JPH04291851A - Node state notice method in loop type lan - Google Patents

Abstract

PURPOSE:To improve the traffic and the reliability by allowing a node whose reception buffer is busy to inform it to other node in the loop type LAN so as to stop the transmission addressed to itself. CONSTITUTION:When an overflow detection section 22 detects a busy state of a reception buffer 19 in a node 1, it is noticed to a transmission buffer read control section 23 and a special packet from a special packet generating section 22 is sent to a transmission line via a repeater 28 and selectors 25, 26. When the release of the busy state of the reception buffer 19 is detected by the overflow detection section 22, the special packet is sent to the transmission line. A busy node address management section 24 of the node 1 receiving the specific packet manages the busy node and stops the transmission to the busy node. Thus, the traffic is improved by the stopped transmission and the reliability in data communication is enhanced.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention is for forming a loop-type transmission path in a local area network (LAN) and transmitting and receiving data between nodes using a plurality of fixed-length frames circulating on this transmission path. Loop type L
This invention relates to a node status notification method in an AN.

0002

[Prior Art] A loop type LAN to which the present invention is applied is
As shown in FIG. 1, a plurality of nodes, for example, three nodes 1-1, 1-2, and 1-3, which transmit and receive data, and a monitoring node 2, which monitors a LAN, are connected by a loop-type transmission path. ing. In the loop type LAN of FIG. 1, for example, when transmitting a frame from node 1-1 to node 1-2, the reception buffer of node 1-2 may overflow or the like and reception becomes impossible (hereinafter referred to as busy state). In this case, since node 1-1 cannot recognize the busy state of node 1-2, node 1-1 will transmit a frame addressed to node 1-2. As a result, the node 1-2 discards the frame or requests retransmission to the source node 1-1 by using the control bit added to the frame.

0003

[Problem to be Solved by the Invention] However, because node 1-1 transmits even though the reception buffer of node 1-2 is busy and cannot receive data, useless frames are sent back and forth on the transmission path. This results in an increase in traffic on the transmission path, and there is also a problem in that data reliability decreases due to frame discards during data transmission because the reception status of the destination node is not known during data transmission.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a node status notification method in a loop-type LAN that reduces traffic on a transmission path and prevents deterioration in data reliability.

[0005]

[Means for solving the problem] The first means for solving the above problem is to notify other nodes of the busy state of the own node when the own node is busy, and to receive this notification. Other nodes stop transmitting to their own node. According to the second means, in addition to the first means, when the busy state of the own node is restored to the normal state, the other node is notified of the normal state of the own node, and the other node receiving this notification This is to cancel the stoppage of transmission to the own node.

[0006]

According to the above means, there is no increase in the number of unreceived frames circulating on the transmission path, and the increase in traffic on the transmission path is minimized. Additionally, frames addressed to busy nodes will be temporarily maintained at the source node, and will be discarded thereafter without reducing the reliability of the data.

[0007]

Embodiment FIG. 2 is a diagram showing a frame format used in the frame transmission/reception method in a loop-type LAN according to the present invention. In Figure 2, as shown in Figure 2(A), one frame includes an 8-byte frame header and 12 bytes.
It is a fixed length frame with a total of 128 bytes including a data area of 0 bytes. The first byte H1 of the frame header indicates the source address SA of the frame, as shown in FIG. 2(B), and the second byte H2 indicates the destination of the frame, as shown in FIG. 2(C). Destination address DA, 3
Byte H3 is a control bit for controlling the frame, as shown in FIG. 2(D). Furthermore, Figure 2 (D
) control bits are comprised of a usage status bit USD, special bit SB, and busy bit BSY.

[0008] Here, the usage status bit USD is a bit indicating whether the frame is valid or invalid, and is "0" when the relevant frame is invalid, but when it is valid (valid data is contained in the data area). ) becomes “1”. In addition,
This usage status bit is manipulated by the sender. The special bit SB is a special frame identification bit, and is set to “1” only when notifying other nodes of the status of the receive buffer of its own node.
This indicates that the packet is not a normal packet, but a special frame to notify that the receive buffer has transitioned to a busy state, or that the busy state has transitioned to a receivable state.
0". Also, when sending a special packet, broadcast is used, and the destination address DA is set to all 1s, that is, "
1111111” is written.

