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Re: DC fiber cut: field report
From: Stephen Sprunk <sprunk () csi net>
Date: Fri, 18 Jul 1997 14:56:55 -0500

At 11:59 07-18-97 -0700, you wrote:
The thing that doesn't make sense to me in all of this is that SONET
is supposed to be built as RINGS.  With a Service side and a Protect side
to each switch.  BIFF should, in theory, only take out one or the other,
but not both.  WHY, with what we pay these carriers every month, do they
not divergent-path route these critical wide-area links so that this isn't
fatal?

The usual response is that carriers are over-provisioning lines (more than
50% of capacity used).  Voice links usually get priority during rerouting;
perhaps all the Tier-1 internet links are being provisioned in the "above
50%" section of the fiber, since Internet outages aren't as costly as voice
outages.

However, what if Backhoe Fade is far more common than advertised, and we
only find out about cuts when BOTH sides of the rings are hit?  Is there
any practical way to measure/detect SONET failover from an endpoint?

Stephen
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