JPH0955746A - CBR signal phase jump prevention method - Google Patents

Abstract

Kind Code: A1 Abstract: The present invention relates to a CBR signal phase jump prevention system in a communication network for transmitting a CBR signal of an SDH network to another SDH network through an ATM network, and an STM signal in which the CBR signal is multiplexed. The purpose is to prevent phase jumps and phase jumps due to erroneous recognition of staff when transmitted by the ATM network and converted again to STM signals. An ATM-STM conversion circuit includes means for detecting cell discard of an ATM cell, means for identifying a CSI signal of AAL, and means for instructing a pointer of a CBR signal. The CBR signal excluding the ATM header and the AAL header is written in the buffer and read in synchronization with the SDH network.
When dummy data is generated when cell discard is detected and the CBR signal pointer is included in the discarded cell, the dummy data value at the pointer position is switched to the previous pointer value.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a phase jump prevention system in a communication network for converting a CBR signal of an SDH network into ATM cells and transmitting the ATM cells.

In recent years, B-ISDN (Broad-band ISD)
Practical application of ATM communication corresponding to N) is under way. In the case of ATM, information is converted into ATM cells and transmitted, but in a transmission network including a trunk line, STM (Sync
hronous Transfer Mode: Transferred in synchronous transfer mode. STM is an internationally standardized SDH (Synch
A unified network is being built by ronous Digital Hierarchy), and this SDH is a user / network interface (U) for realizing services by B-ISDN.
NI) and network node interface (NN)
I) is provided.

On the other hand, a constant bit rate CBR (Constant Bit Rate) which is continuous by time division multiplexing such as a leased line or a relay line.
) In the STM network for transmitting signals, multiplexing information is transmitted by a unit to which a pointer indicating a frame phase is added by a virtual container (VC) of SDH.
In many cases, a network having a configuration in which ATM cells are converted into ATM cells by the TM network and relayed and further transmitted from the ATM network through the existing STM network is used.

In this case, when a signal including SDH pointer information created in the SDH network is converted into ATM cells and transmitted by the ATM network, cell discard occurs when congestion occurs as a characteristic of the ATM network. In this case, if the discarded cell contains a pointer indicating the frame phase, the ATM
Since the original frame phase cannot be maintained when converting from a cell to an STM signal, its prevention is desired.

[0005]

2. Description of the Related Art FIG. 11 is an explanatory diagram of a communication network that relays an SDH network with an ATM network. As shown in FIG. 11, in a communication network that transmits information between the SDH network A and the SDH network B by STM via the ATM network, between the SDH network A and the ATM network and between the ATM network and the SDH network B, respectively. SAC (STM-ATM Converter), a device that performs mutual conversion between STM and ATM
-A and SAC-B are provided. Each of these SACs
Has a function of converting an STM signal conforming to the SDH specification into an ATM cell and outputting the ATM cell, and a function of converting an ATM cell input from the ATM network into an STM signal conforming to the original SDH specification. Prepare

SDH according to the ITU recommendation is known to those skilled in the art, and its outline will be described with reference to FIG. S
The DH multiplexing format adopts a nested structure, and has a multi-layer structure as shown in FIG. Is one of the containers (C1) that accommodates the existing low speed line (64 Kbps for voice, etc.), C11 (1.5 Mbps≈64K)
bps × 24 + control information), which includes 64 Kbps voice and data (CBR signal) for 24 channels. Four cycles of this signal, that is, 125 μs × 4 = 5
A signal (00 μs) to which a path overhead (POH) including 1-byte path management information is added is referred to as VC (Virtual Container) -11. TU (Tributary Un) shown in this VC-11
When mapping it) -11, a TU-11 pointer is added.

The TU-11 pointer is a value (offset value) representing the time difference between the beginning of the fixed frame of the TU-11 and the beginning of the VC-11 (the byte called V5 at the POH position). This TU-11 pointer is 125
μs TU-11 fixed 4 multiframe (500μ
4 from V1 to V4 at the beginning of each frame in s)
Specified in bytes, V4 in this is reserved (unused)
Then, V1 to V3 are defined as shown in FIG.
The identification of each byte of V1 to V4 is performed by the SOH of the upper AU (Administrative Unit) in which this TU-11 is multiplexed.
The first to fourth frames of the multi-frame are displayed by the seventh and eighth bits of the byte called H4 in (Section Over Head).

The TU-11 pointer shown in FIG. 13 will be described. As shown in, the first 4 of the V1 byte
Bit (represented by N) is a new data flag (NDF: New
DataFlag), and the subsequent 2 bits (represented by S) are T
Pointer value with a total of 10 bits of U type (discrimination between TU-11 and TU-2), remaining 2 bits (represented by I and D) and 8 bits of V2 byte (I and D are alternately displayed by 4 bits each). (From the beginning of the multiplexed frame of TU-11, VC-
11 represents the number of bytes up to the position where the first POH of the 11th data is stored. Here, when the NDF is “1001”, it indicates that the pointer is new (changed), the pointer value represented by 10 bits is valid, and when the NDF is “0110”, there is no change, and the lower 2 bytes of the V1 byte are indicated. 8 bits of bit and V2 byte act alternately as a bit representing "I" (increase designation bit) and "D" (decrease designation bit),
When the five D bit values of the previous frame are inverted (inversion 5D), it is identified as an indication of negative stuff (1 byte), and when the five I bit values of the previous frame are inverted ( The inversion 5I) is identified as a positive stuff (1 byte) instruction and a stuffing operation (byte unit) is performed. It should be noted that this inversion judgment is performed by majority logic. Also, the V3 byte is used as a negative action byte when performing negative stuffing. The positive stuff action byte is the byte following the V3 byte.

