JP2000261452A - Network system and terminal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively reduce the number of average transmission waiting nodes on the occurrence of collision of packets in a network system. SOLUTION: On the occurrence of 2-body collision between a terminal 1 and other terminal 2, a 2-body collision detection means 1a detects it and a priority information extract means 1b extracts priority information inserted to a packet sent from the other terminal, compares the extracted priority information with priority information that is inserted to a packet that is going to be transmitted by the terminal 1, and a 1st transmission means 1c starts transmitting the packet when the priority of its own packet is higher. On the other hand, when the priority of its own packet is lower, the other terminal starts transmission. When a transmission operation end detection means 1d detects the end of transmission of the other terminal, a 2nd transmission means 1e starts transmission of a packet.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a network system and a terminal device, and more particularly, to a network system in which a plurality of terminal devices are connected to a broadcast network and a network connected to the broadcast network. The present invention relates to a terminal device constituting a system.

[0002]

2. Description of the Related Art Generally, a LAN (Local Area Network)
In, a plurality of nodes are connected to a bus, and communication between the nodes is performed via the bus. One of the buses used in such a LAN is a broadcast bus.

[0003] A broadcast bus is a bus from which a signal transmitted from a certain node can be received by all other nodes.
As a LAN using this broadcast bus, Ethernet (registered trademark) is known, and a communication protocol is CSMA / CD (Carrier).
Sense Multiple Access / Collision Detection), which is standardized as IEEE802.3.

At present, there are many derivatives of Ethernet, but basic Ethernet uses a coaxial cable as a transmission medium. When a predetermined node transmits a packet when such a coaxial cable is used as a transmission medium, first, a signal state on the coaxial cable is checked to determine whether another node is transmitting a packet. I do.
Then, when another node is not transmitting the packet, the transmission of the packet is started. If another node is transmitting a packet, the node waits for a predetermined period determined by a random number, and then checks the state of the coaxial cable again and attempts retransmission.

However, when a plurality of nodes start sending at the same time, packets on the transmission medium may interfere with each other and normal communication may not be performed. Such a situation is called packet collision.

In Ethernet, the occurrence of a collision can be detected based on the voltage level of the coaxial cable, and when the collision is detected, the node immediately stops transmitting, and
Wait for a period determined by a random number.

Therefore, the CSMA / CD system can perform communication with high efficiency when the communication amount is small, but when the communication amount increases and the frequency of collisions increases, the CSMA / CD system may wait for a time determined by a random number. It is known that the efficiency becomes extremely poor.

In a LAN using a coaxial cable represented by Ethernet, nodes can be easily added by tapping. However, when an optical fiber is used as a transmission medium, it is difficult to add nodes by tapping. Have difficulty.

However, according to the method disclosed in Japanese Patent Application Laid-Open No. 5-252170, nodes can be easily added using an optical fiber as a transmission medium. This is a network system in which the transmission and reception of each node are divided into separate terminals, and all nodes are connected by a star coupler.The transmitted signal is not returned to the reception port of the own node. It is characterized in that it can receive a signal transmitted by another node while transmitting a signal.

[0010] Japanese Patent Application Laid-Open No. 5-25170 discloses that
A communication system using this feature has been proposed. In this method, an identifier indicating a priority is provided in a packet structure, and when two packets collide, the right to use the bus is determined according to the priority identifier.

[0011]

Here, assuming that the frequency of occurrence of packet collision follows the Poisson distribution, the frequency of occurrence of collision increases exponentially with an increase in the number of nodes waiting for packet transmission. Therefore, it is necessary to reduce the number of transmission waiting nodes as much as possible.

For example, CSM used in Ethernet
In the A / CD system, when a collision of a packet is detected, all the nodes that have transmitted the packet suspend the transmission,
It enters a retransmission waiting state (a waiting state for a random period). That is, the number of nodes in the retransmission waiting state does not change in the entire network.

On the other hand, in the method disclosed in Japanese Patent Application Laid-Open No. 5-252170, a node which cannot obtain the right to use the bus in the priority comparison at the time of a collision between two bodies waits for retransmission similarly to the CSMA / CD system. State (standby state for a random period). Therefore, the number of nodes waiting for retransmission of the entire network is reduced by only one.

In the above-mentioned method, the priority of transmission cannot be determined according to the importance of a packet to be transmitted, so that a bus with a limited transmission band is effectively used. There was also a problem that it was difficult.

The present invention has been made in view of such a point, and an object of the present invention is to improve the network transfer efficiency by reducing the number of nodes waiting for retransmission.

Another object of the present invention is to provide a network that can change the priority of packet transmission according to the importance.

[0017]

According to the present invention, in order to solve the above-mentioned problems, in a network system in which a plurality of terminal devices are connected to a broadcast network having bidirectionality, each terminal device comprises: A two-body collision detecting means for detecting a two-body collision caused by another terminal device starting transmission of a packet while transmitting a packet by itself; and the occurrence of a two-body collision is detected by the two-body collision detecting means. In this case, priority information extracting means for extracting priority information indicating the priority of the packet, which is inserted into the packet transmitted from the other terminal device, and the priority information extracting means When the priority information obtained is compared with the priority information of the own packet, if the priority of the own packet is high, the first transmission for executing the transmission of the own packet again is performed. Means, when comparing the priority information extracted by the priority information extracting means with the priority information of the own packet, if the priority of the own packet is low, the information flowing on the network By monitoring the transmission operation end detecting means for detecting the end of the transmission operation of the other terminal device, and detecting that the transmission operation of the other terminal device has been completed by the transmission operation end detection means And a second transmitting means for re-transmitting its own packet.

