JP2006245790A - Annular transmission system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an annular transmission system for achieving inexpensive packet communication, with lower power consumption by minimizing a reception buffer memory amount, by making a transmission path play a role as a virtual memory, by transmitting a packet to be buffered by the reception side to the transmission path, for reducing the load on the transmission side by controlling with the reception side only, and for executing timely control by monitoring a traffic state in-between the terminal of a connection destination and a router, without suppressing transmission requests. <P>SOLUTION: Packet communication is executed by an annular configuration, and a frame continuous in time division of a fixed period is used in the transmission system and device. When there is a risk of overflowing of buffers on the reception side, the packet transmitted and addressed to its own station is once emitted to the transmission path. When it is decided that the risk of the overflow has been avoided, reception of the packet is resumed. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a ring type transmission system, and more particularly to a transmission system that performs packet communication using a ring type transmission line.

  FIG. 22 is a diagram showing a first processing method for conventional overflow countermeasures. In the figure, 1 is a ring type transmission line, 2 is a device A connected to the ring type transmission line 1, 3 is a device C connected to the ring type transmission line 1, and 4 is a device connected to the ring type transmission line 1. B and 5 are devices D connected to the ring-type transmission line 1. It is assumed that ID of the device A = 1, ID of the device B = 2, ID of the device C = 3, and ID of the device D = 4. The device A functions as a transmission unit, and the device C functions as a reception unit.

  Reference numeral 6 denotes a port connected to the device A. Ports 1 to 3 are connected thereto. Reference numeral 7 denotes a port connected to the device C. Ports 1 to 3 are connected. Data is transmitted between the port 6 and the port 7. In the device A, 2a is a switch (SW) to which the ring type transmission line 1 is connected, and 2b is a memory connected to the switch 2a. The memory 2 b is connected to the port 6.

  In the device C, 3a is a switch (SW) to which the ring type transmission line 1 is connected, and 3b is a memory that is connected to the switch 3a and holds received data. The configurations of the transmission unit and the reception unit of the devices A and C are the same for the devices B and D.

  In the system configured as described above, when it is determined that there is a risk of overflow between the receiving port 1 and the connection destination terminal or router during transmission of the packet from the device A to the device C, the device C transmits the packet. A request is sent to the original device A to suppress the amount of packets transmitted from the port, and the device A that has received the request limits the transmission of the packet whose destination is the port 1 of the device C, thereby overflowing. Is avoiding.

  While the suppression request from the device C arrives, the device A keeps transmitting, and more packets are accumulated in the memory 3b of the device C. When the number of accumulated packets increases, a packet discarded as shown in a also appears. After that, when it is determined that the risk of overflow has disappeared in the device C, a cancellation request cancellation is transmitted to the device A, and the device A receives it and cancels the packet transmission suppression. This transmission and reception sequence is performed independently for each port between devices.

  Further, as another control method, there is known a method in which when a data reception from a plurality of addresses causes an overflow, a transmission source address is confirmed and only an address with a small amount of data is preferentially received (for example, Patent Document 1). However, this has no effect when the transmission source is single, and data of a transmission source address not selected is discarded.

  FIG. 23 is a diagram showing a second processing method for conventional overflow countermeasures. The same components as those in FIG. 22 are denoted by the same reference numerals. In this example, a case where a specific dedicated packet is provided is shown (for example, see Patent Document 2). This dedicated packet contains information indicating the remaining amount of the reception buffer for each device node, and circulates in the ring type transmission line 1.

  When performing data transmission, the dedicated packet of the destination node (device C) is received, the remaining buffer capacity is confirmed, it is determined whether or not transmission is possible from the own station based on the remaining capacity, and transmission is performed only when possible. This is a method for preventing overflow. This method is ultimately influenced by the buffer amount on the receiving side, and data that exceeds the buffer amount is still suppressed on the transmitting side.