As described above, a TU pointer including a plurality of types of TU-11 and TU-2 and a higher-order VC (Virtual
The AU (Administrative Unit) pointer used when multiplexing VC-3, etc.
In each of the basic configurations, the A. Similarly, it is possible to perform processing such as synchronization and demultiplexing by detecting the VC start position by being detected by the device that terminates the VC path of each layer in the communication network.

Next, the TUG (Tributary Unit Group) shown in FIG.
-2 is configured. Further, it is called VC-3 indicated by a VC that accommodates 7 sets of this TUG-2, and is prefixed with POH, and is expressed in a format of 9 lines × 85 bytes. This VC-
3 includes 28 VC-11 (about 50 Mbps). Next, 3 sets of this VC-3 are accommodated, and as shown in, the upper 3 rows and the lower 5 rows of the top 9 rows × 9 bytes are SO
STM-1 (Synchronous Transfer M) that stores H (Section Over Head) and stores the AU-3 pointer in the 4th line.
ode 1) is constructed.

Next, the outline of ATM will be described with reference to FIG. A. of FIG. Shows the structure of the ATM layer cell.
The entire ATM cell is composed of 53 bytes, the first 5 bytes are an ATM header, and the last 48 bytes are an information field. In the case of NNI (Network Node Interface), the first 12 bits of the ATM header is VP
I (Virtual Path Identifier), the next 16 bits are VC
I (Virtual Channel Identifier), followed by 3-bit PT (Payroad Type) and 1-bit CLP (CellLoss P
riority) is provided, and the last 8th bit of the 5th byte is HEC (Header Error Control).

In order to absorb the difference in quality condition depending on the type of various information when transferring by the ATM cell, A
A TM adaptation layer (AAL) is provided. AAL is a cell division assembly sublayer (SAR: Segm).
Convergence sublayer (CS: Convergence sub-layer) that performs cell delay fluctuation guarantee, receiver-side line of clock frequency of transmitter side, frame error control, and flow control according to the requirements for quality of service (entry and reassembly sublayer) and quality of service.
Sublayer) and. When the CBR signal is converted into ATM cells and restored to the original signal, ITU Recommendation I.S. 36
3 AAL type 1 is used.

FIG. 1 shows the specifications of the AAL type 1 SAR.
Explaining in Section 4, 4 in the information field of the ATM cell
8 bytes are B. SAR-PDU (Protoc
data unit), and the first 1 byte is SA
R-PDU header, remaining 47 bytes are SAR-PDU
It is the payload. The SAR-PDU header is the C. It has the format shown in, and the first bit (bit position 8) is CSI (Convergence Sublayer Indication).
14 represents the presence or absence of the CS function, and D.I. Shown in That is, D. When CSI = 0 as shown in, the CS function is not displayed (non-P format), and as in CS
When I = 1, the CS function is displayed (P format). In this case, SAR-PDU header (1 byte)
The 1 byte subsequent to indicates the pointer (pointer of the CBR signal), and the position (number of bytes) of the phase information (V1 in FIG. 12) of the original CBR signal is displayed by this pointer. This pointer has the CSI = 1 as shown in
Valid data including SAR-PDU payload, and
It represents any byte position in the valid data (CSI = 0) of the ATM cell that follows.

Bit positions 7 to 5 following the CSI of the SAR-PDU header are sequence numbers (SN: Sequence Numbe).
It represents r), and a number of 0 to 7 is cyclically assigned in 3 bits. Bit positions 4 to 1 are information of sequence number protection (SNP: Sequence Number Protection), control bits of cyclic code check (CRC) are in bit positions 4 and 2, and parity of the control bit and each bit of SN is in bit position 1. Is set.

The sequence number (SN) can detect a cell discard (loss) or an erroneously inserted cell by identifying the SN on the receiving side for each cell, and the erroneously inserted cell is discarded.
When cell discard is detected (when the difference between the SN of the previous cell and the SN of the cell received this time is 2 or more), the number of discarded cells is supplemented with ATM cells having dummy SAR-PDUs.
In addition, the dummy SAR-PDU is inserted in an appropriate number even when the cell does not arrive within the allowable delay variation.
In the CS protocol specification, as a dummy ATM cell,
All "1" or all "0" in the information field,
Alternatively, it is set to any of the specific patterns.

Referring to FIG. As shown in, SAR-PD
U has two types of formats (with and without pointer) according to the CSI display. When CSI is "1" when SN is an even number, the first byte of the SAR-SDU (service data unit) payload is the pointer (above). Different from the TU-11 pointer and the AU pointer of SDH). This pointer is the SDH CBR signal (64K
Boundary position of structured data such as bps × n (n ≧ 2) (start position of VC in TU or AU) is displayed. Bit positions 7 to 1 of this 1-byte are offset fields, and any byte position in the information of 2 cells (46 bytes of the cell and 47 bytes of the subsequent cell) can be displayed.

