JPH0543223B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a network control device that performs addressing control in a system in which terminals on a plurality of local area networks communicate via one backbone network.

[Conventional technology]

In a packet communication system in which multiple local area networks of the same type connecting multiple terminals are connected to multiple nodes of a single backbone network with broadcasting characteristics, communication between the terminals is usually performed as follows.
This is done as follows. Each terminal transmits an information frame with the destination terminal's address and its own terminal's address, regardless of which local area network the other terminal is connected to. If the destination terminal is directly connected to the same local area network as the sending terminal, this destination terminal receives this information frame directly by looking at its destination address. On the other hand, a node looks at the destination address of this information frame and does not receive it if the destination terminal is directly connected to the local area network it hosts. Also, if the destination terminal is not connected to the local area network that it accommodates, it receives this information frame, looks up the table to find out which node the destination terminal is accommodated in, and uses the address of this node. A header within the backbone network, which has the destination address as the destination address and the own node's address as the source address, is added to the front of the received information frame and transmitted onto the backbone network. A node receives an information frame flowing on the backbone network only when the destination address is its own node's address, and after removing the header within the backbone network, sends it to the local area network accommodated in its own node. do.

According to this method, each terminal can communicate with each other as if they were connected to a single local area network, regardless of which local area network the other terminal is connected to. However, each node must maintain a correspondence table between all terminals and the addresses of the nodes that accommodate them. This address correspondence table is
It needs to be changed dynamically according to changes in system configuration, etc. The following method has been considered as an algorithm for dynamically creating an address correspondence table. First, a node receives all information frames on the local area network if it does not know the node where the destination terminal is accommodated, and sends them to a header in the backbone network whose destination address is the broadcast address instead of the destination node address. is added and sent over the core network. Information frames with broadcast addresses are received by all nodes, so they always reach the other party's terminal. On the other hand, once all information frames on the core network are received, the address of the source node written in the header within the core network and the address of the source terminal written inside are read, and from now on the terminal - Create a node address correspondence table. If this method is used, even if the address table is initially empty, once a terminal sends the information frame, that information frame will be broadcast on the backbone network, and all nodes will know the node address where the terminal is accommodated. The next time there is a communication addressed to that terminal, it can be sent to the node using the table. In this way, as time passes, the address table becomes complete, and the number of frames to be broadcast decreases.

[Problem that the invention seeks to solve]

The above-described method has the disadvantage that it places a heavy burden on the node because it must continue to receive all information frames in order to constantly update the address table.

[Means for solving problems]

The network control device of the present invention provides a communication system in which a plurality of local area networks connecting a plurality of terminals are connected to a plurality of nodes of a backbone network having broadcasting properties.
means for sequentially receiving only the portions of information frames that are directly connected to the backbone network and that include communication control information flowing on the backbone network; and a local network that is directly connected to the respective terminals from the received communication control portion The apparatus includes means for knowing the addresses of nodes connected to the area network, and means for broadcasting a correspondence table of the addresses of the terminals and the nodes accommodating them on the communication medium.

〔Example〕

Next, embodiments of the present invention will be described using the drawings.

FIG. 1 is a block diagram showing one embodiment of the network control device of the present invention.

All information frames flowing on the communication medium 1 of the backbone network enter the network control device 2 via the transmitting/receiving device 3, and are stored in the header memory 4 under the control of the injury buffer management device 5 at the header portion.
will be written to. The control unit 6 reads the source node address part and the source terminal address part of the header newly written in the header memory 4, compares it with the contents of the address correspondence table 7, and if the combination has not yet been registered, a new one is added. Add to address list. The timer 8 sends a signal to the control unit 6 at regular intervals, and in accordance with the signal, the control unit 6 transmits the contents of the address correspondence table 7 to the communication medium 1 via the transmitting/receiving device 3.

Next, the operation of this embodiment will be explained with reference to FIG.

FIG. 2 is a block diagram showing an example of the use of the network control device of the present invention, and shows a communication system in which a bus-type local area network is connected to a loop-type backbone network.

In the figure, 11 is the backbone network;
2, 13, and 14 are nodes, 15 is a network control device, 16, 17, and 18 are local area networks, and 19, 20, and 21 are terminals. Let's say we start with an empty address table,
Assume that the terminal 19 first sends a message to the terminal 21. Since the node 12 does not know in which node the terminal 21 is accommodated, it sends it to the backbone network 11 with a broadcast address attached.
Nodes 13 and 14 receive the broadcast address, remove the header to the backbone network, and send it to local area networks 17 and 14, respectively.
18, so that terminal 21 can receive this information frame. On the other hand, the network control device 15 also receives the header part of this information frame,
It is learned that the terminal 19 is accommodated in the node 12. Thereafter, when it is time for the network control device to transmit, the network control device 15 (terminal 19
- Node 12) information from core network 1
Broadcast on 1. Next, for example, terminal 2
0 sends a message to terminal 19, at this time node 13 knows that terminal 19 is accommodated in node 12, so it can send the message onto backbone network 11 using the address of node 12 as the destination address. can.

〔Effect of the invention〕

As explained above, each node only needs to receive the information frames that need to be transferred to the local area network that it accommodates, so the present invention has advantages such as a reduction in load and buffer capacity. be. In addition, the network control device does not need to receive the entire information frame and only needs to receive the header part, but since the header part has a fixed length and is much shorter than the entire information frame, the network control This has the effect of making it easier to manage the buffer of the device itself.

[Brief explanation of the drawing]

FIGS. 1 and 2 are block diagrams showing an embodiment and an example of use of the network control device of the present invention, respectively. 1... Communication medium, 2... Network control device, 3... Transmitting/receiving device, 4... Header memory, 5
. . . buffer management device, 6 . . . control unit, 7 . . . address correspondence table, 8 . . . timer.

Claims (1)

[Claims] 1. In a communication system in which a plurality of local area networks connecting a plurality of terminals are connected to a plurality of nodes of a backbone network having broadcasting properties, the network is directly connected to the backbone network, and means for sequentially receiving only the portions containing communication control information of the information frames flowing through the network; and means for determining, from the received communication control portions, the addresses of nodes connecting the local area networks to which the respective terminals are directly connected. and means for broadcasting, on the communication medium, a correspondence table between the addresses of the respective terminals and the nodes accommodating the terminals.