[0009] The busy bit BSY is a bit that indicates the status of the reception buffer of each node.
0", but becomes "1" when a failure such as an overflow occurs in the reception buffer and reception is not possible.Next, details of each node according to the present invention will be explained with reference to FIGS. 3 and 4. In Fig. 3, 10 is a repeater, and if the transmission path is an optical fiber, it is configured to include an optical/electrical converter.11 stores the data received by the repeater 10 in 8 bits each. 12 is an 8-bit shift register that detects synchronization using a signal from the preamble part of the received frame and generates a timing signal to each part. 13 is a source address (SA) detector that detects synchronization. It detects a frame transmitted from another node by identifying the source address SA indicating the source of the frame in the control bits according to the timing SATIM from the section 12. 14 is a destination address (DA) detection section. Therefore, the timing DAT from the synchronization detection section 12
The frame addressed to the node itself is detected by identifying the destination address DA indicating the destination of the frame in the control bits of the frame on the transmission path according to the IM. 15 is a usage status bit (USD) detection unit, which is a synchronization detection unit 12
A valid frame is detected by identifying the usage status bit USD in the control bits according to the timing CNTTIM from CNTTIM. A special bit (SB) detection section 16 identifies the special bit SB in the control bits according to the timing CNTTIM from the synchronization detection section 12 and detects special packets and normal packets. 17 is a busy bit (BSY) detection unit, which is a synchronization detection unit 1.
The control busy bit BSY is identified in accordance with the timing CNTTIM from 2 to detect the state of the receiving buffer of the other node.

Reference numeral 18 denotes a frame processing unit which performs frame discard, frame reception, frame repeat, busy operation, frame transmission stop, and frame transmission restart according to the detection results of each of the detection units 13 to 17. be. Reference numeral 19 represents a reception buffer for storing received frames, and 20 represents a transmission buffer for storing frames to be transmitted.

Reference numeral 21 denotes a reception buffer write control section, which controls SA, DA, and
It analyzes the results of USD, SB, and BSY and generates the timing for writing to the reception buffer. 22
A reception buffer overflow monitoring section monitors overflow of the reception buffer 19 and notifies the transmission buffer read control section 23 of the monitoring result.

[0012] Reference numeral 24 denotes a busy node address management unit which handles SA and DA detected by the frame processing unit 18.
, USD, SB, and BSY to manage the address of the busy node and notify the transmission buffer read control unit 23 of the node address. The transmission buffer read control unit 23 performs selection control of the data (hereinafter referred to as repeat data) and transmission data taken in from the transmission path of the read timing generation and selection unit 25 of the transmission buffer 20 based on the analysis result of the busy node address management unit 24. Based on the monitoring result by the reception buffer overflow monitoring section 22, the selection section 26 and the selection section 25 control the transmission of the special packet.

Reference numeral 27 denotes a transmission buffer write control unit which detects and identifies the transmission destination address DA, generates a write timing, and performs writing to the address of the transmission buffer corresponding to each transmission destination address. The select unit 25 selects between transmit data and repeat data based on the select timing signal from the transmit buffer read control unit 23, and the select unit 26 selects between special packets and transmit data when the own node's receive buffer overflows. The selection is performed at the selection timing by the transmission buffer read control unit 23.

Reference numeral 28 denotes a repeater, which includes an electrical/optical converter if the transmission line is an optical fiber. Next, the operation of the circuit shown in FIG. 3 will be explained. The reception operation will be explained with reference to FIG. DA by the detection units 13 to 17
, SA, USD, BSY, and SB are detected, the frame processing unit 18 determines in step 401 whether or not the transmission source (SA) is the own node, and in step 402
In step 403, it is determined whether the destination DA is the own node or in another node. In step 403, it is determined whether it is a valid frame (USD="1") or an invalid frame (USD="0").In step 404, a special Determine whether the frame is a frame (SB="1") or a normal frame (SB="0"), and step 40
5, it is determined whether the CPU is in a busy state (BSY="1").

If the source is the own node, step 40
1 proceeds to step 406, where the frame is discarded. Specifically, the selectors 25 and 26 are operated via the transmission buffer read control section 23 to transmit data from the transmission buffer 20. Sender S
If A is another node, the destination DA is the own node, it is a valid frame (USD="1"), and it is a normal frame (SB="0"), the flow proceeds to step 401.
The process proceeds to step 407 via steps 404 to 404, and the received frame is written into the reception buffer 19. Specifically, the reception buffer write control section 21 is operated to write data.

