SONET ring questions
Dave Cooper
dave_cooper at eli.net
Mon Oct 19 17:38:34 UTC 1998
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
>>
>
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