JP3997771B2 - Data transfer method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a data transfer method that can prevent packet loss.
[0002]
[Prior art]
The router station defines a packet passage route in the communication network. Then, the packet is transferred to the next router station according to the passage route. The packet is transferred to the terminal in the target communication network via each router station. Hereinafter, when a packet is exchanged, the one sending out the packet is referred to as “subordinate”. The person who receives the packet is referred to as “upper”.
[0003]
A plurality of slave stations are arranged between the lower router station (lower router station) and the upper router station (upper router station). A slave station is a device that transmits, receives, and relays information. The passage path of the slave station from the lower router station to the upper router station is not limited to one. When there are a plurality of passage routes, the lower router station transfers the packet according to the passage route determined from among the passage routes.
[0004]
Each slave station relays a packet transferred from the lower router station to the upper router station. Each slave station transmits not only the relay of the packet from the lower router station but also the packet of the own station (the packet from which the slave station itself is the transmission source) to the upper router station. Packet transmission from each slave station to the upper router station is performed by polling. When the upper router station receives a packet from each of the slave stations, the upper router station, as a lower router station, transfers the packet further upward.
[0005]
Each router station includes a data storage buffer, and accumulates collected packets in the data storage buffer. Then, the packet in the data storage buffer is transferred to the upper level.
[0006]
[Problems to be solved by the invention]
However, if the amount of packets transmitted from the slave station to the router station is large, the amount of packets to be stored in the router station may exceed the capacity of the data storage buffer. In this case, packets that have not been stored in the data storage buffer are lost. When the amount of packets to be stored in this way exceeds the capacity of the data storage buffer, this is called overflow.
[0007]
An object of the present invention is to provide a data transfer method that can prevent packet loss due to overflow even if the number of packets sent to a router station increases.
[0008]
[Means for Solving the Problems]
The data transfer method according to the present invention is a router station that transmits and receives packets by polling, and a device that is connected to two devices and transmits a packet received from one device to the other device, and relays packets between the router stations. A data transfer method in which a slave station that is a device is a node, and each node receives a received packet Packets sent to the next node Is stored in advance, and a table indicating the correspondence between the average increase amount per unit time of packets stored in the buffer and the average packet amount reached per unit time is held in advance, and the average packet reaching per unit time The average increase amount of packets in the buffer according to the amount is obtained, the time from the average increase amount and the buffer free space until the buffer free space is exhausted is obtained, and whether or not the buffer free space is consumed within the predetermined time. And a buffer monitoring means for determining whether or not an instruction means for transmitting a packet transmission stop command for stopping packet transmission to an adjacent node to receive a packet when it is determined that the free capacity of the buffer will be exhausted within a predetermined time. When a packet transmission stop command is received from the adjacent node that should transmit the packet, the packet transmission to the adjacent node is performed. Characterized by comprising a transmission control means for stopping.
[0009]
The buffer monitoring means of each node monitors the free capacity of the buffer, and the instruction means of each node, when the free capacity of the buffer increases to a predetermined amount or more, to the adjacent node that should receive the packet, A packet transmission resumption command for resuming packet transmission is transmitted, and the transmission control means of each node resumes packet transmission to the adjacent node when receiving a packet transmission resumption command from the adjacent node that should transmit the packet. According to such a configuration, when the number of packets accumulated in the buffer decreases, packet relay can be resumed.
[0010]
When each node receives a packet transmission stop command from an adjacent node that should transmit a packet, each node accumulates the packet to be transmitted to the adjacent node in a buffer.
