JP2004282470A - Data transmission system - Google Patents

Abstract

A data transmission system capable of recovering communication even when data is congested and improving communication quality.
A LAN interface unit in a TDM transmission apparatus adds congestion notification information to a header of frame data stored in a relay buffer when congestion occurs in a reception control unit, and transmits the congestion notification information from a transmission control unit to a transmission line side. While multiplexing the data, when the reception control unit 84 detects congestion notification information in the header of the frame data received, the transmission control unit 83 restricts the inflow of data from the transmission buffer 82.
[Selection] Fig. 2

Description

【００３３】
輻輳通知ビット比較部８４３は、多重分離バス７から受信したフレームデータのヘッダの輻輳通知ビットの内容とバッファ（残量）監視部８７から受け取った輻輳通知ビットの結果を比較し、バッファ（残量）監視部８７から受け取った輻輳通知ビットのほうが小さい又は同じであればヘッダ内の輻輳通知ビットをそのまま中継バッファ８６に渡し、大きければヘッダ内の輻輳通知ビットをバッファ（残量）監視部８７から受け取った輻輳通知ビットの値に書き換え、中継バッファ８６に渡す。また、送信レート設定部８３６（図８参照）は、ヘッダ判定・処理部８４２より受け取った輻輳通知ビットの輻輳レベルに従い、予め設定された制御レベル（例えば上記４レベル毎に設定されているもの）に従い送信データを抑制する。
【００３４】
以上のように、輻輳状態レベルを細分化し、輻輳レベルに応じて送信データの抑制を変化させることで、柔軟な輻輳制御が可能となり、通信のスループットの向上を図ることが可能となる。
【００３５】
【発明の効果】
以上のようにこの発明によれば、それぞれに端末が接続されている複数のＴＤＭ伝送装置が伝送路によりリング状に接続されたデータ伝送システムにおいて、各ＴＤＭ伝送装置が、伝送路側へ送信するデータのヘッダに輻輳通知情報を付加し輻輳時に伝送路につながる各ＴＤＭ伝送装置に輻輳が発生したことを通知する手段と、伝送路側から輻輳通知情報が付加されたデータを受け取ると端末からのデータの流入を一時的に抑制する手段と、を備えたことを特徴とするデータ伝送システムとしたので、伝送路側の輻輳制御が可能となり、輻輳時に端末からのデータの流入を抑制することで通信の回復を図れ、通信の品質を高めることができる。
【図面の簡単な説明】
【図１】この発明によるデータ伝送システムの構成を示す図である。
【図２】図１のＴＤＭ伝送装置の構成の一例を示す図である。
【図３】この発明の実施の形態１による送信制御部の構成を示す図である。
【図４】この発明の実施の形態１による受信制御部の構成を示す図である。
【図５】この発明における多重分離バス上のデータフォーマットの一例を示す図である。
【図６】この発明の実施の形態２による送信制御部の構成の一例を示す図である。
【図７】この発明の実施の形態３による送信制御部の構成の一例を示す図である。
【図８】この発明の実施の形態４、５による送信制御部の構成の一例を示す図である。
【図９】この発明の実施の形態５による受信制御部の構成の一例を示す図である。
【符号の説明】
１ 伝送路、２，２Ａ〜２Ｄ ＴＤＭ伝送装置、３Ａ〜３Ｇ ＬＡＮ、４Ａ〜４Ｇ ＬＡＮ端末、５ 光・電気信号変換部、６ 多重化／多重分離部、７ 多重分離バス、８ ＬＡＮインタフェース部、５１ 光／電気変換部（Ｏ／Ｅ）、５２ 電気／光変換部（Ｅ／Ｏ）、８１ レイヤ２（データリンク層）スイッチ回路、８２ 送信バッファ、８３ 送信制御部、８４ 受信制御部、８５ 受信バッファ、８６ 中継バッファ、８７ バッファ監視部、８３１ ヘッダ付加部、８３２ 送信・中継選択部、８３３ フラグ付加部、８３４ 送信レート制御部、８３５ 送信レート監視部、８３６ 送信レート設定部、８４１ フレームデータ抽出部、８４２ ヘッダ判定・処理部、８４３ 輻輳通知ビット比較部。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a data transmission system in which a plurality of LANs are connected by a TDM (Time Division Multiplexing) transmission device configured in a ring shape and data is transmitted between the plurality of LANs, and more particularly to a congestion control in this system. is there.