Here, the two-body collision detecting means detects a two-body collision that occurs when another terminal device starts transmitting a packet while transmitting the packet by itself. When the occurrence of a two-body collision is detected by the two-body collision detection means, the priority information extraction means includes a priority information indicating the priority of the packet, which is inserted into a packet transmitted from another terminal device. Extract degree information. The first transmitting unit compares the priority information extracted by the priority information extracting unit with the priority information of the own packet. If the priority of the own packet is high, the first transmitting unit Send the message again. The transmission operation end detecting means compares the priority information extracted by the priority information extracting means with the priority information of its own packet. By monitoring the flowing information, the end of the transmission operation of another terminal device is detected. The second transmitting means retransmits its own packet when the transmitting operation end detecting means detects that the transmitting operation of another terminal device has been completed.

Also, in a terminal device connected to a broadcast network having bidirectionality and constituting a network system, it occurs when another terminal device starts transmitting a packet while transmitting a packet by itself. Do 2
A two-body collision detecting means for detecting a two-body collision, and when the two-body collision is detected by the two-body collision detecting means,
Priority information extracting means for extracting priority information indicating the priority of the packet, which is interpolated in a packet transmitted from the other terminal device, and priority information extracted by the priority information extracting means Is compared with the priority information of the own packet, and when the priority of the own packet is higher, the transmission of the own packet is executed again.
And comparing the priority information extracted by the priority information extracting means with the priority information of the own packet. If the priority of the own packet is low, the packet is transmitted over the network. By monitoring the flowing information, it is detected that the transmission operation of the other terminal device has been completed by the transmission operation end detection means for detecting the end of the transmission operation of the other terminal device, and the transmission operation end detection means. And a second transmitting means for re-transmitting the packet of the terminal when the terminal device is provided.

Here, the two-body collision detecting means detects a two-body collision that occurs when another terminal device starts transmitting a packet while transmitting the packet by itself. When the occurrence of a two-body collision is detected by the two-body collision detection means, the priority information extraction means includes a priority information indicating the priority of the packet, which is inserted into a packet transmitted from another terminal device. Extract degree information. The first transmitting unit compares the priority information extracted by the priority information extracting unit with the priority information of the own packet. If the priority of the own packet is high, the first transmitting unit Send the message again. The transmission operation end detecting means compares the priority information extracted by the priority information extracting means with the priority information of its own packet. By monitoring the flowing information, the end of the transmission operation of another terminal device is detected. The second transmitting means retransmits its own packet when the transmitting operation end detecting means detects that the transmitting operation of another terminal device has been completed.

Furthermore, in a network system in which a plurality of terminal devices are connected to a broadcast network, each terminal device calculates an average priority of packets flowing on the network. When,
When sending a packet to the network,
When the network is in use, a transmission operation suspending unit that suspends a transmission operation for a predetermined time, an average priority calculated by the average priority calculation unit, and a priority of a packet to be transmitted by itself. Setting change means for changing the setting of the predetermined time of the transmission operation holding means according to the degree.

Here, the average priority calculating means calculates the average priority of the packets flowing on the network.
The transmission operation suspending unit suspends the transmission operation for a predetermined time when transmitting the packet to the network and when the network is in use. The setting change unit changes the setting of the predetermined time of the transmission operation suspension unit according to the average priority calculated by the average priority calculation unit and the priority of the packet to be transmitted by itself.

Further, in a terminal device connected to the broadcast network and constituting a network system, an average priority calculating means for calculating an average priority of packets flowing on the network, and When transmitting to the network, if the network is in use, a transmission operation suspension unit that suspends a transmission operation for a predetermined time, an average priority calculated by the average priority calculation unit, Setting change means for changing the setting of the predetermined time of the transmission operation holding means according to the priority of the packet to be transmitted by itself,
A terminal device characterized by having:

Here, the average priority calculating means calculates the average priority of the packets flowing on the network.
The transmission operation suspending unit suspends the transmission operation for a predetermined time when transmitting the packet to the network and when the network is in use. The setting change unit changes the setting of the predetermined time of the transmission operation suspension unit according to the average priority calculated by the average priority calculation unit and the priority of the packet to be transmitted by itself.

[0025]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a principle diagram showing the operation principle of the embodiment of the present invention. In this figure, terminal devices 1 to 3 are connected to a bidirectional broadcast network 4, and mutually exchange information. Since the terminal devices 1 to 3 have the same configuration, the terminal device 1 will be described below as an example.

The terminal device 1 includes a two-body collision detecting means 1a, a priority information extracting means 1b, a first transmitting means 1c, a transmitting operation end detecting means 1d, a second transmitting means 1e, a transmitting operation stopping means 1f, an averaging means. Priority calculation means 1g, transmission operation holding means 1h, setting change means 1i, and I / F (Interfac
e) 1j.

Here, the two-body collision detecting means 1a detects a two-body collision that occurs when another terminal device 2, 3 starts transmitting a packet while transmitting the packet by itself.
When the two-body collision detection unit 1a detects the occurrence of a two-body collision, the priority information extraction unit 1b determines the priority inserted in the packets transmitted from the other terminal devices 2 and 3, The priority information shown is extracted.

