cellization / decellulation unit 112, an OAM cell processing unit 113, a cell format conversion unit 114, and a low-speed multiplexing unit access control unit 115.

The processing operation of the 1.5M (low speed) interface unit 110 will be described below. This 1.5
In the M (low speed) interface unit 110, the bipolar signal from the 1.5M multiplexer (TDM) 80 is
After performing code conversion in the M frame generation / separation unit 111 and synchronizing with the synchronization bits included in the frame bits, the frame bits are separated and only the data portion consisting of 24 time slots is sent to the cell / decellulation unit 112. Send out. The celling / decellulating unit 112 extracts designated data for each route from the frame of the 24 time slot configuration, takes it into the designated buffer among the 24 payload buffers, and accumulates data for one cell. The header of the designated destination is added in order from the buffer and output to the OAM cell processing unit 113. The OAM cell processing unit 113 inserts the OAM cell into each connection and extracts it from each connection. When the OAM cell is extracted, the OAM cell processing unit 113 transmits the failure information and the like on this OAM cell to the CP.
Notify U. In the cell format conversion unit 114, a tag required for routing by the ATM switch unit 140, the low-speed interface multiplexing unit 130, and the low-speed multiplexing unit access control unit 115 is added and transmitted to the low-speed multiplexing unit access control unit 115. . The low-speed multiplexing unit access control unit 115 designates a slot allocated to the low-speed bus consisting of 48 cell slots according to the speed of the own interface, and allocates the slot to the own interface unit according to the slot head signal from the low-speed interface multiplexing unit 130. The slot is counted and the cell is transmitted to that slot.

Next, the overall configuration of the celling / decellulating unit 112 will be described in detail with reference to FIGS.

FIG. 4 is a block diagram showing the celling / decellulating unit 1 shown in FIG.
FIG. 12 is a block diagram illustrating a detailed configuration of a deceleration unit in FIG. This decelerating unit is connected to the connection selecting unit 20.
0, connection table 210, time slot mapping section 220, PTI monitoring section 230, sequence number checking section 240, header removing section 250, multiplexing section 26
0. The PTI monitor 23
Blocks from 0 to the multiplexing unit 260 are arranged for each connection, that is, in this embodiment, for 24 channels.

Hereinafter, the processing operation in the decelerating unit will be described. In this decellularization unit, the ATM cell (flow) input from the OAM processing unit 113 (direction)
(A) is sorted by the connection selection unit 200 for each corresponding connection based on the VPI and VCI values set in the connection table 210. The sorted ATM cells (A) are input to the PTI monitor units 230 arranged for each connection, respectively, and the PT values (values indicating user information / network management information) in the cell header are provided.
Is monitored and separated into user cells and OAM cells.
As a result of this separation, the user cell separated from the OAM cell is checked for the sequence number in the cell header by the sequence number check unit 240, and the header part is removed by the header removal unit 250. The payload portion of the user cell from which the header portion has been removed is multiplexed with the OAM cell separated in the multiplexing section 260 and sent to the time slot mapping section 220.
Then, in this time slot mapping section 220,
Based on the value set in the connection table 210,
It is mapped to a predetermined position of the 1.5M transmission frame and output to the next stage (B).

According to this configuration, when there is an OAM cell in the ATM cell stream from the ATM network 90 toward the existing terminal, the OAM cell is replaced by another OAM cell in the decellularization unit in the cellularization / decellularization unit 112. The OAM cell is transferred to another STM line other than the ATM line because the cell is decellularized, that is, the user information is mapped onto the STM frame toward the existing terminal without removing the header information as in the case of the user cell. It becomes possible.

FIG. 5 is a block diagram showing the celling / decellulating unit 1 shown in FIG.
12 is a block diagram illustrating a detailed configuration of a cell unit in FIG. The celling unit includes a connection selecting unit 300, a connection table 310, a cell buffer 320, an OA
M header monitor 330, payload buffer 340,
It comprises a header generation unit 350, an SAR header generation unit 360, and a header multiplexing unit 370. The block from the OAM header monitor 330 to the header multiplexing unit 370 is provided for each connection, that is, in this embodiment, 2 blocks.
The configuration is such that four channels are arranged.