[0016] If the source SA is another node and the destination DA is another node, the flow proceeds to steps 401 and 40.
Repeat processing is performed via 2. Furthermore, if the source SA is another node, the destination DA is the own node, and the frame is invalid (USD="0"), repeat processing is also performed. Specifically, the transmission buffer read control section 2
3, the selector 25 is activated.

[0017] Furthermore, the source SA is another node, the destination DA is the own node, and the frame is valid (USD=
If it is a special frame (SB="1") and is in a busy state (BSY="1"), the flow goes to steps 401, 402, 403, 404,
The process advances to step 409 via step 405, and transmission to the source DA is stopped. Specifically, the busy node address management section 24 is notified, and the transmission operation to the transmission source DA is stopped via the transmission buffer read control section 23. In this case, the busy node address management unit 24 stores the node address DA.

[0018] Furthermore, the source SA is another node, the destination DA is the own node, and the frame is valid (USD=
If the frame is a special frame (SB="1") and is not busy (BSY="0"), the flow goes to steps 401, 402, 403, 404,
The process advances to step 410 via step 405, and transmission to the source DA is resumed. Specifically, the busy node address management unit 24 is notified and the transmission operation to the source DA is restarted via the transmission buffer read control unit 23. In this case, the busy node address management unit 24 deletes the node address DA.

When the busy state (overflow state) of the reception buffer 19 is detected by the overflow detection section 22 in the transmission operation node 1-i in the busy state, the transmission buffer read control section 23 is notified of this fact, and the result is , selector 25,
26, a special packet (frame) is sent out from the special packet generation unit 22 onto the transmission path via the repeater 28. In this case, the special bit SB is "1".

[0020] Sending operation node 1- after clearing the busy state
At i, when the overflow detection section 22 detects that the busy state (overflow state) of the reception buffer 19 has been resolved, the transmission buffer read control section 23 is notified of this, and as a result, the selector 2
5 and 26, a special packet (frame) is sent from the special packet generation unit 22 onto the transmission path via the repeater 28. In this case, the special bit SB is "0".

[0021] The special packet header generation unit 22
Manipulates a busy bit that notifies other nodes of the status of its own node's receive buffer 19 through broadcast communication,
Generating busy special packets and recovery special packets. FIG. 5 shows each detection section 13 to 17 and frame processing section 1 in FIG. 3.
8 is a detailed logic circuit diagram of FIG. That is, in FIG. 5, the frame processing unit 18 is configured with hardware instead of the flowchart (software) in FIG. In FIG. 5, each of the detection units 13 to 17 is constituted by a number of D flip-flops corresponding to the number of bits, and the data of the shift register 11 is supplied to the data input of each D flip-flop. A timing signal from the synchronization detection section 12 is supplied to the clock input. In other words, each data RDAT0 to 7 of the shift register 11
are the timing signals SATIM and DA of the synchronization detection section 12
It is latched into each corresponding D flip-flop by TIM and CMTTIM.

The frame processing section 18 includes a comparator 181 that compares the source address SA latched by the SA detection section 13 with the address of its own node, and a comparator 181 that compares the source address SA latched by the SA detection section 13 with the address of its own node, and a comparator 181 that compares the destination address DA latched by the DA detection section 14 with its own node address. Comparator 182 for comparing, and AND circuits 183 to 185
, a NAND circuit 186, and a buffer 187 having a gate function (EN). Due to the presence of the AND circuit 183, frame discard will only occur if all of the following conditions are satisfied:

1) The received source address SA matches the address of the own node, 2) The received usage status bit USD is “1” (valid)
To be. Due to the presence of AND circuit 184, frame reception occurs only if all of the following conditions are met: 1) The received source address SA does not match the own node address. 2) The received destination address DA matches the own node address. 3) The received valid state bit USD is “1”. (valid), 4) Special bit SB is “0” (normal), 5)
The receive buffer of the own node is not busy (*RBU
F=“0”).

Due to the existence of the AND circuit 185, frame repeat, that is, a received frame is used as a transmitted frame as is, is performed when all of the following conditions are satisfied. 1) The received source address SA does not match the address of the own node. 2) The received usage state bit USD is "1" (usage state).

