Disposition filtering of messages using a single address and protocol table bridge

A bridge for coupling a first network to a second network, said bridge comprising:

• a bus;
• a message filtering database coupled to said bus, said message filtering database having a plurality of database entries including:
• address entries containing addresses of the stations connected to one of said networks;
• and
• protocol-type entries containing protocol-types within the stations connected to said one network;
• a memory, coupled to said bus, for storing disposition information associated with each of protocol-type entry;
• a plurality of port controllers, coupled to said bus, for receiving and transmitting a message between said networks, said port controllers configured to perform direct memory access (DMA) requests in said memory;
• and
• a multi-stage control unit, coupled to said bus, for executing message filtering operations of said bridge in response to said DMA requests.

A bridge for coupling a first network to a second network, said bridge comprising:

• a bus;
• a message filtering database coupled to said bus, said message filtering database having a plurality of database entries including:
• address entries containing addresses of the stations connected to one of said networks;
• and
• protocol-type entries containing protocol-types within the stations connected to said one network;
• a memory, coupled to said bus, for storing disposition information associated with each of protocol-type entry;
• a plurality of port controllers, coupled to said bus, for receiving and transmitting a message between said networks, said port controllers configured to perform direct memory access (DMA) requests in said memory;
• and
• a multi-stage control unit, coupled to said bus, for executing message filtering operations of said bridge, said control unit including:
• a memory allocation stage for responding to DMA requests from said port controllers in response to reception of said message, said memory allocation stage initiating time-multiplexed transfer of said message over said bus to said memory;
• an address filtering stage, coupled to said memory allocation stage, for executing time-multiplexed comparison operations between a destination address of said message and said address entries of said database over said bus;
• a protocol-type filtering stage, coupled to said address filtering stage, for executing time-multiplexed comparison operations between a protocol-type of said message and said protocol-type entries of said database over said bus in response to a match between said destination address and one of said address entries;
• and
• a message disposition stage for disposing of said message in accordance with results of said address filtering and protocol-type filtering stages.

A method for filtering a message received at a bridge from a source station coupled to a first network and destined for a destination station coupled to a second network, said bridge connecting the first network to the second network, said method comprising the steps of:

• (A) comparing a destination address of the received message with address entries contained in a message filtering database, said message filtering database containing only addresses of stations connected to the first network;
• discarding the received message if said destination address of the received message matches any of said address entries contained in said message filtering database;
• (B) comparing a protocol-type of the received message with protocol-type entries contained in said message filtering database if said destination address of the received message does not match any of said addresses contained in said message filtering database;
• forwarding the received message to the second network if said protocol-type of the received message does not match any of said protocol-type entries contained in said message filtering database;
• and
• disposing of the received message in accordance with disposition information, associated with each of said protocol-type entries, stored in said bridge if said protocol-type of the received message matches any of said protocol-type entries contained in said message filtering database.

Bridging apparatus having two ports for coupling to a first medium and a second medium, said apparatus providing selective filtering of messages transmitted between stations on said media, each of said messages including a destination address and a protocol-type code, said apparatus comprising:

• A. means for receiving a message from said first medium;
• B. a single table for storing a message filtering database, said single table having a plurality of database entries capable of supporting each of the two ports of said apparatus, said database entries comprising
• B1. a first portion of entries containing addresses of the stations connected to only one of said first and second media;
• and
• B2. a second portion of entries containing protocol-types within the stations connected to said first and second media,
• C. storage means for storing disposition information associated with each of said protocol-types stored in said database entries;
• D. means for comparing said received message with said addresses and protocol-types stored in said database entries;
• E. means responsive to said comparison means for selectively disposing of each received message in accordance with said disposition information by forwarding said message to said second medium when one of
• said protocol-type of said message does not match one of said protocol-types of said database entries;
• and
• said protocol-type of said message matches one of said protocol-types of said database entries and said disposition information associated with said protocol-type specifies forwarding said message to said second medium .