[0011]
The data transfer method according to the present invention includes an upper router station that receives a packet and a lower router station that transmits the packet to the upper router station, and is connected to two devices and receives a packet received from one device on the other. This is a data transfer method that includes multiple slave stations that are devices that transmit packets to the device and relay packets between the upper router station and the lower router station. A router station that transmits and receives packets. Packets sent to the next node And a table indicating the correspondence between the average amount of increase of packets stored in the buffer per unit time and the average amount of packets reached per unit time, and the average packet reaching per unit time The average increase amount of packets in the buffer according to the amount is obtained, the time from the average increase amount and the buffer free space until the buffer free space is exhausted is obtained, and the free space in which the received packet is to be stored is a predetermined time. If it is determined that the packet will not be received within, send an instruction to stop the packet transmission to the neighboring slave stations that should receive the packet, and each slave station will send a packet to the higher router station in accordance with the instruction from the higher router station. Among the slave stations, the adjacent slave station on the passing path located on the packet passing path from the lower router station to the upper router station receives the received packet. Packets sent to the next node And a table indicating the correspondence between the average amount of increase of packets stored in the buffer per unit time and the average amount of packets reached per unit time, and the average packet reaching per unit time The average increase amount of packets in the buffer according to the amount is obtained, the time from the average increase amount and the buffer free space until the buffer free space is exhausted is obtained, and the free space in which the received packet is to be stored is a predetermined time. If it is determined that the packet passing route will be lost, the lower router station is instructed to change the packet passage route. The lower router station changes the packet passage route to the upper router station according to the instruction, and the changed packet Each child station is notified of the passage route, and each child station relays the packet according to the notified packet passage route.
[0012]
Each slave station instructed to stop packet transmission from the upper router station accumulates packets to be transmitted to the upper router station.
[0013]
The lower router station relays the packets stored in the child stations other than the adjacent child station on the passing path among the slave stations located on the packet passing path before the change to the upper router station via the lower router station. The packet passage route is changed as follows.
[0014]
In addition, when the free space increases and exceeds a predetermined amount, the upper router station instructs each of the adjacent slave stations that should receive the packet to resume transmission of the packet. The packet transmission to the upper router station is resumed in response to the instruction, and the adjacent slave station on the passage route instructs the lower router station to restore the packet passage route, and the lower router station responds to the instruction. Then, the packet passage route to the upper router station is returned to the original state, the restored packet passage route is notified to each slave station, and each slave station relays the packet according to the notified packet passage route. According to such a configuration, when the number of accumulated packets decreases, packet relay can be resumed.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is an explanatory diagram showing an example of a communication network to which the present invention is applied. A plurality of slave stations 10a to 10d are arranged between the router stations 1a and 1b. Hereinafter, a case where the router station 1b is a subordinate of the router station 1a and a packet is transmitted from the router station 1b to the router station 1a will be described as an example. The router stations 1a and 1b, the slave stations 10a to 10d, and the upper station (the upper station than the upper router station 1a) 20 are nodes on the communication network.
[0016]
Each router station 1a, 1b holds a routing table. The routing table is information representing a passage route when transferring collected packets. In the routing table, the packet passage route is determined according to the destination address of the packet. In the routing table of the lower router station 1b, a passage route from the lower router station 1b to the upper router station 1a is determined for a packet whose destination is higher than the upper router station 1a.
[0017]
In the example shown in FIG. 1, there are a route passing through the slave station 10 b and the slave station 10 a and a route passing through the slave station 10 d and the slave station 10 c as a passing route from the lower router station 1 b to the higher router station 1 a. In the routing table of the lower router station 1b, it is assumed that a route passing through the slave station 10b and the slave station 10a is defined as a passing route to the higher router station 1a.
[0018]
When there is a packet destined for the upper station 20, the lower router station 1b determines to transmit to the upper router station 1a via the slave station 10b and the slave station 10a. Then, the lower router station 1b transmits this packet to the child station 10b. Packet exchange is performed by polling. Polling is a communication method in which an information transmitting station receives an inquiry about the presence or absence of information from an information receiving station, and transmits information to the information receiving station if information is present when the inquiry is received. That is, the lower router station 1b receives an inquiry about the presence or absence of a packet from the slave station 10b, and if there is a packet to be transmitted to the slave station 10b, transmits the packet to the slave station 10b.
[0019]
Similarly, the slave station 10b transmits the packet received from the lower router station 1b to the slave station 10a by polling. The slave station 10b transmits not only the packet received from the lower router station 10b but also the packet that is transmitted from the slave station 10b itself to the slave station 10a. The slave station 10a transmits the packet received from the slave station 10b to the upper router station 1a by polling. The slave station 10a transmits not only the packet received from the slave station 10b but also the packet that is transmitted from the slave station 10a itself to the upper router station 1a.
