JP2003087322A - Communication network system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently transmit data between low speed terminals via a transmission line by decreasing a delay in a node device for assembling data from the low speed terminals into cells. SOLUTION: A dummy data attachment section 211 of a transmission section 21 respectively attaches dummy data to each of STM data sent from each of STM terminals 110 and gives the resulting data to an AAL (ATM Adaptation Layer) 1 section 212. A cell assembling section 2121 of the AAL1 section 212 respectively assembles data (STM data + dummy data) resulting from attaching the dummy data to the STM data by the dummy data attachment section 211 into cells, a cell multiplexer section 2122 multiplexes the cells, and transfers the result to an ATM switch section 12. Then the ATM switch section 12 exchange-outputs the multiplexed cells sent from the cell multiplexer section 2122 to a channel on a transmission line 60.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention accommodates low-speed terminals that handle data at a speed lower than the transmission speed of the transmission line in a plurality of node devices connected via the transmission line, and connects the node device and the transmission line to each other. The present invention relates to a communication network system for transmitting data between low-speed terminals via the above, and more particularly, to control for shortening cell formation delay when converting data from the low-speed terminals into cells for transmission on a transmission line in the node device. .

[0002]

2. Description of the Related Art For example, in the field of railway management systems and road management systems, there is known a network configuration in which a plurality of communication devices are arranged in a distributed manner and information from these communication devices is collected and managed in a management center or the like. There is.

As a typical configuration of this type of system,
A plurality of node devices are connected on a transmission line, and each node device corresponds to the communication device and handles low-speed data lower than the transmission speed of the transmission line (for example, STM.
(Synchronous Transfer Mode) terminal], and in each node device, STM data (low speed data) from the STM terminal is converted into cells (high speed data) with the STM terminal to be accommodated. While transmitting to the transmission line, converting the cells from the transmission line into STM data and transmitting to the STM terminal, each node device on the transmission line relays and transmits the cell with the adjacent opposite node device, It is known to realize data transmission between STM terminals.

In the node device of this type of conventional system,
Data from low speed terminals (STM terminals) (STM data)
When converting the data into cells to be transmitted on the transmission line, the data from the low-speed terminal is temporarily stored in the buffer memory, and the data is read from the buffer memory after waiting for a predetermined amount of data to be stored in the buffer memory. It was common to initiate cellization by

According to such a configuration of the conventional system, in the node device, cell formation cannot be started until a predetermined amount of data from the low speed terminal is accumulated in the buffer memory, and depending on the data amount of the data from the low speed terminal, the cell formation is performed. The delay has increased significantly.

[0006]

As described above, in the conventional system, the node device waits until a predetermined amount of data from the low-speed terminal is accumulated in the buffer memory, reads the data from the buffer memory, and starts cell formation. However, there is a problem that the cell formation delay is large.

The present invention solves the above problems and shortens the cellization delay of the data from the low speed terminals in the node device, so that the data transmission between the low speed terminals via the transmission path can be performed more efficiently. An object is to provide a communication network system capable of performing.

[0008]

In order to achieve the above object, the invention of claim 1 is a low speed for handling a data speed lower than a transmission speed of the transmission line to a plurality of node devices connected through the transmission line. In a communication network system that accommodates each terminal and performs data transmission between the low-speed terminal via the node device and a transmission line, the node device transmits low-speed data from the low-speed terminal to a cell transmitting the transmission line. Cell converting means for converting, and the low speed data sent from the low speed terminal and accumulated in the buffer means are read from the buffer means at the cell start timing corresponding to the transmission speed of the transmission line in the cell converting means. When the amount of data is less than the required amount, dummy data adding means for adding dummy data for the shortage of bandwidth to the low speed data and transferring it to the cellizing means. Characterized by comprising.

According to a second aspect of the present invention, in the above-mentioned first aspect of the invention, the dummy data adding means includes the dummy data for each low speed data transmitted from a plurality of low speed terminals accommodated in the own node device. Is added.

