US5124984A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Access controller for local area network
Assignee: Concord Communications LLC
•
Filing: 1990-08-07
•
Granted: 1992-06-23
•
Expires: 2010-08-07
Abstract
Abstract An access controller for peer-to-peer communication networks which monitors the data packets transmitted between stations, determines when an access that needs to be controlled is being made, and then either destroys the packet or transmits one or more packets which appear as legitimate message packets to the stations but which, in fact, terminates or alters the communication path between the two stations. Since the invention is free of any particular protocol restrictions, it can be implemented with any type of protocol and at any layer of that protocol. And since the access control mechanism is neither part of the physical communication path nor part of the communication primitives, the stations cannot detect, in any direct sense, that their access is being controlled, and they do not need to be programmed to follow any special control protocols, or to use encryption. A signature signal can be used as a safety mechanism to prevent multiple access controllers from controlling the same network, to prevent an unauthorized access controller from seizing control of the network.
Inventors
- 👤 Ferdinand Engel
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 23:10
CPC Classifications
H; H04; H04L; H04L63/00; H04L63/12; H04L63/126; H04L12/00; H04L12/02; H04L12/22; H04L63/14; H04L63/1408; H04L63/1416; H04L63/1441
Claims Analysis
Total Claims: 50
Claim 1
Independent Claim
103 words
An access controller for use in a communications network having a plurality of stations which vie for access to a shared physical medium, the access controller comprising: means for passively detecting packets transmitted on the medium; means for determining if a detected packet indicates that one of the stations is attempting an unauthorized access to another station; and means for originating an access termination signal on the medium if the means for determining determines that the detected packet indicates an unauthorized access, the access termination signal selectively terminating the particular unauthorized access while allowing other authorized accesses by the attempting station to continue.
Claim 2
Dependent Claim
103 words
An access controller for use in a communications network having a plurality of stations which vie for access to a shared physical medium, the access controller comprising: means for passively detecting packets transmitted on the medium; means for determining if a detected packet indicates that one of the stations is attempting an unauthorized access to another station; and means for originating an access termination signal on the medium if the means for determining determines that the detected packet indicates an unauthorized access, the access termination signal selectively terminating the particular unauthorized access while allowing other authorized accesses by the attempting station to continue.
Claim 3
Dependent Claim
23 words
An access controller as in claim 1 wherein the means for determining additionally examines a source station identification field in the detected packet.
Claim 4
Dependent Claim
23 words
An access controller as in claim 1 wherein the means for determining additionally examines a destination station identification field in the detected packet.
Claim 5
Dependent Claim
23 words
An access controller as in claim 1 wherein the means for determining additionally examines a protocol type identification field in the detected packet.
Claim 6
Dependent Claim
26 words
An access controller as in claim 1 wherein the means for originating an access termination signal additionally transmits an access controller identification signal on the medium.
Claim 7
Dependent Claim
68 words
An access controller as in claim 5 wherein said network includes another access controller connected to the physical medium, said another access controller includes means for transmitting an access termination signal, and wherein said access controller additionally comprises: means for shutting down the access controller for a predetermined period of time if an access controller identification signal transmitted by said another access controller is detected on the medium.
Claim 8
Dependent Claim
28 words
An access controller as in claim 6 wherein said access controller additionally comprises: means for transmitting a shutdown signal on the medium before shutting down the access controller.
Claim 9
Dependent Claim
64 words
An access controller as in claim 7 wherein said another access controller includes means for transmitting a shutdown signal on the medium before before shutting down the access controller, and wherein said access controller additionally comprises: means for shutting down the access controller for a predetermined period of time if a shutdown signal transmitted by said another access controller is detected on the medium.
Claim 10
Dependent Claim
18 words
An access controller as in claim 1 wherein the means for detecting packets detects data link layer packets.
Claim 11
Dependent Claim
34 words
An access controller as in claim 9 wherein the means for originating an access termination signal destroys the detected packet, if the means for determining determines that the detected packet indicates an unauthorized access.
Claim 12
Dependent Claim
17 words
An access controller as in claim 1 wherein the means for detecting packets detects network layer packets.
Claim 13
Dependent Claim
49 words
An access controller as in claim 11 wherein the means for originating an access termination signal transmits a connection termination packet to the station which was the source of the detected packet, the connection termination packet indicating that a destination station specified in the detected packet is not operable.
Claim 14
Dependent Claim
17 words
An access controller as in claim 1 wherein the means for detecting packets detects transport layer packets.
