EP0508886A1
Expired / Lapsed
EP
⏱️ 0.0 years remaining
Filtering and disposition of messages in a bridge using a single address and protocol table
Assignee: Digital Equipment Corp
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Filing: 1992-04-07
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Granted: —
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Expires: 2012-04-07
Abstract
Abstract An arrangement for selective filtering, e.g. one-way filtering, of messages received by a 2-port bridge from stations connected to two LANs of an extended LAN is provided. The bridge includes a message filtering database containing the addresses of all stations connected to one of the LANs. The database also contains a list of higher-level protocols employed by the stations. Associated with each protocol-type is information used by the bridge to dispose of the message. The message filtering database comprises a single table memory capable of supporting both ports of the bridge. The selective filtering process involves a two-step analysis by the bridge to determine whether to discard the message or forward it to another port. The analysis is based on a destination address and a protocol-type of the received message.
Inventors
- 👤 Stephen D. Metzger
- 👤 Jeffrey A. Lomicka
- 👤 Gary Vacon
- 👤 Pat Gili
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-31 13:14
CPC Classifications
H; H04; H04L; H04L45/00; H04L45/74; H04L45/745; H04L12/00; H04L12/28; H04L12/46; H04L12/4604; H04L12/462; H04L12/4625; H04L45/742
Claims Analysis
Total Claims: 25
Claim 1
Independent Claim
152 words
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: means for receiving a message from said first medium; first storage means for storing a message filtering database, said database including: addresses of the stations connected to only one of said first and second media; and protocol-types within the stations connected to said first and second media; second storage means for storing disposition information associated with each of said protocol-types of said database; means for comparing said received message against said addresses and protocol-types of said database; and means responsive to said comparison means for selectively disposing of each received message in accordance with said disposition information when said comparison means specifies forwarding said message to said second medium.
Claim 2
Dependent Claim
17 words
The bridging apparatus of claim 1 wherein said first storage means comprises a table for said ports.
Claim 3
Dependent Claim
27 words
The bridging apparatus of claim 2 wherein said comparing means comprises means for comparing said destination address of said received message against said addresses of said database.
Claim 4
Dependent Claim
18 words
The bridging apparatus of claim 3 wherein said addresses are addresses of stations connected to said first medium.
Claim 5
Dependent Claim
34 words
The bridging apparatus of claim 4 wherein said selectively disposing means comprises means for discarding said received message when said destination address of said received message matches one of said addresses of said database.
Claim 6
Dependent Claim
44 words
The bridging apparatus of claim 5 wherein said comparing means further comprises means for comparing said protocol-type code of said received message against said protocol-types of said database when said destination address of said received message does not match said addresses of said database.
Claim 7
Dependent Claim
57 words
The bridging apparatus of claim 6 wherein said selectively disposing means further comprises means for forwarding said received message to said second medium when: (i) said protocol-type of said received message matches one of said protocol-types of said database; and (ii) said disposition information associated with said matched protocol-type specifies forwarding said message to said second medium.
Claim 8
Dependent Claim
20 words
The bridging apparatus of claim 7 wherein said table is a content addressable memory (CAM) having a plurality of entries.
Claim 9
Dependent Claim
24 words
The bridging apparatus of claim 8 wherein a first portion of said plurality of entries of said CAM contain said addresses of said database.
Claim 10
Dependent Claim
21 words
The bridging apparatus of claim 9 wherein a second portion of said plurality of entries of said CAM contain said protocol-types.
Claim 11
Dependent Claim
37 words
The bridging apparatus of claim 10 wherein a first flag and a second flag of said second portion of entries of said CAM are set to distingush said second portion from said first portion of said entries.
Claim 12
Dependent Claim
25 words
The bridging apparatus of claim 11 wherein said first flag is a multicast message bit and said second flag is a locally administered message bit.
Claim 13
Dependent Claim
20 words
The bridging apparatus of claim 3 wherein said address entries include the addresses of stations connected to said second medium.
Claim 14
Dependent Claim
34 words
The bridging apparatus of claim 13 wherein said selectively disposing means comprises means for discarding said received message when said destination address of said received message does not match said addresses of said database.
