JPH0470235A - flow control device - Google Patents

Abstract

PURPOSE:To efficiently execute a processing when reception packets are concentrated on a specified node by supervising the token accumulated quantity of a reception buffer and controlling the erasure and reproduction of the token. CONSTITUTION:When transmission concentrates on one node 20 from plural nodes, a reception buffer supervisory part 22 detects it and informs a token control part 24 of it. Then, the control part 24 acquires the token erases the token, and the token is prevented from circulating to a ring type transmission line 1. Thus, it is restricted that a packet flows into the node 20. The processing in the node 20 is executed during that time and the control part 24 reproduces the token again so as to cause it to flow in the ring type transmission line 1 when the supervisory part 22 recognizes that the preserved data quantity of the reception buffer 21 becomes less. Thus, the processing when the reception packets concentrate on the specified node is efficiently executed.

Description

[Detailed Description of the Invention] [Summary] Regarding a flow control device in a system that performs transmitter arbitration using tokens in a throttling type LAN (Local Area Network), when received packets are concentrated on a specific node. In order to realize a system in which only one communication device can transmit at the same time among at least three communication devices housed in a throttling type LAN, In a system that performs transmitter arbitration control using multiple independent tokens for each station, received data is temporarily stored in the node that sends and receives packets between the communication device and the ring-type transmission path. A reception buffer, a reception buffer monitoring section that monitors the amount of storage in the reception buffer, a token inspection section that detects reception of tokens addressed to its own node, and a token deletion/determination section.
It is configured by providing a token control unit that executes playback.

[Industrial Field of Application] The present invention relates to a flow control device in a system that performs transmitter arbitration using tokens in a throttled LAN (Local Area Network).

Packet communication enables the integration of various media by transmitting all data (line type and non-line type) as packets, making it possible to combine lines that were previously configured individually depending on the nature of the data to be communicated. This is important in moving forward. Hereinafter, a slot will refer to a container for transferring data, and a packet will refer to data transferred by a slot.

[Prior Art] A throttling LAN is a LAN in which all data is transmitted based on fixed-length mini-packets. This LAN
Since the transmission frame length in the ring is always kept constant, there is always a constant number of slots on the ring. FIG. 5 is a conceptual diagram of the configuration of a throttling type LAN. In the figure, 1 is a ring type transmission line, and a plurality of communication devices [2] are connected to the ring type transmission line 1. A series of data consisting of fixed-length slots 3 is constantly flowing through the ring-shaped transmission path 1, and the communication device 2 sends data to the ring-shaped transmission path 1 or transfers data from the ring-shaped transmission path 1 as necessary. You can import it.

As shown in Fig. 386, the slot 3 includes a slot identification number (ID) 3g, a status indicator 3b indicating whether the slot is in an active state (busy) or not (idle), and a source communication device. It is composed of an address section 3c consisting of an address, a destination communication device address, and a data section 3d. By always using a certain slot for communication, a constant bandwidth can be obtained regardless of the ID number of the used slot.

In this type of system, in order to realize communication in which only one communication device 2 can transmit at the same time between multiple (three or more) communication devices accommodated in the throttling type LAN, the transmitter It is necessary to conduct mediation. In other words, when the communication device 2 that has acquired the transmitter transmits one communication frame (a unit of data processing), it passes the transmitter to the next communication f2, thereby increasing the number of continuous transmissions and receptions of one communication frame and the communication opportunity. Fairness has been realized.

This transmitter acquisition control can also be realized in the upper layer of the communication control protocol between communication devices, but
In order to obtain high communication efficiency, throttling type LAN
As a function of itself, it is necessary to perform high-speed processing by realizing it in a lower layer. Such transmitter arbitration is performed, for example, according to the following procedure.

That is, first, a slot indicating a transmitter called a token is installed in the throttling 12 LAN for each node (a device that interfaces between the communication device 2 and the ring-type transmission path 1, and is connected to the communication device 2). Define each. In other words, the token is made to circulate within the ring-type transmission path 1 shown in FIG.

Only one of this token exists. Then, only the communication device that has acquired this token can send data to the ring type transmission path 1.