  FIG. 24 is a diagram showing a conventional basic frame configuration. The beginning of the frame is a frame header (FH), which contains a frame synchronization bit (SYNC). Next, a packet header (PH) is entered. The packet header is composed of USE (used / unused state), RV (slot reservation status), DA (destination address), and SA (source address). The packet header is followed by INFO (packet data). The INFO is followed by a packet header, followed by packet data.

In this frame, the head position is detected in synchronization with the frame header, and then a packet header exists for each time slot. The packet data (main data) after the packet header exists with a fixed length. Use / unuse is determined by the USE bit in the packet header, and it is confirmed by the RV bit whether it is reserved (fixed allocation). Thereafter, the destination is confirmed by SA (source address) / DA (destination address), and if it is addressed to itself, the packet is captured. The reserved time slot is fixed for each device, and other devices cannot be used.
JP-A-2-084840 (page 6, upper right column, line 11 to same page, lower right column, line 5, FIG. 1) JP-A-6-276205 (paragraphs 0016 to 0032, FIGS. 1 to 3)

  In the above-described prior art, since the packet transmission control is performed on the transmission side after receiving the packet control request from the reception side, the packet continues to be transmitted during that time, and accumulates in the reception buffer. Is discarded, and there is a disadvantage that there is no other way but to retransmit it by an upper protocol. Also, as the speed increases, the amount of packets transmitted by this time lag increases, so the effectiveness due to this sending and receiving side sequence (in response to the suppression request) is not seen in the gigabit class, and there are cases where it is not adopted.

  In addition, this sequence is congested by arbitrary nodes in the ring, complicating the transmission conditions and increasing the burden. In addition, the specifications of the opposing devices are individualized, making it versatile. poor. Another means is to increase the amount of memory, but this leads to an increase in cost and power consumption.

  The present invention has been made in view of such a problem, and transmits a packet to be originally buffered on the receiving side to the transmission path 1 and plays a role as a virtual memory, thereby receiving a reception buffer memory amount. To realize low-cost, low-power-consumption packet communication, and control only on the receiving side, reducing the burden on the transmitting side and reducing the transmission request as much as possible with the destination terminal and router. It is an object of the present invention to provide a ring type transmission system that can perform timely control in view of the traffic state of the network.

  In the present invention, a temporary storage memory for temporarily storing received packets and a free channel search function for determining whether to use / unuse from the packet header are provided separately from the reception buffer. If it is determined that there is a risk of overflow, the received packet is stocked in this temporary storage memory, an empty channel is searched from the next frame onward, and the stored packet is transmitted to the local station and circulated in the ring. In the meantime, a configuration is adopted in which packet reception is started when the risk of overflow disappears during this period.

  In addition, a sequence number is added when transmitting from the temporary memory to prevent the order of received packets from being changed. In this way, a ring-type transmission system characterized by minimizing the memory by virtually setting the transmission path as a part of the reception buffer is provided. In addition, since it can be controlled only on the receiving side, there is no conventional transmission / reception sequence, reducing the burden on the transmitting side, and fluid traffic status information can be obtained immediately, allowing timely control. It becomes.

(1) According to the first aspect of the present invention, there is a risk of overflow of the receiving buffer in a transmission system or apparatus that performs packet communication in a ring configuration and uses frames that are continuous in a time-sharing manner with a constant period. In this case, the packet addressed to the local station is once released to the transmission line,
A feature is that reception of a packet is started again when it is determined that the risk of overflow has been avoided.

  (2) The invention according to claim 2 is characterized in that a sequence number is assigned to a transmission line release packet of a packet addressed to the own station, and when the packet reception is started again, the packet is received in the order of the sequence number.

  (3) The invention described in claim 3 initializes the reception buffer memory of the own station when there are no more empty packets on the transmission path, and erases the packets addressed to the own station being released on the transmission path. It has a function of releasing as a frame.

  (4) The invention according to claim 4 is provided with a function of limiting the number of transmission path released packets of packets addressed to the own station to a preset number or less as means for avoiding occupancy of empty frames of a specific station. Features.

