Re: Muni fiber: L1 or L2?

[Scott Helms <khelms () zcorum com>]

On Wed, Feb 6, 2013 at 5:31 PM, Masataka Ohta <
mohta () necom830 hpcl titech ac jp> wrote:

> 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.
>
> You miss ATM switches to connect the card to multiple modems.

No, because that's not required with PPPoE.  Remember, you can easily
encapsulate PPPoE frames inside ATM but encapsulating PPPoA frames inside
Ethernet is problematic (though I have to admit not remembering why its
problematic).  Most PPPoE L2TP setups have no ATM besides the default PVC
between the modem and the DSLAM.  My point was if you need to have an ATM
circuit from the LEC to carry the L2TP traffic (usually because they
haven't upgraded their LAC) its not that big of a deal.


> > > Because, for competing ISPs with considerable share, L1
> > > unbundling costs less.
> > >
> > > They can just have routers, switches and DSL modems in
> > > collocation spaces of COs, without L2TP or PPPoE, which
> > > means they can eliminate cost for L2TP or PPPoE.
>
> > You realize that most commonly the L2TP LAC and LNS are just routers
> right?
>
> Who, do you think, operate the network between LAC and LNS?

Most often the the LAC and the LNS are directly connected (from an IP
standpoint) for purposes of PPPoE termination.


> The largest DSL operator in Japan directly connect their routers
> in COs with dark fibers to form there IP backbone. There is no
> LAC nor LNS.

OK, that's great but that neither makes it right nor wrong.  The largest
DSL provider in the US (ATT) does it how I've described and that again
doesn't make it right or wrong.

> > You're not getting rid of boxes, you're just getting rid of the only open
> > access technology that's had significant success in the US or Europe.
>
> At least in France, fiber is regulated to be open access at L1
> much better than poor alternative of L2 unbundlinga as
> Jerome Nicolle wrote:
>
> > Smaller ISPs usually go for L2 services, provided by the
> > infrastructure operator or another ISP already present on
> > site. But some tends to stick to L1 service and deply
> > their own eqipments for many reasons.

Again, that's neither right nor wrong.  We do lots of things because of
regulations.  I don't believe (could be wrong) that most of the people in
this conversation have the same problems or solutions as the tier 1
operators.  Its simply a different world and despite your belief L2
unbundling is not a poor alternative.

>                                                 Masataka Ohta


-- 
Scott Helms
Vice President of Technology
ZCorum
(678) 507-5000
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