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North American Network Operators Group Date Prev | Date Next | Date Index | Thread Index | Author Index | Historical Re: Statistical Games Providers Play (RE: availability and resiliency)
Sean et al., Excluding force-majeure from availability is not totally unuseful (provided you can still compare apples with apples), on the basis that (historically at least) many other things are likely to cause more worry than failure of your internet/telecoms service in the event of war/asteroid strike etc. However, I've seen force-majeure clauses which exclude for instance weather (drizzle?), actions by telecoms providers (mmm.. didn't even exclude the contracting party and its suppliers) etc. etc. - these are about as useful as excluding actions by backhoe operators and train derailments. Part of the problem is noone ever reads these clauses, often titled (at least in the UK) 'Acts of God'. Many of us do not consider backhoe operators to be God. Also it's reasonable common to exclude actions by the customer or failures of their equipment - given many /system/ faults are still down to customer power etc., this may give telecoms elements with higher availability than the system as a whole, which is what you were refering to with FEDWIRE. (i.e. when users look at their systems they need to combine availability data and carefully consider whether the probabilities of failures of particular elements are or are not independent). Some ISPs exclude the tail circuit from their availability figures in its entirity. Finally, the availability number is meaningless unless there is a clear way of measuring what period it applies to. Five nines availabilty over a day is completely different to five nines availability over a year, if there is a fixed MTTR (think about it). IE availability numbers are *not* useless - but they generally aren't comparible without looking at the contract, and system in depth. -- Alex Bligh VP Core Network, XO Communications - http://www.xo.com/ (formerly Nextlink Inc, Concentric Network Corporation GX Networks, Xara Networks)
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