(5) The invention according to claim 5 is a means for avoiding occupancy of empty frames of a specific station, constantly monitoring the number of empty frames on the transmission line, and when the number of empty frames is less than a certain number, It is characterized in that it has a function of limiting the number of packets transmitted through the transmission path.
(6) Also, in the present invention, when the number of packets transmitted to the own station exceeds the limit value, the receiving buffer memory of the own station is initialized and addressed to the own station emitting on the transmission path. It has a function of deleting a packet and releasing it as an empty frame.

  (1) According to the first aspect of the present invention, when the buffer of the local station is at risk of overflow, the received packet is circulated through the ring-type transmission line, and the packet is cleared when there is no risk of overflow. Therefore, packet communication can be realized at a low cost and with low power consumption by minimizing the amount of reception buffer memory.

  (2) According to the invention described in claim 2, since the sequence number is given to the packet to be transmitted to the transmission line and then transmitted, when these packets are fetched later, they can be fetched in the order of the sequence number, and the data number order is switched. Nothing will happen.

  (3) According to the invention described in claim 3, when there are no more empty packets in the transmission path, the reception buffer memory of the own station is initialized, the packets addressed to the own station being released to the transmission path are deleted, and the initialization is performed. Can be performed.

(4) According to the invention described in claim 4, congestion of packets in the transmission path can be avoided by limiting the number of transmission path release packets of packets addressed to the own station to a certain number or less.
(5) According to the fifth aspect of the present invention, when the number of empty frames on the transmission path is equal to or less than a predetermined number, the number of transmission path released packets of packets addressed to the own station is limited to avoid congestion of the transmission path. it can.

  (6) In this case, when the number of packets transmitted on the packet transmission path addressed to the own station exceeds the limit value, the reception buffer memory of the own station is initialized and addressed to the own station that circulates on the ring type transmission path. The system can be initialized by deleting the packet.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a diagram showing an operation state 2 of the present invention. The same components as those in FIG. 22 are denoted by the same reference numerals. In the device C, 3a is a switch (SW1) to which the ring type transmission line 1 is connected, 3b is a reception buffer for temporarily storing received data via the switch 3a, and 3c is a temporary memory for temporarily storing received data. is there. The state at this time is shown as <State 3> in FIG.

  In this state, the device C shows a state in which the traffic of the received packet from the device A has increased. FIG. 2 shows a state in which this state continues and it is recognized that there is a risk of overflow. FIG. 2 is a diagram showing an operation state 3 of the present invention. In this state, the received packet b is temporarily stored in the temporary memory 3c, and at the same time, an unused (empty) frame on the ring transmission path (hereinafter simply referred to as the transmission path) 1 is searched.

  When an unused frame is detected, the packet stored in the temporary storage memory 3c is inserted and sent to the transmission path 1 addressed to the own station. This state is referred to as state 3. FIG. 3 is a diagram showing an operation state 3 of the present invention. When an empty frame is found, the held packet b is read from the temporary storage memory 3c, and is given a sequence number via the switch SW3a and sent out on the transmission line 1 as a packet b '.

  The state at this time is shown as <State 3> in FIG. FIG. 9 shows the operation during the frame lap. <State 1> indicates a normal state. That is, the packet data A and A on the transmission path 1 are stored in the reception buffer 3b. State 2 is a normal state, but traffic is increasing. The reception buffer 3b stores twice as much data A as in the state 1. In state 3, an overflow is detected. The packet data once stored in the temporary memory 3c is sent again to the transmission path 1.

  FIG. 11 shows the operation of states 1 and 2 of the present invention, and FIG. 12 shows the operation of state 3 of the present invention. In this example, it is assumed that the packet headers 6 and subsequent are all unused. In the case of FIG. 11, port 1 data after the packet header PH1, port 1 data after the packet header 2, port 1 data after the packet header 3, port 2 data after the packet header 4, and port header 5 after the packet header 5. Port 3 data is stored. For example, in the case of packet A data, DA is device C and SA is device A. USE is in use and RV is reserved.