Claim 15
Dependent Claim
35 words
An access controller as in claim 13 wherein the means for originating an access termination sequence transmits a connection termination packet to both a destination station and a source station specified in the detected packet.
Claim 16
Dependent Claim
126 words
A network access controller comprising: an interface circuit, connected to transmit and detect data packets on a physical medium shared by a plurality of network stations; a memory, having stored therein data which represents a list of authorized network access types; and processor means, connected to the interface circuit and the memory, for receiving a detected packet from the interface circuit, and for comparing the detected packet with the list of authorized network protocol types, to determine whether the detected packet indicates an unauthorized access, and, if the detected packet indicates an unauthorized access, for causing the interface circuit to transmit an access termination signal on the physical medium, the access termination signal selectively terminating the unauthorized access while allowing other authorized accesses to be attempted.
Claim 17
Dependent Claim
126 words
A network access controller comprising: an interface circuit, connected to transmit and detect data packets on a physical medium shared by a plurality of network stations; a memory, having stored therein data which represents a list of authorized network access types; and processor means, connected to the interface circuit and the memory, for receiving a detected packet from the interface circuit, and for comparing the detected packet with the list of authorized network protocol types, to determine whether the detected packet indicates an unauthorized access, and, if the detected packet indicates an unauthorized access, for causing the interface circuit to transmit an access termination signal on the physical medium, the access termination signal selectively terminating the unauthorized access while allowing other authorized accesses to be attempted.
Claim 18
Dependent Claim
38 words
An access controller as in claim 1 wherein the network uses a carrier sense multiple access with collision detection (CSMA/CD) physical layer and the access termination signal is a signal that causes a collision with the detected packet.
Claim 19
Dependent Claim
16 words
An access controller as in claim 1 wherein the network uses a token ring physical layer.
Claim 20
Dependent Claim
75 words
An access controller as in claim 1 additionally comprising: means for detecting a station address indicated by a destination field in the detected packet, and wherein the access termination signal transmitted by the access controller is a packet having a source address field set equal to the destination field in the detected packet, and a field indicating that the station specified by the destination field in the detected packet is not able to receive packets.
Claim 21
Dependent Claim
53 words
An access controller as in claim 1 additionally comprising: means for detecting a station address indicated by a source field in the detected packet, and wherein the access termination signal transmitted by the access controller is a packet having a source address field set equal to the source field in the detected packet.
Claim 22
Dependent Claim
110 words
An access controller for use in a communications network having a plurality of stations which vie for access to a shared physical medium, the access controller comprising: means for passively detecting packets transmitted on the medium; means for determining if a detected packet indicates that one of the stations is attempting an unauthorized access to another station; and means for transmitting an access termination signal to a source station which originated the detected packet, if the means for determining determines that the detected packet indicates an unauthorized access, and the access termination signal indicating to the source station that a destination station specified in the detected packet is not operable.
Claim 23
Dependent Claim
110 words
An access controller for use in a communications network having a plurality of stations which vie for access to a shared physical medium, the access controller comprising: means for passively detecting packets transmitted on the medium; means for determining if a detected packet indicates that one of the stations is attempting an unauthorized access to another station; and means for transmitting an access termination signal to a source station which originated the detected packet, if the means for determining determines that the detected packet indicates an unauthorized access, and the access termination signal indicating to the source station that a destination station specified in the detected packet is not operable.
Claim 24
Dependent Claim
123 words
An access controller for use in a peer-to-peer communications network having a plurality of stations which vie for access to a shared physical medium, the access controller comprising: means for passively detecting packets transmitted on the network; means for determining if a detected packet indicates that a communication between a first station and a second station is being attempted, and that the attempted communication is of a type which is unauthorized; and means for originating a termination signal which causes the unauthorized communication between the first and second station to terminate, while allowing the first and second stations to continue other authorized communications with each other, and allowing each of the first and second stations to continue other authorized communications with other stations.
Claim 25
Dependent Claim
123 words
An access controller for use in a peer-to-peer communications network having a plurality of stations which vie for access to a shared physical medium, the access controller comprising: means for passively detecting packets transmitted on the network; means for determining if a detected packet indicates that a communication between a first station and a second station is being attempted, and that the attempted communication is of a type which is unauthorized; and means for originating a termination signal which causes the unauthorized communication between the first and second station to terminate, while allowing the first and second stations to continue other authorized communications with each other, and allowing each of the first and second stations to continue other authorized communications with other stations.