The first transmitting unit 1c compares the priority information extracted by the priority information extracting unit 1b with the priority information of its own packet, and when the priority of its own packet is high, Executes its own packet transmission again. In addition, the first transmission unit 1c performs normal transmission (2
Transfer other than body transfer) is also executed.

The transmission operation end detecting means 1d compares the priority information extracted by the priority information extracting means 1b with the priority information of its own packet, and when the priority of its own packet is low, Detects the end of the transmission operation of the other terminal devices 2 and 3 by monitoring information flowing on the network 4.

The second transmitting means 1e executes its own packet transmission again when the transmission operation completion detecting means 1d detects that the transmission operations of the other terminal devices 2 and 3 have been completed.

When a collision occurs between two terminals 2 and 3 other than the terminal device 2, the transmission operation stopping means 1 f transmits its own new transmission until the transmission operation by these two terminal devices 2 and 3 is completed. Stop executing the operation.

The average priority calculating means 1g calculates the average priority of packets flowing on the network 4. The transmission operation suspending unit 1h suspends the transmission operation for a predetermined time when the network 4 is in use when transmitting a packet to the network 4.

The setting change unit 1i changes the setting of the standby time of the transmission operation suspension unit 1h according to the average priority calculated by the average priority calculation unit 1g and the priority of the packet to be transmitted.

The I / F 1j appropriately converts the format of data flowing between the terminal device 1 and the network 4 and executes various procedures necessary for communication. Next, the operation of the above principle diagram will be described.

For example, assume that the terminal device 1 and the terminal device 2 shown in FIG. In this case, since a two-body collision occurs, the two-body collision detecting means 1a detects this and notifies the priority information extracting means 1b and the transmission operation stopping means 1f.

The priority information extracting means 1b outputs the priority information indicating the priority of the packet, which is inserted into the packet transmitted from the terminal device 2 flowing on the network 4 via the I / F 1j. Extract and supply to the first transmitting means 1c.

The first transmitting means 1c and the priority information supplied from the priority information extracting means 1b (priority information inserted into the packet transmitted by the terminal device 2) and the first transmitting means 1c are trying to transmit. The priority information included in the packet is compared with the priority information, and when the priority of the own priority information is high, the packet is retransmitted to the network 4 via the I / F 1j.

For example, if the priority information of the terminal device 1 is “1”
0 "and the priority information of the terminal device 2 is" 2 ", it is determined that the priority of the packet of the terminal device 1 having a large value of the priority information is high, and as a result, the first transmission is performed. The means 1c transmits the packet to the network 4 via the I / F 1j.
Is sent to

The priority information supplied from the priority information extracting means 1b is compared with the priority information inserted in the packet which the user is trying to transmit, and the priority of the own priority information is determined. If it is low, the transmission operation end detecting means 1d detects it.

In this case, since the priority of the packet to be transmitted by the terminal device 2 is high, the same processing as in the above case is executed in the terminal device 2,
The terminal device 2 starts sending packets to the network 4.

The transmission operation end detecting means 1 d
When it is detected that the transmission of the packet from has been completed, it notifies the second transmitting means. As a result, the second transmitting unit 1e immediately executes the packet retransmission operation.

When a two-body collision occurs, the normal C
In the SMA / CD system, the transmission operation is performed again after both terminal devices are in a standby state for a predetermined time (random time). Therefore, in such a method, a waiting time is generated, and the transfer efficiency of the network is reduced. Also, after the waiting time has elapsed,
When transmission is attempted again, a two-body collision with the third terminal device may occur. In that case, the standby state is resumed and the transfer efficiency is further reduced.

In the network system according to the present invention,
When a two-body collision occurs, the first order / the last order is determined according to the priority information inserted in the packet, and the first transmission unit of the terminal device that has become the first order transmits the packet. After the execution, the transmission of the packet is immediately performed by the second transfer means of the terminal device in the rear order, so that the waiting state is eliminated and the communication between the terminal device and the third terminal device is performed two times. Further occurrence of a body collision can be prevented.

By the way, when a packet is to be transmitted to the network 4, the other terminal devices 2,
When the network 3 is using the network 4, the average priority calculation means 1g, the transmission operation holding means 1h, and the setting change means 1i cooperate and wait for a time corresponding to the packet to be transmitted. , And a packet.

That is, the average priority calculating means 1g acquires the packets flowing on the network 4, and extracts the priority information inserted in the acquired packets. Then, by calculating the average value of the plurality of pieces of extracted priority information, the average priority of the packets flowing on the network 4 is calculated.

The setting change means 1i obtains the average priority calculated by the average priority calculation means 1g, compares it with the priority inserted in the packet to be transmitted by itself, and adds the result to the comparison result. Transmission operation suspension means 1 according to
The hold time (standby time) of the transmission operation of h is changed.

That is, when the priority of the own packet is high, the holding time, which is the time during which the transmission operation holding means 1h holds the transmission while the network 4 is in use, is set shorter than usual. On the other hand, if the priority of the own packet is low, the hold time is set longer than usual.

According to such an operation, when the priority of the packet which the user is trying to transmit is higher than the average priority of the packet flowing on the network 4 (the own packet has an average If it is more important than the packet), by setting the hold time short, it is possible to reduce the average time required for transmitting its own packet.