  FIG. 10 is a diagram showing a frame configuration example of the present invention. 24 is different from the conventional frame shown in FIG. 24 in that a sequential number SQ is added to the packet header PH. Other configurations are the same as those in FIG. In FIG. 3, a temporary packet is sent to an empty time slot. In addition, the sequence number (SQ No.) at this time is added. All packets that come while the packet b 'circulates are all SQNo. 01-XXX.

  In the present invention, it is assumed that the packet header 6 and subsequent packets are all unused. Further, the USE bit in the packet header is monitored on the transmission line to determine whether it is used / unused. If it is not used, the temporarily stored packet is read from the temporary storage memory 3c, and the packet header in the same frame is read. And a sequence number is added to the transmission path 1 (packet b ′).

  Thereafter, until the packet b 'circulates and reaches the device C again, the same group of sequence numbers is used, and consecutive packets are added (for example, 01-01 to 01-04 in the figure).

  FIG. 4 is a diagram showing an operation state 4 of the present invention. This figure shows a case where a packet b 'that has finished its circulation arrives. If there is a risk of overflow at this point, the packet b 'continues to circulate again using the same frame. When new packet data C is received, as in the case of packet B, it is temporarily stored in the temporary memory 3c (packet c '), an empty frame is searched again, and the packet c in the temporary memory 3c is retrieved. Insert '. Also in this case, a sequence number is added as in the case of packet b '. According to this embodiment, since the sequence number is assigned to the packet to be transmitted to the transmission path and then transmitted, when these packets are captured later, they can be captured in the order of the sequence numbers, and the data number order is not changed.

  FIG. 5 is a diagram showing an operation state 4 of the present invention, in which the packet c is read from the temporary storage memory 3c and sent to the transmission line 1 as a packet c '. The state at this time is shown as <state 4> in FIG. Details of the frame in the same state are shown in FIG.

  Thereafter, when it is determined that there is no longer any risk of overflow in the device C, fetching (dropping) of packets sent so far is started. The state at this point is shown in FIG. Moreover, it shows as the state 5 in FIG. In state 5, the data D of the transmission line 1 is taken into the temporary storage memory 3c and sent again as d 'to the transmission line 1, but the packet data b' after two rounds is taken into the reception buffer 3b. According to this embodiment, when the buffer of the local station is at risk of overflow, the received packet is circulated through the link-type transmission line, and the packet is captured when the risk of overflow disappears. Therefore, it is possible to realize packet communication at a low cost and low power consumption by minimizing the amount of reception buffer memory.

  Further, FIG. 14 shows a frame configuration in the same state. When receiving, confirm the sequence number and import in the order of additional number. In the case of FIG. 14, when the data b ′ is captured, the area where the data b ′ is stored is released as a free area. The state at this time is shown in FIG. FIG. 6 shows the operating state 5. In this state, while the packet c 'circulates, it is determined that the traffic has decreased and there is no danger of overflow, and reception is started. At this time, the receiving order is determined by the sequence number. <State 5> in FIG. 9 shows the state at this time.

  In this example, the packet b 'is first received. FIG. 7 shows the state at this time. That is, the packet data b 'circulating around the transmission path 1 is received. Subsequently, the packets are captured in the order of packet c ′ → packet d ′ → packet e ′. The state at this time is shown in FIG. Further, it is shown in <State 6> and <State 7> in FIG. <State 8> and <State 9> in FIG. 9 indicate data transmission / reception after returning to the normal state.

  FIG. 14 is an explanatory diagram of packet reception, and shows the operation when the risk of overflow disappears after the lap. Dropping (capturing) in the order of the sequence number, the area after the capturing becomes an empty area, and the unused area expands to PH (packet header) 6. FIG. 15 is an explanatory diagram of packet reception, and shows a case where there is still a risk of overflow after circulation. In this case, when DA is ID = 3, SA is ID = 3, and USE is in use, an empty slot is continuously used.