According to a third aspect of the present invention, in the second aspect of the invention, the cell assembling means comprises a cell assembling section for cellizing each of the low speed data to which the dummy data is added, and the cell assembling. And a cell multiplexing unit that multiplexes each cell made into a cell by the unit.

According to a fourth aspect of the present invention, in the above-mentioned second aspect of the present invention, a multiplexing unit for multiplexing the low speed data to which the dummy data is added is arranged in front of the cell forming means, It is characterized in that each of the low-speed data to which dummy data is added is multiplexed by the multiplexing unit and then converted into cells by the cell conversion unit.

According to a fifth aspect of the present invention, in the first aspect of the present invention, the node device starts to monitor an instruction state of an activation signal for instructing whether or not to send data to the low speed terminal. It is characterized by comprising signal monitoring means and dummy data addition control means for controlling the dummy data adding means to add the dummy data only during a period in which the activation signal is in a state of instructing data transmission.

According to a sixth aspect of the present invention, in the above-mentioned first aspect of the invention, the node device decellizes the cell from the transmission path into low speed data, and decellizes by the decellizing means. And dummy data removing means for removing dummy data from the generated low speed data.

According to a seventh aspect of the present invention, in the above-mentioned first aspect, the low speed terminal is in a synchronous transfer mode (ST).
M) is an STM terminal that transmits and receives the STM data that is low-speed data, and the node device is an ATM switching device that converts the STM data into the cells and transmits the cells in an asynchronous transfer mode (ATM). .

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 is a diagram showing the overall configuration of a communication network system according to the present invention.

This system includes a plurality of node devices 100.
-1 (N1), 100-2 (N2), 100-3 (N
3), 100-4 (N4), 100-5 (N5) are connected in a ring shape via the transmission line 60 to form a ring network system.

Each node device 100 (100-
1,100-2,100-3,100-4,100-
5) includes one or more local terminals 11 respectively.
0 (in the example of FIG. 1, the local terminals 110a, 110b,
110c, 110d, 110e, 110f, 110g,
110h exists) is connectable.

In this system, the node device 100
For example, the asynchronous transfer mode (ATM: Asynch
ronous Transfer Mode) An exchange is used. In this case, the transmission line 60 is realized by an ATM transmission line. The transmission path 60 can be constructed by either wire or wireless.

The ATM exchange is connected to an ATM transmission line (60) realized by a two-level network of VP (Virtual Path) and VC (Virtual Channel) and has a fixed length fetched from an input port. Cell (ATM cell) of VPI (Virtual Path Identifier) and VCI (Virtual Channel Identifie) included in this ATM cell.
r: virtual channel identifier), and has a function of performing exchange processing to an output port.

In FIG. 1, each node device 100 receives the data (ATM cell) sent from the opposite node device 100 via the transmission line 60 by the above ATM switching processing function, and the opposite node device 100 on the opposite side. Relay transmission via the transmission line 60.

Further, each node device 100 in the ring is
Each of the data from the local terminal 110 connected to its own node is converted into an ATM cell and relayed to the opposite node device 100, and the AT from the opposite node device 100 is transmitted.
Corresponding local terminal 110 connected to its own node device after converting the M cell into data for local terminal 110
It also performs a cell exchange operation for the local terminal to be sent to the.

In the system of the present invention, the local terminal 110 may be the ITU-T Recommendation X.264. 21 and V.I. 24
A low-speed STM terminal conforming to the above is used.

STM data handled by an STM terminal (hereinafter, referred to as the same reference numeral 110 as a local terminal for convenience) is
The data is slower than the data (ATM cell) transmitted through the transmission line 60.

That is, in each node device 100 of the system of the present invention, the process of converting STM data from the STM terminal 110 into cells and converting cells from the transmission line 60 into STM data for the STM terminal 110 is slow. It is nothing but a data conversion process between data and high-speed data.