The VC signal obtained by multiplexing the CBR signal by SDH shown in FIG. 12 is the SAC-signal shown in FIG.
At A, it is converted to an ATM cell. In that case, the original information is divided and the payload of the ATM cell (S for AAL
Stored as 1 byte for AR-PDU header and 47 bytes (excluding pointer byte when CSI is “1”) (46 bytes if there is a pointer), make ATM cells and input to ATM network, At the time of output from the network to the STM network, the SAC-B is decellized (cell assembly) except for the ATM cell header and converted into the original CBR multiplexing information.

[0018]

In the ATM network in the communication network of FIG. 11, the C.C. of FIG. 14 is controlled by AAL. The sequence number (SN) of the SAR-PDU header shown in is checked, and if cell loss is detected, dummy data is generated and transmitted to the receiving side of the network. However, in the ATM cell lost due to the loss, as shown in FIG.
TU pointers (V1 to V) added by the STM network shown in
If either of 2) is included, the content of the cell (SAR-PDU header and payload) changes to all "1" or all "0" or a specific pattern due to the dummy data complement.

B. of FIG. To explain using the example shown in
Is the contents of the bytes of V1 and V2 included in the SDH information transmitted from the STM network.
The contents are the same when the SDH network normally receives the data via the TM network. Is an ATM including the above V1 and V2 information
A cell is lost in the ATM network due to cell loss, dummy data is stored, and the state becomes all "1". Thus, when V1 and V2 in the previous frame change as in the subsequent frame, when A.V. As described above, 4 I bits of 2 bits of V1 byte and 8 bits of V2 byte are inverted,
It is mistakenly recognized as a stuffing instruction in the positive direction by the majority logic. In this case, if a positive stuff operation is performed in the STM network according to the instruction, a phase jump of VC occurs, and C
The BR signal cannot be demultiplexed accurately. Also, depending on the bit of the previous frame, there is a case where it is mistakenly recognized as a negative stuffing instruction. Such a problem similarly occurs in the case of the pointer added to the unit such as AU3, AU4, etc. to which the upper VC-3, VC-4 etc. are mapped.

According to the present invention, when the STM signal in which the CBR signal is multiplexed is transmitted through the ATM network and converted into the STM signal again,
It is an object of the present invention to provide a phase jump prevention method for a CBR signal due to cell discard, which can prevent a phase jump due to data complement due to cell discard in an ATM network and a phase jump due to erroneous staff recognition.

[0021]

FIG. 1 is a diagram showing the principle configuration of the present invention. The configuration of FIG. 1 is such that the CBR signal of the SDH network is converted into an ATM cell and transmitted through the ATM network, and then SD.
SAC (STM-ATM converter) for passing to H network
Is provided.

In FIG. 1, 1 is a buffer means including write and read control for converting an ATM cell into an STM signal of an SDH network, and 2 is an SN processing means for processing a sequence number (SN) by the AAL of the ATM cell. , 3 is A
CSI (Convergence Sublayer I) according to AL CS specifications
CSI which controls writing and reading by identifying (ndication)
A processing means, 4 is a cell pointer processing means for detecting the position of the cell pointer (frame phase information (offset value) of the CBR signal in the cell) and outputting the position, and 5 is a CBR signal read from the buffer means 1. Pointer processing means for holding and terminating the pointer, 6 is front pointer holding means for holding the pointer of the CBR signal received last time,
Reference numeral 7 is a switching means for selecting one of the output of the pointer processing means 5 and the output of the previous pointer holding means 6.

The present invention uses the S contained in the AAL of the ATM cell.
The cell discard is detected by using the N information to control the writing to the decellizing buffer, the CSI included in the AAL is used to determine whether the pointer is included, and the area of the CBR signal is extracted and stored in the buffer. The cell pointer is obtained by CSI of AAL, the pointer end and the pointer of the previous frame are held according to the information, and when the discarded cell includes the pointer, only the pointer value is switched to the value of the previous frame. .

ATM cells are supplied to the buffer means 1,
The original CBR signal (valid data) excluding the control information of the header and AAL specifications is write-controlled to the buffer means 1. When the SN processing means 2 detects a cell misdelivery, control is performed so as not to perform writing, and when cell discard is detected, control is performed so that reading is not performed by the length of the CBR signal corresponding to the number of discarded cells. The dummy signal (all "1" or all "0") is complemented. The CSI processing means 3 is
The CS control of the AAL specification of the cell is performed, and whether or not the pointer (1 byte) in the ATM cell is included is identified by the CSI display, and if it is included, the buffer means 1 is instructed to write 46 bytes as valid data. If the cell pointer is not included, an instruction to write 47 bytes as valid data is issued to the buffer means 1. The cell pointer processing means is AT
When it is indicated that the CSI in the M cell includes the cell pointer, the head cell pointer (1 byte) in the 47-byte AAL payload is extracted and the cell pointer value is output to each part. .