  FIG. 16 is a diagram illustrating an operation when there is no empty frame during transmission path transmission. The same components as those in FIG. 1 are denoted by the same reference numerals. If the risk of overflow persists and there are no more empty frames in the middle, no further relief is possible. For this reason, the temporary memory 3c is initialized, and the packet released to the transmission path 1 is discarded after being received, and the frame used so far is released.

Thus, this function may cause a specific port to occupy the transmission line 1. In order to avoid this, the following method can be considered.
1) The number of empty frames on the transmission path is counted and compared with the amount of packets addressed to the own station, the amount of packets that can be retransmitted is determined, and retransmission control to the transmission path is limited.
2) The amount of packets to be retransmitted to the transmission path is determined in advance, and is limited when this threshold is exceeded. According to this embodiment, when there are no more empty packets on the transmission path, the reception buffer memory of the own station can be initialized, the packets addressed to the own station being released to the transmission path can be deleted, and initialization can be performed.

  FIG. 17 is a block diagram showing a configuration example of the transmission path occupation avoiding means. In this transmission path occupation avoidance means, one of the means is selected, and if the condition is satisfied, temporary memory is initialized and re-transmission control is stopped on the transmission side, and re-transmission packet erasure control is performed on the reception side. It is. In the figure, 21 is a packet header detection unit that is connected to a transmission line and detects a packet header (PH), 22 is a counter that receives the output of the packet header detection unit 21 and counts the number of packets addressed to itself. Is an empty frame detection unit that receives an output of the packet header detection unit 21 and detects an empty frame.

  24 is a counter that counts the number of empty frames in response to the output of the empty frame detector 23, and 25 is a transferable device that receives the outputs of the packet counter 22 and the empty frame counter 24 to determine the number of transferable packets. It is a packet number judgment part. Reference numeral 26 denotes an insertion packet number fixed value setting unit for setting a fixed value for the number of inserted packets, and 27 denotes an avoidance by selecting an avoidance means in response to outputs from the insertion packet number fixed value setting unit 26 and the transferable packet number determination unit 25. It is a means selection part.

  Reference numeral 27 denotes a receiving unit connected to the avoiding means selecting unit 27, and 28 denotes a transmitting unit connected to the avoiding means selecting unit 27. 28a is a retransmission packet erasure unit for erasing the retransmission packet, 29a is a retransmission packet control stop unit for stopping the control of the retransmission packet, and 29b is a temporary memory initialization unit for initializing the temporary memory 3c. is there. The operation of the circuit thus configured will be described as follows.

  When the packet header is detected by the packet header detector 21, the packet number counter 22 addressed to its own station counts the number of packets. On the other hand, the empty frame detection unit 23 receives the output of the packet header detection unit 21 and detects an empty frame. The empty frame detection unit 23 sends the detection result to the empty frame number counter 24. The empty frame number counter 24 counts the number of empty frames.

  The output of the packet number counter 22 addressed to the own station and the output of the empty frame number counter 24 are sent to the transferable packet number determination unit 25. The transferable packet number determination unit 25 calculates the transferable packet number. On the other hand, the inserted packet number fixed value setting unit outputs the inserted packet number fixed value. The avoidance means selection unit 27 compares the output of the transferable packet number determination unit 25 with the output of the inserted packet number fixed value setting unit 26. According to this embodiment, it is possible to avoid congestion of packets in the transmission path by limiting the number of transmission path released packets addressed to the own station to a certain number or less.

  The output of the avoidance means selection unit 27 is given to the reception unit 28 and the transmission unit 29. In the receiving unit 28, the retransmit packet erasure unit 28a deletes the retransmit packet, in the transmission unit 29, the retransmit packet control stop unit 29a stops the retransmit packet control, and the temporary memory initialization unit 29b stores the temporary memory. Initialize 3c.

