JP3121423B2 - Network system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a LAN connection device and a network system in a connection device for connecting a plurality of LANs.

[0002]

2. Description of the Related Art Conventionally, as a method of connecting a plurality of LANs, a method of connecting LANs without using a bridge to form a physical loop has been proposed. This method
With a simple configuration, duplication of packets and generation of loops can be prevented.

As a method of providing a plurality of communication paths between LANs, an arbitrary connection such as a mesh is performed between LANs using a bridge, and the management of the bridge is controlled by IEEE (American Institute of Electrical and Electronics Engineers) 802.1. A method of applying the spanning tree algorithm specified in (1) has been put to practical use. The spanning tree algorithm is an algorithm in a system in which a plurality of LANs are interconnected by using a bridge, and the system configuration is such that a logical tree structure is formed from an arbitrary physical structure. As a result, even if the configuration is physically arbitrary, no loop is formed in the logical configuration, and the occurrence of packet duplication due to bridge relay can be prevented.

[0004]

However, in the above-mentioned method of connecting LANs using bridges, packet delay becomes a problem as the number of LAN connections increases. Also, in order to provide a plurality of communication paths between LANs without using the spanning tree algorithm, in order to prevent packet duplication or loop, refer to the destination address of the packet and perform protocol processing of an upper layer. -Data and gateways are required, and the device becomes complicated.

An object of the present invention is to provide a simple LA system in a system including a physical loop structure in which a plurality of LANs are connected.
It is an object of the present invention to provide a network system that can prevent packet duplication and looping and transfer packets with minimum packet delay by using an N-to-N connection device.

[0006]

In order to achieve the above object, in a network system having a plurality of networks, the network comprises one or more terminal accommodating circuits to which communication terminals are connected, and another terminal accommodating circuit. A connection device for connecting the network, and a bus for connecting the terminal accommodating circuit and the connection device, wherein the connection device is provided corresponding to another network, and a terminal in the own network is connected to the other network. When communication is performed, information is transmitted to another network, information from another network is received and transmitted to a bus of the own network, and information from another network is not transmitted to another network.

The terminal accommodating circuit outputs a reception notice when receiving information addressed to a terminal connected to the terminal accommodating circuit, and the connection device, when receiving information from another network, The information is sent to the network bus and a transmission notification is output to another connection device of the own network. If there is a reception notification from the terminal accommodating circuit, the information is discarded, and the other connection device of the own network receives the notification. When there is a transmission notification, the information is discarded, and when there is no reception notification from the terminal accommodation circuit and there is no transmission notification from another connection device, when a terminal in the own network communicates with another network. The information is sent to another network as there is.

[0008] As means for making the above-mentioned transmission notification and reception notification, a transmission notification signal line for performing a transmission notification between connecting devices in the own network is connected to a terminal accommodating circuit and a connecting device in the own network. In addition, a reception notification signal line for notifying reception from the terminal accommodation circuit may be further provided to perform transmission notification and reception notification.

In addition, instead of the transmission notification signal line,
When the connection device receives information from another network, it adds a predetermined code as a transmission notification to the information, sends the information to the bus of the own network, and receives the information from the bus of the own network. Sometimes, it is detected whether the code is added to the information, and if the code is added, it is determined that there is a transmission notification and the information is discarded. If the code is not added, there is no transmission notification It may be.

[0010] Further, the connection device can set in advance whether or not to output a transmission notification when information from another network is received.

[0011]

The terminal accommodation circuit outputs a reception notification via the reception notification signal line when receiving information addressed to the terminal connected to the terminal accommodation circuit.

When the connection apparatus receives information from another network, the connection apparatus sends the information to a bus of the own network and sends a transmission notification to another connection apparatus of the own network via a transmission notification signal line. Output, the information is discarded when there is a reception notification from the terminal accommodation circuit, and the information is discarded when there is a transmission notification from another connection device of the own network, and there is no reception notification from the terminal accommodation circuit. When there is no transmission notification from another connection device, the terminal sends the information to another network on the assumption that it is time for a terminal in its own network to communicate with another network.

[0013] In addition, in order to perform transmission notification, the connection device may add a predetermined code to the information instead of passing through the transmission notification signal line and transmit the information to the bus of the own network. In this case, when receiving the information from the bus of the own network, the connection device detects whether or not the code is added to the information. Is discarded and there is no transmission notification when the code is not added.