The CBR signal written in the buffer means 1 is read so as to form a frame of the SDH network. The pointer processing means 5 reads the CB read from the buffer means 1.
A pointer (for example, SDH TU-11 pointer) indicating the start position of the frame phase included in the R signal is extracted by the pointer value designated by the cell pointer processing means 4, and the buffer means 1 outputs the CBR signal. The phase of the reading is controlled. At this time, the previous pointer holding means 6 also has a configuration in which the same pointer is input and held, and at the same time, the pointer received last time (in the previous frame) is also held simultaneously, and the pointer of the previous frame is generated from the output side. The switching means 7 selects the signals that have passed through the pointer processing means 5 and outputs them to the SDH network except for the pointer value (TU-11 pointer or the like) of the CBR signal, but at the pointer position designated by the cell pointer processing means 4. Regarding the signal, when the output of the SN processing means 2 indicates the cell discard, the previous pointer holding means 6 switches to select the previous pointer, and when the cell discard does not occur, from the pointer processing means 5 Select the pointer to be output.

As a result, even when an ATM cell is discarded and a dummy signal (all "1" or all "0") having a length corresponding to the cell is complemented, the discarded cell includes a pointer. In this case, only the pointer value in the dummy signal is replaced with the previous pointer value, and SD
It is possible to prevent phase jumps in the H network.

[0027]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 2 is a block diagram of the first embodiment.
3 and 4 are timing charts (part 1) and (part 2) of the first embodiment at the time of normal operation, and FIGS. 5 and 6 are timing charts (part 1) when the cell is abandoned of the embodiment 1 (part 1). 2).

Reference numerals 10 to 12 in FIG. 2 denote buffer means 1 in FIG.
1 corresponds to each means represented by reference numerals 2 to 7 in FIG. 1, 10 is a decellizing buffer, 11 is a write address counter, 12 is a read address counter, 13 is an SC processing unit, Reference numeral 14 is a CSI processing unit, 15 is a cell pointer processing unit, 16 is a pointer processing unit, 17 is a previous pointer holding unit, and 18 is a pointer replacement unit.

First, the operation of the embodiment will be described with reference to FIGS. The ATM cell is a. Enter as shown in. A SAR-PDU header added by the AAL protocol is added to each ATM cell,
The SN processing unit 13 checks the SN (sequence number) therein. If it is normal, b. As shown in, the SN number in the SAR-PDU header is 0 to
It occurs in the order of 7 and returns from 7 to 0. In addition, c. In the example shown in (2), the determination results of the cell discard in the SN processing unit 13 are sequentially OK determination results indicating that all are normal.

The CSI processing unit 14 is the AAL of the ATM cell.
The CSI of the first bit of the SAR-PDU header of the specification is extracted, and the received ATM cell is the P format cell (see FIG. 1).
D.4. No.) or a non-P format cell (D. in FIG. 14) is detected. SN of SN processing unit 13
According to the check result and the determination result of the CSI processing unit 14,
The write address counter 11 generates a write address for writing the valid data of the ATM cell into the decellization buffer 10. The write address is enabled only in the area of the CBR signal and is disabled when the header portion and the cell discard are detected, so that only the area of the valid CBR signal is written in the decellization buffer 10.

3 and 4d. , CSI = 1 for cell 1-0, and CSI = 0 thereafter. A
Valid data (CBR signal) in the payload of TM cell
C. of FIG. As described above, it is 46 bytes when CSI = 1 and 47 bytes when CSI = 0. As shown in, the write address of the write address counter 11 corresponding to the CSI value is
4 from 0-0 to 0-45 for cell 1-0 (CSI = 1)
6 bytes, 1-0-1 for cell 1-1 (CSI = 0)
A write address of -46 of 47 bytes is generated. In response to this, the read address counter 12 is also shown in FIGS.
J. As shown in, a read address having the number of bytes corresponding to each written cell is generated after a certain delay time (in this example, a delay time of one cell), and reading is performed.

The cell pointer is the information indicating the frame boundary of the CBR signal.
It becomes the frame phase information when the CBR signal is read from. According to the phase information, C
The BR signal is read in synchronization with the frame. Further, the phase of the pointer included in the CBR signal can be specified by this phase information, and the pointer end and the previous (previous frame) pointer are held according to the information. In the example of FIG. 3, a. CSI of cell 1-0 shown in FIG. It is "1" as shown in, and it can be seen that the pointer (indicated by P) is set in the ATM cell. When the pointer (P) is extracted by the cell pointer processing unit 15, the CBR pointer stored in the point value in the data designated by P is extracted. In addition, the front pointer holding unit 17
The value of the new pointer is held and the previous pointer is also held and output.

More specifically, the cell pointer processing unit 15 includes the f. The cell pointer down counter shown in FIG. 2 (not shown in FIG. 2) is provided, and when the pointer P (whose numerical value is m) is extracted, the numerical value (= m) is set and each byte read from the decellization buffer 10 It counts down one by one, and when it reaches 0, C
The pointer of the BR signal (the value represented by X1 included in the cell 1-1 of FIG. 3a) is g. It is extracted at the timing shown in. After the extraction of the pointer X1 (a pointer address, which is a generalized representation of V1 and V2) of the CBR signal, it occurs every fixed number of bytes (n bytes in the examples of FIGS. 3 and 4), and almost One pointer (X3, X5, X7, ...) Appears in two cells.