[0020]
The slave station 10d transmits a packet, which is transmitted from the slave station 10d itself, to the slave station 10c by polling. The slave station 10c transmits the packet received from the slave station 10d and the packet that is the transmission source of the slave station 10c itself to the upper router station 1a by polling.
[0021]
The upper router station 1a has address information of the adjacent slave stations 10a and 10c. The upper router station 1a sequentially inquires the adjacent slave stations 10a and 10c about the presence or absence of a packet, and collects information from the slave stations 10a and 10c. In this way, the upper router station 1a collects packets transferred from the lower router station 1b and packets that are transmitted from each of the slave stations 10a to 10d. Then, the upper router station 1a transmits the collected packets to the upper station 20 by polling.
[0022]
Here, the flow when the upper router station 1a collects packets from the lower router station 1b and the slave stations 10a to 10d and transmits them to the upper station 20 has been described. When the upper router station 1a transmits a packet to an upper router station, the upper router station 1a performs the same operation as the above-described lower router station 1b. When the lower router station 1b shown in FIG. 1 collects information from a lower router station, the same operation as that of the upper router station 1a is performed. As a result, the packet is relayed between the router stations and transmitted to the destination node.
[0023]
Each of the router stations 1a and 1b and each of the slave stations 10a to 10d includes a data storage buffer. The data storage buffer is a storage area for storing packets collected from lower nodes. The upper router station 1a accumulates the packets collected from the lower child stations 10a and 10c in the data storage buffer, and transmits the packets to the upper station 20 by polling. If there are more packets collected by the upper router station 1a than packets transmitted by the upper router station 1a to the upper station 20, the free capacity of the data storage buffer decreases. When the upper router station 1a determines that there is no more free space in the data storage buffer within a predetermined time, the upper router station 1a transmits a packet transmission stop command to each of the adjacent slave stations 10a and 10c that should receive the packet. . After receiving the packet transmission stop command, each of the slave stations 10a and 10c does not transmit a packet even when there is an inquiry about the presence or absence of a packet.
[0024]
When each slave station 10a, 10c stops packet transmission to the upper router station 1a, packets are accumulated in the data storage buffer of each slave station 10a, 10c. If the slave stations 10a and 10c determine that there is no free space in the data storage buffer within a predetermined time, the slave stations 10a and 10c transmit a packet transmission stop command to the slave stations 10b and 10d, respectively. The slave stations 10b and 10d that have received the packet transmission stop command operate in the same manner as the slave stations 10a and 10c.
[0025]
On the other hand, since the upper router station 1a transmits packets to the upper station 20, the number of packets stored in the data storage buffer decreases. When the free capacity of the data storage buffer exceeds a predetermined amount, the upper router station 1a transmits a packet transmission restart command to the adjacent slave stations 10a and 10c. When each of the slave stations 10a and 10c receives the packet transmission restart command, it restarts packet transmission to the upper router station 1a. The slave stations 10a and 10c also transmit a packet transmission restart command to the slave stations 10b and 10d, respectively, when the free capacity of the data storage buffer exceeds a predetermined amount. The slave stations 10b and 10d that have received the packet transmission restart command operate in the same manner as the slave stations 10a and 10c.
[0026]
In each slave station, if the upper line speed and the lower line speed are equal, overflow will not approach until a packet transmission stop command is received from the upper station. For example, if the line speeds of the slave station 10b and the lower router station 1b are equal to the line speeds of the slave station 10b and the slave station 10a, the slave station 10b overflows until a packet transmission stop command is received from the slave station 10a. Never approach.
[0027]
Next, the configuration of each router station and each slave station that performs communication by polling will be described. FIG. 2 is a block diagram showing an example of the configuration of each router station and each slave station. The transmission / reception unit 31 performs packet transmission / reception processing with another node (slave station or router station) to be connected in accordance with the subordinate correspondence unit 32 and the higher level correspondence unit 33. The interface units 35a and 35b are communication interfaces with an upper node and a lower node, respectively.
