Trevor G. Hammonds wrote: > From: SIP > Sent: Saturday, August 04, 2007 2:57 PM > > >> Stephen Bosch wrote: >> >>> Douglas Garstang wrote: >>> >>> >>>> I confused by this. Don't ITSP's have redundancy? Don't they have >>>> multiple edge systems for accepting incoming calls? Don't their multiple >>>> edge systems have multiple interfaces, connected to multiple subnets, >>>> via multiple switches? And, don't they have multiple upstream providers? >>>> About the only thing that could go wrong that affects all service like >>>> this would be a badly pushed out software update, affecting all systems? >>>> >>> >>> >>> Don't be confused. The answer to most of your questions is no. >>> >>> Barriers to entry are too small for ITSPs, and there are lots of >>> basement operations masquerading as big carriers. >>> >>> -Stephen- >>> >>> >>> >> There are also lots of big carriers masquerading as big carriers. ;) >> >> >> If the ONLY people who could get into the business were the ones who >> could, before offering any services to customers, afford to build out >> multiple edge systems for accepting incoming calls, each with multiple >> interfaces connected to multiple subnets via multiple switches using >> multiple upstream providers, you would have ONE single choice for an ITSP. >> >> And AT&T doesn't have that amount of redundancy in their network. >> Working in the carrier networking business, I can assure you that we've >> NEVER run across a SINGLE carrier network (not from the largest to the >> smallest) that has redundancy in ALL aspects (or even MOST aspects) of >> its network. This is why there are uptime policies that allow a >> percentage of outages to occur. Triple 9 uptime (Exceedingly rare, but a >> purported goal -- 99.999%) still allows 15 full hours of downtime a >> year. And that rarely includes the occasional lost packet or latency. >> > > Your math is incorrect. FIVE nines (99.999) allows only 5.26 MINUTES of > annual downtime. Triple nine (99.9%) allows for 8.76 hours of annual > downtime. Keep in mind that most SLAs do not include "planned" maintenance > in their guaranteed uptime. > You are quite right, sir. I've no idea what I was doing with my math there. I can't even REPLICATE what I was doing with my math there.
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