On the other hand, when the priority of the own packet is lower (when the own packet is less important than the average packet flowing through the network 4), the hold time is set to be longer. Is transmitted with priority.

Next, a configuration example of the embodiment of the present invention will be described. FIG. 2 is a schematic diagram of an optical communication network system including a bidirectional broadcast bus.

As shown in this figure, the network system according to the present invention comprises a plurality of nodes 101a to 101d,
102a-102d, 103a-103d, and 1
04a to 104d are connected by star couplers 101 to 104, respectively.

Each node is, for example, a personal computer or a printer. Star couplers 101-104
Distributes the optical signal input to one end to the other seven terminals and outputs the same. The star couplers 101 to 104 do not require a power supply because they are constituted by passive elements. However,
Since the signal intensity of the output light is reduced to 1/7, repeater amplifiers 105 to 108 are inserted between the star couplers to amplify the optical signal intensity.

The nodes connected by the same star coupler are mutually connected by the star coupler,
In addition, since the star couplers are connected to each other via the relay amplifier, the optical signal transmitted from one node in the network system can be received by all other nodes.

FIG. 3 is a schematic diagram of an interface for mutually converting an optical signal and an electric signal in a node. The signal processing unit 201 that controls the optical element based on the communication method is L
The input / output interface includes a parallel bus having a width of 8 bits, which is configured by an SI (Large Scale Integrated Circuit) or the like.

The transmission data output from the signal processing unit 201 is subjected to 8B / 10B conversion by the serializer 202 and then converted into a serial signal synchronized with the transmission speed. Here, the 8B / 10B conversion is a process of projecting and converting an 8-bit signal into a 10-bit signal according to a predetermined table.

Since the converted 10-bit bit string is such that "1" or "0" does not continue for more than 5 bits, it is easy to extract the synchronous clock from the serial signal during reception.

The serial signal converted by the serializer 202 is converted into an optical signal by a laser diode (LD) unit 204. Laser diode unit 204
The optical signal emitted from the optical fiber 206 enters the optical demultiplexer / combiner 208 via the optical fiber 206.

The optical demultiplexer / combiner 208 is connected to the optical fiber 20.
The optical signal incident from 6 is emitted to the star coupler via the optical fiber 209. On the other hand, an optical signal emitted from the star coupler and incident via the optical fiber 209 is extracted by the optical demultiplexer / multiplexer 208, and guided to the photodiode (PD) unit 205 via the optical fiber 207.

The photodiode unit 205 converts an optical signal into an electric signal, outputs the electric signal to the deserializer 203, generates a carrier sense signal indicating that a signal exists on the bus, and supplies the signal to the signal processing unit 201.

The deserializer 203 first extracts a synchronous clock from the input serial signal, and converts the received signal supplied from the photodiode unit 205 into a 10-bit parallel signal based on the extracted synchronous clock. Then, the 10-bit parallel signal obtained by the conversion is converted to an 8-bit parallel signal by performing 10B / 8B conversion.

When a pattern not described in the conversion table exists at the time of 10B / 8B conversion, the deserializer generates a code violation signal and supplies it to the signal processing unit 201. Note that a code violation occurs when signals transmitted from a plurality of nodes collide with each other and cannot be normally received.
In that case, the corresponding processing is executed by the signal processing unit 201.

The 8-bit parallel signal generated by the deserializer 203 by the 10B / 8B conversion is
01, and the receiving process is executed. FIG. 4 is a diagram showing an example of the structure of a packet exchanged in the present embodiment.

As shown in this figure, the packet used in the present embodiment is obtained by adding a priority identifier 301 which is an identifier indicating a priority to an Ethernet packet. Here, a symbol is an 8-bit signal.
Represents a code unit when converted to 10 bits by B / 10B conversion.

First, the preamble 300 is composed of 64 special symbols meaning a preamble. The priority identifier 301 stores information of four symbols (for example, a numerical value indicating the priority) indicating the priority of the packet.

Note that a portion obtained by combining the preamble 300 and the priority identifier 301 is called an essential transmission section, and it is necessary to transmit the data up to this point when the transmission processing is started. The destination address 302 stores information of six symbols indicating the destination of the packet.

The source address 303 stores information of six symbols indicating the source of the packet. The data format identifier 304 stores information of two symbols indicating the format of the data stored in the data body 305.

The data body 305 has a variable length.
Data having a symbol length of 1500 is stored. The frame check CRC 306 is a four-symbol CRC (Cyclic Redundancy) as a means for detecting a transmission error in order to check whether an error has occurred in the entire frame.
Check) sign is added.

Next, with reference to FIG. 5, the state transition when each node sends out a packet will be described. As shown in FIG. 5, when a transmission request is made to a node, the node transits to a state S1 and enters a carrier sense state for checking whether data is flowing on the network. Note that carrier sensing is performed by not using the carrier sense signal generated by the photodiode unit directly, but by checking the internal state CS of a sequential circuit (to be described in detail later) representing the carrier sense state.

If CS = 1 in state S1, it means that there is already a packet on the network. Therefore, in that case, the process proceeds to the state S9, waits for a random period, returns to the state S1, and starts again from the carrier sense.

On the other hand, if CS = 0 in state S1, it means that the network is free. In that case, the state transits to state S2 and immediately transmits to the essential transmission section (see FIG. 4). Starts sending.