By acting as described above, duplication and looping of packets can be prevented, and packet delay can be minimized.

[0015]

FIG. 1 is a block diagram of a network system according to an embodiment of the present invention.

In FIG. 1, a packet switching system 1
a, 1b, and 1c each constitute a LAN and exchange packets, and the LAN connection devices 3a, 3b,
They are connected by 3c, 3d, 3e and 3f, and can exchange packets between the respective LANs. A connection line 1 between LANs is provided between the connection devices 3b and 3c, between the connection devices 3d and 3e, and between the connection devices 3f and 3a.
0a, 10b, and 10c, which communicate bidirectionally. Here, a case where three LANs are connected is shown, but when four or more LANs are connected, one L
This can be realized by providing connection devices corresponding to all LANs from the AN and connecting via the connection devices (connecting LANs in a mesh form). For example, when connecting four LANs, one LAN has three other LANs.
Are provided, and each of them communicates with another LAN on a one-to-one basis. Connection devices 3b, 3c, 3d, 3
e, 3f and 3a can be realized by a single device like an existing bridge. Some LANs have a bus type, a star type, a ring type, or the like. Also,
As a bus-type configuration, for example, an IVDLAN (Integrated Voice) incorporating a plurality of high-speed packet buses is used.
and Data LAN). IVDLAN is IEEE8
The standardization is being promoted by the 22.9 committee, and introduced in IEICE Transactions on Information Technology, BI Vol.J72-B-1 No.11 November 1989 "Composition and Performance Evaluation of Integrated Voice and Data LAN" There is a method that incorporates a high-speed packet bus as described. The packet switching system 1a includes terminal accommodation circuits 2a and 2a.
b and the connection devices 3 a and 3 b exchange packets via the packet bus 4. The packet bus 4 is a bus in which packets flow in both directions, although shown as a pipe in the figure. Each of the LAN terminals 5a and 5b is a data terminal, a voice terminal, or the like, and is provided with an address indicating an identification number in advance. The LAN terminals 5a and 5b are connected to the terminal accommodation circuits 2a and 2b via the terminal accommodation lines 6a and 6b, respectively. Send and receive. The connection device and the terminal accommodating circuit cannot receive the packet while the device is transmitting the packet. The access control circuit 7 is a circuit that controls the right of transmission of the terminal accommodating circuits 2a and 2b and the connection devices 3a and 3b to the packet bus 4 via the access control signal line 8. Examples of the transmission right control method include a polling method and an attraction method. For example, in the case of using the polling method, the access control circuit 7 sends polling to each LAN terminal via the access control signal line 8, and when there is a packet to be sent, the LAN terminal polls. To send the packet after acquiring the transmission right. The terminal accommodating circuits 2a and 2b determine the destination of the packet and transmit the packets addressed to the LAN terminals 5a and 5b to the respective LAN terminals. That is, when a packet is received from the packet bus 4, the terminal accommodation circuit 2a transmits the destination address of the packet to the LAN terminal 5a.
With the address of When the addresses match as a result of the comparison, the terminal accommodation circuit 2a transmits the received packet to the LAN terminal 5a, asserts the reception notification signal line 9 during transmission, and negates after the transmission is completed. . The connection device discards the received packet when the reception notification signal line 9 is asserted. If they do not match, the terminal accommodation circuit 2a connects to the reception notifying signal line 9
Sends a packet to the packet bus 4 while negating. The same applies to the terminal accommodation circuit 2b. The reception notifying signal line 9 is used to discard the packets received by the LAN terminals 5a and 5b of the packet switching system 1a at the connection devices 3a and 3b so as not to transmit the packets to another packet switching system. That is, when each terminal accommodation circuit receives a packet addressed to the LAN terminals 5a and 5b in the packet switching system 1a, the reception notification signal line 9
Is asserted, the connection device discards the packet so as not to send it to another packet switching system, and negates the reception notifying signal line 9 when there is no packet addressed to the LAN terminals 5a and 5b. The transmission notification signal line 11 is for preventing duplication and looping of packets at the time of connection between LANs. Connection device 3a
And 3b receive a packet from another packet switching system and send it to the packet bus 4,
a and 3b assert the transmission notification signal line 11,
The packet is not transferred to another packet switching system, and the other negates the transmission notification signal line 11. When a LAN terminal in the packet switching system transmits to another packet switching system, the reception notification signal line 9 and the transmission notification signal line 11 can be transmitted from the connection device for negation. The packet switching systems 1b and 1c have the same configuration as the packet switching system 1a.