As described above, in the system of the present invention, each node device 100 is sequentially connected on the high-speed transmission line (transmission line 60), and each node device 100 handles data at a lower speed than the high-speed transmission line. STM terminal 1 as a low speed terminal
Each of the node devices 10 accommodates one or more 10
0, the STM terminal 110 accommodates S
Low-speed data (STM data) from TM terminal 110
TM cells (high-speed data) are converted and sent to the high-speed transmission line, and ATM cells from the high-speed transmission line are converted into low-speed data (S
(TM data) and sends it to the STM terminal 110, while each node device 100 relays ATM cells to and from the adjacent opposite node device 100 on the high-speed transmission path, so that Node device 10
0 and data transmission via the high-speed transmission path.

FIG. 2 is a diagram showing the configuration of the node device 100 in the system of the present invention (see FIG. 1).

As shown in FIG. 2, the node device 100 is
The control unit 10, ring transmission line interface (I / F) units 11a and 11b, ATM switch unit 12, and STM interface (I / F) unit 13 are provided.

The ring transmission line I / F units 11a and 11b exchange data (AT) with each virtual path of the ring-shaped transmission line 60.
It controls the transmission and reception of M cells.

The STM I / F unit 13 controls the data transmission / reception with the low speed line to which the STM terminal 110 is connected.

The ATM switch section 12 has a ring transmission line I.
A cell exchange operation is performed between the / F units 11a and 11b and the STM I / F unit 13 to output an input cell through an output port corresponding to the input port of the cell.

The control unit 10 has a storage unit that stores a switching table in which the input ports and output ports of cells are registered in association with VPI and VCI, and the cell switching operation in the ATM switch unit 12 is performed according to this switching table. Control.

In the node device 100, the normal cell transmission direction on the transmission line 60 is set from the left side to the right side in FIG. 2, for example. That is, the transmission line extending from the left side to the right side in the figure is used as the active transmission line. The transmission path in the direction opposite to the working transmission path, that is, from the right side to the left side in FIG. 2, is secured as a backup transmission path for looping back the transmission path to form a detour when a failure occurs.

In this node device 100, the STM
The I / F unit 13 converts the STM data from the STM terminal 110 into ATM cells, sends them to the ATM switch unit 12, and sends the ATM cells from the ATM switch unit 12 to ST.
An exchange operation is performed in which M data is decellized and sent to the STM terminal 110.

In the cellizing process, as in the conventional case,
In the method of fetching the STM data from the STM terminal 110 at a normal speed of the STM data and waiting until the STM data is accumulated in the buffer memory to start the cell formation, a cell formation delay corresponding to the wait time is generated.

Therefore, in the present invention, dummy data is added to the STM data from the STM terminal 110 to reduce the above-mentioned waiting time, and the cell formation delay is reduced accordingly.

Next, a mechanism for adding dummy data in the node device 100 (STM I / F unit 13) of the system according to the present invention will be described with reference to first to third embodiments.

FIG. 3 is a diagram showing a schematic configuration of the STM I / F unit 13 of the node device 100 according to the first embodiment of the present invention.

In the first embodiment, the STM I / F unit 13 comprises a transmission unit 21, a reception unit 23 and an activation control unit 25.

The transmitting unit 21 transmits data from each STM terminal 110 in the line direction on the transmission line 60, and includes a dummy data adding unit 211 and an AAL1 unit 212.

The dummy data adding section 211 performs processing of adding dummy data for reducing cell formation delay to the STM data from each STM terminal 110.

The AAL1 section 212 performs a process of cellizing the data after the dummy data is added, and a cellizing section 2121 that cellizes the data (STM data + dummy data) corresponding to each STM terminal 110. And a cell multiplexing unit 2122 that multiplexes the cells that have been converted into cells by the cell converting unit 2121.

The receiver 23 receives each S from the line on the transmission line 60.
It transmits data toward the TM terminal 110, and includes an AAL1 unit 231 and a dummy data removing unit 232.

The AAL1 section 231 performs processing for returning the multiplexed cells from the line on the transmission line 60 to STM data, and separates the multiplexed cells into cells corresponding to each STM terminal 110. It comprises a unit 2311 and a decellizing unit 2312 for decellizing each cell separated by the cell separating unit 2311 into STM data.

The dummy data removing unit 232 removes the dummy data from the decellized data (STM data + dummy data) in the decellizing unit 2312 by the reverse process of the dummy data adding process in the dummy data adding unit 211. To do.

