The present invention relates to a connection integrity monitor and, more particularly, to a method and apparatus for ensuring that connection faults in data paths are detected.
Monitoring of connection integrity at the device level is usually unnecessary. In telecommunication protocols such as SONET, for example, information is imbedded in a data stream indicating its source. Generally speaking, telecom networks are homogeneous and by monitoring the imbedded information, misconnection errors are readily identifiable. However, in systems where source information is unavailable, or difficult to monitor, another means of ensuring integrity is required.
As is known, in some applications it is necessary to select an output from several inputs. A device to perform this function where there is only one output may be referred to as a multiplexer or selector. It several outputs may be selected uniquely from the inputs, the device may be referred to as a crosspoint switch or a cross-connect. In these applications, it is often necessary to detect when a fault has occurred. A fault mode, wherein the output is connected to an input different than the programmed input, may be especially difficult to detect if the input signals are similar.
A data path often includes selectors and cross-connects so that connections can be configured electronically. Should these devices fail such that an incorrect input is connected to a given output, the fault would often be undetected. In some applications, it is not possible to extract information from the payload to determine if the correct payload is being carried. It is therefore necessary to ensure that any point where a misconnection may occur is monitored to detect such a failure.
As a consequence of not detecting a connection fault, the wrong traffic may be connected on the output to downstream equipment. Further, the traffic cannot be guaranteed, nor can the fault be isolated when detected by some means external to the transmission system.
The present invention provides a method and apparatus for ensuring that connection failures occurring in a data path will be detected. This allows the fault to be isolated, protected and alarmed, thus avoiding improper traffic routing and facilitating subsequent repair.
In accordance with one aspect of the present invention, there is provided a method of determining connection fault of an output signal in a data path selector circuit. The method includes providing a selector circuit having a plurality of data inputs, providing a second circuit, independent of the selector circuit, for comparing at least one output of the selector circuit with an expected input, comparing, with the independent circuit, the output with the expected input to determine whether the output is in accordance with the expected input and detecting, if present, a connection fault. In another aspect of tho invention a connection integrity monitor is provided for carrying out this method.
In accordance with another aspect of the present invention, there is provided a method of determining connection fault of an output signal in a data path cross-connect circuit. The method includes providing a cross-connect circuit having a plurality of data inputs, providing a second circuit, independent of the cross-connect circuit, for comparing at least one output of the cross-connect circuit with an expected input, comparing, with the independent circuit, the output with the expected input to determine whether the output is in accordance with the expected input and detecting, if present, a connection fault. In another aspect of the invention a connection integrity monitor is provided for caring out this method.
In accordance with a further aspect of the present invention, there is provided a method of checking integrity of a connection control path connected to a primary connection map of a primary circuit and to a secondary connection map of an integrity monitor, including maintaining activity on one of a plurality of data inputs to the primary circuit and the integrity monitor with an input signal which is unique as compared with other possible signals on the plurality of data inputs. The method further includes, where the connection integrity monitor indicates a no fault connection for a given output of the primary circuit based on a comparison between a data signal on the given output and a corresponding data signal generated by the connection integrity monitor, where a connection origin for the given output is one of the plurality of data inputs, and where a connection origin for the corresponding data signal is one of the plurality of data inputs, writing a new connection origin for the given output to the primary connection map. The method also includes checking for an indication by the connection integrity monitor of a faulty connection for the given output and if the checking step fails to indicate a faulty connection, indicating a potential connection control address bus failure.
In accordance with another aspect of the present invention, there is provided a method of checking for a connection fault in a switched data path connection circuit including providing a fault indicating output path corresponding with each output data path of the switched data path connection circuit and a fault indicating input path corresponding with each input data path of the switched data path connection circuit The method further includes receiving connection control signals for the switched data path connection circuit, receiving an input data signal at each fault indicating input path corresponding with each data path input of the switched data path connection circuit and utilising the connection control signals, each the input data signal and each output data signal on each output data path to check for a connection fault.
In accordance with another aspect of the present invention, there is provided a method of checking for a connection fault in a switched data path connection circuit, including providing a fault indicating output path corresponding with each output data path of the switched data path connection circuit and a fault indicating input path corresponding with each input data path of the switched data path connection circuit. Further, the method includes receiving connection control signals for the switched data path connection circuit, receiving an input data signal at each fault indicating input path corresponding with each data path input of the switched data path connection circuit and mapping the received data signal on the corresponding fault indicating input path to one the fault indicating output path based on the connection control signals. To conclude, the method includes comparing a signal on the one fault indicating output path with a signal on a corresponding output path of the switched data path connection circuit to check for a connection fault.
In accordance with another aspect of the present invention, there is provided a method of checking for a connection fault in a switched data path connection circuit, including providing a fault indicating output path corresponding with each output data path of the switched data path connection circuit and a fault indicating input path corresponding with each input data path of the switched data path connection circuit. The method further includes receiving connection control signals for the switched data path connection circuit and receiving an input data signal at each fault indicating input path corresponding with each data path input of the switched data path connection circuit. The method also includes, for each output data path of the switched data path connection circuit, comparing a signal on each output data path to each input data signal and connecting a connection fault indicating signal resulting from the comparing step to one the fault indicating output path based on the connection control signals.
Other aspects and features of the present invention will become apparent to those ordinarily skilled in the art upon review of the following description of specific embodiments of the invention in conjunction with the accompanying figures.