Due to the presence of NAND 186 and AND circuit 187, transmission is stopped when all of the following conditions are met. 1) The received source address SA does not match the address of the own node, 2) The received destination address DA matches the address of the own node, 3) The received usage status bit USD is “ 4) The received special bit SB is "1" (special frame); 5) The received busy bit BSY is "1" (busy state).

[0026] Also, a NAND 186 and an AND circuit 18
Due to the existence of 7, transmission suspension will be released if all of the following conditions are met: 1) The received source address SA does not match the address of the own node, 2) The received destination address DA matches the address of the own node, 3) The received usage status bit USD is “ 4) The received special bit SB is "1" (special frame); 5) The received busy bit BSY is "0" (non-busy state). .

Based on the above latched results of each bit, processes such as packet discard, packet reception, packet repeat, and transmission stop/restart to the busy node are performed. Note that busy bit BSY is recognized only when special packets are received.
In the transmission stop and transmission restart processing, the source address SA and busy bit BSY are detected and managed from the received special packet, and based on the results, the data in the transmission buffer addressed to each node is read and the reading is stopped.

Next, an example of the operation when the nodes shown in FIGS. 3 and 4 (or FIG. 5) according to the present invention are used in the ring LAN of FIG. 1 will be described with reference to FIG. As shown in FIG. 6A, when transmitting a frame from node 1-1 to node 1-2, the destination address DA is the node address of node 1-2, for example "2", and the source address SA is For example, the node address of node 1-1 is "1", and the usage status bit USD is "1" indicating that the frame is in use.
"0" is written into the busy bit BSY and "0" is written into the special bit SB.

[0029] In normal operation, a frame is received at node 1-2, the received frame is repeated as is, returns to node 1-1, and is sent to node 1-1, which is the source of the transmission.
1, the usage status bit USD is set to "0", and the frame is sent out again to the transmission path, and is used by the downstream node that has the transmission frame. Next, when the reception buffer becomes busy in the node 1-2, the frame header detection unit 15 detects an invalid frame, and as shown in FIG. 6(B), the special packet header generation unit 22
Packet generated in (SB="1", BS
Y=“1”, SA=own node address, DA=11
111111) is written and sent to each node. Each node that receives the special packet stops transmitting to node 1-2.

Similarly, when the node 1-2 recovers from the busy state, the packet generated by the special packet header generator 22 (SB="1", BSY="0",
SA = own node address, DA = 11111111
) and send it to each node. Each node that receives the recovery notification resumes transmission to node 1-2.

[0031]

[Effects of the Invention] As explained above, according to the present invention, a node whose reception buffer is in a busy state notifies other nodes of the busy state, thereby stopping transmission from other nodes to the own node. Traffic can be improved, and since data destined for busy nodes is stocked to the capacity of the receive buffer, reliability in data communication is also improved.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a loop-type LAN to which the present invention is applied.

FIG. 2 is a diagram showing a frame fart according to the present invention.

FIG. 3 is a block circuit diagram showing a node according to the present invention.

FIG. 4 is a flowchart illustrating the operation of the circuit shown in FIG. 3;

FIG. 5 is a detailed view of a portion of FIG. 3;

FIG. 6 is a diagram showing an example of the operation of the loop LAN according to the present invention.

[Explanation of symbols]

1-1, 1-2, 1-3...node 2...Monitoring node 13... Source address detection unit 14...Destination address detection unit 15...Usage status bit detection unit 16...Special bit detection section 17...Busy bit detection section 18...Frame processing section 25, 26...Selector 19...Reception buffer 20...Transmission buffer

Claims (2)

[Claims] [Claim 1] In a loop type LAN in which a plurality of nodes (1-1 to 1-3) are connected by a loop type transmission line,
In a loop type LAN characterized in that when the own node is in a busy state, the other node is notified of the busy state of the own node, and the other node that receives the notification stops transmission to the own node. Node status notification method. 2. When the busy state of the own node is restored to a normal state, the other node is notified of the normal state of the own node, and the other node that receives the notification stops transmission to the own node. 2. The node status notification method in a loop type LAN according to claim 1, wherein the node status notification method in a loop type LAN is canceled.