[0002]
[Prior art]
In a conventional data transmission system of this type, a transmission device included in a network system is provided with a storage unit for storing temporary transmission data to transmit data (for example, see Patent Document 1).
[0003]
[Patent Document 1]
JP-A-61-210743 (pages 11-18, FIG. 4)
[0004]
[Problems to be solved by the invention]
In a conventional ring-shaped data transmission system, a storage unit is provided in a transmission device forming a network system to temporarily store data, and the stored data is transmitted using an idle time of data transmission. However, when data is congested in the transmission device and the idle time of data transmission is reduced, there is a problem that data cannot be easily transmitted or data overflows from the storage unit.
[0005]
SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and has as its object to obtain a data transmission system capable of recovering communication even when data is congested and improving communication quality.
[0006]
[Means for Solving the Problems]
In view of the above object, the present invention relates to a data transmission system in which a plurality of TDM transmission devices, each of which is connected to a terminal, are connected in a ring by a transmission line. A means for adding congestion notification information to the header and notifying each TDM transmission device connected to the transmission line that congestion has occurred at the time of congestion, and a flow of data from the terminal when receiving data with congestion notification information added from the transmission line side And a means for temporarily suppressing data transmission.
[0007]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described according to each embodiment.
Embodiment 1 FIG.
FIG. 1 is a structural diagram of a data transmission system provided with a congestion control device according to an embodiment of the present invention. In the figure, a transmission line 1 is a transmission line for synchronous communication data connected in a ring by an optical fiber; The transmission devices 2A to 2D are devices for transmitting a plurality of communication line data by the TDM method, and these TDM transmission devices 2A to 2D are ring-connected by the transmission line 1. LANs 3A to 3G are communication networks configured by connecting terminals 4A to 4G via communication lines. The access control method for the LANs 3A to 3G is assumed to use CSMA / CD, but other access control methods may be used. The LAN terminals 4A to 4G are terminals such as computers.
[0008]
FIG. 2 shows a detailed configuration of one TDM transmission apparatus 2. In FIG. 2, an optical / electrical signal converter 5 converts an optical / electrical signal for converting synchronous communication data from the transmission line 1 from an optical signal to an electric signal. It is composed of an electrical / optical converter (O / E) 51 and an electrical / optical converter (E / O) 52 for converting synchronous communication data from the multiplexing / demultiplexing bus from an electrical signal to an optical signal. The multiplexing / demultiplexing unit 6 demultiplexes and converts the data into demultiplexed data (data obtained by separating a plurality of time slots of synchronous communication data), and sends the demultiplexed data to the demultiplexing bus 7. Conversely, it multiplexes the demultiplexed data from the demultiplexing bus 7 and converts it to synchronous communication data, and sends out the synchronous communication data to the transmission line 1 side. The demultiplexing bus 7 transmits the demultiplexed data, and the LAN interface unit 8 is connected to the terminals 4A and 4B via the LANs 3A and 3B, and has a function of converting asynchronous communication data and synchronous communication data.
[0009]
In the LAN interface section 8, the layer 2 (data link layer) switch circuit 81 relays frame data on the terminals 4A and 4B side and frame data on the demultiplexing bus 7 side mutually, and the transmission buffer 82 The transmitted frame data is temporarily stored. The transmission control unit 83 multiplexes the frame data from the transmission buffer 82 and the relay buffer 85 onto the demultiplexing bus 7. The reception control unit 84 demultiplexes data from the demultiplexing bus 7. The reception buffer 85 temporarily stores data from the reception control unit 84. The relay buffer 86 temporarily stores data from the reception control unit 84. The buffer monitoring unit 87 monitors the remaining buffer capacity of the relay buffer 86 and notifies the reception control unit 84 of the result.
