JPH08274805A - Bridge circuit - Google Patents

Abstract

PURPOSE: To provide a bridge circuit with which a frame can be efficiently repeated by preventing the frame from being uselessly repeated. CONSTITUTION: This bridge circuit is provided with means 34a and 34b for receiving transfer frames transmitted from plural communication networks LAN-1 and LAN-2, means 40 for analyzing the transmission sources and destination networks of received transfer frames, and filtering means 42 for abandoning the transfer frame when its analyzed transmission source is equal with the destination network but for transmitting a prescribed message to the respective networks except for the transmission destination when they are not equal and further, a control means 40 is provided to decide the transfer destination network of frame based on whether the message is returned or not and to transfer the frame only to that decided network.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bridge circuit for interconnecting a plurality of communication networks, and particularly to IEEE8
The present invention relates to a bridge circuit that interconnects a plurality of local area networks (LANs) based on the 02.1D MAC bridge standard.

[0002]

2. Description of the Related Art FIG. 3 shows an IEEE802.1D MA.
The configuration of a conventional bridge circuit based on the C-bridge standard is shown. This bridge circuit interconnects the LAN (a) to which the communication stations 1a and 2a are connected and the LAN (b) to which the communication stations 1b and 2b are connected, and LAN (a) and (b), respectively. ) Connected to LANCEs 10a, 10b and internal buses 12a, 12
b, the buffer memory 14 connected to the LANCEs 10a and 10b, the bridge operation control unit 16 connected to the LANCEs 10a and 10b by the signal lines 20a and 20b, and the buffer memory 1 by the MPU bus 22.
4 and a filtering table RAM 18 connected to the bridge operation control unit 16. The bridge operation control unit 16 is usually composed of a microprocessor for controlling the operation of the bridge circuit, a program, a working memory, and the like. The buffer memory 14 is usually composed of a buffer memory and a memory controller.

The conventional bridge circuit configured as described above receives all frames transmitted / received on the LANs (a) and (b) as shown in the IEEE802.1D MAC bridge standard, The “source address (MAC address)” of the received frame and the “information indicating to which LAN the source station is connected (LAN name)” are stored in the filtering table RA.
It is stored in M18 (see FIG. 4). For example, when receiving a frame from station (1a), LANCE1
0a checks the frame for errors, and
The received frame is stored in the buffer memory 14 via 2a. At the same time, the reception notification is transmitted to the bridge operation control unit 16 via the signal line 20a. The bridge operation control unit 16 searches whether the MAC address (1a) of the station 1a and its belonging LAN (a) are stored in the filtering table RAM 18. If the station 1a is a filtering table RA
If it is not registered in M18, the information of the station 1a is newly registered.

In the bridge circuit, it is determined whether the received frame should be relayed, and the frame is transferred based on this. Filtering table RA
The information stored in M18 is searched, and if the source and destination stations are connected to different LANs, the frame is relayed. On the other hand, when the source station and the destination station are connected to the same LAN, it is not necessary to use the bridge circuit to relay the frame, and the frame is discarded (no relay is performed). However, if the “MAC address of the destination station” and the “name of the LAN to which the destination belongs” are not stored in the filtering table RAM 18, frames are transmitted to all LANs connected to the bridge circuit except the source LAN. Relay the frame. For the frame relay operation, the frame once stored in the buffer memory 14 is taken out, and the required L level is passed through the LANCE 10a or 10b.
This is done by sending to the AN.

[0005]

However, in the conventional bridge circuit, the destination MAC address is the multicast MAC address or the broadcast MAC address.
If it is an address, it will be transmitted to all LANs to which the bridge circuit is connected. For example, LAN
When the station 1a of (a) transmits a frame having the destination MAC address of the multicast address, the bridge circuit unconditionally transmits the frame to the LAN.
Send to (b). That is, even if no station on the LAN (b) requires the frame, the frame is automatically relayed.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a bridge circuit which can prevent useless frame relay and can efficiently perform frame relay. To do.

[0007]

In order to achieve the above object, according to the present invention, a station to which a frame addressed to a multicast MAC address or a broadcast MAC address to be relayed is to be received on a network to which a bridge circuit is connected. It is checked whether it is connected or not, and the necessity of relay operation is judged based on this. That is, the bridge circuit according to the present invention includes means for receiving transfer frames transmitted from a plurality of communication networks, means for analyzing the source and destination networks of the received transfer frames, and analyzed sources. If the destination networks are the same, the transfer frame is discarded, and if they are not the same, the filter means that sends a predetermined message to each network other than the destination, and the transfer of the frame based on whether the message is returned or not. The destination network is defined, and control means for transferring the frame only to the defined network is provided.