Claim 15
Dependent Claim
44 words
The bridging apparatus of claim 14 wherein said comparing means further comprises means for comparing said protocol-type code of said received message against said protocol-types of said database when said destination address of said received message matches one of said addresses of said database.
Claim 16
Dependent Claim
56 words
The bridging apparatus of claim 15 wherein said selectively disposing means further comprises means for forwarding said received message to said second medium when: (i) said protocol-type of said received message matches one of said protocol-types of said database; and (ii) said disposition information associated with said protocol-type specifies forwarding said message to said second medium.
Claim 17
Dependent Claim
20 words
The bridging apparatus of claim 16 wherein said table is a content addressable memory (CAM) having a plurality of entries.
Claim 18
Dependent Claim
24 words
The bridging apparatus of claim 17 wherein a first portion of said plurality of entries of said CAM contain said addresses of said database.
Claim 19
Dependent Claim
21 words
The bridging apparatus of claim 18 wherein a second portion of said plurality of entries of said CAM contain said protocol-types.
Claim 20
Dependent Claim
37 words
The bridging apparatus of claim 19 wherein a first flag and a second flag of said second portion of entries of said CAM are set to distingush said second portion from said first portion of said entries.
Claim 21
Dependent Claim
25 words
The bridging apparatus of claim 20 wherein said first flag is a multicast message bit and said second flag is a locally administered message bit.
Claim 22
Dependent Claim
204 words
Bridging apparatus for coupling a first network to a second network and for providing filtering of messages transmitted between stations connected to said networks, each of said messages including a destination address, said apparatus comprising: means for receiving a message from said first network; means for comparing said destination address of said received message against addresses contained in an address table of said apparatus, said address table containing addresses of said stations connected to one of said first and second networks; means for forwarding said received message to said second network when said address table contains the addresses of said stations connected to said first network and said destination address of said received message is not stored in said table, and when said table contains the addresses of said stations connected to said second network and said destination address is stored in said table; and means for discarding said received message when said address table contains the addresses of said stations connected to said first network and said destination address of said received message is stored in said table, and when said table contains the addresses of said stations connected to said second network and said destination address is not stored in said table.
Claim 23
Dependent Claim
199 words
For a bridging apparatus coupling a first network to a second network, a method for filtering messages transmitted between stations connected to said networks, each of said messages including a destination address, said method comprising the step of: receiving a message from said first network; comparing said destination address of said received message against addresses contained in an address table of said apparatus, said address table containing addresses of said stations connected to one of said first and second networks; forwarding said received message to said second network when said address table contains the addresses of said stations connected to said first network and said destination address of said received message is not stored in said table, and when said table contains the addresses of said stations connected to said second network and said destination address is stored in said table; and discarding said received message when said address table contains the addresses of said stations connected to said first network and said destination address of said received message is stored in said table, and when said table contains the addresses of said stations connected to said second network and said destination address is not stored in said table.
Claim 24
Dependent Claim
115 words
Bridging apparatus for coupling a first medium to a second medium and for providing filtering of messages transmitted between stations connected to said first and second media, each of said messages including a field identifying a photocol carried therein, said apparatus comprising: means for receiving a message from said first medium.; first means for storing a list of protocol-types existing within the stations connected to said first and second media; second means for storing disposition information associated with each of said protocol-types; means for comparing said protocol field of said received message against said protocol-types; and means responsive to said comparison means for selectively disposing of said received message in accordance with said disposition information.
Claim 25
Dependent Claim
101 words
For a bridging apparatus coupling a first medium to a second medium, a method for filtering messages transmitted between stations connected to said first and second media, each of said messages including a field identifying a protocol carried therein, said method comprising the step of: receiving a message from said first medium; storing a list of protocol-types existing within the stations connected to said first and second media; storing disposition information associated with each of said protocol-types; comparing said protocol field of said received message against said protocol-types; and selectively disposing of said received message in accordance with said disposition information.
References Cited (Backward Citations)
No citation records indexed.
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