JP3253470B2 - High Efficiency Cell Multiplexing Scheme by Controlling Dynamic PVC in Asynchronous Communication Network - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for dynamically suppressing a permanent virtual circuit (PVC) configured for circuit emulation or the like.

[0002]

2. Description of the Related Art There is a circuit emulation system as one of services in an ATM switching network for performing data transfer based on an ATM (asynchronous transfer mode) system.

In this method, as shown in FIG. 4, an STM signal 405 transmitted synchronously is transferred to an ATM cell 406 transmitted asynchronously in an ATM switching network, and the ATM cell 405 is transmitted.
6 to STM signal 407 having the same timing as the transmitting side
This is a method of reproducing.

[0004] According to this method, a synchronization signal such as an audio signal or an image signal is kept while maintaining its synchronization timing.
It can be transferred within the ATM switching network, which is an asynchronous network.
Here, the CLAD device on the transmission side (cell decellularization device) 40
In the transmission buffer 4 for temporarily holding the STM signal 405,
03 is provided, and a reception buffer 404 for temporarily holding an ATM cell 406 is provided in the CLAD device 402 on the receiving side. Sent from the sender using these buffers
STM signal 405 and STM signal 4 received on the receiving side
07 are synchronized.

[0005] As a data protocol for carrying the STM signal 405 on the ATM cell 406, an ATM adaptation layer is used.
(AAL) A protocol called type 1 is adopted. AA
In L type 1, as shown in FIG.
A 5 octet ATM header and a 48 octet
In the ATM information field, 1 is added to the ATM information field.
A SAR-PDU (Segmentation and Reassembly sublayer) consisting of an octet header and a 47 octet payload
A protocol data unit called Protocol Data Unit is inserted.

[0006] In the lower 46 octets of the payload of the 47 octet SAR-PDU, the STM signal 405 itself in FIG. 4 is divided and inserted as user information. In the case of structured data, a pointer field (P) is added as an option, and information for transmitting the timing of the frame boundary point in the STM signal 405 on the transmitting side to the receiving side is transferred. That is, in the STM signal, a plurality of time slots collectively constitute one frame. This frame configuration is necessary for establishing synchronization between time slots, transmitting control information using specific bits in specific time slots in a frame, and the like. Therefore, the STM signal 405 on the transmitting side
The timing of the frame boundary point in
The M signal 407 also needs to be accurately restored.
Actually, the CLAD device 401 on the transmitting side detects a timing signal called a frame pulse shown in FIG. 6 at a timing when a frame boundary point of the STM signal 405 is input. The pointer P of the payload of the SAR-PDU shown in FIG. 5 is set.

As shown in FIG. 5, the header of the SAR-PDU has an SN (Sequence Number) and a
SNP (Sequence Number Protecti
on). Both the SN and SNP fields are used to detect cell loss or misinsertion in the ATM switching network. The SN field indicates a sequence number for identifying the order of transmitting cells. The SNP field performs error detection and correction for the SN field.

FIG. 7 is a functional explanatory diagram of the circuit emulation system. In the CLAD device 401 on the transmitting side, ST
The M signal 405 is temporarily stored in the transmission buffer 403,
Therefore, it is simply divided and stored in the payload of the SAR-PDU, and the SAR-PDU obtained as a result is stored in the ATM cell 406 and transmitted to the ATM switching network. In this case, as shown in FIG. 7, a continuous sequence number is assigned to the SN field of the header part of the SAR-PDU stored in the sequentially transmitted ATM cell 406.

The ATM cell 406 is transmitted in the ATM switching network and received by the CLAD device 402 on the receiving side. A transmission delay occurs during the transmission of the ATM cell 406 in the network. This transmission delay is absorbed by the reception buffer 404 in the CLAD device 402 on the receiving side, and the STM signal 406 is restored in the sequence number order. You. ATM cell 40
If 6 is discarded in the network, the receiving CL
The AD device 402 cannot receive the cell within a certain time. In this case, the receiving CLAD device 402
For example, the STM signal 406 is restored by generating a dummy signal having an all 1 value.

[0010] Here, there is a case where an ATM leased line is drawn between two node devices via an ATM switching network and communication of a circuit emulation method is performed on the ATM leased line as in intra-company communication or the like. FIG. 8 is a diagram showing the image.

An ATM is connected between two nodes 801 of #A and #B.
An ATM dedicated line 803 is laid via a switching network 802. The ATM leased line 803 has a variable rate (VBR: Var) used by the ATM terminal 808 connected to the node 801.
iALE Bit Rate) communication path 805 and PBX (Private Branch Exchange) 8 connected to node 801
STM terminal 807 that is connected via synchronous communication and performs synchronous communication
There is a fixed rate (CBR: Constant Bit Rate) system communication path 804 used by. This CBR communication path 804 is
Permanent Virtual Circuit (PVC: Permanent Vi
rtual circuit), and this path is normally set at all times. Then, the CBR communication path 804
Is used to perform communication by the circuit emulation method. In other words, in order to execute communication that requires timing reproduction as in the circuit emulation method, it is necessary to eliminate the processing overhead as much as possible. Implementing as a PVC that does not require processing can simplify the network architecture and result in a better system.