When the transmission by the essential transmission unit is completed, the state transits to the state S3, and the carrier sense is executed in parallel while continuing the transmission operation of the remaining part of the packet. Then, when the state of CS = 0 is held until the transmission is completed, the state transits to the state S12, waits for a certain time, and ends normally.

If CS = 1 during transmission, it is assumed that a packet collision has occurred, so that the state transits to state S4. In state S4, Neg (Negotiat) indicating that a packet collision has occurred
ion) While transmitting the jamming signal, the priority identifier 301 included in the packet transmitted by the collision partner is received.

By the way, in the CSMA / CD communication system used for Ethernet, when a collision is detected, transmission is immediately interrupted, a random period is waited, and then a retry is performed from carrier sense. On the other hand, JP-A-5-2521
In the communication system 70 or the communication system of the present invention, the jamming signal is continuously transmitted until an identifier indicating the priority of the collision partner packet in the essential transmission unit is received.

The Neg jamming signal transmitted at this time is:
Since a symbol to be assigned is different from a Nor (Normal) jamming signal to be described later, these can be distinguished.

In state S4, if a predetermined period or more elapses (time-out) or a code violation is detected (three-body collision) until an identifier indicating the priority of the collision partner is received, the state transits to state S8. After transmitting Nor jamming for a certain period of time, the process transits to the state S9, waits for a random period, transits to the state S1, and starts again from the carrier sense.

In the state S4, when an identifier indicating the priority of the collision partner is received, the state transits to the state S5,
The priority of the packet sent by itself, and 3
Compare the size as a 2-bit integer.

As a result of the comparison, when the priority identifier of the packet transmitted by itself is larger, the packet is transmitted in the first order, so that the state transits to the state S6 and the transmission of Neg jamming is continued for a predetermined time. After transiting to state S7 and executing carrier sense and confirming that CS = 0,
The state transits to the state S2 and the transmission processing is executed again.

As a result, in the case where a two-body collision occurs, if the self is in the first order, the transmission process is executed without waiting for a random period, so that the network utilization rate is improved. It is possible to do.

If the self is in the first order, Ne
Since the jamming is transmitted, the other nodes (nodes that do not cause a two-body collision) cannot perform new transmission because the result of the carrier sense in the state S1 is CS = 1. The two nodes that have caused the collision will be processed preferentially.

Next, if CS = 1 in the carrier sense in the state S7, it is estimated that some abnormality has occurred in the network. In this case, the state transits to the state S8 and Nor jamming is performed. Is transmitted for a certain period of time, and then waits for a random period in state S9, returns to state S1, and starts again from carrier sense.

In the comparison of the priorities in the state S5, if the own packet and the other packet have the same identifier, the order of retransmission cannot be determined. Both nodes are in state S
8, and after sending Nor jamming for a certain time,
In the state S9, the process waits for a random period and starts again from the carrier sense in the state S1.

However, since it is desirable to avoid such a situation as much as possible, for example, when a bit string unique to the transmission source node is incorporated in a part of the priority identifier and the same identifier is used, Can be avoided by comparing the magnitude of this part.

In the state S5, when the other party's identifier is larger in the priority comparison,
Since the self is in the backward order, the state transits to the state S10. In state S10, transmission of Neg jamming is stopped,
Transition to the state S11. In state S11, carrier sense is performed, and when CS = 1, the partner node is transmitting a packet, and thus the state of state S11 is maintained. When CS = 0, it is determined that the transmission of the partner node has been completed, and the state transits to the state S2 to start transmitting its own packet. Further, state S11
In the case where a code violation or Nor jamming is detected, the state transitions to state S9 and waits for a random period, and then transitions to state S1 to execute carrier sense.

By the way, in the communication system disclosed in Japanese Patent Application Laid-Open No. 5-252170, after the node in the rear order interrupts the transmission, the node waits for a random period and then starts again from the carrier sense. However, in the case of the present embodiment, the backward node immediately stops transmission, executes carrier sense, and waits until the packet transmission of the forward node is completed.
Upon detecting the completion of the transmission, the packet transmission process is started immediately.

With such a structure, Japanese Patent Application Laid-Open No. 5-252
In the communication method of 170, when only two nodes collided, only one node was able to execute transmission processing, whereas in the communication method of the present invention, both nodes can retransmit in order, and Efficiency can be improved.

By the way, after the preceding node finishes transmission,
Until the subsequent node starts transmission, a state where there is no packet on the network for a short time (for example, several to several tens of nanoseconds) may occur, and the third node may start transmission. There is. When the third node starts transmission, a packet collision occurs with the subsequent node.