This CBR pointer (X1,
The data of the CBR signal including X3) is read from the decellization buffer 10 by the read address counter 12 to the CBR signal.
The signal is delayed by one cell and read as shown in j of FIGS. 3 and 4, and the timing at the time of reading the CBR pointer address (X1 etc.) is g. Is delayed by one cell h. It is the timing shown in. This h. Signal is generated from the cell pointer processing unit 15, the CBR pointer discard determination is performed at this timing, and as shown by i, A
OK or NG is generated for every two TM cells. The pointer processing unit 16 and the previous pointer holding unit 17 are the same as those shown in FIG.
CBR pointers (X7, X1, X3, X
5, X7 ...) Are sequentially supplied every two cells.

The pointer processing unit 16 outputs the current CBR pointer at the timing when the CBR pointer is read, outputs the read signal (CBR signal) from the decellization buffer 10 at other timings, and outputs it from the previous pointer holding unit 17. The previous C at the timing of the CBR pointer
Output the BR pointer. Selection is made in the pointer replacement unit 18. The read address counter 12
Generates a dummy data as will be described later (FIGS. 5 and 6) when cell discard occurs.

The pointer replacement unit 18 outputs the cell discard determination output from the SN processing unit 13 (c. In FIGS. 3 and 4) and the timing of the CBR pointer from the cell pointer processing unit 15 (see FIGS. 3 and 4). h.) and cell discard occurs at the timing of the CBR pointer, the pointer held in the previous pointer holding unit 17 is selected, but in other cases, the pointer of the current frame output from the pointer processing unit 16 is selected. select. In the case of FIGS. 3 and 4, k. As shown in
As the CBR pointer, the pointer of the current frame (delayed by one cell from the time of writing) is selected. Thus, as shown by l in FIG. 3 and FIG. 4, the AT in the ATM cell including the CBR pointer selected by the pointer replacement unit 18 is included.
Continuous CBR signals are output except for the M header and the AAL header. In this case, the original X7 and X1 contained in the ATM cell are used as they are as the CBR pointer.

The operation of the first embodiment when a cell discard occurs will be described with reference to FIGS. 5 and 6 mainly with respect to the difference from the normal operation. FIG. 5 a. If the cells 1-3 shown in 1 are discarded, b. When the SN processing unit 13 (FIG. 2) detects the discard as shown in FIG. As shown in FIG.
When 4 is input, a discard determination (NG) output is generated. The write address counter 11 stops writing even during the discard cell. After a delay time of one cell from the time when it is assumed that the CBR signal of this discarded cell is received, as shown in j of FIG. 6, the read address counter 12 from the decellization buffer 10 stops the reading of the discarded section to supplement it. Data (use all "1" dummy data)
The CBR signal complemented by is read out.

On the other hand, the CBR pointer discard determination output (see FIG. 6)
I) becomes NG and indicates that the discarded cell includes the CBR pointer, the pointer replacement unit 18 drives the CBR pointer position (1 byte) in the complementary data by the cell pointer processing unit 15. , Its contents are replaced with the CBR pointer (X1 in the example of FIG. 6) held by the previous pointer holding unit 17. As a result, the l in Figure 6
As shown in, the discarded cell data (all "1") is lost, but the pointer value is different from the discarded value, but is replaced with the previous value.

Thus, even when the discarded cell includes the CBR pointer, it is possible to prevent the erroneous staff recognition due to the complementary (dummy) data in the SDH network which converts the cell from the ATM network into the STM and transmits the cell. . Even if the pointer contained in the discarded cell indicates some pointer action (positive stuff, negative stuff), the pointer action is discarded and the pointer action cannot be transferred, but the pointer is updated due to the continuous matching of the pointers received thereafter. By doing so, it is possible to deal with NDF (new data flag: see A in FIG. 13) enable and increase / decrease of pointers of positive and negative stuff addresses.

In the first embodiment, when the discarded cell contains a pointer, only the pointer value is replaced with the previous pointer. Normally, the pointer is discarded and then restored normally (the pointer is no longer discarded)
The determination as to whether or not is normally made by confirming that the same content is received a certain number of times continuously (protection of pointer value), but the pointers are replaced as in the first embodiment. In this case, it is updated with the pointer value received the first time without confirmation (protection) multiple times. As a result, S
It is possible to quickly execute the pointer increase / decrease in the DH network.

FIG. 7 is a block diagram of the second embodiment. In FIG. 7, reference numerals 10 to 18 are the same as the respective parts having the same reference numerals in the first embodiment shown in FIG. Reference numeral 19 is an all "1" complementing unit, and 20 is a discard cell counter.

In the second embodiment, basically, similar to the first embodiment of FIG. 2, when the cell including the pointer is discarded, the value of the previous pointer stored as the CBR pointer in the complementary data is switched. It was However, when cell discard occurs and the stuff action is included in the cell discard, the stuff action instructed by the transmitting SDH network A (see FIG. 11) is caused by the cell discard in the receiving SDH network B (see FIG. 11). If the pointer increase / decrease is delayed, SDH network A and SDH network B
Byte adjustment (frequency justification) cannot be performed due to the frequency deviation of, and data bit errors may occur.

