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 The information contained in this e-mail message is confidential, intended only for the use of the individual or entity named above. If the reader of this e-mail is not the intended recipient, or the employee or agent responsible to deliver it to the intended recipient, you are hereby notified that any review, dissemination, distribution or copying of this communication is strictly prohibited. If you have received this e-mail in error, please contact Walt Disney Internet Group at 206-664-4000. -----Original Message----- From: owner-nanog@merit.edu [mailto:owner-nanog@merit.edu] On Behalf Of Robert E. Seastrom Sent: Friday, May 21, 2004 5:09 AM To: Dan Armstrong Cc: nanog@merit.edu Subject: Re: fiber cut 19 May/PM -> 20 May/AM in Ashburn, VA (lawnmower?!) Dan Armstrong <dan@beanfield.com> 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. ---rob