The activation control unit 25 determines whether or not to start the transfer of STM data from each STM terminal 110.
A start signal for instructing the M terminal is sent to each STM terminal 1
The control given to 10 is performed.

First, the operation of the transmitter 21 will be described.

In the transmitting unit 21, the dummy data adding unit 211 controls each ST sent from each STM terminal 110.
Dummy data is added to each of the M data and sent to the AAL1 unit 212.

In the AAL1 unit 212, each data (S
(TM data + dummy data) is converted into cells by the cell conversion unit 2121 and these cells are further converted into cell multiplexing units 212.
The data is multiplexed by 2 and transferred to the ATM switch unit 12.

After that, the ATM switch section 12 exchanges and outputs the multiplexed cells sent from the cell multiplexing section 2122 to the line on the transmission line 60.

Next, the operation of the receiving section 23 will be described.

In the receiving section 23, the ATM switch section 1
The multiplexed cell exchange-transferred from the line on the transmission line 60 by 2 is input to the AAL1 unit 231.

In the AAL1 unit 231, after the multiplexed cell is separated into individual cells by the cell separation unit 2311, each of these cells is decelled by the decellization unit 2321 and the decellized data (STM data + Dummy data) to the dummy data removing unit 232.

When the dummy data removing section 232 receives the respective data sent from the decellizing section 2312, the dummy data removing section 232 removes the dummy data from these respective data, and each remaining STM.
Data (ST sent from the STM terminal 110 of the transmission source
M data) to each corresponding STM terminal 110.

Next, a dummy data adding operation in the dummy data adding section 211 will be described.

FIG. 4 is a conceptual diagram showing a dummy data adding operation in the dummy data adding section 211 of the node device 100 according to the first embodiment.

As shown in FIG. 4, the dummy data adding unit 2
Reference numeral 11 denotes a buffer memory 2111 that temporarily stores the STM data sent from each STM terminal 110 before transferring it to the AAL1 unit 212 in the subsequent stage, and the buffer memory 21.
11 for controlling writing of STM data from each STM terminal 110 to the STM terminal 11 and data from the buffer memory 2111 to the AAL1 unit 212 (ST
A read control unit 2113 for controlling read of (M data + dummy data) is provided.

In this dummy data adding section 211,
The line speed of the line on the transmission line 60 is set in the write control unit 2112, and the AAL is set in the read control unit 2113.
The transfer rate of cells from the first unit 212 to the above line is set.

Write controller 2112 and read controller 21
13 is each STM from each STM terminal 110.
A process of writing data in the buffer memory 2111 and a process of reading each written data from the buffer memory 2111 are performed.

At this time, the write control unit 2112 and the read control unit 2113 cooperate with each other, and based on the respective setting conditions (line speed and transfer speed), (transfer speed-line speed = dummy data band) ... The dummy data band satisfying (1) is determined, and the STM terminal 1
If each STM data sent from the STM 10 is less than the transfer rate, the dummy data for the band obtained by the above equation (1) is added to each STM data and the buffer memory 211 is added.
Accumulate to 1.

As a result, the buffer memory 2111 is S
The TM data and the dummy data have a data amount that satisfies the transfer rate, and the data (STM data + dummy data) is immediately read from the buffer memory 2111 and transferred to the AAL1 unit 212.

Each data (STM data + dummy data) read from the buffer memory 2111 is made into cells by the AAL1 section 212 and further cell-multiplexed by the above-mentioned method, and then transmitted through the ATM switch section 12. Road 6
0 is sent to the line above.

As described above, in the dummy data adding section 211 according to the first embodiment, the STM data sent from the STM terminal 110 and accumulated in the buffer memory 2111 becomes the transmission rate of the transmission line 60 in the AAL1 section 212. The buffer memory 211 is synchronized with the corresponding cell start timing.
If the amount of data to be read from 1 is less than, the dummy data for the insufficient band is added to the STM data and AAL is added.
Processing for transferring to the first unit 212 is performed.

