Quantitative Network Engineering with Fault Tree Analysis

This is a simple paper outlining how to use some Risk Analysis Techniques with Network Engineering to obtain quantitative results. An attempt to turn network engineering from an artful guessing game into a science.

Gates

Gates are the devices that link all of the events together and provide the logic on how the lower events contribute to the occurance of the ones it links further up the tree. A gate represents an event which is being further developed. Basic logic functions from boolean algebra serve as gates, but there are only five that are used. Of these, the AND and OR gates get by far the most use.

OR
The "or" gate provides output if any of the contributing input events are true.
AND
The "and" gate provides output if all of the contributing input events are true.
XOR
The "exclusive or" provides output if any of the contributing input events are true, however if one of the contributing events is true, the others cannot happen.
Voting gate
Like an or gate, but only provides output if a specified number of inputs is true. This is drawn as an OR gate with a fraction denoting the number of inputs out of the total that has to be true for the event to be true.
Priority AND
Research this one.
Inhibit
Research this one.

Transfer Gates

Transfer gates don't provide any additional logic, but allow a fault tree diagram to be broken down into multiple diagrams. Transfer gates are labeled to link them together.

Transfer In
Indicates an incoming link to a separate sub-tree of the model.
Transfrer Out
Indicates that the sub-tree of the diagram flows into another part of the fault tree.




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