Muni fiber: L1 or L2?
Mikael Abrahamsson
swmike at swm.pp.se
Thu Feb 7 08:51:27 UTC 2013
On Wed, 6 Feb 2013, Scott Helms wrote:
> The cost difference in a single interface card to carry an OC-3/12 isn't
> significantly more than a Gig-E card. Now, as I said there is no
> advantage to doing ATM, but the real cost savings in a single interface
> are not significant.
There has always been a substantial price difference for ATM/POS compared
to ethernet.
But when designing ETTH networks, the cost saving is in the use of very
simple devices. L2/L3 switches all the way. No tunneling, no fancy
encap/decap Q-in-Q etc. Enough intelligence to do the BCP38 stuff to
prevent spoofing, MitM-attacks, nothing more, but still deliver needed
services over unicast and multicast.
So as soon as the design contains any of the words L2TP, PPPoE/A, ATM,
POS, OC-whatever, xPON or anything like it, you're incurring unneccessary
cost, especially for high bw services.
The most inexpensive device to L3-terminate 10GE worth of traffic from a
few thousand customers is in the few thousand dollar range, what's the
cost if you want to do the same using L2TP or PPPoE ? What about ATM? I
don't even know if ATM on OC192/STM64 is even widely available. My guess
is anyhow that you're not looking at a device that costs at least 5-10x
the cost.
Designing a fiber plant very much like the traditional copper plant, ie
aggregating thousands of households in a single pop, and letting "anyone"
terminate that fiber, is a very future proof and scalable approach. The
fiber can be lit up using any technology (active p-t-p ethernet, or PON,
or whatever is desired), this doesn't have to be chosen at time of
actually drawing the fiber. Yes, it's a high initial cost but I firmly
believe that over tens of years of lifetime of the fiber, this cost is
lower than other solutions.
--
Mikael Abrahamsson email: swmike at swm.pp.se
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