At 10:42 AM 10/19/98 -0500, Dave Cooper wrote:
At 10:36 PM 10/16/98 +0100, Manar Hussain wrote:
How many significant digits do you consider acceptable? Even in an ideal APS environment, link failure detection and protection switching does take finite time. You might get 99.999% uptime, but probably not 99.9999999%.
The thing that always got me was that there never seems to be a mention of the sampling period for the stat.
Methinks that you've been subjected to Marketing. ;-)
Well ... I'll give you 99.9999999% on any system you like - with a sampling period of say every billion years. I think that allows me to stay down for the first 100 years, long enough to extend beyong the life of any stressed sysadmin :)
More seriously - SLA's that specify a sampling period then also give an indication what is considered too long an outage. If you get just under the .1% downtime allowed per year all in one go you may well be pretty pissed at being told the 8 hour outage was within the SLA.
The quasi Engineering guidelines for many CLECs when calculating average downtime over a year's span is 52 minutes (meaning .0001% downtime over the year). Anything above and beyond this estimate would be suspect.
Sorry, drop the % on the .0001 -> should be .01%. Coffee wasn't strong enough this morning. Thanks Barry. -dave cooper eli
Obviously, these Engineering baselines vary from carrier to carrier. Also, this 52 minute guideline relates to the SONET ring and the muxes and not the tributaries (OC-3 or OC-12) or the optical/electrical hand-offs that might fail due to bad terminations/bad wiring/or misconfigured nodes. A common failure for OC-3c or OC-12c is the 2-fiber optical handoff to the customer which has nothing to do with the SONET ring itself or the associated SONET gear.
Dave Cooper Electric Lightwave, Inc. Disclaimer: Comments above reflect my experience with numerous CLECs and not specifically ELI.
Manar