  18 and 19 are flowcharts of packet reception processing. As a system, FIGS. 1 and 17 are shown. For example, in the device C that is a receiving device, first, a frame is detected (S1), and then, when a frame is detected, the packet header detector 21 detects a packet header (S2). Next, the packet header detector 21 extracts DA / SE / USE / RV (S3). Next, the packet number counter 22 addressed to the own station checks whether there is a packet addressed to the own station (S4). If not, the received frame is set to packet through (S5). Here, the packet through means that the switch 3a passes through the transmission line 1 as it is.

  If it is determined in step S4 that the packet is addressed to the own station, the device C checks whether or not the reception buffer amount is exceeded (S6). If not, the packet is transferred to the reception buffer 3b (S7). In step S6, if the number of reception buffers is likely to be exceeded, it is checked whether an empty time slot is available (S8). If it is usable, the packet is transferred to the temporary storage memory 3c (S9). Then, an empty time slot is searched (S10), and it is checked whether an empty time slot has been found (S11).

  If an empty time slot cannot be used in step S8, and if an empty time slot cannot be found in step S11, the received packet is discarded (S12). If an empty time slot is found in step S11, a sequential number is added to the packet header (S13), and the sequential number (SQNo.) Is changed to SQNo. = SQNo. Set to +1 (S14). Next, the packet in the temporary memory 3c is retransmitted to an empty time slot on the transmission line 1 (S15).

  Next, it is checked whether or not the reception buffer 3b exceeds the threshold (S16). If it does not exceed the threshold value, a re-send packet reception process is started (S17). If the reception buffer 3b exceeds the threshold value in step S16, the temporary memory initialization unit 29b initializes the temporary memory 3c (S18). Then, the retransmission packet control stop unit 29a stops the control of the retransmission packet (S19).

  FIG. 20 is a diagram illustrating a re-send packet reception process flowchart. First, the packet header detector 21 detects a frame (S1). Next, the packet header is detected (S2). Next, DA / SA / USE / RV is extracted (S3). Next, it is checked whether the received packet is a retransmission packet (S4). If it is not a retransmitted packet, packet through is set (S5).

  In step S4, if the packet is a retransmission packet, the reception buffer 3b checks whether the retransmission packet can be received (S6). If it can be received, the sequential No. Is confirmed to be n (S7), the packet is transferred to the reception buffer 3b (S8), and the previous packets are released as empty slots (S9).

  If it is determined in step S6 that the reception buffer cannot receive the retransmitted packet, it is checked whether the retransmitted packet amount is within the set threshold value set by the inserted packet number fixed value setting unit 26 (S10). If the number of retransmitted packets is within the set threshold range, packet through is set (S11). If it is outside the set threshold value in step S10, the retransmit packet is discarded (S12). According to this embodiment, when the number of empty frames on the transmission path is equal to or less than a certain number, it is possible to limit the number of transmission path release packets of packets addressed to the own station and avoid congestion of the transmission path.

  FIG. 21 is a block diagram showing an embodiment of the present invention. The frame header detection unit 31 detects synchronization from the data received from the transmission path 1, recognizes the head of the frame, and then detects the packet header by the packet header detection unit 32. The SA / DA extraction unit 33a and the USE extraction unit At 33b, the SA / DA destination address and the USE bit indicating whether or not the time slot is used are extracted.

  Based on the contents of SA / DA, it is determined whether the detection unit 34a addressed to the own station is addressed to the own station, and the empty frame detection unit 34b detects the presence / absence of an empty frame. The determination result information is passed to the DROP / INS control unit 35. Based on this information, the DROP / INS control unit 35 performs DROP control if addressed to the own station, and performs through control otherwise. Packets dropped for the local station are buffered in the reception buffer 44 and sent to the Ethernet router or terminal. In the case of the through control, in the case of the DROP control, the packet data detected by the packet header detecting unit 32 enters the through unit 37a through the switch (SW) 36, and passes through the through unit 38c and through the switch (SW) 39 to the packet header. After entering the adding unit 41, the sequence number adding unit 40 adds the sequence number, the frame header adding unit 42 adds the frame header, and the frame header is sent to the transmission line 1 (when it is not addressed to the own station).