In the second embodiment, when the SN processing section 13 detects cell discard, the number of discarded cells is counted by the discarded cell counter 20. The discard cell counter 20 generates an output when the count value exceeds a preset number n, and drives the all-1 complementing section 19. All 1
The complementing unit 19 sends continuous all "1" data when driven. SDH network that receives this output (SD in FIG. 11
In the H network B), the continuous all "1" is identified as an alarm signal (AIS: Alarm Indication Signal),
Faults in the ATM network can be transmitted to the SDH network B.

Next, FIGS. 8 and 9 show the configuration of the third embodiment,
FIG. 8 shows the structure of the STM-ATM converter of the third embodiment, and FIG. 9 shows the structure of the ATM-STM converter of the third embodiment. The third embodiment prevents the occurrence of a phase jump in the SDH network even if the cell discard including the pointer occurs in the ATM network. The configuration shown in FIG.
9 corresponds to AC-A, and the configuration of FIG.
Equivalent to B.

In FIG. 8, reference numeral 30 is a cell formation buffer, and 3
Reference numeral 1 is an AAL type 1 header addition unit, 32 is a first cell header addition unit, and 33 is a second cell header addition unit. CBR
The data is a continuous signal (for example, TU-1 in FIG. 12).
1), it is stored in the cell assembling buffer 30, and then the AAL type 1 header adding section 31 adds a 1-byte header (see C. in FIG. 14). This time,
Pointer indicating the frame phase of CBR data (TU-1
In the case of 1, in the case of a cell instructing V1), the head CSI
Set the bit to "1", create a header with SN and SNP added, set a pointer indicating the position of the V1 byte in the subsequent 1 byte, and set the CBR data in the remaining 46 bytes of the ATM cell. The payload is formed.
If the pointer is not included, the CSI bit in the AAL type 1 header is set to "0", and the payload of the ATM cell in which the 47-byte CBR signal following the header is set is formed. The signal of the payload section formed by the AAL type 1 header adding section 31 is supplied in parallel to the first and second cell header adding sections 32 and 33. The first cell header addition unit 32 and the second cell header addition unit 33 each add a 5-byte ATM header (see A in FIG. 14), but each VPI (virtual path identifier) is made different, and the ATM is used as a destination. The receiving circuit on the working side and the receiving circuit on the protection side of the -SDH converter (FIG. 9) are designated. Therefore, the paths corresponding to two different VPIs of the ATM network correspond to the working path and the backup path, respectively, and have the same C
ATM cells containing BR signals are input to the working and protection receiving circuits shown in FIG. 9, respectively.

In FIG. 9, each part 10a to 16a constitutes a working system circuit, and 10b to 16b constitutes a standby system circuit, each corresponding to each part 10 to 16 of the first embodiment shown in FIG. Although not described, reference numeral 21 is a selector that selects one of the outputs of the pointer processing units 16a and 16b of both systems.

The active and standby ATM cells transmitted to the ATM network by the configuration shown in FIG. 8 are received by the active and standby input terminals of FIG. 9 via another route and input to the respective circuits. To be done. In the circuits of each system, the SN processing units 13a and 13b detect cell discard, the CSI processing units 14a and 14b identify CSI, and control writing and reading to and from the decellization buffers 10a and 10b. The pointer processing units 15a and 15b perform the pointer processing of the CRB signal in each system in the same manner as in the first embodiment. In this case, the payload portions of the ATM cells of both systems have exactly the same information, and the cell pointers are also the same, so the read phases of the CBR data from the decellizing buffers 10a and 10b are also synchronized.

In this configuration, the selector 21 has the SN
When the output from the processing unit 13a indicates that cell discard is not detected, the cell pointer processing unit 15a selects the output of the active pointer processing unit 16a at the pointer position of the CBR signal. However, the active S
When the cell discard processing output is generated from the N processing unit 13a and the output of the cell pointer processing unit 15a identifies that the pointer of the CBR signal is included therein, the selector 21 simply determines that the pointer processing unit of the backup system is included. Switching is performed so as to select the standby system pointer output from 16b.

In the configuration of FIG. 8 of the third embodiment, the STM-
CB from the SDH network in the device for converting ATM
When converting the R signal into ATM cells, two ATM cells are generated by using the first and second cell header adding units 32 and 33. The use of the two cell header adding units in this way increases the hardware configuration, and there is a method of improving this. It generates a cell having one type of VPI and sends it as an active cell, copies the cell, adds a VPI which is a route different from the original cell, and sends it as a backup. When each of these ATM cells is received by the configuration shown in FIG. 9, the active and standby processes are synchronized and the pointer can be selected.

Further, the SNs of the active and standby ATM cells
(Sequence number) is monitored, and if the pointer is included in the discard cell of the active system only, the pointer of the standby system is selected, and if the cell containing the same pointer in both systems is discarded, Select the pointer. Further, in the configuration of FIG. 9, when both the SNs of the active system and the standby system are monitored and the discard cell of the active system only includes the pointer,
When the pointer of the spare system is selected and cells containing the same pointer are discarded in both systems, consecutive all 1's are generated by the same circuit as the all 1 complementing unit 19 of the above-described second embodiment (see FIG. 7). SDH network for sending and receiving (Fig. 1
By detecting AIS in SDH network 1)
Network faults can be communicated to the SDH network.