[0028]
The transmission / reception unit 31 receives an inquiry about the presence / absence of a packet or receives a packet transmission stop command or a packet transmission restart command from an upper node through the interface unit 35a. Also, the packet is transmitted to the upper node.
[0029]
Further, the transmission / reception unit 31 inquires about the presence / absence of a packet or transmits a packet transmission stop command or a packet transmission restart command to a lower node via the interface unit 35b. A packet is received from a lower node.
[0030]
The data storage buffer 34 is a storage area for accumulating packets collected by the transmission / reception unit 31. The transmission / reception unit 31 accumulates the collected packets in the data storage buffer 34, and transmits the accumulated packets to the host.
[0031]
When the subordinate correspondence unit 32 collects packets by polling, the subordinate correspondence unit 32 holds the address of a lower node to be inquired about the presence or absence of the packet. Then, the transmission / reception unit 31 collects packets from lower nodes.
[0032]
Further, the subordinate handling unit 32 monitors the free capacity of the data storage buffer 34 and the average amount of packets that arrive per unit time. Then, based on the free capacity and the average amount of packets reached per unit time, it is determined whether or not there is no free capacity in the data storage buffer 34 within a predetermined time.
[0033]
The average increase amount of packets accumulated in the data storage buffer 34 per unit time varies depending on the average amount of packets that arrive per unit time. The subordinate correspondence unit 32 holds a table indicating the correspondence between the two in advance, and obtains an average increase amount of packets in the data storage buffer 34 according to the average packet amount that arrives per unit time. The subordinate handling unit 32 obtains the time until the free space is exhausted from the average increase amount and the free space, and determines whether the free space is exhausted within a predetermined time based on the time. If the subordinate handling unit 32 determines that there is no free space within a predetermined time, the subordinate handling unit 32 causes the transmission / reception unit 31 to transmit a packet transmission stop command to a lower node.
[0034]
Thereafter, when the accumulated packets decrease and the free capacity of the data storage buffer 34 exceeds a predetermined amount, the transmission / reception unit 31 transmits a packet transmission restart command to a lower node.
[0035]
When the transmission / reception unit 31 receives an inquiry about the presence / absence of a packet from an upper node, the upper correspondence unit 33 causes the transmission / reception unit 31 to transmit the packet stored in the data storage buffer 34. However, if the packet is not accumulated, the packet is not transmitted.
[0036]
In addition, when the transmission / reception unit 31 receives a packet transmission stop command or a packet transmission restart command from a higher-level node that should transmit a packet, the transmission / reception unit 31 notifies the higher-level correspondence unit 33 of the command. After receiving the packet transmission stop command, the upper correspondence unit 33 does not cause the transmission / reception unit 31 to transmit the packet. Thereafter, when a packet transmission restart command is received, the transmission / reception unit 31 restarts packet transmission.
[0037]
In the above example, the buffer monitoring means is realized by the subordinate correspondence unit 32. The instruction means is realized by the subordinate correspondence unit 32 and the transmission / reception unit 31. The transmission control means is realized by the upper correspondence unit 33 and the transmission / reception unit 31.
[0038]
Next, an example of processing progress of the transmission / reception unit 31 when transmitting / receiving a packet will be described. Here, the transmission / reception unit 31 of the upper router station 1a will be described as an example.
[0039]
When the transmission / reception unit 31 of the upper router station 1a receives an inquiry about the presence or absence of a packet from the upper station 20, the transmission / reception unit 31 notifies the upper corresponding unit 33 to that effect. The upper correspondence unit 33 checks whether or not the packets to be transmitted to the upper station 20 are accumulated in the data storage buffer 34. If the packet is stored, the transmission / reception unit 31 is instructed to transmit the packet to the upper station 20. The transmission / reception unit 13 transmits the packet to the upper station 20 in accordance with this instruction.
[0040]
The transmission / reception unit 31 of the upper router station 1a sequentially inquires the slave stations 10a and 10c about the presence / absence of a packet in accordance with the subordinate correspondence unit 32. Addresses of the slave stations 10a and 10c necessary for the inquiry are given from the subordinate correspondence unit 32.