In the present embodiment, in order to avoid such a situation, the carrier sense method is improved. FIG. 6 shows a sequential circuit for giving a result of carrier sense (a circuit built in the signal processing unit 201 shown in FIG. 3).
It is a figure which shows the transition of the state of FIG. As shown in this figure, the sequential circuit of this embodiment has four states. The details will be described below. [State S20] No carrier The carrier sense internal state CS is 0. When the photodiode unit 205 does not detect a carrier, the state of “no carrier” is maintained. If a carrier is detected, the flow goes to the state S21. [State S21] Carrier present A Carrier sense internal state CS is 1. At this time, N
If eg jamming is detected, the flow goes to the state S22. If the carrier is lost, the flow goes to the state S20. Note that when a code violation or Nor jamming is detected, the state is not changed. [State S22] Carrier present B Carrier sense internal state CS is 1. This state is
This indicates that the retransmission order determination process after the packet collision is being performed. If the carrier is lost in this state, it indicates that the transmission of the preceding node has been completed, and the state transits to State S23. When a carrier or Neg jamming is detected, it is determined that the preceding node is transmitting and this state is maintained. Further, if a code violation or Nor jamming is detected, it means that the retransmission order determination processing has failed due to a three-body collision or the like, and in that case, the state transits to the state S21. [State S23] Standby for a fixed period The carrier sense internal state CS is 1. This state is
This is a state indicating that the prior node has completed transmission. In this state, if a predetermined time has elapsed, the state transits to the state S20. As a result, the carrier sense internal state CS becomes 1 for a certain period of time after the transmission of the preceding node is completed, so that the third node does not start transmitting the packet and collides with the transmission of the subsequent node. Can be prevented.

Next, an example of a specific operation when a two-body collision occurs will be described. FIG. 7 is a time chart showing the operation when two packet collisions occur. This diagram describes the operation when nodes A, B, and C are connected to a network.

Here, it is assumed that the nodes A and B are connected at a predetermined distance on the network, and the node C is connected between them. Also, on the premise that it takes a predetermined time for a signal to reach one from the other, after node A starts sending a packet, before the signal sent by node A reaches node B, node B also Assume that transmission of a packet has started.

Now, as shown in FIG.
Starts transmitting data, and while transmitting the preamble, it is assumed that the node B starts transmitting data as shown in FIG. 7B.

At this time, the node A detects the signal from the node B while transmitting the transmission data after transmitting the essential transmission section (CS = 1 in the state S3 in FIG. 5). In this case, the node A immediately interrupts the data transmission process, starts Neg jamming transmission, and detects a priority identifier from a collision partner (state S4 in FIG. 5).

At this time, since the same processing is executed in the node B, the priority identifier of the node A is also detected in the node B. When the priority identifier is detected, the node A compares the priority identifier with the priority identifier inserted in its own packet (state S5 in FIG. 5). For example, assuming that the packet being transmitted from the node A has a higher priority, the node A transmits Neg jamming for a certain period of time (state S6 in FIG. 5), executes carrier sense, and executes CS = 0 (network Is empty), the data whose transmission has been interrupted by the two-body collision is retransmitted (return to state S2 in FIG. 5).

As a result, as shown in FIG. 7A, the preamble, the priority identifier, the transmission data, and the CRC are sequentially transmitted from the node A, and the node A waits for a predetermined time (state S12 in FIG. 5). After that, it ends normally.

At this time, the node B detects the signal of the node A during the transmission of the essential transmission unit. However, after the transmission operation is continued until the transmission of the essential transmission unit is completed, the node B receives the priority identifier of the node A. Until Neg jamming is performed.

After receiving the priority identifier of the node A, it recognizes that the node A is in the backward order by comparing with the priority identifier of the node A (in the state S5 in FIG. 5, the order is in the backward order). The transmission is stopped (state S10 in FIG. 5), and the process waits until the transmission from the node A is completed (state S11 in FIG. 5).

When the node B detects that the retransmission of the node A has been completed and the carrier on the network has been lost (CS = CS in state S11 in FIG. 5).
0), immediately starts retransmission of the packet. as a result,
As shown in FIG. 7B, after a predetermined time has elapsed after the transmission of the node A is completed, as in the case of the node A,
Preamble, priority identifier, transmission data, and C
RCs are transmitted in order, and after waiting for a certain period of time (state S12 in FIG. 5), the process ends normally.

As described above, according to the present embodiment, even when a two-body collision occurs, packet retransmission processing of both nodes is executed in order. next,
The operation of the received data at the third node C and the carrier sense sequential circuit will be described. Here, for simplicity, it is assumed that the node C is located between the nodes A and B, and propagation delays from both nodes are equal. In the time chart, the propagation delay is represented as 0.

As shown in FIG. 7 (C), when node A starts transmission, node B has not performed transmission yet, so node C determines that normal communication is being performed. Therefore, the carrier sense sequential circuit of the node C makes a transition to the state S21 shown in FIG.

Then, since the node B also starts transmission,
Both packets collide on the network, and as a result, a code violation signal is detected. But,
In the carrier sense sequential circuit, as shown in FIG. 6, when a code violation is detected in the state S21, the state of the state S21 is maintained. Therefore, as shown in FIG. The state is maintained.

The Ne of the Node B is determined by comparing the priority identifiers.
When the transmission of the g-jamming is stopped, the node C detects the Neg jamming of only the node A, so that the node C is in a state of detecting the Neg jamming as shown in FIG. 7C.

When Neg jamming is detected, the carrier sense sequential circuit of node C sets the state S shown in FIG.
Since the state transitions to 22, there is a carrier present state B as shown in FIG.

Thereafter, the state in which the node A stops transmitting Neg jamming and continuously retransmits the packet is normally observed from the node C. When the retransmission of the node A is completed, the carrier sense sequential circuit of the node C transits to the state S23 shown in FIG.
As shown in (D), the node C is in a standby state for a certain period, and the carrier sense internal state CS maintains "1" for a certain period regardless of the reception state. Therefore, node A
Completes the retransmission and before the Node B starts the retransmission, even though the packet is temporarily lost from the bus, the transmission of the packet from the third node is started. Absent.