[0008]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. In FIG. 1, IEEE802.1D
The configuration of a bridge circuit according to an embodiment based on the MAC bridge standard is shown. This bridge circuit is a LAN (1) to which the communication stations 30a and 32a are connected.
And the LA to which the communication stations 30b and 32b are connected
N (2) are connected to each other, and each is a LAN
LANCE 34a, 34b connected to (1), (2)
And the internal bus 36a, 36b causes the LANCE 34
buffer memory 38 connected to a and 34b, and LANCE 34a and 34b by signal lines 44a and 44b.
Bridge operation control unit 40 connected to the MPU bus 4
6 includes a buffer memory 38 and a filtering table RAM 42 connected to the bridge operation control unit 40. The bridge operation control unit 40 is usually composed of a microprocessor for controlling the operation of the bridge circuit, a program, a working memory, and the like. The buffer memory 38 is usually composed of a buffer memory and a memory controller.

The bridge circuit configured as described above is
As shown in the IEEE802.1D MAC bridge standard, all frames transmitted and received on LAN (1) and (2) are received, and the "source address (MAC address)" of the received frame and its " The information indicating which LAN the transmission source station is connected to (the name of the belonging LAN) "is added to the filtering table RAM 42.
To be stored. For example, when the frame from the station (30a) is received, the frame error check is performed by the LANCE 34a, and the received frame is stored in the buffer memory 38 via the internal bus 36a. At the same time, the reception notification is transmitted to the bridge operation control unit 40 via the signal line 44a. Bridge operation control unit 40
Searches for the MAC address of the station 30a and its belonging LAN (1) stored in the filtering table RAM 42.

The received frame is "IAB RFC79
1 Internet Protocol (IP) ”, the destination MAC address is a multicast MAC address or a broadcast MAC address, and the destination IP address is a multicast IP
If it is an address, the following operation is performed on a network other than the network that transmitted the frame (1-4).

[Internet group management defined in [IAB RFC1112 Host Extension IP Multicasting]
A "host membership query" type message of "protocol (IGMP)" is transmitted to the destination multicast IP address (1-5). "host·
For the message of "Membership queri" type,
If no "host membership report" type message is returned, then the received frame is not sent to the network (1-6). On the other hand, "host
For the message of "Membership queri" type,
When the "host membership report" type message is returned, it is detected whether or not the multicast IP address of the frame is stored in the message (1-7). Then, when the multicast IP address of the frame is stored in the message, the frame is relayed to the network (1-8). On the other hand, when the multicast IP address of the frame is not stored in the message,
Do not relay frames to the network (1-
9).

[0012]

As described above, according to the bridge circuit of the present invention, it is possible to prevent useless frame relay and efficiently perform frame relay.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a bridge circuit according to an embodiment of the present invention.

FIG. 2 is a flow chart for explaining the operation of the embodiment of FIG.

FIG. 3 is a block diagram showing a configuration of a conventional bridge circuit.

FIG. 4 is an explanatory diagram for explaining the action and operation of the embodiment of FIG.

[Explanation of symbols]

30a, 30b, 32a, 32b ... Communication station 34a, 34b ... LANCE 36a, 36b ... Internal bus 38 ... Buffer memory 40 ... Bridge operation control unit 42 ... Filtering table RAM 46. ..MPU bus

Claims (2)

[Claims] 1. A plurality of communication networks are interconnected,
In a bridge circuit that transfers a frame containing data indicating a source network and a destination network, means for receiving a transfer frame transmitted from the plurality of communication networks, and a source network and a destination network of the received transfer frame And a filter for discarding the transfer frame when the analyzed source and destination networks are the same and transmitting a predetermined message to each network other than the network which transmitted the frame when they are not the same. A bridge circuit comprising: means and a control means that determines a transfer destination network of a frame based on whether or not the message is returned, and transfers the frame only to the determined network. 2. A bridge circuit interconnecting a plurality of local area networks according to the IEEE802.1D MAC bridge standard, wherein frames from the plurality of networks are received, and the received frames are "IAB RFC791 Internet Protocol (IP). ) ”, The destination MAC address is a multicast MAC address or a broadcast MAC address, and the destination IP address is a multicast IP address, a means for outputting a first signal; Based on the signal, [IAB RFC
1112: means for transmitting a "host membership query" type message of "Internet Group Management Protocol (IGMP)" defined in "1112 Host Extension IP Multicasting" to the destination multicast IP address "Host Membership Report" to the message of "Host Membership Queries"
Type message is returned, and a means for relaying the frame only to a network in which the multicast IP address of the frame is stored in the message, and a bridge circuit.