  If the received packet is addressed to the own station, the DROP unit 37 b sends the received packet to the switch (SW) 43. The output of the switch 43 is sent to the router 60 via the reception buffer 44. In the reception buffer 44, the buffer monitoring unit 45 monitors the buffer amount, detects the risk of buffer overflow in advance according to the traffic state with the router 60, and transmits the information to the temporary placement determination unit 46. ing.

  When it is diagnosed that there is a risk of overflow, the temporary placement determination unit 46 determines whether or not temporary placement is possible. When the temporary placement determination unit 46 determines that temporary placement is possible from the frame empty information, the temporary placement determination unit 46 performs a write operation to the temporary placement memory 47. Thereafter, the data is read from the temporary memory 47 to the temporary packet insertion unit 38a and inserted at the position of the empty frame. At this time, the sequence number adding unit 40 adds the sequence number to the packet header and sends it out. When temporary packets are inserted continuously for the next packet, the sequence number is counted up.

  If the risk of overflow disappears while the temporary packet circulates in the transmission path, drop control of the temporary packet is started. At this time, the sequence number is monitored and dropped in order of the sequence number to prevent replacement. During the temporary placement control, if the danger of overflow continues and there is no longer an empty frame, no further relief is possible. The storage memory 47 is initialized, and a temporary packet circulating around the transmission path is received and discarded, and released as an empty frame. According to this embodiment, when the number of packets transmitted on the packet transmission path addressed to the local station exceeds the limit value, the reception buffer memory of the local station is initialized and addressed to the local station that circulates on the ring type transmission path. The system can be initialized by deleting the packet.

  If a specific device or port occupies and uses all the empty frames, other devices cannot perform this control. As countermeasures, there are a method of fixing the number of inserted frames in advance and a method of counting the number of empty frames and judging from the empty conditions, and these can be selected. In response to this determination result, the DROP / INS control unit 35 performs packet transmission / reception processing.

  When data is transmitted from the router side to the transmission path side, the data is temporarily stored in the transmission buffer 49 from the router 60, and then read out and entered from the insertion unit 38b into the packet header addition unit 41 via the switch 3a. A sequence number is added from the sequence number adding unit 40 by the header adding unit 41, and a frame header is added by the frame header adding unit 42, and then output to the transmission line side.

  The empty frame counter 50 receives the output of the empty frame detector 34b and counts empty frames. The output of the empty frame counter 50 enters the insertion byte number determination unit 51. In response to the output of the inserted byte count determination unit 51, the no-empty detection unit 53 notifies the temporary memory initialization unit 48 of an initialization signal. The selector 54 receives the outputs of the insertion byte number fixed value setting unit 52 and the insertion byte number determination unit 51, selects one of them, and gives a control signal to the DROP / INS control unit 35 and the temporary placement determination unit 46. The switches 36 and 39 in FIG. 21 correspond to the switch 3a in FIG. 1, the temporary storage memory 47 corresponds to the temporary storage memory 3c in FIG. 1, and the reception buffer 44 corresponds to the reception buffer 3b in FIG.

  As described above in detail, according to the present invention, a packet that should be buffered on the receiving side is sent to the transmission line, and the amount of reception buffer memory is minimized by acting as a virtual memory. Packet communication can be realized at low cost and low power consumption. Also, by controlling only on the receiving side, the burden on the transmitting side is reduced, and timely control is possible by looking at the traffic state with the terminal and router at the connection destination. At the same time, the free channel can be used effectively. This makes it possible to realize a highly reliable ring transmission communication system with low cost, low power consumption, and maximum packet relief, contributing to cost reduction, low power consumption, and high reliability. Can do.

(Supplementary note 1) In a transmission system or apparatus that performs packet communication in a ring configuration and uses continuous frames in a time-sharing manner with a fixed period,
When the buffer on the receiving side has a risk of overflow, the packet addressed to its own station is once released to the transmission path,
A ring-type transmission system configured to start receiving a packet again when it is determined that the risk of overflow has been avoided.

