Muni fiber: L1 or L2?

Sun Feb 3 02:35:07 UTC 2013

In a message written on Sat, Feb 02, 2013 at 09:28:06PM -0500, Scott Helms wrote:
> I'm not saying that you have to, but that's the most efficient and
> resilient (both of those are important right?) way of arranging the gear.
>  The exact loop length from the shelves to the end users is up to you and
> in certain circumstances (generally really compact areas) you can simply
> home run everyone.  Most muni networks don't look that way though because
> while town centers are generally compact where people (especially the
> better subdivisions) live is away from the center of town in the US.  I
> can't give you a lot insight on your specific area since I don't know it,
> but those are the general rules.

If the goal is the minimize the capital outlay of a greenfield
build, your model can be more efficient, depending on the geography
covered.  Basically you're assuming that the active electronics to
make a ring are cheaper than building high count fiber back to a
central point.  There are geographies where that is both true, and
not true.  I'll give you the benefit of the doubt that you're model is
cheaper for a majority of builds.

On the other hand, I am not nearly as interested in minimizing the
up front capital cost.  It's an issue, sure, but I care much more
about the total lifecycle cost.  I'd rather spend 20% more up front
to end up with 20-80% lower costs over 50 years.  My argument is
not that high count fiber back to a central location is cheaper in
absolute, up front dollars, but that it's at worst a minimal amount
more and will have neglegable additonal cost over a 40-80 year
service life.

By contrast, the ring topology you suggest may be slightly less
expensive up front, but will require the active parts that make up
the ring to be swapped out every 7-20 years.  I believe that will
lead to greater lifecycle cost; and almost importantly impeed
development of new services as the existing gear ends up incompatable
with newer technologies.

-- 
       Leo Bicknell - bicknell at ufp.org - CCIE 3440
        PGP keys at http://www.ufp.org/~bicknell/
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