Claim 26
Independent Claim
91 words
A method for controlling access to a communications network in which a plurality of stations vie for access to a shared physical medium, the method comprising the steps of: detecting packets transmitted on the medium; determining if information in a detected packet indicates that one of the stations is attempting an unauthorized access to another station; and if the detected packet indicates an unauthorized access, transmitting an access termination signal on the medium which selectively terminates the particular unauthorized access while allowing other authorized accesses by the attempting station to continue.
Claim 27
Independent Claim
91 words
A method for controlling access to a communications network in which a plurality of stations vie for access to a shared physical medium, the method comprising the steps of: detecting packets transmitted on the medium; determining if information in a detected packet indicates that one of the stations is attempting an unauthorized access to another station; and if the detected packet indicates an unauthorized access, transmitting an access termination signal on the medium which selectively terminates the particular unauthorized access while allowing other authorized accesses by the attempting station to continue.
Claim 28
Dependent Claim
36 words
A method as in claim 22 wherein the step of determining if one of the stations is attempting an unauthorized access additionally comprises the step of: examining a source station identification field in the detected packet.
Claim 29
Dependent Claim
36 words
A method as in claim 22 wherein the step of determining if one of the stations is attempting an unauthorized access additionally comprises the step of: examining a destination station identification field in the detected packet.
Claim 30
Dependent Claim
43 words
A method as in claim 22 wherein the step of determining if one of the stations is attempting an unauthorized access additionally comprises the step of: comparing a protocol type identification field in the detected packet to a list of authorized protocol types.
Claim 31
Dependent Claim
26 words
A method as in claim 22 wherein the step of transmitting an access termination signal additionally comprises: transmitting an access controller identification signal on the medium.
Claim 32
Dependent Claim
52 words
A method as in claim 26 wherein the network includes another access controller which transmits identification signals on the physical medium, and the method additionally comprises the steps of: waiting a predetermined period of time if an access controller identification signal transmitted by said another access controller is detected on the medium.
Claim 33
Dependent Claim
26 words
An access controller as in claim 27 additionally comprising the step of: transmitting a shutdown signal on the medium before waiting a predetermined period of time.
Claim 34
Dependent Claim
37 words
A method as in claim 28 additionally comprising the step of: waiting for a predetermined period of time if the step of detecting packets detects a shutdown signal transmitted on the medium by said another access controller.
Claim 35
Dependent Claim
23 words
A method as in claim 22 wherein the step of transmitting an access termination signal includes the step of destroying the detected packet.
Claim 36
Dependent Claim
32 words
A method as in claim 22 wherein the step of transmitting an access termination signal includes the step of transmitting a connection termination packet to the station which originated the unauthorized access.
Claim 37
Dependent Claim
62 words
A method as in claim 22 wherein the detected packet includes a source address field and a destination address field, and the step of transmitting an access termination signal includes the steps of transmitting a connection termination packet to a station indicated by the source address field; and transmitting a connection termination packet to a station indicated by the destination address field.
Claim 38
Dependent Claim
41 words
A method as in claim 22 wherein the network uses a carrier sense multiple access with collision detection (CSMA/CD) physical layer and the step of transmitting an access termination signal includes the step of causing a collision with the detected packet.
Claim 39
Dependent Claim
17 words
A method as in claim 22 wherein the network uses a token ring data link layer .
Claim 40
Dependent Claim
56 words
A method as in claim 22 additionally comprising the steps of: determining a station address indicated by a source field in the detected packet; and wherein the step of transmitting an access termination signal includes the step of transmitting a packet having a destination address field set equal to the source field in the detected packet.
Claim 41
Dependent Claim
67 words
A method as in claim 22 additionally comprising the steps of: determining a station address indicated by a destination field in the detected packet, and wherein the step of transmitting an access termination signal includes the step of transmitting a packet having a source address field set equal to the destination field in the detected packet, and a field indicating that the attempted access should be terminated.
Claim 42
Dependent Claim
67 words
A method as in claim 22 additionally comprising the steps of: determining a station address indicated by a source field in the detected packet, and wherein the step of transmitting an access termination signal includes the step of transmitting a packet having a destination address field set equal to the source field in the detected packet, and a field indicating that the attempted access should be terminated.
Claim 43
Independent Claim
104 words
A method for controlling access to a communications network having a plurality of stations which vie for access to a shared physical medium, the method comprising the steps of: passively detecting packets transmitted on the medium; determining if a detected packet indicates that one of the stations is attempting an access to another station which is unauthorized; and if the detected packet indicates an unauthorized access, transmitting an access termination signal over the medium to a source station which originated the unauthorized access, the access termination signal indicating to the source station that a destination station specified in the detected packet is not operable.