[0010]
FIG. 3 shows a detailed configuration of the transmission control unit 83. The header adding unit 831 adds a header to the frame data from the transmission buffer 82. The transmission / relay selection unit 832 selects the transmission buffer 82 and the relay buffer 86, extracts data, and multiplexes the data on the demultiplexing bus 7. The flag adding unit 833 further adds a flag to the data.
[0011]
FIG. 4 shows a detailed configuration of the reception control unit 84. The frame data extracting section 841 extracts a frame data portion from the data received from the demultiplexing bus 7. The header determination / processing unit 842 determines the contents of the header added to the frame data.
[0012]
FIG. 5 shows a format of data transmitted to the demultiplexing bus 7.
[0013]
Next, the operation will be described. The asynchronous communication data (frame data) transmitted from the terminals 4A to 4G to the LANs 3A to 3G is received by the LAN interface unit 8 of the TDM transmission devices 2A to 2D. When receiving the frame data from the LAN 3, the layer 2 switch circuit 81 of the LAN interface unit 8 checks the destination address of the frame data, and sends the frame data to the transmission buffer 82 when the relay destination is the demultiplexing bus 7 side. Then, the frame data is stored in the transmission buffer 82.
[0014]
When the transmission / relay processing unit 832 of the transmission control unit 83 detects that the frame data is stored in the transmission buffer 82, the frame data is extracted from the transmission buffer 82, and is uniquely set to each LAN interface 8 by the header adding unit 831. The header including the ID number and the congestion notification information is added to the frame data, and the frame data is transmitted to the demultiplexing bus 7. When the transmission / relay processing unit 832 detects that the frame data has been stored in the relay buffer 86, it extracts the frame data from the relay buffer 86 and sends the frame data to the demultiplexing bus 7.
[0015]
The multiplexing / multiplexing / demultiplexing unit 6 multiplexes the data output to the multiplexing / demultiplexing bus 7 according to a normal TDM process to generate synchronous data, and converts the synchronous data from an electric signal to an optical signal by the E / O 52 and transmits the signal. Send it out to Road 1.
[0016]
On the other hand, the TDM transmission device 2 receives the synchronization data from the transmission line 1. The multiplexing / multiplexing / demultiplexing unit 6 multiplexes the synchronous data converted from the optical signal into the electric signal by the O / E 51 from the transmission line 1 and demultiplexes the received synchronous data into multiplexed / demultiplexed data. To the demultiplexing bus 7. The demultiplexed data is received by the reception control unit 84 of the LAN interface unit 8. If the frame data is separated from the flag by the frame data extraction unit 841 in the reception control unit 84 and the ID number in the header of the frame data matches the ID number of the own LAN interface 8 by the header determination / processing unit 842, The frame data is discarded as having made one round of the ring. If they do not match, the frame data is stored in the reception buffer 85 and the relay buffer 86. Further, one frame of frame data is transmitted from the reception buffer 85 to the layer 2 switch circuit 81. When the frame data is received, the layer 2 switch circuit 81 checks the destination address of the frame data and sends the frame data to the destination terminal 4. The frame data is transmitted to the LAN 3 to be connected.
[0017]
In the above system, the LAN interface unit 8, the buffer monitoring unit 87, when the usage of the relay buffer 86 exceeds a predetermined threshold value, determines that the state is congested, and the header determination / processing unit 842 of the reception control unit 84. To the congestion state. Upon receiving the congestion notification, the header determination / processing unit 842 overwrites the congestion notification area in the header of the frame data stored in the relay buffer 86 with a value indicating the congestion state, and transmits the value to the relay buffer 86. Thus, at the time of congestion, the header and the frame data carrying the congestion information are transmitted from the relay buffer 86 to the transmission line 1.
[0018]
On the other hand, the header determination / processing unit 842 multiplexes the frame data received from the demultiplexing bus 7 in the frame whose ID number in the header matches the own LAN interface unit 8 (the own LAN interface unit 8 multiplexes the frame data from the terminal 4). In a frame that has been multiplexed on the separation bus 7 and returned around the transmission path 1), the information of the congestion notification in the header is read, and when the congestion state is detected, the transmission / relay selection unit 832 is notified of the congestion notification. Upon receiving the notification of the congestion detection, the transmission / relay selection unit 832 preferentially selects the relay buffer 86 for a certain period of time, and temporarily stops sending data from the transmission buffer 82 to the transmission path 1.
