Inter-LAN connection equipment

• US 5,477,547 A
• Filed: 07/29/1994
• Issued: 12/19/1995
• Est. Priority Date: 07/29/1993
• Status: Expired due to Term

• Current Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Original Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Inventors: Sugiyama, Takashi
• Primary Examiner(s): Safourek, Benedict V.
• Application Number:
  US08/282,438
• Time in Patent Office: 508 Days
• Field of Search: 370/61, 370/85.13, 370/85.14, 370/94.1
• US Class Current: 370/401
• CPC Class Codes: H04L 12/46 Interconnection of networks

Abstract

An inter-LAN bridge equipment is for performing the following operation. That is, a connected to a plurality of LANs. A LANs includes a destination address and source address is extracted from a terminal address. Address information containing the extracted terminal address and corresponding LAN port address is registered in a table memory at a corresponding entry area. When a packet is received from the LAN after address learning, the packet is inputted to a FIFO memory from its start side and held there. The address information is read out of the table memory and comparison is made, by the terminal address comparing circuit, between the terminal address of the address information and a destination address of the received packet. Further, comparison is also made, by a LAN port address comparing circuit, between a LAN port address of the address information and a receive-side LAN port address. A discard operation is performed when a result of comparison by the terminal address comparing circuit shows a coincidence and a result of comparison by the LAN port address comparing circuit show a coincidence. A forward operation is performed when the result of comparison by the terminal address comparing circuit shows a coincidence and the result of comparison by the LAN port address comparing circuit shows a noncoincidence.

Claims

1. An inter-LAN bridge equipment connected to at least two LANs comprising:

address learning means, provided for each LAN, for receiving from a given LAN a packet including a destination address and a source address, and for generating address information having the source address and a LAN port address for distinguishing the given LAN;

table memory address generating means, provided for each LAN, for generating a table memory address on the basis of the source address;

a shared table memory for allowing the address information which is generated from the address learning means to be registered in an entry designated by the table memory address generating means;

a first in--first out memory, provided for each LAN, for allowing the packet which is sent from the LAN to be stored therein;

first comparing means, provided for each LAN, for receiving the packet sent from the LAN, for extracting a destination address in the packet, for taking out the address information from the shared table memory at an entry corresponding to the destination address and for comparing the destination address with the source address in the address information;

second comparing means, provided for each LAN, for taking out the address information and for comparing a LAN port address of the LAN with the LAN port address in the address information from the shared table memory

discarding means, provided for each LAN, for discarding the packet sent from the LAN when a result of comparison by the first and second comparing means represents a coincidence; and

forward means, provided for each LAN, for allowing the packet which is stored in the first in--first out memory to be sent to the LAN corresponding to the LAN port address of the read address information when a result of comparison by the first comparing means shows a coincidence and a result of comparison by the second comprising means shows a noncoincidence.

2. The inter-LAN bridge equipment according to claim 1, wherein the forward means includes means for connecting an output of the first in--first out memory to a port of the transmit-destination LAN.

3. The inter-LAN bridge equipment according to claim 2, wherein the forward means includes means for preventing any forward from being made during a time period in which the port of the transmit-destination LAN is used.

4. The inter-LAN connection equipment according to claim 3, wherein the first in--first out memory is of a one-bit data width type.

5. The inter-LAN bridge equipment according to claim 1, wherein the forward means includes means for, when the destination address of the packet corresponds to a multicast address, controlling transmission of the packet to all other LAN irrespective of the results of comparison by the first and second comparing means.

6. An inter-LAN bridge equipment connected to at least two LANs comprising:

address learning means, provided for each LAN, for receiving from a given LAN a packet including a destination address and a source address, and for generating address information having the source address and a LAN port address for distinguishing the given LAN;

table memory address generating means, provided for each LAN, for generating a table memory address on the basis of the source address;

a shared table memory for allowing the address information which is generated from the address learning means to be registered in an entry designated by the table memory address generated from the table memory address generating means;

a first in--first out memory, provided for each LAN, for allowing the packet which is sent from the LAN to be stored therein;

first comparing means, provided for each LAN, for receiving the packet sent from the LAN, for extracting a destination address in the packet, for taking out the address information from the shared table memory at an entry corresponding to the destination address and for comparing the destination address with the source address in the address information;

second comparing means, provided for each LAN, for taking out the address information and for comparing a LAN port address of the LAN with the LAN port address in the address information from the shared table memory;

discarding means, provided for each LAN, for discarding the packet sent from the LAN when a result of comparison by the first and second comparing means represents a coincidence;

forward means, provided for each LAN, for allowing the packet which is stored in the first in--first out memory to be sent to the LAN corresponding to the LAN port address of the read address information when a result of comparison by the first comparing means shows a coincidence and a result of comparison by the second comparing means shows a noncoincidence; and

means for, when the destination address of the packet corresponds to a multicast address, controlling to transmit the packet to all the other LAN irrespective of the results of comparison by the first and second comparing means.

7. The inter-LAN bridge equipment according to claim 6, wherein the forward means includes means for connecting an output of the first in--first out memory to a port of the transmit-destination LAN.

8. The inter-LAN bridge equipment according to claim 7, wherein the forward means includes means for preventing any forward from being made during a time period in which the port of the destination LAN is used.

9. The inter-LAN connection equipment according to claim 8, wherein the first in--first out memory is of a one-bit data width type.

10. An inter-LAN bridge equipment connected to at least two LANs comprising:

address learning circuit, provided for each LAN, for receiving from a given LAN a packet including a destination address and a source address, and for generating address information having the source address and a LAN port address for distinguishing the given LAN;

table memory address generating circuit, provided for each LAN, for generating a table memory address on the basis of the source address;

a shared table memory for allowing the address information which is generated from the address learning circuit to be registered in an entry designated by the table memory address generated from the table memory address generating circuit;

a first in--first out memory, provided for each LAN, for allowing the packet which is sent from the LAN to be stored therein;

first comparing circuit, provided for each LAN, for receiving the packet sent from the LAN, for extracting a destination address in the packet, for taking out the address information from the shared table memory at an entry corresponding to the destination address and for comparing the destination address with the source address in the address information;

second comparing circuit, provided for each LAN, for taking out the address information and for comparing a LAN port address of the LAN with the LAN port address in the address information from the shared table memory;

discarding circuit, provided for each LAN, for discarding the packet sent from the LAN when a result of comparison by the first and second comparing circuit represents a coincidence; and

forward circuit, provided for each LAN, for allowing the packet which is stored in the first in--first out memory to be sent to the LAN corresponding to the LAN port address of the read address information when a result of comparison by the first comparing circuit shows a coincidence and a result of comparison by the second comparing circuit shows a noncoincidence.

11. The inter-LAN bridge equipment according to claim 10, wherein the forward circuit includes a circuit for connecting an output of the first in--first out memory to a port of the transmit-destination LAN.

12. The inter-LAN bridge equipment according to claim 11, wherein the forward circuit includes circuit for preventing any forward from being made during a time period in which the port of the transmit-destination LAN is used.

13. The inter-LAN connection equipment according to claim 12, wherein the first in--first out memory is of a one-bit data width type.

14. The inter-LAN bridge equipment according to claim 10, wherein the forward circuit includes a circuit for, when the destination address of the packet corresponds to a multicast address, controlling transmission of the packet to all other LAN irrespective of the results of comparison by the first and second comparing circuit.