According to this processing, even if the STM data from the STM terminal 110 is less than the amount of data read from the buffer memory 2111 at the cell start timing corresponding to the transmission speed of the transmission line 60, the dummy data is used. The data (data + dummy data) can be immediately read out by filling the band and transferred to the AAL1 unit 212 in time for the cell formation start timing, whereby the STM data from the accommodated STM terminal 110 in the node device 100 can be transferred. It is possible to greatly reduce the cellization delay.

FIG. 5 is a diagram showing a data structure relating to a dummy data adding operation in the dummy data adding section 211.

FIG. 5A shows STM data to be added with dummy data, which is sent from the STM terminal 1110, and FIG. 5B shows the STM data of FIG.
-Data (AAL-S) with dummy data added for less than the standard data amount in SDU (Service Data Unit)
DU data), and FIG. 6C shows A shown in FIG.
Data (cellization target data) to which a predetermined unit of dummy data is added with the reference data amount of AL-SDU data as a unit is shown.

In this example, the dummy data addition target data is 48 kbps STM data [see FIG. 5 (a)].

In this case, the ATM AAL-SDU is 64.
Since it is kbps, the dummy data adding unit 211 first adds dummy data of 16 kbps to STM data of 48 kbps to generate AAL-SDU data of 64 kbps [FIG. 5 (b)].

Next, in order to shorten the cell formation time, the necessary amount of dummy data is added in consideration of the delay time to generate the cell formation target data [FIG. 5 (c)]. The data amount (bandwidth) of the dummy data added in this case is, for example,
It can be obtained by the above equation (1).

In this example, as shown in FIG.
3 bytes for AAL-SDU data of 4 kbps (19
2 kbps) of dummy data is added, and all the data to be made into cells (STM data + dummy data) is 256 kbps.

In this case, the cellization delay in the AAL1 section 212 subsequent to the dummy data adding section 211 is 64 kbps.
The delay time of 1/4 of that of the data will be sufficient.

FIG. 6 is a diagram showing a schematic configuration of the STM I / F unit 13b of the node device 100 according to the second embodiment of the present invention.

In the second embodiment, the STM I / F unit 13b is composed of a transmitting unit 21b, a receiving unit 23b and an activation control unit 25.

STM I / F unit 1 according to the second embodiment
In 3b, as for the transmission unit 21b, the AAL1 unit 212 of the transmission unit 21 of the STM I / F unit 13 (see FIG. 3) according to the first embodiment is replaced with the AAL1 unit 212b and the multiplexing unit 213, and the reception unit. For 23b, the first
The AAL1 unit 231 of the receiving unit 23 of the STM I / F unit 13 according to the embodiment of FIG.
Has been replaced by 33.

Further, the dummy data adding section 211b in the transmitting section 21b and the dummy data removing section 2 in the receiving section 231b are included.
32b, in accordance with the configuration replaced above, respectively,
The configuration of the dummy data addition unit 211 and the dummy data removal unit 232 according to the first embodiment is modified.

First, the operation of the transmitter 21b will be described.

In the transmitting section 21b, the dummy data adding section 211b adds dummy data to each STM data sent from each STM terminal 110 and sends it to the multiplexing section 213.

The multiplexing unit 213 multiplexes each data (STM data + dummy data) sent from the dummy data addition unit 211b and sends it to the AAL1 unit 212b.

The AAL1 section 212b has a multiplexing section 213.
The multiplexed data sent from the cell conversion unit 212
After the cells are formed into cells in 3, the cells are sent to the ATM switch section 12.

After that, the ATM switch unit 12 exchanges and outputs the cells sent from the cell assembling unit 2123 to the line on the transmission line 60.

Next, the operation of the receiving section 23b will be described.

In the reception section 23b, the cells exchange-transferred from the line on the transmission line 60 by the ATM switch section 12 are input to the AAL1 section 231b.

In the AAL1 unit 231b, the decellization unit 23
13 decelles the above cell, and multiple (STM data +
Data in a state in which dummy data is multiplexed (multiplex S
It is sent to the separation unit 233 as TM data).