[0012]

Here, the ATM dedicated line 8
Communication using the CBR communication path 804 is not always performed on the communication network 03. However, in the past, even during periods when there was no communication, CBR using PVC
System communication path 804 is always set,
CBR communication path 8 during periods when no communication is occurring
Since an empty cell has been transmitted to the ATM dedicated line 804, the transmission band of another VBR communication path 805 on the ATM dedicated line 803 that does not use PVC is squeezed.
There is a problem that the multiplexing efficiency of the M cell 406 is reduced.

In particular, the above problem is serious on a transmission line having limited transmission line resources, such as an ATM leased line 803. An object of the present invention is to realize efficient multiplexing of a CBR communication path and a VBR communication path.

[0014]

FIG. 1 is a block diagram of the present invention. According to the present invention, a first communication path for performing a fixed bit rate communication using a permanent virtual circuit and a second communication path for performing a variable bit rate communication are set on the asynchronous communication path 101. It is assumed that a cell multiplexing method is used in which cells transmitted using a path are multiplexed on the asynchronous communication path 101.

First, the synchronous communication path terminating means 102 (terminal side interface 203) terminates the synchronous communication path 107 for transmitting a synchronous signal for fixed bit rate communication.
Asynchronous communication path terminating means 103 (line side interface 2
05) terminates the asynchronous communication path 101.

Fixed bit rate communication conversion means 104 (AT
The M cell assembling / disassembling unit 204) includes a synchronous signal on the synchronous channel 107 terminated by the synchronous channel terminating unit 102 and an asynchronous channel 10 terminated by the asynchronous channel terminating unit 103.
And the cells transmitted using the first communication path on 1
Convert to each other.

The communication presence / absence detecting means 105 (call control signal processing section 206) detects whether or not the synchronous communication path 107 terminated by the synchronous communication path terminating means 102 is communicating.
The communication presence / absence detecting means 105 detects whether or not the synchronous communication path 107 is performing communication, for example, by detecting whether or not the call setting signal is multiplexed with the synchronization signal.

The control means 106 (control section 207)
When the communication presence / absence detecting unit 105 detects that the synchronous communication path 107 is performing communication, the cell storing the synchronization signal is asynchronously transmitted from the asynchronous communication path terminating unit 103 using the first communication path. When the communication presence / absence detection means 105 detects that the synchronous communication path 107 is not performing communication, the cell storing the synchronization signal is transmitted from the asynchronous communication path termination means 103 to the communication path 101. First
Is controlled so as not to be transmitted to the asynchronous communication path 101 using the communication path of (1).

[0019]

When no synchronous signal communication is performed on the synchronous communication path 107, transmission of cells to the asynchronous communication path 101 using the first communication path for performing fixed bit rate communication is suppressed. As a result, the second performing the variable bit rate communication
, The transmission band of the communication path is sufficiently secured, and the utilization efficiency of the asynchronous communication path 101 can be improved.

[0020]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 2 is a configuration diagram of an embodiment of the present invention.

In FIG. 2, the ATM switching network DCE equipment 201
Corresponds to the CLAD device 401 in FIG. 4 or the node 801 in FIG. The voice / data DTE device 202 is the PBX of FIG.
806. Voice / data DTE device 202 and AT
M Switching network DCE device
M line 209 is laid, and ATM switching network DCE equipment 2
01 is not particularly shown via the ATM dedicated line 210
Connected to ATM switching network.

In the ATM switching network DCE device 201, the terminal side interface 203 accommodates the STM line 209,
The line interface 205 accommodates the ATM dedicated line 210.

The terminal interface 203
The STM signal received from the line 209 is temporarily stored in a transmission buffer (not shown) in the ATM cell assembling / disassembling section 204, where it is simply divided and stored in the SAR-PDU payload (FIG. 5). The resulting SAR-PDU is
The ATM cell is stored in the ATM cell, and the ATM cell is transmitted to the ATM dedicated line 210 by the cell transmission mechanism 208 in the line side interface 205. In this case, as described with reference to FIG. 7, the SAR-PD stored in the sequentially transmitted ATM cells is used.
A continuous sequence number is assigned to the SN field (FIG. 5) in the header of U. Also, when the STM signal is stored
A CBR communication path is included in the header of the ATM cell (see Fig. 8).
VPI (Virtual Pass Identifier)
Identifier) and VCI (Virtual Channel Id)
entifier). This path becomes the PVC.

On the other hand, of the ATM cells received by the line-side interface 205 from the ATM leased line 210, the ATM cells to which the VPI / VCI corresponding to the above-mentioned PVC is assigned are AT cells
The data is received by a receiving buffer (not shown) in the M cell assembling / disassembling unit 204. Then, the ATM cell assembling / disassembling section 204 compensates for the transmission delay, loss, erroneous insertion, etc. of the ATM cell in the ATM switching network, and adds the ATM cell to the header of the SAR-PDU stored in the ATM cell. The STM signal is restored in the order of the sequence numbers (SNs), and is transmitted from the terminal side interface 203 to the STM line 209.

