fiber cut 19 May/PM -> 20 May/AM in Ashburn, VA (lawnmower?!)

Burton, Chris Chris.Burton at
Fri May 21 17:28:37 UTC 2004

	I would agree that most Telco's put the initial ring fiber pairs
in the same conduit due to cost savings and build out permits; but
sometimes the issue is not cost; but laziness on the part of the company
or the engineer.  In the past I worked for a company that designed and
installed MAN rings and more often then not the company would work a
ring into a single conduit just because it was easier to do.

Chris Burton
Network Engineer
Walt Disney Internet Group: Network Services

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-----Original Message-----
From: owner-nanog at [mailto:owner-nanog at] On Behalf Of
Robert E. Seastrom
Sent: Friday, May 21, 2004 5:09 AM
To: Dan Armstrong
Cc: nanog at
Subject: Re: fiber cut 19 May/PM -> 20 May/AM in Ashburn, VA

Dan Armstrong <dan at> writes:

> Forgive me, but
> Isn't Sonet usually deployed in a ring?  Why the heck would a fiber
> this important not be?

sonet, obviously, does not *have* to be in a ring, but it often is.
unfortunately, a fair percentage of the time, the additional
protection offered by a ring topology is a mirage, due to a
configuration known as "collapsed backbone".  in this instance, both
pairs of fiber ride in the same conduit for some portion of the
distance (most notably laterals to building entrances, but sometimes
for a fair distance down the street).  the driving factor in building
this way is usually cost savings.

while this arrangement does protect against failures of optics and
electronics (which in fairness are indeed more common than fiber
cuts), it provides no protection against hungry construction (or in
this case, lawn maintenance) equipment.


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