[0019]
Therefore, when a congestion state occurs in a certain LAN interface 8 and the congestion state is set in the congestion notification of the header and transmitted to the transmission line 1, the LAN interface unit 8 of the TDM transmission device 2 connected to the transmission line 1 The header (congestion notification) is relayed one after another, and the transmission of data from the transmission buffer 82 is suppressed one after another by the LAN interface unit 8 that has received the congestion notification. As a result, transmission of new frame data to the transmission path 1 is suppressed for a predetermined period, and the frame data transmitted to the transmission path 1 is discarded by the LAN interface 8 of the transmission source. Free bandwidth will increase. As a result, the used capacity of the relay buffer 86 falls below a predetermined threshold, and it becomes possible to transmit frame data to the transmission line 1 from the transmission buffer 82 of the LAN interface unit 8 that has notified the congestion.
[0020]
As described above, according to the first embodiment, congestion control on the transmission line 1 side can be performed in the TDM transmission device system configured in a ring shape, and a frame is prevented from being lost due to overflow of the relay / transmission buffer. As a result, communication quality can be improved, and communication can be recovered by suppressing the inflow of other terminal data during congestion.
[0021]
Embodiment 2 FIG.
In the first embodiment, the data from the transmission buffer 82 of the LAN interface 8 which has detected the congestion notification is completely temporarily stopped, and the communication delay may be temporarily increased. Therefore, in the second embodiment, as shown in FIG. 6, the transmission control unit 83 is provided with a transmission rate control unit 834 that controls the rate at which data is extracted from the transmission buffer 82.
[0022]
Next, the operation will be described. The transmission rate control unit 834 normally draws data from the transmission buffer 82 at the maximum possible rate, but when notified of congestion detection from the header determination / processing unit 842, the transmission rate control unit 834 transmits data from the transmission buffer 82 according to a preset value. The amount of data for multiplexing this data on the demultiplexing bus 7 is temporarily suppressed.
[0023]
As described above, according to the second embodiment, even when a congestion notification is detected, the transmission rate control unit 834 secures communication at a constant rate, thereby suppressing communication interruption and increase in communication delay. It becomes possible.
[0024]
Embodiment 3 FIG.
In the second embodiment, when a congestion notification is detected, the transmission load suppression value at the time of congestion is determined by a preset fixed value regardless of the actual transmission load of the LAN interface unit 8, so that the transmission load is light. However, there is a possibility that the control will be unfair, in which the amount of decrease is large. Therefore, in the third embodiment, as shown in FIG. 7, the transmission control unit 83 is provided with a transmission rate monitoring unit 835 that monitors the transmission rate from the transmission buffer 82 to the demultiplexing bus 7.
[0025]
Next, the operation will be described. The transmission rate monitoring unit 835 monitors the transmission rate from the transmission buffer 82 to the demultiplexing bus 7. The transmission rate control unit 834 normally draws data from the transmission buffer 82 at the maximum possible rate, but when notified of congestion detection from the header determination / processing unit 842, the transmission rate control unit 834 checks the transmission rate from the transmission rate monitoring unit 835. According to the information, the transmission rate is suppressed. At this time, the suppression value of the transmission rate is set higher as the transmission rate is higher, so that the LAN interface unit 8 with a higher transmission load is suppressed.
[0026]
As described above, according to the third embodiment, when congestion notification is detected, the degree of suppression of the transmission rate can be controlled according to the transmission load of each LAN interface unit 8, so that balanced control is possible. Become.
[0027]
Embodiment 4 FIG.
In the second embodiment, since the transmission rate is suppressed by a uniform value when congestion is detected, it may not be possible to cope with a case where the priority of the traffic of the specific terminal 4 is to be increased. Therefore, in the fourth embodiment, as shown in FIG. 8, a transmission rate setting unit 836 that can set the transmission rate is provided.