The communication device that wants to transfer the data then captures this token. When it recognizes that it has acquired the transmitter by capturing it, it erases this token. As a result, the tokens no longer circulate on the ring-type transmission path 1, so that data will not flow from other communication devices to the ring-type transmission path 1. Therefore, the source communication device can concentrate on transmitting data for one frame to the destination communication device. When the communication device 2 finishes one frame communication, it reproduces the token and sends it to the ring transmission path 1. As a result, the token circulates around the ring-type transmission line 1 again, so the communication device 2 that wants to transmit data only needs to capture this token.

[Problems to be Solved by the Invention] In the conventional throttling type LAN described above, flow control was not performed when transmitter arbitration using tokens was performed. FIG. 7 is a conceptual diagram of flow control.

The sending side has a sending buffer 11, and this buffer 11
The data stored in the network 12 is sequentially read out and
will be sent to.

The data that has passed through the network 12 is sequentially stored in a receiving buffer 13 on the receiving side. Here, the reception buffer 13
The amount of data accumulated is constantly monitored, and when a certain amount or more is accumulated, a control signal is sent to the transmitting side to suppress the amount of data sent on the transmitting side. When the amount of data held in the reception buffer 13 becomes small, a control signal is used to request data transfer from the transmitting side.

As a result of such flow control not being performed, when transmissions from multiple nodes to a certain node are concentrated (congestion state), there is a risk that the receive buffer 13 will overflow and packets will be discarded. . Therefore, this problem is dealt with probabilistically by increasing the capacity of the receiving buffer 13 to such an extent that buffer overflow does not occur. However, there were problems as shown below.

(2) If flow control is not performed at all, packets will be discarded during congestion, and as a result, data will be retransmitted by the error correction function between upper layers, resulting in a vicious cycle in which the state of congestion continues.

■With the spread of workstations, there is an increasing demand for distributed processing systems that connect multiple medium- and low-speed LANs using a high-speed, large-capacity, throttling-type LAN as a backbone network. The frequency of communication with nodes (servers) is increasing, making it easier for communication to become concentrated.

■A large amount of data communication is becoming necessary due to the increase in scale and capacity of systems, and it is difficult to suppress the packet discard rate simply by increasing the capacity of the receive buffer 13 to deal with congestion of received data. It has become.

The present invention has been made in view of such problems, and an object of the present invention is to provide a flow control device that can efficiently perform processing when received packets are concentrated at a specific node.

[Means for Solving the Problems] FIG. 1 is a block diagram of the principle of the present invention. Components that are the same as those in FIG. 5 are designated by the same reference numerals. The communication device 2 is connected to the ring type transmission line 1 via a node 20. The communication device 2 sends data and takes in data via the node 20. In other words, packets are transmitted and received between the communication device 2 and the ring-type transmission path 1 via the node 20. The configuration of the node is shown below.

In the figure, 21 is a reception buffer that temporarily stores received data, 22 is a reception buffer monitoring unit that monitors the amount of storage in the reception buffer 21, and 23 is a token inspection unit that detects reception of a token addressed to its own node. 24 is a token control unit that erases and reproduces tokens. 25 analyzes the contents of the packet header, branches the packet from the slot when receiving the packet, and sends the packet to the reception buffer 21.
26 is a reception buffer 21
This is a packet assembly/disassembly unit that assembles data read from the communication device 2 into a communication frame and disassembles data sent from the communication device 2 into packets.

[Operation: When transmissions are concentrated on one node from a plurality of nodes, the reception buffer monitoring section 22 detects this and notifies the token control section 24 of this fact. When the receiving node's token packet 24 is notified, it captures the token and erases the token. As a result, tokens no longer circulate on the ring-type transmission path 1, making it possible to restrict packets from flowing into the receiving node. During this time, when the processing within the node 20 progresses and the reception buffer monitoring unit 22 recognizes that the amount of data stored in the reception buffer 21 has decreased, the token control unit 24 regenerates the token again and flow to. In this manner, according to the present invention, processing can be efficiently performed when received packets are concentrated at a specific node.

[Example] Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIG. 2 is a block diagram showing an embodiment of the present invention. Components that are the same as those in FIG. 1 are designated by the same reference numerals. In the illustrated embodiment, only one communication device 2 is connected to the node 20, but a configuration in which a plurality of communication devices share the node is also possible. In this case, packet assembly/
It is necessary to provide as many parts as the number of connected units below the disassembly unit 26.