The ATM switching network DCE device 201 also accommodates an ATM terminal (not shown), and ATM cells input / output to / from the terminal are directly input / output to / from the ATM dedicated line 210. An individual VPI / VCI indicating a VBR communication path (see FIG. 8) is added to the header of such a cell.

Here, as a feature particularly relevant to the present invention, the voice / data DTE device 202 transmits the data from the ATM switching network DCE.
A voice / data DTE device 202 is connected to the device 201 by the STM.
Call setting information indicating whether signal communication is being performed is notified (A in FIG. 2).

The call setting information is notified using, for example, the least significant bit (LSB) of each time slot of the STM signal synchronously transmitted on the STM line 209 as shown in FIG. If 1, the call is set up on the STM line 209, and if LSB = 0, it is displayed that the call is not set up.

The above LSB value is extracted by the call control signal processing unit 206 in the terminal side interface 203.
It is output to the control unit 207 (FIG. 2B). Control unit 207
As shown in FIG. 3, if LSB = 1, the cell transmission mechanism 208 in the line side interface 205
The ATM cell storing the STM signal output from the M cell assembling / disassembling unit 204 is taken into a transmission queue in the same mechanism,
If LSB = 0, the ATM cell assembling / disassembling unit 204 is sent to the cell transmitting mechanism 208 in the line side interface 205.
ATM cells that store the STM signal output by are discarded instead of being taken into the transmission queue in the same mechanism.

By the above control operation, when the communication of the STM signal is not performed, the transmission of the ATM cell having the VPI / VCI corresponding to the CBR communication path (PVC) to the ATM dedicated line 210 is suppressed. . As a result, the transmission band of the VBR communication path is sufficiently ensured, and the utilization efficiency of the ATM dedicated line 210 can be improved.

[0030]

According to the present invention, when the communication of the synchronization signal is not performed on the synchronous communication channel, the cell is transmitted to the asynchronous communication channel using the first communication path for performing the fixed bit rate communication. Because of the suppression, the transmission band of the second communication path for performing the variable bit rate communication is sufficiently secured, and the utilization efficiency of the asynchronous communication path can be improved.

[Brief description of the drawings]

FIG. 1 is a block diagram of the present invention.

FIG. 2 is a configuration diagram of an embodiment of the present invention.

FIG. 3 is an explanatory diagram of an embodiment of the present invention.

FIG. 4 is a functional configuration diagram of a circuit emulation system.

FIG. 5 is a data format diagram of a SAR-PDU and an ATM cell used in circuit emulation.

FIG. 6 is an explanatory diagram of a frame boundary point in an STM signal.

FIG. 7 is an explanatory diagram of functions of a circuit emulation method.

FIG. 8 is an explanatory diagram of a multiplexing method of CBR-based communication and VBR-based communication on an ATM leased line.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 101 Asynchronous communication path 102 Synchronous communication path terminating means 103 Asynchronous communication path terminating means 104 Fixed bit rate communication conversion means 105 Communication existence detecting means 106 Control means 107 Synchronous communication path

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-3-235448 (JP, A) JP-A-4-331530 (JP, A) JP-A-4-86044 (JP, A) JP-A-4- 138744 (JP, A) JP-A-8-111683 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H04L 12/56 H04J 3/00

Claims (2)

(57) [Claims] 1. A first communication path for performing a fixed bit rate communication using a permanent virtual circuit and a second communication path for performing a variable bit rate communication are set on an asynchronous communication path. In a cell multiplexing system in which cells transmitted using the same are multiplexed on the asynchronous communication path, a synchronous communication path terminating means for terminating a synchronous communication path for transmitting a synchronous signal for the fixed bit rate communication; An asynchronous communication path terminating means for terminating a communication path; a synchronization signal on the synchronous communication path terminated by the synchronous communication path terminating means; and a first communication path on the asynchronous communication path terminated by the asynchronous communication path terminating means. A fixed bit rate communication converting means for mutually converting cells transmitted using the communication channel, and the synchronous communication path terminated by the synchronous communication path terminating means performs communication. A communication presence / absence detecting means for detecting whether or not the communication signal is being transmitted, and when the communication presence / absence detection means detects that the synchronous communication path is performing communication, the cell in which the synchronization signal is stored is transmitted to the asynchronous communication path. The terminal means controls so as to be transmitted to the asynchronous communication path using the first communication path, and when the communication presence / absence detecting means detects that the synchronous communication path is not performing communication, Control means for controlling a cell in which a synchronization signal is stored so as not to be transmitted from the asynchronous communication path terminating means to the asynchronous communication path using the first communication path. Dynamic PV within
A high-efficiency cell multiplexing method by suppressing C. 2. The communication presence / absence detecting means detects whether or not a call setup signal is multiplexed on the synchronization signal, thereby detecting whether or not the synchronization communication path is performing communication. 2. The high-efficiency cell multiplexing method according to claim 1, wherein dynamic PVC is suppressed in the asynchronous communication network.