IntraLATA vs. InterLATA Ckt Reliability

Ron Buchalski rbuchals at hotmail.com
Wed Jun 18 02:33:36 UTC 2003


You can request circuit diversity, and ask for the circuit layout record 
(CLR/DLR) to verify that the paths are diverse.  Standard practice is to 
assign circuits onto available facilities, and treat each circuit 
independently.  So, there's no concern about whether the circuits share 
common facilities, unless the orders are flagged that way.

Unfortunately, future circuit grooming may result in your circuits being put 
onto a common path somewhere.

You can try to get the telco to guarantee diversity in writing, with 
financial penalties if they fail to maintain diversity.  You'll need to 
provide backup for lost revenue, to determine how much the financial 
penalties should be.

By the way, there's no guarantee that intralata circuits will always be 
diversely routed, either.  It's all dependent on the available facilities.

For interlata circuits, even if you were to go with two different IXCs, 
you'll need to insure that they don't share common facilities, or lease 
capacity on the same fiber.  Years ago, a train wreck in the NY-DC corridor 
caused multiple carriers to experience fiber outages.  Seems that one 
carrier trenched fiber on the right side of the tracks, and another carrier 
trenched fiber on the left side of the tracks.  The derailment dug up both 
sides!

-rb

>From: "William R. Lorenz" <wrl at express.org>
>To: nanog at merit.edu
>Subject: IntraLATA vs. InterLATA Ckt Reliability
>Date: Mon, 16 Jun 2003 17:11:42 -0400 (EDT)
>
>
>Can someone with a bit of experience in telco line engineering speak to
>IntraLATA vs. InterLATA DS-1 circuit reliability?  More specifically, is
>it more likely for multiple DS-1 circuits to be aggregated using a single
>piece of multiplexing equipment when heading into another LATA, thus
>increasing the chance of combined failure of two diverse circuits at a
>single point?  I would love to have two diverse T1 circuits coming into
>the offices, but it looks like they'll ultimately traverse the same telco
>switches, both at the local and regional interconnection levels (? more
>info ?), and it seems as though this presents increased risk.  We have
>entrance failities for just one LEC in our office building here, and I
>understand that a new telco buildout would require lots of investment.
>
>I've actually talked with LEC engineers about the various switching
>stations in the area, and it seems as though everything is aggregated
>through a single central office before hitting the other LATAs.  Have
>others encountered this same kind of topology in the past?  What are some
>of the things that can be done to help ensure circuit diversity?
>
>Lots and lots of questions, I know. ;)  Any insight into standard telco
>engineering practices would be great and very much appreciated!  Tnx.
>
>--          _
>__ __ ___ _| | William R. Lorenz <wrl at express.org>
>\ V  V / '_| | http://java.sun.com/; http://www.linux.org/
>  \./\./|_| |_| "[...] But it's turtles all the way down."
>

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