In the configurations of the above-described first to third embodiments, the STM-
C input to the ATM conversion device (SAC-A in FIG. 11)
The BR signal pointer includes a stuff action (indication of positive stuff and negative stuff shown in A. of FIG. 13), and an ATM-STM conversion device (SAC-B of FIG. 11) which receives an ATM cell including this. In the case where the pointer is discarded in the above, the countermeasure is taken.
In the TM-ATM converter, the CBR signal is made into cells so that the stuffing caused by the difference in clock frequency between the SDH network and the ATM network is completely absorbed and no stuffing action occurs in the ATM-STM converter. Is.

FIG. 10 is a block diagram of the fourth embodiment. In the figure,
Reference numeral 40 is a frame counter for counting clocks of the SDH network A (see FIG. 11), 41 is a write address address generator corresponding to the output of the frame counter, and 42 is CB.
A stuff absorption buffer for writing R data and performing stuff absorption for reading, 43 is a frame counter for counting ATM network clocks, 44 is a read address generation unit, 45 is a pointer addition unit, and 46 is a cell assembly buffer.

The operation will be described. In the STM-ATM converter, the cellized CBR signal is temporarily stored in the stuff absorption buffer 42. At this time, the SDH network clock is used to operate the frame counter 40 of the CBR signal, and the count value of the counter is changed to the write address 4
1, the pointer of the CBR signal is excluded (for example, ST
M's VC-11, VC-2, VC-3, VC-4 etc. virtual container) data is written. Also, terminate the pointer included in the CBR signal of the SDH network on the input side,
When positive / negative stuff is detected, the write phasing is adjusted according to the instructed stuffing (positive / negative) phase.

For example, when TU-11 is terminated and positive stuff is detected, writing of the byte next to the V3 byte (negative stuff action byte shown in A. of FIG. 13) of the detected frame is disabled, In the case of negative stuff, the phase adjustment is performed by enabling the writing of the V3 byte of the same frame. Thus, when writing to the stuff absorption buffer 42, the pointer in the SDH network on the input side is terminated.

When reading from the stuff absorption buffer 42, the clock from the ATM network is used, the frame counter 43 of the CBR signal is operated, and the data excluding the pointer of the CBR signal is read according to the count value. A fixed pointer value synchronized with the clock of the ATM network is added to the read data by the pointer adding section 45, and the read data is made into cells through the cell forming buffer 46 and output to the ATM network.

When the cell containing the pointer value is discarded, the fixed pointer value is complemented in SAC-B (see FIG. 11). With the configuration of FIG. 10, the signal transmitted through the ATM network does not need any pointer action in the ATM network, and the reliability can be improved.

[0057]

According to the present invention, the synchronous mode (STM)
In a communication network for converting information into asynchronous transfer mode (ATM) information and transmitting it, it is possible to prevent a phase jump due to data complement due to cell discard in the ATM network and a phase jump due to erroneous staff recognition.

[Brief description of drawings]

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

FIG. 2 is a configuration diagram of a first embodiment.

FIG. 3 is a timing chart (No. 1) at the time of normal operation of the first embodiment.

FIG. 4 is a diagram showing a timing chart (No. 2) in the normal operation of the first embodiment.

FIG. 5 is a diagram showing a timing chart (No. 1) when a cell discard occurs in the first embodiment.

FIG. 6 is a diagram showing a timing chart (No. 2) when a cell discard occurs in the first embodiment.

FIG. 7 is a configuration diagram of a second embodiment.

FIG. 8 is a diagram illustrating a configuration of an STM-ATM conversion unit according to a third exemplary embodiment.

FIG. 9 is a diagram illustrating a configuration of an ATM-STM conversion unit according to a third embodiment.

FIG. 10 is a configuration diagram of a fourth embodiment.

FIG. 11 is an explanatory diagram of a communication network that relays an SDH network with an ATM network.

FIG. 12 is an explanatory diagram of an outline of SDH according to ITU recommendation.

FIG. 13 is an explanatory diagram of a TU-11 pointer.

FIG. 14 is an explanatory diagram of an outline of ATM.

[Explanation of symbols]

 1 buffer means 2 SN processing means 3 CSI processing means 4 cell pointer processing means 5 pointer processing means 6 front pointer holding means 7 switching means

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁶ Identification number Internal reference number FI Technical display location 9466-5K H04L 11/20 B (72) Inventor Shinji Takao Hakata Ekimae, Hakata-ku, Fukuoka-shi, Fukuoka C. 22-8 Fujitsu Kyushu Digital Technology Co., Ltd. (72) Inventor Hiroaki Shirai 1015 Kamiodanaka, Nakahara-ku, Kawasaki-shi, Kanagawa Prefecture Fujitsu Limited (72) Kenichi Hashimoto, Ueda-ken, Nakahara-ku, Kawasaki, Kanagawa Prefecture 1015 Address within Fujitsu Limited (72) Inventor Toshiaki Watanabe Kamiodanaka, Nakahara-ku, Kawasaki City, Kanagawa 1015 Address Within Fujitsu Limited (72) Inventor, Shinji Ota 1015 Kamiodanaka, Nakahara-ku, Kawasaki City, Kanagawa Within Fujitsu Limited (72) ) Inventor Hitoshi Uematsu 1-1-6 Uchisaiwaicho, Chiyoda-ku, Tokyo Nihon Telegraph and Telephone Corporation