[0041]
In response to this inquiry, each of the slave stations 10a and 10c transmits the packet if it has been accumulated. The operation of the transmitting / receiving unit 31 of the slave station at this time is the same as the operation when the transmitting / receiving unit 31 of the upper router station 1a transmits a packet to the upper station 20. The transmission / reception unit 31 of the upper router station 1a receives packets from the slave stations 10a and 10c and stores the packets in the data storage buffer 34.
[0042]
In the upper router station 1a, if there are more packets collected from the slave stations 10a and 10c than packets transmitted to the upper station 20, the free capacity of the data storage buffer 34 decreases. The subordinate correspondence unit 32 monitors the free capacity of the data storage buffer 34 and the average amount of packets that arrive per unit time, and calculates the time until the free capacity is exhausted based on the free capacity and the average amount of packets that are reached. . If this time is within a predetermined time, the subordinate handling unit 32 causes the transmission / reception unit 31 to transmit a packet transmission stop command. The transmission / reception unit 31 transmits a packet transmission stop command to the subordinate slave stations 10a and 10c according to the subordinate handling unit 32.
[0043]
When receiving the packet transmission stop command from the upper router station 1a, the transmission / reception unit 31 of the slave stations 10a and 10c notifies the upper response unit 33 of the packet transmission stop command. Thereafter, the upper correspondence section 33 of the slave stations 10a and 10c does not cause the transmission / reception section 31 to transmit the packet even if the packet is accumulated. Therefore, the transmission / reception unit 31 stops packet transmission to the upper router station 1a. Then, the number of packets in the data storage buffer 32 of the slave stations 10a and 10c increases, and the free capacity decreases. The subordinate correspondence unit 32 of the slave stations 10a and 10c calculates the time until there is no more free space in the same way as the subordinate correspondence unit 32 of the upper router station 1a. The station 10b, 10d) is caused to transmit a packet transmission stop command.
[0044]
Since the upper router station 1a stops packet transmission from the slave stations 10a and 10c, the free capacity of the data storage buffer 34 increases as packets are transmitted to the upper station 20. The subordinate handling unit 34 monitors the free capacity of the data storage buffer, and when the free capacity exceeds a predetermined amount, causes the transmission / reception unit 31 to transmit a packet transmission restart command. The transmission / reception unit 31 transmits a packet transmission resume command to the subordinate slave stations 10a and 10c according to the subordinate handling unit 32.
[0045]
When receiving the packet transmission restart command from the upper router station 1a, the transmission / reception unit 31 of the slave stations 10a and 10c notifies the upper response unit 33 of the packet transmission restart command. The upper correspondence unit 33 of the slave stations 10a and 10c causes the transmission / reception unit 31 to resume packet transmission. That is, if a packet is stored when an inquiry about the presence or absence of a packet is received, the packet is transmitted to the transmission / reception unit 31. As a result, the free capacity of the data storage buffer 34 of the slave stations 10a and 10c increases. The subordinate handling unit 34 monitors the free capacity of the data storage buffer, and causes the transmission / reception unit 31 to transmit a transmission restart command when the free capacity exceeds a predetermined amount. The transmission / reception unit 31 of the slave stations 10a and 10c transmits a packet transmission restart command to the slave stations 10b and 10d, respectively, according to the subordinate handling unit 32. The operations of the slave stations 10b and 10d that have received the packet transmission restart command are the same as those of the slave stations 10a and 10d.
[0046]
As described above, in the present invention, when it is determined that the free capacity of the data storage buffer 34 of the upper router station 1a will disappear within a predetermined time, the upper router station 1a issues a packet transmission stop command to the slave stations 10a and 10c, Prevent overflow. If each of the slave stations 10a to 10d is determined that the free capacity of the data storage buffer 34 will be exhausted within a predetermined time, the slave station 10a to 10d issues a packet transmission stop command to a lower level to prevent overflow. Therefore, no packet loss occurs.
[0047]
Next, another embodiment of the present invention will be described.
The configuration and operation of the router station in this example are the same as those described above. However, each slave station does not transmit a packet transmission stop instruction to the lower level, but instead changes the packet path from the lower level router station to the higher level router station.