In the figure, a node 20 is a device that performs data conversion and media access control for the communication device 2' to access the ring-type transmission line 1.

Reference numeral 27 denotes a transmission line synchronization detection unit, which extracts a clock and generates various timings by detecting synchronization of transmission frames from the transmission line 1 and distributes them to each block within the node 20. When receiving a packet by analyzing the content of the packet header, the packet branching/insertion unit 25 branches the packet from the slot, notifies the reception buffer monitoring unit 22 of the reception, and stores the received data in the reception buffer 21 .

In addition, when transmitting a packet, the packet branching/insertion unit 25 transfers the packet from the reception buffer 28 or the token packet (in an empty state or a used state) from the token control unit 24 to the transmission path according to a request from the token control unit 24. Insert into.

However, the reception of the token is only inspected by the token inspection section 23, and the reception buffer monitoring section 22 and the reception buffer 21
is not stored.

When the token inspection unit 23 receives a token from the transmission path 1, the token inspection unit 23 inspects the type (to which node the token is addressed) and notifies the token control unit 24. The reception buffer monitoring unit 22 controls writing of data to the reception buffer 21 in accordance with a packet reception instruction from the packet add/drop unit 25 .

Further, in response to a request from the communication frame transmission control unit 29, data reading from the reception buffer 21 is controlled in order to disassemble packets and assemble communication frames. Furthermore,
The status of the reception buffer 21 is monitored, and if the buffer amount exceeds a predetermined threshold A and congestion occurs (for example, the amount of data waiting to be processed in the buffer becomes 1/1 of the buffer capacity).
2), the token controller 24 is notified to enable flow control.

Under the control of the reception buffer monitoring unit 22, the reception buffer 21 stores the packet branched from the transmission path 1 by the packet add/drop unit 25, and waits for read control from the reception buffer monitoring unit 22. The communication frame transmission control unit 29 reads the packets stored in the reception buffer 21 and controls writing of communication frames to the transmission buffer 30 according to the packet header analysis result of the packet assembly/disassembly unit 26.

Further, when the assembly of the communication frame is completed in the transmission buffer 30, reading control is performed to transmit the communication frame to the communication device 2 in accordance with a request from the interface control unit 31.

The packet assembly/disassembly unit 26 assembles packets read from the reception buffer 21 into communication frames and disassembles communication frames read from the reception buffer 28 into packets. When assembling the packet, use Table 3
The packet header information notified from 2 is added. The transmission buffer 30 stores communication frames assembled under the control of the communication frame transmission control section 29, and waits for read control from the communication frame transmission control section 29.

The interface control unit 31 connects the node 20 and the communication device 2.
control the interface between the two, and control the transmission and reception of communication frames. The reception buffer 28 stores communication frames in accordance with reception instructions from the interface control section 31 under the control of the transmission and reception control section 33 .
Wait for read control from. The transmission/reception control unit 33 controls writing of communication frames into the reception buffer 28 in accordance with reception instructions from the interface control unit 31 . After writing data for one communication frame into the reception buffer 28, a transmission request is made to the token control unit 24. It also controls reading of communication frames from the reception buffer 28 in order to transmit packets according to instructions from the token control unit 24.

The table 32 is a table in which communication bus definition information is set in a packet header in order to disassemble a communication frame into packets and transmit them.

In response to instructions from the transmission/reception control section 33, the packet assembly/disassembly section 26 generates the packet header information retrieved when receiving the communication frame, and assembles the packet.

The token control section 24 controls the packet drop/insertion section 25 so that the received token is relayed as is when the transmission/reception control section 33 is not making a transmission request. When the transmission/reception control section 33 is requesting transmission, the token inspection section 2
3 notifies reception of the token, and if the type and destination match, the communication frame is transmitted from the reception buffer 28 without relaying (erasing) the token. When the transmission of the communication frame is completed, the erased token is regenerated and transmitted using an appropriate empty slot. Furthermore, in response to a request from the reception buffer monitoring unit 22 or the communication device 2, the token addressed to the own node can be deleted to stop the inflow of received packets, or the token can be regenerated to start the inflow of received packets. .