The demultiplexing unit 233 receives the multiplexed STM data sent from the decellizing unit 2323 from each STM terminal 11.
The data is separated into data (STM data + dummy data) corresponding to 0 and sent to the dummy data removing unit 232b.

The dummy data removing section 232b is equivalent to the separating section 2
The dummy data is removed from each of the above-mentioned data sent from 33, and the remaining data (source STM terminal 1
STM data sent from 10) corresponding STM
Transfer to the terminal 110.

STM I / F according to the second embodiment
The part 13b and the STM I / O according to the first embodiment described above.
Comparing with the F section 13, the ST according to the first embodiment is
In the MI / F unit 13, dummy data is added to the STM data from the STM terminal 110, and these data (STM data + dummy data) are made into cells and cell-multiplexed to form an ATM.
While sending out to the route and demultiplexing the multiplexed cells from the ATM route into STM data,
In the STM I / F unit 13b according to the embodiment of
Dummy data is added to the STM data from the terminal 110, these data (STM data + dummy data) are first multiplexed and then cellized and sent to the ATM route, while cells from the ATM route are decellized to STM data. , The difference is that they are separated after that.

Next, a dummy data adding operation in the dummy data adding section 211b will be described.

FIG. 7 is a conceptual diagram showing an operation of adding dummy data in the dummy data adding section 211b of the node device 100 according to the second embodiment.

As shown in FIG. 7, the dummy data addition unit 2
11b is a buffer memory 2111b for temporarily storing the STM data sent from each STM terminal 110 before sending it to the multiplexing section 213 in the subsequent stage, and each STM terminal 110.
From the buffer memory 2111b to the multiplexing unit 213, and a read control unit 2113b that controls reading of data (STM data + dummy data) from the buffer memory 2111b to the multiplexing unit 213. To be done.

The read control unit 2113b is provided with a band setting unit 2114 that sets a used band for each port corresponding to each STM terminal 110. Here, the band setting unit 211
The setting of the used band for each port in No. 4 is performed by designating the first time slot (TS) and the last time slot (TS).

In the dummy data adding section 211b, the write control section 2112b writes STM data from each STM terminal 110 into the buffer memory 2111b for each corresponding port, and the read control section 2112b.
113b performs a process of reading data from the buffer memory 2111b for each port.

At this time, the read control unit 2113b refers to the band used for each port set in the band setting unit 2114, and the leading time slot (T
The data is read so that the data is transmitted in each TS from S) to the final time slot (TS).

During this time, the STM from the STM terminal 110 corresponding to the corresponding port in the arbitrary TS before reaching the final TS.
When the data is lost, read control is performed so that dummy data is transmitted in each TS from the arbitrary TS to the final TS.

By the above read control, the buffer memory 2
From 111b, the first TS to the last TS assigned to each port are used for each port (STM data +
Dummy data) is read out, and the multiplexing unit 21
Sent to 3.

As described above, in the dummy data adding section 211b according to the second embodiment, the head TS and the last TS of the used bands divided for each port are set in the band setting unit 2
By setting it to 114, it is possible to determine how many bytes of dummy data are added. Then, by the dummy data addition processing in the dummy data addition unit 211b, the second data
Also in this embodiment, the same cell formation delay reduction effect as in the first embodiment can be expected.

Next, another embodiment will be described.

The above-described first and second embodiments are based on the assumption that dummy data is always added. In this case, cells are always transferred even if there is no STM data,
Along with this, the ATM band is always used even though there is no STM data, so that the ATM band cannot be effectively used.

As a countermeasure for this, in the third embodiment, attention is paid to the activation signal given when the STM data is transferred, the STM data is recognized from the activation signal, and the STM data is transferred. Dummy data is added only during transfer.

FIG. 8 is a diagram showing a start control unit 25 in the STM I / F unit 13 of the node device 100 according to the third embodiment.
It is a figure which shows the structure of. The node device 100 according to this embodiment is based on, for example, the node device 100 according to the first embodiment shown in FIG.