Next, the configuration and operation of each means will be described in detail with reference to the drawings.

FIG. 2 shows a hardware block diagram of a connection device using the transmission notification signal line 11. As shown in FIG. In FIG. 2, a connection device is a device for connecting the respective packet switching systems, and includes a reception buffer 12 and a transmission buffer 1.
4, a buffer control circuit 13, a reception notification line packet filter 15, a transmission notification line packet filter 16, and a processor 17. The reception buffer 12 temporarily stores a packet received from another packet switching system, and sends the packet to the packet bus 4 under the control of the buffer control circuit 13. When there is a received packet from another packet switching system, the buffer control circuit 13 asserts the transmission notification signal line 11 and instructs the reception buffer 12 to transmit the signal. The reception notification line packet filter 15 discards the packet when the reception notification signal line 9 is asserted, that is, when the terminal accommodation circuit receives a packet addressed to the LAN terminal.
When the transmission notification signal line 11 is asserted, that is, the transmission notification line packet filter 16 discards a packet received from another packet switching system. The reception notification line packet filter 15 and the transmission notification line packet filter 16 allow only packets to be transmitted to other packet switching systems to pass. The transmission buffer 14 temporarily stores only packets to be transmitted to another packet switching system among the packets from the packet bus 4 and transmits the packets.

Next, the operation of the connection device shown in FIG. 2 will be described. A packet received from another packet switching system via the LAN-to-LAN connection line 10a
To the packet bus 4 via. At this time, the buffer control circuit 13 that controls the buffer and asserts the transmission notification signal line 11 asserts the transmission notification signal line 11. For packets received from the packet bus 4, the reception notification line packet filter 15 monitors the reception notification signal line 9, and the transmission notification line packet filter 16 monitors the transmission notification signal line 11. When the notification signal line 9 and the transmission notification signal line 11 are not asserted, the signal is transmitted to the LAN connection line 10a via the transmission buffer 14. When the reception notification signal line 9 or the transmission notification signal line 11 is asserted, the packets received by the reception notification line packet filter 15 or the transmission notification line packet filter 16 are discarded. The processor 17 also transmits packets to a packet switching system that is not connected in a mesh.
When the system is started, it is possible to stop the assertion of the transmission notification signal line 11 in the buffer control circuit 13 and stop the discarding of the packet in the transmission notification line packet filter 16 at the time of system startup.

Next, the flow of a packet in the network system shown in FIG. 1 will be described with reference to FIG. FIG.
FIG. 3 is an explanatory diagram illustrating a flow of a packet in the network system of the present embodiment. First, a case where a packet is transmitted from the LAN terminal 5a of the packet switching system 1a to the LAN terminal 5a of the packet switching system 1C will be described as an example. First, the LAN terminal 5a acquires an access right via the access control signal line 8, and transmits a packet from the LAN terminal 5a of the packet switching system 1a to the packet bus 4. The connection devices 3a and 3b are connected to the packet bus 4
, Respectively. In this case, since the reception notification signal line and the transmission notification signal line are not asserted, the connection devices 3a and 3b are connected to the LAN connection line 1.
The packet is transmitted as it is to 0a and 10c. The connection devices 3c and 3f are connected to the LAN connection line 10a.
, And stores the received packet in the reception buffer. The connection device 3c acquires the access right through the access control signal line 8, transmits the packet received from the connection device 3a from the reception buffer to the packet bus 4, and transmits the packet to the connection device 3d during transmission. Asserts the reception notifying signal line 9 and negates it after the end of transmission. The connection device 3d that has received the packet from the packet bus 4
The received packet is discarded because the reception notification signal line is asserted. Similarly, the connection device 3f acquires the access right via the access control signal line 8, transmits the packet received from the connection device 3b from the reception buffer to the packet bus 4, and, while transmitting, transmits the packet. 3
Assert the reception notification signal line 9 with respect to e and negate it after the transmission is completed. The connection device 3e that has received the packet from the packet bus 4 discards the received packet since the reception notification signal line is asserted. The same applies to packets transmitted from LAN terminals of the packet switching systems 1b and 1c.