FIG. 3 is a flowchart showing the operation of the apparatus of the present invention. First, the token control unit 24 checks whether a token has been received (Sl). When a token is received, the type of the token is checked (S2). If the token is addressed to another node, the data will be sent from the own node. In this case, it is checked whether the frame is waiting for transmission (S3).

If the packet is not waiting for transmission, the token control unit 24 controls the packet drop/add unit 25 to relay the input token to the ring transmission path 1 as is. Therefore, the tokens that come in go out as they are. Here, the control of whether to transmit the communication frame or to relay the token after receiving the token can be realized by using a simple comparison circuit, and can be performed within the delay time in the packet drop/add unit 25. I can do it.

If a transmission request has been issued from the transmission/reception control unit 33, that is, if a frame is waiting to be transmitted, check whether the destination nodes match (S4), and if so, delete the token without relaying it. One communication frame is transmitted from the reception buffer 28 (S5). When the transmission of one frame is completed, the erased token is regenerated (S6) and transmitted using an appropriate empty slot.

In step S2, if the token type is addressed to the own node, the reception buffer monitoring unit 22 checks whether the reception buffer 21 is congested (S7).

If congestion is occurring, that is, if the accumulated amount in the receiving buffer 21 of the own node exceeds a predetermined threshold A, the token is temporarily deleted (S8). When a token is deleted, other nodes cannot capture the token and cannot send data to the node itself.

During this time, if the processing within the own node is promoted and the reception buffer monitoring unit 22 detects that the accumulated amount in the reception buffer 21 has become lower than the threshold B (≦A), that is, the congestion in the reception buffer 21 is detected. When the condition is resolved, the token control unit 2
4 regenerates the token and sends it to the ring type transmission line 1. This makes it possible to receive frame data from other nodes again.

As explained above, in the present invention, the throttling type L
On the AN ring, when transmissions from multiple nodes are concentrated on one node between nodes that perform transmitter arbitration using tokens, and congestion occurs, the receiving node clears the token. Flow control is achieved by restricting the inflow of packets and processing the received packets, then regenerating the token and restarting packet reception. This type of control can be achieved quickly by hardware control between nodes in a throttling LAN, eliminating the need to prepare a large capacity buffer at the receiving node, and eliminating the need for receiving buffer overflow when flow control is not performed. Communication efficiency can be improved by preventing retransmission (error correction function) between higher-level devices when a packet is discarded.

FIG. 4 is a block diagram showing a system to which the present invention is applied. Components that are the same as before are indicated with the same reference numerals.

The system shown in the figure is a system in which a bridge device is connected to a throttling type LAN to realize inter-LAN connection.

In the figure, 208 to 20d are nodes to which the present invention is applied. 1 is a ring type transmission line (throttling type LAN) connecting these nodes 20a to 20d in a ring shape.

Reference numeral 50 denotes a central control node for delay time adjustment provided within the ring-type transmission path 1, to which no communication device is connected.

40a to 40d are the bridge devices mentioned above and are bus type LAN.
51a to 51d are connected to each other. These bus type LANs 51a to 51d are IEEE802.3
This is a LAN defined by 41a to 41d are communication terminals (diskless workstations) accommodated in the bus-type LANs 51a to 51d, and 42 is a communication terminal (disk server) also accommodated in the bus-type LAN 51d.

In this system, since the communication terminals 41a to 41d do not have disk devices, they always access the disk server 42 when accessing files. That is, node 2
Communication between 0a to 20c and node 20d is more frequent than communication between other nodes, and transmission packets are likely to be concentrated on node 20d.

In such systems, throttling type LAN
When starting up, the central control node 50 transmits one token to each of the nodes 20a to 20d as initialization information for the transmission line 1. When the initialization data generated by the central control node 50 circulates around the ring 1 and returns, the central control node 50 completes the initialization by making appropriate delay adjustments and making the transmission frame length constant. Nodes 20a and 2
Assuming that 0C is in a state of waiting for transmission of a communication frame to node 20d, transmitter arbitration using tokens is performed as follows.

