Passive bus communication using alternate CRC
AssigneeRacal Data Communications Inc.
InventorsRafael E. Salcedo, Norman J. Donaghue, Jr.
Life of this patent
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Abstract
An apparatus for providing passive bus communication in an ISDN without use of services of a central office uses an alternative error checking (CRC) technique for communication between devices on the passive bus. This alternate CRC is interpreted as an error at the central office so that local frames are discarded by the central office.
Claims26
An apparatus for providing communication over a passive bus in an ISDN without use of services of a central office, said ISDN using a predefined error checking operation at said central office, the apparatus comprising in combination:
- echo receiving means, coupled to said passive bus, for receiving D-echo channel frames which are transmitted from a device connected to said passive bus and echoed by a network termination device;
- and
- alternate error checking means, coupled to said receiving means, for performing an alternate error checking operation on said D-echo channel frames, said alternate error checking operation being different from said predefined error checking operation used at said central office so that frames generated using said alternate error checking operation appear to contain an error when checked by said predefined error checking operation.
A method for providing communication over a passive bus in an ISDN without use of services of a central office, said ISDN using a predefined error checking operation at said central office, the method comprising the steps of:
- receiving a D-echo channel frame which is transmitted from a device connected to said passive bus and echoed by a network termination device;
- and
- performing an error checking operation on said D-echo channel frame, said error checking operation being different from said predefined error checking operation used at said central office such that frames generated using said error checking operation would appear to contain an error if checked by said central office.
An apparatus for providing communication between two devices coupled to a common passive bus of an ISDN without intervention by a central office, comprising in combination:
- determining means for determining that information is to be transmitted to a local device on said passive bus;
- apparent error generating means for generating a D-channel frame which, when checked by said central office, will apparently contain an error but in fact does not;
- and
- transmitting means for transmitting said D-channel frame over said passive bus.
A method for providing communication between two devices coupled to a common passive bus of an ISDN without intervention by a central office, comprising the steps of:
- determining that information is to be transmitted to a local device on said passive bus;
- generating a D-channel frame which apparently contains an error when viewed by said central office;
- and
- transmitting said D-channel frame over said passive bus.
A method of transmitting messages over a passive bus from one TE device to another TE device without central office intervention, comprising the steps of:
- determining that a frame of information is to be destined for a TE device situated on the same passive bus as a TE device which is to transmit;
- and
- introducing an alteration to the frame of information in relation to what a standard ISDN frame of information would normally be so that the central office will interpret the frame as containing an error and discard the frame.
A method for providing communication between two devices coupled to a common passive bus of an ISDN without intervention by a central office, comprising the steps of:
- determining that information is to be transmitted to a local device on said passive bus;
- generating a D-channel frame containing at least a portion of said information in a data field thereof, and a Service Access Point Identifier (SAPI) which is undefined in said central office and thus results in no operation by said central office;
- and
- transmitting said D-channel frame over said passive bus.
Dependencies are inferred from the claim text.