[0048]
It is assumed that this example is applied to the communication network shown in FIG. Further, it is assumed that the lower router station 1b defines a route passing through the slave station 10b and the slave station 10a as a passing route to the higher router station 1a.
[0049]
Each of the slave stations 10a to 10d has the same configuration as that shown in FIG. However, the subordinate handling unit 32 does not cause the transmission / reception unit 31 to transmit the packet transmission stop command and the packet transmission restart command.
[0050]
If the upper router station 1a determines that there is no more free space in the data storage buffer 34 within a predetermined time, it sends a packet transmission stop command to the subordinate slave stations 10a and 10c.
[0051]
Since the slave station 10a is a packet passage path from the lower router station 1b to the higher router station 1a, the free space of the data storage buffer 34 tends to disappear before the slave station 10c. When the slave station 10a determines that there is no more free space in the data storage buffer 34 within a predetermined time, the slave station 10a transmits a path change command to the lower router station 1b. As described above, of the adjacent slave stations 10a and 10c from which the upper router station 1a should receive a packet, the slave station on the passage route from the lower router station 1b to the upper router station 1a (adjacent child station on the passage route). 10a transmits a route change command. The slave station 10a transmits a route change command to the lower router station 1b via the slave station 10b.
[0052]
The lower router station 1b that has received the route change command changes the passage route to the upper router station 1a to a route that passes through the slave station 10d and the slave station 10c. Also, the lower router station 1b receives from the slave station 10b the packets stored in the slave station 10b (the slave stations other than the adjacent slave stations on the pass path among the slave stations located on the packet pass path before the change). The route is changed so that the lower router station 1b, the slave station 10d, and the slave station 10c are transmitted to the upper router station 1a through a passing route.
[0053]
The lower router station 1b notifies each of the slave stations 10a to 10d of the changed passage route. Each of the slave stations 10b, 10c, 10d and the lower router station 1b transmits a packet according to the changed passage route. That is, the slave station 10b transmits a packet to the router station 1b by polling. The lower router station 1b transmits the packets collected from the child station 10b and the packets collected from the lower child station (not shown) to the child station 10d by polling. The slave station 10d transmits the packets collected from the lower router station 1b to the slave station 10c by polling.
[0054]
As a result of the change of the passage route, the packet accumulated in the slave station 10b returns to the lower router station 1b again and is transferred to the slave station 10c via the slave station 10d.
[0055]
During this time, since the upper router station 1a does not collect packets from the slave stations 10a and 10c, the free capacity of the data storage buffer 34 increases. Then, the upper router station 1a transmits a packet transmission restart command to the subordinate slave stations 10a and 10c. The slave station 10a that has received the packet transmission restart command transmits the stored packet to the upper router station 1a. The slave station 10c transmits the packet transferred from the slave station 10b or the lower router station 1b to the slave station 10a.
[0056]
Further, after receiving the packet transmission restart command, the slave station 10a transmits a command for returning the passage route to the lower router station 1b. The slave station 10a transmits this command to the lower router station 1b via the slave station 10b. In response to this command, the lower router station 1b notifies each child station 10a to 10d of the passage route before the change. Then, the slave stations 10a and 10b relay the packet through the original route.
[0057]
In the slave station 10a of this example (among the slave stations adjacent to the upper router station 1a, the slave station on the path from the lower router station 1b to the upper router station 1a), the subordinate correspondence unit 32 receives the data within a predetermined time. When it is determined that there is no free space in the storage buffer 34, the transmission / reception unit 31 is caused to transmit a path change command. The transmission / reception unit 31 transmits a path change command to the lower router station 1b according to the subordinate handling unit 32.
[0058]
Further, the subordinate handling unit 32 of the slave station 10a causes the transmission / reception unit 31 to transmit a command for returning the passage route when the slave station 10a receives a packet transmission restart command from the upper router station 1a. The transmission / reception unit 31 transmits an instruction to return the passage route to the lower router station 1b according to the subordinate correspondence unit 32.