In FIG. 8, the start control unit 25 controls each ST
A logical sum circuit (OR circuit) 251 that outputs a signal corresponding to the logical sum of the activation signals that respectively instruct the M terminals 110 to transfer the STM data, and holds the states of the activation signals (for which line) Status register 252 (holding status information indicating whether a start signal is generated) (252-1, 252-2, 252-3, 2)
52-4).

In this activation control unit 25, each STM terminal 110 is paired with an activation signal [logic "0" or "1" signal]. This activation signal is, for example, ITU
-T Recommendation X. 21 is a C signal, and the recommendation V. 24
Then, it is an RS signal.

Each STM terminal 110 sends out STM data when the activation signal given to itself is logic "1".

On the other hand, in the activation control unit 25, the activation signal is logically ORed by the number of lines by the OR circuit 251, and the activation signal obtained as a result of this operation is notified to the control unit 10 as an interrupt signal. As a result, the control unit 10 can immediately detect the activation signal.

After detecting the start-up signal by the above method, the control unit 10 sends status registers 252 (252) for all lines.
-1,252-2,252-3,252-4) is polled. As a result of this polling, if there is a status register 252 indicating the activated state (logical “1”), the dummy data adding unit 211 adds dummy data to the STM data of the line corresponding to the status register 252. Instruct.

The dummy data adding section 211 executes a process of adding dummy data to the data of the line based on the above instruction. The dummy data adding process in the dummy data adding unit 211 can be performed by the method shown in FIG. 4, for example.

The activation signal becomes logic "0" before the cell conversion of all the data is completed, and the buffer memory 2111
If the data to be transferred remains, the dummy data is added to the remaining data to form a cell and the data is transferred.

As described above, in the third embodiment, it is determined whether or not the STM data is sent to the STM terminal 110 by the logical "1".
Alternatively, the dummy data is added to the cells only when the activation signal designated by “0” is the logical “1”, that is, when the STM data is transferred from the STM terminal 110, so that the data is always dummy even if there is no data. Compared to the case where data is added and cells are always transferred, the ATM band can be used more effectively because the use of the ATM band when there is no data is suppressed.

In FIG. 8, the method of adding dummy data only when the activation signal is logic "1", which is a characteristic of the third embodiment, is the same as that of the first embodiment (see FIG. 3). Although the example in the case of application is described, it is also applicable to the second embodiment (see FIG. 6).

In addition, the present invention is not limited to the embodiments described above and shown in the drawings, but can be appropriately modified and implemented within the scope of the invention.

For example, in the configuration of the ring network shown in FIG. 1, each node device N1, N2, N3, N4.
For example, any one of N5 is connected to the center node (C
It is also possible to connect to another communication network via the exchange as N) and to transmit / receive the data transmitted / received in the ring to / from the communication network via the exchange under the control of the CN. .

[0111]

As described above, according to the present invention,
If the low-speed data sent from the low-speed terminal and accumulated in the buffer means is less than the amount of data read from the buffer means at the cell start timing corresponding to the transmission speed of the transmission line in the cell formation means, the insufficient bandwidth Since the node device is provided with the dummy data adding means for adding the dummy data of the above to the low speed data and transferring it to the cell forming means, the low speed data from the low speed terminal is synchronized with the cell start timing corresponding to the transmission speed of the transmission line. Even if the amount of data read out from the buffer means is less than that, the data (data + data +
(Dummy data) can be read out and transferred to the cell assembling means in time for the cell assembling start timing, thereby significantly shortening the cell assembling delay of the data from the low speed terminal in the node device and passing through the high speed transmission line. Data transmission between low speed terminals can be performed more efficiently.

[Brief description of drawings]

FIG. 1 is a diagram showing an overall configuration of a communication network system according to the present invention.

FIG. 2 is a diagram showing the configuration of a node device 100 in FIG.

FIG. 3 is an STM I of the node device according to the first embodiment.
The figure which shows schematic structure of the / F section.

FIG. 4 is a conceptual diagram showing a dummy data adding operation in a dummy data adding unit of the node device according to the first embodiment.

FIG. 5 is a diagram showing a data structure relating to a dummy data addition operation in a dummy data addition unit.