  (Supplementary note 2) The ring-type transmission system according to supplementary note 1, wherein a sequence number is assigned to a transmission path release packet of a packet addressed to the own station, and the packet is received in the order of the sequence number when reception of the packet is started again.

  (Supplementary note 3) When there are no more empty packets on the transmission path, the reception buffer memory of the own station is initialized, and the packet addressed to the own station being released on the transmission path is erased and released as an empty frame. The ring-type transmission system according to appendix 1 or 2, wherein

  (Additional remark 4) As a means to avoid the occupation of the empty frame of a specific station, it has the function to restrict | limit the number of transmission line discharge | release packets of a packet destined for a self-station to below a preset number, It is characterized by the above-mentioned The ring-type transmission system described.

  (Supplementary note 5) As a means of avoiding the occupancy of the empty frame of the specific station, the number of empty frames on the transmission path is constantly monitored. The ring transmission system according to appendix 1 or 2, further comprising a function of restricting

  (Appendix 6) When the number of packets sent to the transmission station exceeds the limit value, the reception buffer memory of the own station is initialized and the packet addressed to the own station being released on the transmission path is deleted. The ring-type transmission system according to appendix 4 or 5, further comprising a function of releasing as an empty frame.

It is a figure which shows the operation state 2 of this invention. It is a figure which shows the operation state 3 of this invention. It is a figure which shows the operation state 3 of this invention. It is a figure which shows the operation state 4 of this invention. It is a figure which shows the operation state 4 of this invention. It is a figure which shows the operation state 5 of this invention. It is a figure which shows the operation state 5 of this invention. It is a figure which shows the operation states 6 and 7 of this invention. It is a figure which shows the operation | movement during frame circulation. It is a figure which shows the example of a flame | frame structure of this invention. It is a figure which shows operation | movement of the states 1 and 2 of this invention. It is a figure which shows operation | movement of the state 3 of this invention. It is a figure which shows operation | movement of the state 4 of this invention. It is explanatory drawing of reception of a packet. It is explanatory drawing of reception of a packet. It is a figure which shows operation | movement when an empty frame is lost on the way. It is a block diagram which shows the structural example of a transmission path avoidance means. It is a figure which shows a packet reception process flowchart. It is a figure which shows a packet reception process flowchart. It is a figure which shows a resending packet reception process flowchart. It is a block diagram which shows one embodiment of this invention. It is a figure which shows the 1st processing method of the conventional overflow countermeasure. It is a figure which shows the 2nd processing method of the conventional overflow countermeasure. It is a figure which shows the example of a conventional basic frame structure.

Explanation of symbols

1 Ring-type transmission line 2 Device A
2a switch 2b memory 3 device C
3a Switch 3b Reception buffer 3c Positional memory 4 Device B
5 Device D
6 port 7 port

Claims (5)

In a transmission system or device that performs packet communication in a ring configuration and uses continuous frames in a time-sharing manner with a fixed period,
When the buffer on the receiving side has a risk of overflow, the packet addressed to its own station is once released to the transmission path,
A ring-type transmission system configured to start receiving a packet again when it is determined that the risk of overflow has been avoided.   2. The ring type transmission system according to claim 1, wherein a sequence number is assigned to a transmission path release packet of a packet addressed to the own station, and the packet is received in the order of the sequence number when reception of the packet is started again.   When there are no more empty packets on the transmission path, the reception buffer memory of the own station is initialized, and the packet addressed to the own station being released on the transmission path is erased and released as an empty frame. The ring-type transmission system according to claim 1 or 2.   3. The ring according to claim 1, further comprising a function for limiting the number of packets transmitted to the local station to a predetermined number or less as a means for avoiding occupancy of an empty frame of a specific station. Type transmission system.   Function to constantly monitor the number of empty frames on the transmission path as a means to avoid occupying empty frames of a specific station, and to limit the number of packets sent to the local station when the number of empty frames is less than a certain number The ring-type transmission system according to claim 1 or 2, further comprising:

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