Hereinafter, the processing operation in the cell forming section will be described. In this cell unit, data (C) input from the preceding 1.5M frame generation / separation unit 111
Are sorted by the connection selection unit 300 for each corresponding connection based on the time slot value set in the connection table 310. The sorted data streams are assigned to Os assigned to each connection.
A data string that is input to the AM header monitor 330 and matches header information VPI, VCI, PT, etc. of the corresponding OAM cell is monitored. As a result of this monitoring, when a matching data string is detected, the OAM header monitor section 330 reproduces a 53-byte OAM cell including the data string from the input data stream, and a cell buffer at the next stage. 320. On the other hand, as a result of the monitoring, a normal data string is stored in the next-stage payload buffer 340.
When the data for one cell is stored and sent to the header multiplexing unit 370 at the next stage, the data is sent to the next stage. Then, the header multiplexing unit 3
At 70, the header generation unit 350, SAR (Segmentaitio
(n And Reassemble Sublayer) The header information from the header generation unit 360 is added, and the packet is sent to the next cell buffer 320 as an ATM cell.

Thus, the cell stream input to the cell buffer 320 is transmitted to the next stage together with the clock and the cell head signal based on the value set in the connection table 310 (D).

According to this configuration, when the OAM information corresponding to the OAM cell is included in the STM frame input from the existing line, the part is recognized as an OAM cell and the OAM cell is reproduced. As a result, the OAM information mapped onto the STM frame in the decelerating unit and transmitted to the existing line is detected from the STM frame looped back from the existing line, and the OA is again detected.
It can be reproduced as M cells.

Next, the overall configuration of the OAM header monitor 330 will be described in detail with reference to FIGS. FIG. 6 is a diagram showing the overall configuration of the OAM cell used in the present embodiment, FIG. 6A is a diagram showing the overall configuration of the OAM cell, and FIG. ) Is AIS (alarm display signal) / RDI
(Far end reception failure) and the function type is LOOPBACK
It is a figure showing the composition of the function field at the time of (loop back). FIG. 7 is a diagram showing a detailed circuit configuration of the OAM header monitor unit 330 shown in FIG. The OAM header monitor 330 detects a data string that matches the header information VPI, VCI, PT of the corresponding OAM cell from the data string in the input STM frame, and furthermore, detects the data string in the normal user information. The above OA
If there is a data string that coincides with the header information VPI, VCI, and PT of the M cell, the OAM cell is erroneously detected. Therefore, the unused byte 6Ah pattern corresponding to the 50th and 51st bytes of the OAM cell is used. "0110101
"0" is also monitored at the same time, and is output as an OAM cell only when all of them match.

The detailed processing operation of the OAM header monitor 330 will be described below with reference to FIG. 7, the OAM header monitor 330 first converts the input serial data separated for each connection by the connection selector 300 shown in FIG.
The data is converted into parallel data of 32 bits by 1 and input to the OAM header comparison unit 332 of the next stage. This OAM header comparison unit 33
2, the VP set in the connection table 310
I value (8 bits), VCI value (16 bits) and OA
The value is compared with a total of 27 bits of the PT value (3 bits “101”) indicating the M cell.
Then, the 6Ah pattern comparing unit 333 compares whether or not it matches the 6Ah pattern “01101010” of the 50th and 51st bytes of the OAM cell.
The output of the M header comparing unit 332 and the AND circuit 336
D, and if the header part matches 50 and 51 respectively, the data stored in the data buffer 334 is
The cell output gate 337 to the cell buffer 32 shown in FIG.
The value is output to 0 under the control of the read control unit 339, and when they do not match, the data is output from the normal data output gate 338 to the payload buffer 340 shown in FIG.

With this configuration, the OAM cell and the normal data are separated, and the OAM cell is sent to the cell buffer 320.
Normal data is sent to the payload buffer 340.

As described above, when a data stream not in the ATM cell format exists on the line, a means for identifying the OAM cell is provided in the celling / decellifying unit 112 in order to insert the OAM cell on the line. This enables OAM cell transfer between an existing terminal and an ATM exchange accommodating the existing terminal when the existing terminal is accommodated in the ATM network.

That is, according to the above-mentioned embodiment, as shown in FIG.
The transfer route of the OAM cell inserted from the M interface unit 120 is transferred from the 1.5M interface unit 110 of the ATM switch 100a to the other ATM switch 100b.
In the present application, what can be performed only up to the 1.5M interface unit 110, as shown in FIG.
Since the data can be transferred to the M multiplexer (TDM) 80, the continuity of the line can be confirmed using the OAM cell even on a line other than the ATM line.

