Muni fiber: L1 or L2?

Sun Feb 3 03:53:04 UTC 2013

On Sat, Feb 2, 2013 at 10:32 PM, Leo Bicknell <bicknell at ufp.org> wrote:

> In a message written on Sat, Feb 02, 2013 at 10:17:24PM -0500, Scott Helms
> wrote:
> > Here's the thing, over the time frame your describing you're probably
> going
> > to have to look at more fiber runs just because of growth in areas that
> you
> > didn't build for before.  Even if you nail the total growth of homes and
> > businesses in your area your chances of getting both the numbers right
> > _and_ the locations are pretty slim. Also, you're going to have to
> replace
> > gear no matter where it is core or nodes on a ring.  Granted gear that
> > lives in a CO can be less expensive but its not that much of a difference
> > (~1% of gear costs).  Having a ring topology is basically the best way
> > we've come up with as of yet to hedge your bets, especially since you can
> > extend your ring when you need.
>
> I'm not sure I understand your growth argument; both models will
> require additional build costs for growth to the network, and I
> think they roughly parallel the tradeoff's we've been discussing.
>

Yes, but the reason why a ring with nodes is often the
better architecture is because while both situations require more fiber to
accomidate growth in areas that didn't previously have customers the
distance from $new_area to existing ring is going to be shorter almost
invariably than the distance from $new_area to CO.  This matters not only
from the stand point of it costs a certain amount per mile to bury or hang
fiber but also because of right of ways and other hurdles that involve
getting from point A to point B.

>
> As for the gear, I agree that the cost per port for the equipment
> providing service (Ethernet switch, GPON bits, WDM mux, whatever)
> is likely to be roughly similar in a CO and in the field.  There's
> not a huge savings on the gear itself.
>
> But I would strongly disagree the overall costs, and services are
> similar.  Compare a single CO of equipment to a network with 150
> pedistals of active gear around a city.  The CO can have one
> generator, and one battery bank.  Most providers don't even put
> generator with each pedistal, and must maintain separate battery
> banks for each.  A single CO could relatively cheaply have 24x7x356
> hands to correct problems and swap equipment, where as the distributed
> network will add drive time to the equation and require higher
> staffing and greater costs (like the truck and fuel).
>

Absolutely, getting a separate power meter for each enclosure, dealing with
batteries there, and just remote gear all increases operational costs and
the more nodes you have the greater that cost will be.

>
> Geography is a huge factor though.  My concept of home running all fiber
> would be an extremely poor choice for extremely rural, low density
> networks.  Your ring choice would be much, much better.  On the flip
> side, in a high density world, say downtown NYC, my dark fiber to the
> end user network is far cheaper than building super-small rings and
> maintaining the support gear for the equipment (generators and
> batteries, if you can get space for them in most buildings).
>
> Still, I think direct dark fiber has lower lifecycle costs for 70-80% of
> the population living in cities and suburban areas.
>

This is where the math gets hard and the specifics of each situation
dictate what you need to do.  IF you know precisely what your service area
can be and that area is already densely populated then you're probably
going to be able to cover all of that area with a single build.  Downtown
NYC is a scenario I'd completely agree with since you probably would also
struggle trying to find places to install enclosures and you have a very
tightly defined area that is densely populated today.  I'd also say that
this is not the normal muni network in the US today, since generally
speaking muni networks spring up where the local area is poorly served by
commercial operators.

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

-- 
Scott Helms
Vice President of Technology
ZCorum
(678) 507-5000
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http://twitter.com/kscotthelms
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