Claim 44
Independent Claim
104 words
A method for controlling access to a communications network having a plurality of stations which vie for access to a shared physical medium, the method comprising the steps of: passively detecting packets transmitted on the medium; determining if a detected packet indicates that one of the stations is attempting an access to another station which is unauthorized; and if the detected packet indicates an unauthorized access, transmitting an access termination signal over the medium to a source station which originated the unauthorized access, the access termination signal indicating to the source station that a destination station specified in the detected packet is not operable.
Claim 45
Independent Claim
123 words
A method for controlling access to a peer-to-peer communications network which includes a plurality of station that vie for access to a shared medium, the method comprising the steps of: passively detecting packets transmitted on the shared medium; determining if a detected packet indicates that a communication between a first station and a second station is being attempted, and that the attempted communication is of a type which is unauthorized; and originating a termination signal on the medium which causes the unauthorized communication between the first and second station to terminate, while allowing the first and second stations to continue other authorized communications with each other, and allowing each of the first and second stations to continue other authorized communications with other stations.
Claim 46
Independent Claim
123 words
A method for controlling access to a peer-to-peer communications network which includes a plurality of station that vie for access to a shared medium, the method comprising the steps of: passively detecting packets transmitted on the shared medium; determining if a detected packet indicates that a communication between a first station and a second station is being attempted, and that the attempted communication is of a type which is unauthorized; and originating a termination signal on the medium which causes the unauthorized communication between the first and second station to terminate, while allowing the first and second stations to continue other authorized communications with each other, and allowing each of the first and second stations to continue other authorized communications with other stations.
Claim 47
Independent Claim
137 words
A method for preventing unauthorized accesses to a communication medium shared by a plurality of network stations which communicate by exchanging data packets, the steps of the method performed by an access controller station which masquerades as one of the stations indicated as a destination address in an unauthorized access, the method comprising the steps of: detecting information which indicates the type of data packet presently being communicated on the medium; comparing the detected data protocol type to a list of authorized data protocol types, to determine if the protocol type presently being communicated on the medium is unauthorized; and transmitting a reply packet on the medium, the reply packet appearing as a legitimate response by an intended destination station indicated by the detected packet, while terminating the unauthorized access and allowing other authorized accesses to continue.
Claim 48
Independent Claim
137 words
A method for preventing unauthorized accesses to a communication medium shared by a plurality of network stations which communicate by exchanging data packets, the steps of the method performed by an access controller station which masquerades as one of the stations indicated as a destination address in an unauthorized access, the method comprising the steps of: detecting information which indicates the type of data packet presently being communicated on the medium; comparing the detected data protocol type to a list of authorized data protocol types, to determine if the protocol type presently being communicated on the medium is unauthorized; and transmitting a reply packet on the medium, the reply packet appearing as a legitimate response by an intended destination station indicated by the detected packet, while terminating the unauthorized access and allowing other authorized accesses to continue.
Claim 49
Independent Claim
106 words
A method for preventing a selected attempted communication by a first station with a second station within a network of stations connected by a physical medium, where the communication is being attempted in accordance with a packet-type communication protocol which provides a mechanism for effecting termination of the communication, said method comprising the steps of: detecting the presence on the medium of a packet representing said selected attempted communication; and preventing said selected attempted communication by said first station by originating on said physical medium an access prevention signal in accordance with said communication terminating mechanism, while allowing other communications by said first station to continue.
Claim 50
Independent Claim
106 words
A method for preventing a selected attempted communication by a first station with a second station within a network of stations connected by a physical medium, where the communication is being attempted in accordance with a packet-type communication protocol which provides a mechanism for effecting termination of the communication, said method comprising the steps of: detecting the presence on the medium of a packet representing said selected attempted communication; and preventing said selected attempted communication by said first station by originating on said physical medium an access prevention signal in accordance with said communication terminating mechanism, while allowing other communications by said first station to continue.
References Cited (Backward Citations)
US4413258A
Cited
US4580872A
Cited
US4799153A
Cited
US4891639A
Cited
DE3904403A1
Cited
US4896319A
Cited
US4897874A
Cited
US4962449A
Cited
US4930159A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1995-06-23 | 1995-12-23 | 1996-06-23 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1999-06-23 | 1999-12-23 | 2000-06-23 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2003-06-23 | 2003-12-23 | 2004-06-23 | $7700.00 | Window Closed / Lapsed |