[0028]
Next, the operation will be described. The transmission rate control unit 834 normally extracts data from the transmission buffer 82 at the maximum possible rate, but when notified of congestion detection from the header determination / processing unit 842, the transmission rate control unit 834 follows the transmission rate value from the transmission rate setting unit 836. , The amount of data for multiplexing the data from the transmission buffer 82 onto the demultiplexing bus 7 is temporarily suppressed. In the transmission rate setting section 836, the transmission rate value can be set freely.
[0029]
As described above, according to the fourth embodiment, it is possible to assign the priority of traffic to each terminal by the transmission rate setting unit 836, and the LAN interface unit 8 to which the terminal 4 with high priority is connected has the transmission rate setting unit 836. In the LAN interface unit 8 to which the transmission rate value of the unit 836 is set high and the terminal 4 with a low priority is connected, the transmission rate of the transmission rate setting unit 836 is set to be low so that communication of high-priority traffic can be performed even during congestion. A large amount can be secured, and communication quality can be improved from the viewpoint of the importance of traffic.
[0030]
Embodiment 5 FIG.
In the third embodiment, there are two values, that is, congestion and non-congestion. Therefore, even when the congestion state is not severe, there is a possibility that communication is reduced due to excessive suppression. Thus, in the fifth embodiment, as shown in FIG. 9, a congestion notification bit comparison unit 843 is provided in the reception control unit 84.
[0031]
Next, the operation will be described. The buffer (remaining amount) monitoring unit 87 sets a plurality of threshold values of the remaining buffer amount, divides the level of the congestion state into small parts, and notifies the result to the congestion notification bit comparing unit 843. For example, in the following example, the congestion state is divided into four levels, and two congestion notification bits are prepared. To control the congestion level more finely, the bit width of the congestion notification bit may be increased.
[0032]

[0033]
The congestion notification bit comparing unit 843 compares the content of the congestion notification bit of the header of the frame data received from the demultiplexing bus 7 with the result of the congestion notification bit received from the buffer (remaining amount) monitoring unit 87, and If the congestion notification bit received from the monitoring unit 87 is smaller or the same, the congestion notification bit in the header is passed to the relay buffer 86 as it is, and if larger, the congestion notification bit in the header is transmitted from the buffer (remaining amount) monitoring unit 87. Rewrite the received congestion notification bit value and pass it to the relay buffer 86. The transmission rate setting unit 836 (see FIG. 8) controls a preset control level (for example, one set for each of the above four levels) according to the congestion level of the congestion notification bit received from the header determination / processing unit 842. The transmission data is suppressed according to the following.
[0034]
As described above, by subdividing the congestion state level and changing the suppression of transmission data according to the congestion level, flexible congestion control becomes possible and communication throughput can be improved.
[0035]
【The invention's effect】
As described above, according to the present invention, in a data transmission system in which a plurality of TDM transmission devices each connected to a terminal are connected in a ring by a transmission line, each TDM transmission device transmits data to be transmitted to the transmission line side. Means for adding congestion notification information to the header of each TDM transmission device connected to the transmission line at the time of congestion, and a means for notifying the occurrence of congestion, and receiving data to which the congestion notification information is added from the transmission line side, and receiving data from the terminal. And a means for temporarily suppressing the inflow, so that it is possible to control congestion on the transmission line side and to recover communication by suppressing the inflow of data from the terminal at the time of congestion. And improve communication quality.
[Brief description of the drawings]
FIG. 1 is a diagram showing a configuration of a data transmission system according to the present invention.
FIG. 2 is a diagram illustrating an example of a configuration of a TDM transmission device in FIG. 1;
FIG. 3 is a diagram showing a configuration of a transmission control unit according to the first embodiment of the present invention.
FIG. 4 is a diagram showing a configuration of a reception control unit according to the first embodiment of the present invention.
FIG. 5 is a diagram showing an example of a data format on a demultiplexing bus according to the present invention.
FIG. 6 is a diagram illustrating an example of a configuration of a transmission control unit according to a second embodiment of the present invention.