Further, L in the same packet switching system
A case where a packet is transmitted from the AN terminal 5a to the LAN terminal 5b will be described. First, the LAN terminal 5a acquires an access right via the access control signal line 8, and transmits a packet from the LAN terminal 5a of the packet switching system 1a to the packet bus 4. The terminal accommodation circuit 2b receives the packet from the packet bus 4, and compares the destination address of the packet with the address of the LAN terminal 5b. If the addresses match as a result of the comparison, the terminal accommodation circuit 2a
Transmits the received packet to the LAN terminal 5a and the packet bus 4, and asserts the reception notifying signal line 9 during transmission. If they do not match, the terminal accommodation circuit 2a keeps the reception notification signal line 9 negated. The connection devices 3a and 3b receive packets from the packet bus 4, respectively. Since the reception notification signal line 9 is asserted, the packet received from the packet bus 4 is discarded.

By operating as described above, duplication and looping of packets can be prevented, and packet delay can be minimized.

In addition, instead of the transmission notification signal line 11, a packet having information equivalent to that of the signal line is used for the LAN.
Connections can also be made between them. FIG. 4 shows the format of the packet in this case. In FIG. 4, a packet is composed of fields indicating a packet length, a destination address, a transmission address, a transmission notification field, an information field, and a frame check sequence for error detection. Be composed. In the transmission notification field shown in FIG. 4, when there is a packet received from another packet switching system, the connection device sets a predetermined code indicating the transmission notification.

FIG. 5 shows a hardware block diagram of a connection device using a packet having information equivalent to that of the signal line instead of the transmission notification signal line 11. In FIG. 5, the connection device includes a reception buffer 12, a transmission buffer 1
4, a packet processing circuit 18, a reception notification line packet filter 15, a connection device packet filter 19, and a processor 17. The reception buffer 12 temporarily stores packets received from another packet switching system, and the packet processing circuit 18 indicates a transmission notification in a transmission notification field when there is a packet received from another packet switching system. Set a predetermined code. The reception notification line packet filter 15 is connected to the reception notification signal line 9.
Is asserted, that is, when the terminal accommodation circuit receives a packet addressed to the LAN terminal, the packet is discarded. The connection device packet filter 19 includes:
The transmission notification field is monitored, and when a predetermined code indicating the transmission notification is set, the packet is discarded. The transmission buffer 14 temporarily stores only packets to be transmitted to another packet switching system among the packets from the packet bus 4 and transmits the packets.

Next, the operation of the connection device shown in FIG. 5 will be described. In FIG. 5, a packet received from another packet switching system via an inter-LAN connection line 10a receives a packet from a packet processing circuit 1 which sets predetermined code information in a reception buffer 12 and a packet transmission notification field.
8 to the packet bus 4. At this time, the packet processing circuit 18 sets the transmission notification code in the packet transmission notification field. For packets received from the packet bus 4, the reception notification line packet filter 15 monitors the reception notification signal line 9, and the connection device packet filter 19 controls the packet transmission notification filter.
When the reception notification signal line is negated and no information is set in the packet transmission notification field, the LAN connection line 1 is transmitted via the transmission buffer 14.
0a. When the reception notification signal line is asserted, the reception notification line packet filter 15 discards the received packet. When information is set in the packet transmission notification field, the connection device The packet received by the packet filter 19 is discarded. In addition, in order to transmit a packet to a packet switching system that is not connected in a mesh form, when the system is activated by a control signal from the processor 17, the setting of information in the packet transmission notification field in the packet processing circuit 18 is stopped. , And the connection device packet filter 19 can stop the packet discarding.

As described above, by providing the transmission notification field in the packet, duplication and looping of the packet can be prevented without providing a transmission notification signal line.