FIG. 6 is an STM I of the node device according to the second embodiment.
The figure which shows schematic structure of the / F section.

FIG. 7 is a conceptual diagram showing a dummy data adding operation in a dummy data adding unit of the node device according to the second embodiment.

FIG. 8 is an STM I of the node device according to the third embodiment.
The figure which shows the structure of the starting control part in / F section.

[Explanation of symbols]

60 transmission lines 100, 100-1 (N1), 100-2 (N2), 1
00-3 (N3), 100-4 (N4), 100-5
(N5) Node device 110, 110a, 110b, 110c, 110d, 1
10e, 110f, 110g, 110h Local terminal [STM (Synchronous Transfer Mode) terminal] 10 Control units 11a, 11b Ring transmission line interface (I /
F) section 12 ATM switch section 13, 13b STM interface (I / F) section 21, 21b Transmitting section 211, 211b Dummy data adding section 2111, 2111b Buffer memory 2112, 2112b Write control section 2113, 2113b Read control section 2114 Band setting Unit 212, 212b AAL1 unit 213 multiplexing unit 2121, 2123 cell assembling unit 2122 cell multiplexing unit 23, 23b receiving unit 231, 231b AAL1 unit 2311 cell separating unit 2312, 2313 decellizing unit 232, 232b dummy data removing unit 233 separation Unit 25 Startup control unit 251 Logical sum (OR) circuit 252, 252-1, 252-2, 252-3, 252
-4 Status register

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 5K028 AA11 CC05 DD01 DD02 EE09                       KK01 KK03 KK32 KK35 MM12                       SS24 TT01                 5K030 GA03 HA10 HB09 HB15 HB29                       HC15 JA01 JA06 KA03 KA13                       KX02 KX11 LA15 LE06                 5K031 AA02 CA08 DB04 DB11 DB14

Claims (7)

[Claims] 1. A plurality of node devices connected via a transmission line each accommodate a low-speed terminal that handles data at a speed lower than the transmission speed of the transmission line, and the low-speed terminals are connected via the node device and the transmission line. In the communication network system for performing the data transmission of, the node device includes a cellizing unit that converts low-speed data from the low-speed terminal into a cell that transmits the transmission line, and a node that is sent from the low-speed terminal and stored in a buffer unit. If the low-speed data is less than the amount of data read from the buffer means in synchronization with the cell start timing corresponding to the transmission speed of the transmission path in the cellization means, dummy data for the insufficient band is set to the low-speed data. A communication network system comprising: dummy data adding means for adding and transferring to the cell forming means. 2. The communication network according to claim 1, wherein the dummy data adding unit adds the dummy data for each low speed data transmitted from a plurality of low speed terminals accommodated in the own node device. system. 3. The cell assembling means comprises a cell assembling section for cellizing each of the low-speed data to which the dummy data is added, and a cell multiplexing section for multiplexing each cell as cellified by the cell assembling section. The communication network system according to claim 2, further comprising: 4. A multiplexing unit, which multiplexes the low speed data to which the dummy data is added, is arranged in a stage preceding the cell assembling unit, and the low speed data to which the dummy data is added is multiplexed to the multiplex unit. 3. The communication network system according to claim 2, wherein the cell is converted into cells by the cell conversion unit after being multiplexed by. 5. The node device, a start signal monitoring means for monitoring an instruction state of an activation signal for instructing whether or not to transmit data to the low speed terminal, and a state in which the activation signal instructs data transmission. 2. The communication network system according to claim 1, further comprising dummy data addition control means for controlling the dummy data addition means to add the dummy data only for a certain period. 6. The node device includes a decellizing unit for decellizing cells from the transmission line into low speed data, and a dummy data removing unit for removing dummy data from the low speed data decellized by the decellizing unit. The communication network system according to claim 1, further comprising: 7. The low speed terminal is in a synchronous transfer mode (ST
M) is an STM terminal that transmits and receives the STM data that is the low-speed data, and the node device is an ATM switching device that converts the STM data into the cells and transmits the cells in an asynchronous transfer mode (ATM). Claim 1
The described communication network system.