Claims (8)

[Claims] 1. In a communication network for transmitting a CBR signal of an SDH network to another SDH network via an ATM network, said AT
ATM-STM provided between the M network and the other SDH network
The conversion circuit includes an SN processing means for detecting cell discard of an ATM cell, a CSI processing means for identifying a CSI signal of an AAL header, a cell pointer processing means for detecting a cell pointer and instructing a pointer of a CBR signal, and an ATM. Cell A
Buffer means for writing the CBR signal excluding the TM header and AAL header and for reading the data in synchronism with the SDH network, and generating specific dummy data when detecting cell discard.
Pointer processing means for processing the pointer of the CBR signal read from the buffer means, front pointer holding means for holding the previous pointer, and switching means for selecting one of the output of the pointer processing means and the front pointer holding means. The switching means normally selects the output of the pointer processing means, and selects the pointer of the previous pointer holding means when the pointer of the CBR signal is included in the discarded cells. Signal phase jump prevention method. 2. The switching means according to claim 1, wherein when the output of the previous pointer holding means is selected by the switching means and the cell discard detection disappears, the first received pointer value is selected thereafter. A method for preventing a phase jump of a CBR signal via an ATM network characterized by switching. 3. The discard cell counter according to claim 1 or 2, wherein the SN processing means counts the detection output of the discard cell, and the discard cell counter is driven when the discard cell counter exceeds a certain level, and the output from the switching means is continuously 1 A method for preventing phase jump of a CBR signal via an ATM network, which is provided with an all-1 complementing unit for converting the data of the above. 4. In a communication network for transmitting a CBR signal of an SDH network to another SDH network via an ATM network, a conversion unit provided between the SDH network on the transmission side and the ATM network is a CBR.
After converting the signal into cells and adding an AAL header, a different V
It is provided with first and second cell header adding units for adding an ATM cell header having a PI, and outputs the outputs of the two cell header adding units to the ATM network respectively, and is provided between the ATM and the SDH network on the receiving side. The converting unit includes a working and a spare converting circuit, and each of the working and the spare converting circuits includes an SN processing means, a CSI processing means, a cell pointer processing means, a buffer means, and a pointer processing means. And a selector to which the output from the pointer processing means of each of the working and spare conversion circuits is input, the selector being used when the working conversion circuit does not detect cell discard including the pointer of the CBR signal. The output of the circuit is selected, and when the cell discard including the pointer of the CBR signal is detected in the current conversion circuit, the output of the spare conversion circuit is selected. Phase jump prevention system CBR signal to. 5. In a communication network for transmitting a CBR signal of an SDH network to another SDH network via an ATM network, a conversion unit provided between the SDH network on the transmission side and the ATM network is a CBR.
A cell header adding section for adding a ATM cell header and sending an ATM cell after the signal is made into cells and adding an AAL header;
The VPI of the TM cell header is changed and transmitted, and the ATM
The converter provided between the SDH network on the receiving side and the SDH network on the receiving side includes the working and standby converting circuits according to claim 4, and the selector for selecting an output of the converting circuit. CBR signal phase jump prevention method. 6. The ATM according to claim 4 or 5.
The active conversion circuit of the conversion unit provided between the SDH network on the receiving side and the SDH network on the receiving side is a switching means for selecting one of the front pointer holding means and the output of the pointer processing means or the front pointer holding means according to claim 1. And the selector monitors both the SN processing means and the pointer processing means of each of the working and spare conversion circuits, and when only the working side includes the pointer in the discarded cell, the spare conversion circuit. Output of the switching means on the active side is selected when both of the discard cells include pointers. 7. The selector according to claim 4 or 5, wherein the selector monitors both the SN processing means and the pointer processing means of both the working and spare conversion circuits, and only the working side includes the pointer in the discarded cell. If the output of the spare conversion circuit is selected, and if both discarded cells contain the same pointer, all 1 data is sent to detect an alarm signal to the network. Phase jump prevention method. 8. A STM for converting a CBR signal input from the SDH network into an ATM cell in a communication network for transmitting the CBR signal of the SDH network to the other SDH network through the ATM network.
The -ATM conversion unit has a stuff absorption buffer, and when writing, the frame counter operating with the clock of the SDH network on the input side removes the CBR signal pointer from the C counter.
In addition to writing BR data, positive / negative stuffing by the pointer of the CBR signal is performed by adjusting the phase at the time of writing, and at the time of reading from the stuff absorption buffer, the frame counter operated by the clock of the ATM network causes the pointer of the CBR signal. Phase jump of the CBR signal, characterized in that the data except the above is read, a pointer synchronized with the clock of the ATM network is added to the read data, and the data is converted into ATM cells in the cell assembling circuit and sent to the ATM network. Prevention method.