[0059]
In the slave station 10b of this example, when the transmission / reception unit 31 is notified of the changed passage route from the lower router station 1b, the transmission / reception unit 31 notifies the upper correspondence unit 33 of information on the passage route. The upper correspondence unit 33 causes the transmission / reception unit 31 to transmit a packet according to the changed passage route. That is, when there is an inquiry about the presence or absence of a packet from the lower router station 1b, the lower router station 1b is caused to transmit a packet.
[0060]
The subordinate correspondence unit 32 of the lower router station 1b also causes the transmission / reception unit 31 to collect packets according to the changed passage route after the passage route is changed. That is, the transmission / reception unit 31 collects packets from the slave station 10b.
[0061]
In this example, when it is determined that the free capacity of the data storage buffer 34 of the upper router station 1a will disappear within a predetermined time, the upper router station 1a issues a packet transmission stop command to the slave stations 10a and 10c to prevent overflow. . Further, when it is determined that the free space in the data storage buffer 34 will be exhausted within a predetermined time, the slave station 10a changes the passage route to the upper router station 1a and transfers the packet of the slave station 10b to the lower router station 1b. Let me return. During this time, the free capacity of the data storage buffer 34 of the upper router station 1a increases. Therefore, packet loss due to overflow can be reduced.
[0062]
The communication network to which the present invention is applied is not limited to that shown in FIG. For example, FIG. 1 shows a communication network having two types of passage paths as a passage route from the lower router station 1b to the upper router station 1a. However, a communication network having three or more types of passage paths may be used. Further, instead of the slave stations 10a to 10d, other router stations may be arranged, and other slave stations may be connected to the lower level of the router station.
[0063]
【The invention's effect】
According to the present invention, each node has a buffer for storing received packets; A table showing the correspondence between the average amount of packets accumulated in the buffer per unit time and the average packet amount that arrives per unit time is stored in advance, and the buffer is stored according to the average packet amount that reaches per unit time The average increase amount of the packet is calculated, and the time until the buffer free space runs out from the average increase amount and the buffer free space is determined, Packet monitoring means for determining whether or not the buffer free space will be consumed within a predetermined time, and when it is determined that the buffer free space will be exhausted within the predetermined time, packet transmission to the adjacent node that should receive the packet And a transmission control means for stopping packet transmission to an adjacent node when a packet transmission stop command is received from an adjacent node to which the packet is to be transmitted. Therefore, packet loss due to overflow can be prevented.
[0064]
Further, according to the present invention, the upper router station Holds a buffer that stores received packets, and a table that shows the correspondence between the average amount of packets accumulated in the buffer per unit time and the average amount of packets that arrive per unit time. Obtain the average increase amount of packets in the buffer according to the average packet amount to be obtained, obtain the time until the buffer free space runs out from the average increase amount and the buffer free space, When it is determined that there is no more free space in which to store the received packet within a predetermined time, the next slave station that should receive the packet is instructed to stop packet transmission. In response to the instruction, the packet transmission to the upper router station is stopped, and among the slave stations, the neighboring slave station on the passage route located on the packet passage route from the lower router station to the upper router station is Holds a buffer that stores received packets, and a table that shows the correspondence between the average amount of packets accumulated in the buffer per unit time and the average amount of packets that arrive per unit time. Obtain the average increase amount of packets in the buffer according to the average packet amount to be obtained, obtain the time until the buffer free space runs out from the average increase amount and the buffer free space, When it is determined that there is no more free space to store received packets within a predetermined time, the lower router station is instructed to change the packet passage route, and the lower router station responds to the upper router station according to the instruction. The packet passing route is changed, the changed packet passing route is notified to each slave station, and each slave station relays the packet according to the notified packet passing route, so that packet loss due to overflow can be reduced.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram showing an example of a communication network to which the present invention is applied.
FIG. 2 is a block diagram illustrating an example of the configuration of a router station and a slave station.