FIG. 7 shows a system configuration diagram of the second embodiment of the present invention. Packet switching systems 1a, 1b and 1
c has the same configuration as that described above, and the packet switching system 1d is connected to the packet switching system 1c by connection devices 3g and 3h via an inter-LAN connection line 10d. The packet switching system 1c includes the connection device 3g
And the connection device 3f can transmit the same packet, and the other configuration in the packet switching system has the same configuration as that described above. The packet switching system 1d has the same configuration as the packet switching systems 1a, 1b and 1c.
At the time of startup, the connection devices 3g and 3h are instructed in advance by a control signal from a processor in the connection device to stop asserting the transmission notification signal line and stop discarding packets by the transmission notification line packet filter. This allows a LAN configuration as shown in FIG.

Furthermore, the connection device in the system configuration diagram of one embodiment of the present invention is combined with the connection device that stops the assertion of the transmission notification signal line and stops the packet discarding by the transmission notification line packet filter. By using this, an arbitrary configuration in a plurality of LANs is possible.

Next, a network system according to a third embodiment will be described. In the third embodiment, two LANs are connected.
A case where load distribution is performed by providing two communication paths will be described. FIG. 6 shows a configuration diagram of a network system according to the third embodiment. The configuration shown in FIG. 6 has a configuration in which another connection device is further provided in the packet switching system 1a having the configuration shown in FIG. Each of the packet switching systems 1a and 1b constitutes a LAN, performs packet switching, and connects the LAN connection devices 3a and 3e with the LA.
It is connected by the N connection devices 3b and 3d, and can exchange packets between the respective LANs, and can also be connected to other packet switching systems. The packet switching system 1a exchanges packets from the LAN terminals 5a and 5b and the connection devices 3a, 3b and 3c via the packet bus 4. The packet switching system 1b has the same configuration as the packet switching system 1a. Between the connection devices 3b-3d and the connection device 3c-
3e is connected by the LAN connection lines 10a and 10b, and is different from the connection device in the above-described embodiment.
An example in which the respective packet switching systems are not connected in a mesh form will be described. The connection devices 3b and 3d
It is used when a LAN terminal in its own packet switching system sends out a packet to another packet switching system, and the connection devices 3c and 3e receive the packet from the other packet switching system. This is used when sending a packet to another packet switching system when the packet is not a packet addressed to a LAN terminal within the network. When receiving a packet from another packet switching system, the connection device 3 a asserts the connection device notification signal line 20 and sends the packet to the packet bus 4. When the packet is not a packet addressed to a LAN terminal in the packet switching system (when the reception notification signal line 9 is negated), the connection device 3c can send the packet to the packet switching system 1b. In this case, the connection device 3b
Discards the packet since the connection device notification signal line 20 is asserted. The connecting device 3f is connected to the connecting device 3a.
Similarly to the above, when a packet is received from another packet switching system, the connection device notification signal line 20 is asserted, and the packet is transmitted to the packet bus 4. When transmitting to the packet switching system 1a, the connection device notification signal line 20 is asserted. When a packet is received from the packet switching system 1a, the packet is transmitted to another packet switching system regardless of the connection device notification signal line 20. To send to. Similarly, the connection device 3b receives a packet from the corresponding connection device 3d, and transmits the packet to the packet bus 4 of the packet switching system 1a without asserting the connection device notification signal line 20. Also, the connection device 3c
Asserts the connection device notification signal line 20 when receiving a packet from the opposing connection device 3e and transmitting the packet to the packet bus 4 of the packet switching system 1a, and when the connection device notification signal line 20 is not asserted. The packet received from the packet bus 4 is discarded. The connection device 3e operates in the same manner as the connection device 3c.

Next, the flow of a packet will be described. When receiving a packet from another packet switching system, the connection device 3 a asserts the connection device notification signal line 20 and sends the packet to the packet bus 4. When the packet is not a packet addressed to a LAN terminal in the packet switching system (when the reception notification signal line 9 is negated), the connection device 3c can send the packet to the packet switching system 1b. The packet is transmitted to the packet bus 4 of the switching system 1b. In this case, the connection device 3b
Discards the packet since the connection device notification signal line 20 is asserted. On the other hand, the packet switching system 1
The packet transmitted from the LAN terminal 5a to the packet bus 4 is transmitted to the packet bus 4 of the packet switching system 1b using the connection devices 3b and 3d. Also,
Packets transmitted from the connection device 3f to the packet bus 4 of the packet switching system 1b are connected to the connection devices 3e and 3e.
c, the packet bus 4 of the packet switching system 1a.
Sent to. On the other hand, LA of the packet switching system 1b
The packet transmitted from the N terminal 5a to the packet bus 4 is transmitted to the packet bus 4 of the packet switching system 1a using the connection devices 3d and 3b.

