Re: SONET ring questions

["Dave Cooper" <dave_cooper () eli net>]

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