FIG. 7 is a diagram showing an example of a configuration of a transmission control unit according to a third embodiment of the present invention.
FIG. 8 is a diagram illustrating an example of a configuration of a transmission control unit according to Embodiments 4 and 5 of the present invention.
FIG. 9 is a diagram showing an example of a configuration of a reception control unit according to a fifth embodiment of the present invention.
[Explanation of symbols]
1 transmission line, 2, 2A-2D TDM transmission device, 3A-3G LAN, 4A-4G LAN terminal, 5 optical / electrical signal converter, 6 multiplexing / multiplexing / demultiplexing unit, 7 multiplexing / demultiplexing bus, 8 LAN interface unit, 51 optical / electrical conversion unit (O / E), 52 electric / optical conversion unit (E / O), 81 layer 2 (data link layer) switch circuit, 82 transmission buffer, 83 transmission control unit, 84 reception control unit, 85 Reception buffer, 86 relay buffer, 87 buffer monitoring unit, 831 header addition unit, 832 transmission / relay selection unit, 833 flag addition unit, 834 transmission rate control unit, 835 transmission rate monitoring unit, 836 transmission rate setting unit, 841 frame data Extraction unit, 842 header determination / processing unit, 843 congestion notification bit comparison unit.

Claims (7)

In a data transmission system in which a plurality of TDM transmission devices, each of which is connected to a terminal, are connected in a ring by a transmission line, each TDM transmission device adds congestion notification information to a header of data to be transmitted to the transmission line side, thereby causing congestion. Means for notifying each TDM transmission device connected to the transmission path at the time that congestion has occurred, and means for temporarily suppressing the inflow of data from the terminal when receiving data to which congestion notification information is added from the transmission path side, A data transmission system comprising: A plurality of TDM transmission devices to which respective terminals are connected are connected in a ring shape by a transmission line, and each TDM transmission device transmits data from its own terminal to a terminal of another TDM transmission device on a transmission line, Also, in a data transmission system that takes in data on a transmission path, relays the data, and sequentially transfers the data to another TDM transmission apparatus connected to the transmission path, the TDM transmission apparatus includes:
Receiving data from the transmission path side, fetching the data and passing it to the relay means, and upon receiving a notification of data congestion from the relay means, adding congestion notification information to the data to the relay means, and also receiving data from the transmission path side Reception control means for notifying the transmission control means of congestion detection when congestion notification information has been added to data from its own terminal,
The data passed from the reception control means is temporarily stored for transmission to the next TDM transmission apparatus, and a congestion notification is sent to the reception control means when the currently stored data amount exceeds a predetermined value. Relay means;
Transmits data from the own terminal to the terminal of another TDM transmission device and the data of the relay means to the transmission line side, and when notified of the congestion detection from the reception control means, gives priority to the data of the relay means. Said transmission control means for selecting and transmitting to the transmission path side,
A data transmission system comprising: 3. The data transmission system according to claim 2, wherein the transmission control means temporarily stops data from the own terminal to a terminal of another TDM transmission device when receiving the notification of the congestion detection. 3. The data transmission according to claim 2, wherein the transmission control unit temporarily suppresses a data transmission rate from the terminal to the terminal of another TDM transmission device when the notification of the congestion detection is received. system. 5. The transmission control unit according to claim 4, wherein the transmission control unit monitors a data transmission rate from its own terminal to a terminal of another TDM transmission apparatus, and increases the suppression value as the transmission rate increases in a congested state. Data transmission system. In the transmission control means, a desired transmission rate at the time of data congestion from its own terminal to a terminal of another TDM transmission device is set in advance for each of the TDM transmission devices, and suppression is performed according to the desired transmission rate. The data transmission system according to claim 4, wherein: The relay means sends a congestion notification based on a plurality of levels predetermined according to the amount of data stored to the reception control means, and the reception control means and the transmission control means notify the congestion notification and the congestion detection based on the plurality of levels. 7. The data transmission system according to claim 6, wherein suppression is performed at a transmission rate set in advance for each of the plurality of levels according to:

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