[Explanation of symbols]
1a, 1b Router station
10a to 10d Slave station
31 Transceiver
32 Subordinate department
33 High-order correspondence part
34 Data storage buffer
35a, 35b interface section

Claims (7)

A router station that transmits and receives packets by polling and a slave station that is connected to two devices and that transmits packets received from one device to the other device and relays packets between router stations The data transfer method
Each node has a buffer that accumulates received packets that are sent to neighboring nodes ;
A table showing the correspondence between the average amount of packets accumulated in the buffer per unit time and the average packet amount that arrives per unit time is stored in advance, and the buffer is stored according to the average packet amount that reaches per unit time Buffer monitoring for determining the average increase amount of packets, determining the time from the average increase amount and the buffer free capacity until the buffer free capacity is exhausted, and determining whether the buffer free capacity is exhausted within a predetermined time Means,
Instructing means for transmitting a packet transmission stop command for stopping packet transmission to an adjacent node to receive a packet when it is determined that the free space of the buffer will disappear within a predetermined time;
A data transfer system comprising: a transmission control unit that stops packet transmission to the adjacent node when a packet transmission stop command is received from the adjacent node to which the packet is to be transmitted. The buffer monitoring means of each node monitors the free capacity of the buffer,
The instruction means of each node transmits a packet transmission restart command for resuming packet transmission to an adjacent node that should receive a packet when the free space of the buffer increases to a predetermined amount or more,
The data transfer method according to claim 1, wherein the transmission control means of each node restarts packet transmission to the adjacent node when receiving a packet transmission restart command from the adjacent node to which the packet is to be transmitted.   3. The data transfer method according to claim 1, wherein each node stores a packet to be transmitted to the adjacent node in a buffer when receiving a packet transmission stop command from the adjacent node to transmit the packet. . A higher-level router that has a higher-level router station that receives packets and a lower-level router station that transmits packets to the higher-level router station, and that is connected to two devices and transmits packets received from one device to the other device. A data transfer method comprising a plurality of slave stations that are devices that relay packets between a station and a lower router station,
The upper router station and the lower router station are router stations that transmit and receive packets by polling.
The upper router station includes a buffer that stores received packets that are transmitted to the adjacent node, an average increase amount per unit time of packets stored in the buffer, and an average packet amount that arrives per unit time. And a table indicating the correspondence relationship between the buffer, the average increase amount of packets in the buffer corresponding to the average packet amount that arrives per unit time is obtained, and the buffer free capacity is determined from the average increase amount and the buffer free capacity. Find the time until it runs out, and when it is determined that there is no free space in which to store the received packet within a predetermined time, instruct each neighboring slave station to receive the packet to stop sending the packet,
Each of the slave stations stops packet transmission to the upper router station according to the instruction of the upper router station,
Among the slave stations, the neighboring slave station on the passage route located on the packet passage route from the lower router station to the upper router station includes a buffer that stores received packets that are transmitted to the adjacent nodes. Holds a table indicating the correspondence between the average increase amount of packets accumulated in the buffer per unit time and the average packet amount reached per unit time, and a buffer corresponding to the average packet amount reaching per unit time The average increase amount of packets in the packet is obtained, the time until the buffer free space is exhausted from the average increase amount and the buffer free space is obtained, and it is determined that there is no free space to store the received packet within the predetermined time. The lower router station is instructed to change the packet passing path,
The lower router station changes the packet passage route to the upper router station according to the instruction, and notifies each child station of the changed packet passage route,
A data transfer method in which each slave station relays a packet according to a notified packet passage route.   5. The data transfer system according to claim 4, wherein each slave station instructed to stop packet transmission from the upper router station accumulates packets to be transmitted to the upper router station.   The lower router station relays the packets stored in the child stations other than the adjacent child station on the passing path among the slave stations located on the packet passing path before the change to the upper router station via the lower router station. The data transfer method according to claim 4 or 5, wherein the packet passage route is changed as described above. When the free space increases and exceeds a predetermined amount, the upper router station instructs each adjacent slave station that should receive the packet to resume packet transmission,
Each of the slave stations resumes packet transmission to the upper router station according to the instruction of the upper router station,
The adjacent slave station on the passing route instructs the lower router station to restore the packet passing route,
The lower router station returns the packet passage route to the upper router station according to the instruction, notifies the child passage of the restored packet passage route,
The data transfer method according to any one of claims 4 to 6, wherein each slave station relays a packet according to the notified packet passage route.

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