■Token (token addressed to node 2Od) is node 20
received by a. Since the node 20a is waiting to transmit a communication frame, it learns that it has acquired a transmitter, erases the token, and starts transmitting packets. node 2
When 0a finishes transmitting one frame, it transmits a token to the following empty slot (token regeneration).

(2) The token is received by the node 20b, but since the node 20b is not in a waiting state for transmission, the token is relayed to the ring transmission line 1 as is.

■The token is then received by node 20c. node 2
0c is in a state of waiting for the transmission of a communication frame, and the token is transmitted after the transmission of one communication frame is completed by the same procedure as in (2).

■The token is then received by node 20d. If no conflict occurs, the token is relayed as is.

In this way, transmitters circulate between nodes and transmitter arbitration is achieved.

Next, assuming that the nodes 20a, 20b, and 20c are in a state of waiting for transmission of a communication frame to the node 20d, flow control of the node 20d is performed as follows.

(2) The token (addressed to node 2Od) is received by node 20a, and one communication frame is transmitted to node 2Od, thereby transmitting the token.

(2) The token is then received by the node 20b, which transmits the token after transmitting one communication frame.

(2) The token is received by the node 20c, and after transmitting one communication frame, the token is transmitted.

■The token is received by the node 20d. node 20d
``Since the amount accumulated in the reception buffer exceeds the threshold value A, the token is captured and erased to prevent any more packets from flowing in.

■The node 20d has a reception buffer with a storage amount of threshold B (≦
A) Since the following has occurred, packet reception is resumed by regenerating the token.

[Effects of the Invention] As described above in detail, according to the present invention, in a system in which transmitter arbitration is performed using tokens in a throttling type LAN, congestion in which received packets are concentrated on a specific node can be avoided. By performing flow control when a problem occurs, it is possible to reduce the amount of hardware by eliminating the need for a large-capacity receive buffer, and to provide an error correction function between upper-level devices when packets are discarded due to congestion. It is possible to prevent a decrease in communication efficiency due to retransmission of frames, and it is possible to efficiently perform processing when received packets are concentrated on a specific node.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of the principle of the present invention, Fig. 2 is a block diagram of the configuration of an embodiment of the present invention, Fig. 3 is a flowchart showing the operation of the device of the present invention, and Fig. 4 is a system to which the present invention is applied. 5 is a conceptual diagram of the configuration of a throttling type LAN, FIG. 6 is a diagram illustrating an example of the configuration of slots, and FIG. 7 is a conceptual diagram of flow control. In FIG. 1, 1 is a ring type transmission path, 2 is a communication device, 20 is a node, 21 is a reception buffer, 22 is a reception buffer monitoring section, 23 is a token inspection section, 24 is a token control section, 25 is a packet drop/addition Section 26 is a packet assembly/disassembly section.

Claims (4)

[Claims] (1) At least three communication devices accommodated in a throttling type LAN (2) In order to realize a system in which only one communication device can transmit at the same time, multiple independent In a system that performs transmitter arbitration control using tokens, received data is temporarily stored in a node (20) that sends and receives packets between a communication device (2) and a ring-type transmission path (1). A reception buffer (21) that accumulates in the reception buffer (21), a reception buffer monitoring unit (22) that monitors the amount of storage in the reception buffer (21), a token inspection unit (23) that detects reception of tokens addressed to its own node, Token control unit (24) that executes erasure/regeneration
) is provided. (2) When the reception buffer monitoring unit (22) detects that the accumulated amount in the reception buffer (21) of its own node exceeds a predetermined threshold A, the token control unit (24) temporarily stores the token. and delete it from the own node's receive buffer (2
1) The token is regenerated when the accumulated amount in 1) becomes lower than a threshold value B (≦A) to control the amount of packets received to the node (20). Flow control device. (3) When there is a request to stop reception from the communication device (2), the token control unit (24) of the receiving node temporarily erases the token, and when there is a request to resume reception from the communication device (2), the token is temporarily deleted. 2. The flow control device according to claim 1, wherein the token control unit (24) reproduces the token to control the amount of received packets flowing into the node (20). (4) The communication device (2) normally requests the node (20) to erase the token addressed to itself, and only reproduces the token when the reception buffer (21) is available. 2. The flow control device according to claim 1, wherein only the amount of packets commensurate with the processing speed of the receiving side can be received.