As described above, the packet switching system 1a-
By connecting the LANs with two pairs of connecting devices using the connecting devices 3b, 3c, 3d, and 3e, the load can be distributed using the connecting device that can be realized by ordinary hardware. it can.

[0032]

According to the present invention, in a system including a physical loop structure in which a plurality of LANs are connected, duplication and looping of packets can be prevented, and packet delay can be minimized.

[Brief description of the drawings]

FIG. 1 is a system configuration diagram according to an embodiment of the present invention.

FIG. 2 is a block diagram of a connection device using a signal line according to one embodiment of the present invention.

FIG. 3 is an explanatory diagram showing a packet flow in the system according to the embodiment of the present invention;

FIG. 4 is a format of a packet.

FIG. 5 is a block diagram of a connection device according to another embodiment.

FIG. 6 is a configuration diagram of a system that performs load distribution according to a third embodiment.

FIG. 7 is a system configuration diagram of a second embodiment.

[Explanation of symbols]

1a, 1b, 1c, 1d: Packet switching system, 2a
... 2b: terminal accommodation circuit, 3a, 3b, 3c, 3d, 3e
・ 3f ・ 3g ・ 3h ... connection device, 4 ... packet bus, 5
a, 5b, 5c: LAN terminal, 6a, 6b: terminal accommodation line, 7: access control circuit, 8: signal line for access control, 9: signal line for reception notification, 10a10b10c10d
... LAN connection line, 11 ... Transmission notification signal line, 12 ...
Reception buffer, 13: buffer control circuit, 14: transmission buffer, 15: reception notification line packet filter, 16: transmission notification line packet filter, 17: processor, 18 ...
Packet processing circuit, 19: connection device packet filter,
20: Signal line for notification of connected device.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-1-255340 (JP, A) JP-A-5-219064 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H04L 12/28

Claims (6)

(57) [Claims] 1. A network system comprising a plurality of networks, wherein the network includes one or more terminal accommodation circuits to which terminals for communication are connected, a connection device for connecting another network, and a terminal accommodation circuit. And a bus for connecting the connection device. The connection device is provided corresponding to another network, and transmits information to another network when a terminal in the own network communicates with the other network. A network system which receives information from another network and sends it to a bus of its own network, and does not send information from another network to another network. 2. The terminal accommodating circuit according to claim 1,
When receiving information addressed to a terminal connected to the terminal accommodating circuit, the reception device outputs a reception notification. When the connection device receives information from another network, the connection device sends the information to a bus of the own network. And a transmission notification is output to another connection device of the own network, and the information is discarded when there is a reception notification from the terminal accommodation circuit, and the information is discarded when there is a transmission notification from another connection device of the own network. However, when there is no reception notification from the terminal accommodation circuit and no transmission notification from another connected device,
A network system for transmitting information to another network on the assumption that a terminal in the own network communicates with another network. 3. A transmission notification signal line for notifying transmission between connection devices in the own network according to claim 2,
A network system, further comprising: a signal line for receiving notification for connecting a terminal accommodating circuit in the own network and a connection device to notify reception from the terminal accommodating circuit. 4. The connection device according to claim 2, wherein when the connection device receives information from another network, the connection device adds a predetermined code to the information as a transmission notification and sends the information to a bus of the own network. When information is received from the bus of the own network, it is detected whether or not the code is added to the information. If the code is added, the information is discarded as a transmission notification, and the code is discarded. A network system characterized in that there is no transmission notification when it is not added. 5. The connection device according to claim 2, wherein the connection device can set in advance whether or not to output a transmission notification when receiving information from another network. Network system. 6. A connection device for connecting a network to which a plurality of communication terminals are connected, the connection device being provided corresponding to another network and transmitting information when a terminal in the own network communicates with the other network. A connection device for transmitting to another network, receiving information from another network, transmitting the information to a bus of the own network, and not transmitting information from another network to another network.