Also, as in the prior art, the existing terminal 80 '
From the ATM switch 100 'accommodating the existing terminal 8
It is not necessary to prepare a separate tester to check the line continuity up to 0 '.

[0035]

As described above, according to the present invention,
In a form in which an existing line is accommodated in an ATM network, the OAM cell can be transferred to the existing line side as well, thereby checking the continuity of the line using the OAM cell regardless of the ATM line or the existing line. Can be. In addition, the continuity of each connection can be confirmed without affecting other connections even during communication through a plurality of connections.

[Brief description of the drawings]

FIG. 1 is a configuration conceptual diagram showing one embodiment of the present invention.

FIG. 2 is a diagram showing an overall configuration of a communication system according to the present invention.

FIG. 3 shows a 1.5 (low speed) interface unit 1 shown in FIG.
FIG.

FIG. 4 is a diagram showing a configuration of a decellularizing unit of the celling / decellularizing unit 112 shown in FIG. 3;

FIG. 5 is a diagram showing a configuration of a cell unit of the cell unit / decell unit 112 shown in FIG. 3;

FIG. 6 is a diagram showing a configuration of an OAM cell.

7 is an OAM header monitor unit 3 of the cell unit shown in FIG.
FIG.

FIG. 8 is a diagram showing an overall configuration of a conventional communication system.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 STM terminal 2 ATM network 3 OAM cell detection means 4 Mapping means 5 OAM information detection means 6 OAM cell reproduction / transmission means 7 OAM information storage means 80 1.5M multiplexer (TDM) 81 1.5M existing line 90 ATM network 100 ATM switch 110 1.5M (low speed) interface unit 111 1.5M frame generation / separation unit 112 cellization / decellulation unit 113 OAM cell processing unit 114 cell format conversion unit 115 low speed multiplexing unit access control unit 120 155M (high speed) interface Unit 130 low-speed interface multiplexing unit 140 ATM switch unit 200 connection selecting unit 210 connection table 220 time slot mapping unit 230 PTI monitor unit 240 sequence number checking unit 250 header removing unit 260 multiplexing 300 Connection selection unit 310 Connection table 320 Cell buffer 330 OAM header monitor unit 331 Serial / parallel conversion unit 332 OAM header comparison unit 333 6A pattern comparison unit 334 Data buffer 335 46 byte counter 336 AND circuit 337 OAM cell output gate 338 Normal data output gate 339 Read control unit 340 Payload buffer 350 Header generation unit 360 SAR header generation unit 370 Header multiplexing unit

Claims (3)

[Claims] 1. An S which communicates in a synchronous transfer mode (STM)
In a communication system in which a TM terminal is connected to an ATM network via an ATM (Asynchronous Transfer Mode) exchange, the ATM exchange detects an OAM cell from an ATM cell stream from the ATM network side. OAM cell detection means, mapping means for mapping the detected OAM cells as STM format OAM information to an STM frame to be transmitted to the STM terminal side, and detecting the OAM information in the STM frame received from the STM terminal side A communication system comprising: an OAM information detection unit that performs OAM cell reproduction; and an OAM cell reproduction transmission unit that reproduces and transmits an OAM cell from the detected OAM information. 2. The OA detected by the OAM cell detecting means.
An OAM information storage unit for storing OAM information of the M cell; wherein the OAM information detection unit detects an information portion that matches the OAM information stored in the OAM information storage unit from the STM frame received from the STM terminal side The communication system according to claim 1, wherein the communication is performed. 3. An S which communicates in a synchronous transfer mode (STM)
In an OAM cell transfer method of a communication system in which a TM terminal is connected to an ATM network via an ATM (asynchronous transfer mode) switch, the ATM switch performs a maintenance operation management (OAM) from an ATM cell flow from the ATM network side. ) Detecting a cell, mapping the detected OAM cell to an STM frame as OAM information in the STM format, transmitting the STM frame to the STM terminal, detecting the OAM information in the STM frame received from the STM terminal, An OAM cell transfer method, comprising: reproducing and transmitting an OAM cell from the detected OAM information; and transmitting and receiving the OAM cell via a transfer path to the STM terminal.