After a certain period of time, the node C
The carrier sense sequential circuit of state S2 shown in FIG.
Although the state transits to 0, the state immediately transits to the state S21 because the node B is transmitting and the carrier is detected. As a result, as shown in FIG. 7, the state becomes the state A with the carrier, and when the transmission of the node B is completed, the state transits to the state of "there is no carrier" which is the state of the state S20.

In the above, the case where a two-body collision has occurred has been described. In the present embodiment, a packet having a higher priority is transmitted preferentially by using a priority identifier inserted in each packet. It is also possible.

FIG. 8 is a flowchart for explaining an example of a process for calculating the average priority of packets flowing on the network for such a process. When this flowchart is started, the following processing is executed. [S40] The signal processing unit 201 sets an initial value to the variable Pb. [S41] The signal processing unit 201 resets the loop counter (sets the value “0”). [S42] The signal processing unit 201 determines whether a priority identifier has been received. If the priority identifier has been received, the process proceeds to step S43; otherwise, the process proceeds to step S44. [S43] The signal processing unit 201 calculates a value obtained by adding the value of the input priority identifier Pin and the value of the variable Pb,
The value divided by the value “2” is substituted for the variable Pb. [S44] The signal processing unit 201 sets the value of the counter to “1”.
Only increment. [S45] If the value of the counter has become larger than the specified value, the signal processing unit 201 proceeds to step S46,
Otherwise, the process returns to step S41 and the same processing is repeated. [S46] The signal processing unit 201 stores the value obtained by halving the value stored in the variable Pb again for the variable Pb. As a result, when the non-detection state of the packet continues for a certain period or more, the priority of the network is set low, so that the priority of the packet to be transmitted can be relatively increased.

According to the above processing, the average priority of the packets flowing on the network during a predetermined period can be obtained. By using such an average priority, when the packet is retransmitted, the average priority and
When comparing the priorities of the packets to be retransmitted, if the average priority is higher, the random waiting period is set to be longer than usual (for example, twice as long as normal).
Packets with low priority have less chance of retransmission, and packets with high priority are transmitted preferentially.

Note that the calculation method shown in FIG. 8 is an example,
It is not limited only to such a case. As described above, according to the embodiment of the present invention, in the event of a two-body collision, the average number of nodes waiting to be transmitted can be effectively reduced, thereby improving the network use efficiency. Can be.

Further, the average priority of the packets flowing on the network is calculated, and the standby time at the time of retransmission is appropriately changed by comparing the priority of the packet to be transmitted with the average priority. Therefore, it is possible to effectively use a network having a limited transmission speed.

[0109] In the above embodiment, the communication system using light has been described as an example, but it is needless to say that the present invention is not limited to such a case.

[0110]

As described above, according to the present invention, in a network system in which a plurality of terminal devices are connected to a bidirectional broadcast network, each terminal device is transmitting its own packet. A two-body collision detecting means for detecting a two-body collision caused by another terminal device starting transmission of a packet, and when the two-body collision is detected by the two-body collision detecting means, Priority information extracting means for extracting priority information indicating the priority of the packet, which is interpolated in the packet transmitted from the terminal device; priority information extracted by the priority information extracting means; When comparing the priority information of the packet with the priority information of the packet, if the priority of the own packet is high, the first transmitting means for executing the transmission of the own packet again and the priority information extracting means When the priority information extracted by the above is compared with the priority information of the own packet, if the priority of the own packet is low, the information flowing on the network is monitored, and the other terminal device is monitored. Transmitting operation end detecting means for detecting the end of the transmitting operation, and transmitting the own packet again when the transmitting operation end detecting means detects that the transmitting operation of the other terminal device has been completed. Since two transmission means are provided, when the network is congested, the average number of nodes waiting for transmission can be effectively reduced, so that the network use efficiency can be improved.

Also, in a terminal device connected to a broadcast network having bidirectionality and constituting a network system, a problem occurs when another terminal device starts transmitting a packet while transmitting a packet by itself. Do 2
Two-body collision detection means for detecting a body collision, and when the occurrence of a two-body collision is detected by the two-body collision detection means, the packet of the packet inserted into another terminal device is interpolated. Priority information extracting means for extracting priority information indicating the priority; and comparing the priority information extracted by the priority information extracting means with the priority information of the own packet. If the degree is high,
When comparing the first transmitting means for executing the transmission of the own packet again, the priority information extracted by the priority information extracting means, and the priority information of the own packet,
When the priority of the own packet is low, the transmission operation end detecting means for detecting the end of the transmission operation of another terminal device by monitoring the information flowing on the network, When it is detected that the transmission operation of the terminal device has been completed, the terminal device has a second transmitting means for re-transmitting its own packet. Is constructed, when the network is congested, the average number of nodes waiting for transmission can be effectively reduced, so that the use efficiency of the network can be improved.

Further, in a network system in which a plurality of terminal devices are connected to a broadcast network, each terminal device has an average priority calculating means for calculating an average priority of packets flowing on the network. When sending a packet to the network, if the network is in use, the transmission operation holding means for holding the transmission operation for a predetermined time, the average priority calculated by the average priority calculation means, Setting change means for changing the setting of the predetermined time of the transmission operation holding means in accordance with the priority of the packet to be transmitted by itself. It can be used depending on the degree.

Further, in a terminal device connected to the broadcast network and constituting a network system, an average priority calculating means for calculating an average priority of packets flowing on the network, and transmitting the packets to the network. If the network is in use when transmitting, the transmission operation holding means for suspending the transmission operation for a predetermined time, the average priority calculated by the average priority calculation means, Setting change means for changing the setting of the predetermined time of the transmission operation holding means according to the priority of the packet to be set, so that when a network is constructed by connecting a plurality of such terminal devices, Can use the limited transmission band of the network according to the priority of the packet.

[Brief description of the drawings]

FIG. 1 is a principle diagram showing an operation principle of the present invention.

FIG. 2 is a schematic diagram of an optical communication network system including a bidirectional broadcast bus.

FIG. 3 is a block diagram illustrating a configuration example of an interface for mutually converting an optical signal and an electric signal in the node illustrated in FIG. 2;

FIG. 4 is a diagram showing a structure of a packet transmitted in the embodiment shown in FIG.

FIG. 5 is a diagram illustrating an example of state transition when a node transmits a packet.

FIG. 6 is a state transition diagram of a sequential circuit showing a carrier sense state.

FIG. 7 is a time chart illustrating an operation when a two-body collision of packets occurs.

FIG. 8 is a flowchart illustrating an example of a process for calculating a bus average priority.

[Explanation of symbols]

 1-3 Terminal device 1a Two-body collision detection means 1b Priority information extraction means 1c First transmission means 1d Transmission operation end detection means 1e Second transmission means 1f Transmission operation stop means 1g Average priority calculation means 1h Transmission operation suspension Means 1i Setting change means 4 Network 101 to 104 Star coupler 101a to 101d node 102a to 102d node 103a to 103d node 104a to 104d node 105 to 108 Relay amplifier 201 Signal processing unit 202 Serializer 203 Deserializer 204 Laser diode unit 205 Photodiode unit 206 , 207 Optical fiber 208 Optical demultiplexer / combiner 209 Optical fiber

Claims (7)

[Claims] 1. In a network system in which a plurality of terminal devices are connected to a bidirectional broadcast network, each terminal device transmits a packet while another terminal device transmits a packet. To detect a two-body collision caused by starting
When the occurrence of a two-body collision is detected by the two-body collision detection means, the two-body collision detection means indicates the priority of the packet inserted in the packet transmitted from the other terminal device. Priority information extracting means for extracting priority information, When comparing the priority information extracted by the priority information extracting means with the priority information of its own packet,
If the priority of the own packet is high, first transmitting means for executing transmission of the own packet again; priority information extracted by the priority information extracting means; and priority information of the own packet. When compared to
When the priority of its own packet is low, transmission operation end detection means for detecting the end of the transmission operation of the other terminal device by monitoring information flowing on the network, and the transmission operation end detection means And a second transmission unit for re-executing transmission of its own packet when it is detected that the transmission operation of the other terminal device has been completed. 2. When the two-body collision occurs with a terminal device other than the own terminal device, a transmission operation stop that stops execution of a new transmission operation relating to the self device until the transmission operation by these two terminal devices is completed. 2. The network system according to claim 1, further comprising means. 3. The transmission operation stopping means stops execution of a new transmission operation relating to itself until a predetermined time elapses after completion of the transmission operation by the terminal device in the first order. The network system according to claim 2. 4. A terminal device connected to a broadcast network having bidirectionality and constituting a network system, which is generated when another terminal device starts transmitting a packet while transmitting a packet by itself. Detect two-body collision 2
When the occurrence of a two-body collision is detected by the two-body collision detection means, the two-body collision detection means indicates the priority of the packet inserted in the packet transmitted from the other terminal device. Priority information extracting means for extracting priority information, When comparing the priority information extracted by the priority information extracting means with the priority information of its own packet,
If the priority of the own packet is high, first transmitting means for executing transmission of the own packet again; priority information extracted by the priority information extracting means; and priority information of the own packet. When compared to
When the priority of its own packet is low, transmission operation end detection means for detecting the end of the transmission operation of the other terminal device by monitoring information flowing on the network, and the transmission operation end detection means And a second transmitting means for re-transmitting its own packet when it is detected that the transmission operation of the other terminal device has been completed by the terminal device. 5. In a network system in which a plurality of terminal devices are connected to a broadcast network, each terminal device calculates an average priority of packets flowing on the network. And sending a packet to the network,
When the network is in use, a transmission operation holding unit for holding a transmission operation for a predetermined time; an average priority calculated by the average priority calculation unit; and a priority of a packet to be transmitted by itself. And a setting changing means for changing the setting of the predetermined time of the transmission operation holding means according to the degree. 6. The network system according to claim 5, wherein said average priority calculating means sets said average priority to a low value when no packet has been flowing through said network for a certain period of time. 7. A terminal device connected to a broadcast network and constituting a network system, comprising: an average priority calculating means for calculating an average priority of packets flowing on the network; When sending to
When the network is in use, a transmission operation holding unit for holding a transmission operation for a predetermined time; an average priority calculated by the average priority calculation unit; and a priority of a packet to be transmitted by itself. Terminal setting means for changing the setting of the predetermined time of the transmission operation holding means according to the degree.