Re: Muni fiber: L1 or L2?

[Jay Ashworth <jra () baylink com>]

----- Original Message -----
> From: "Scott Helms" <khelms () zcorum com>

> > > Owen
> > > I think the confusion I have is that you seem to want to create
> > > solutions
> > > for problems that have already been solved. There is no cost
> > > effective
> > > method of sharing a network at layer 1 since DWDM is expensive and
> > requires
> > > compatible gear on both sides and no one has enough fiber (nor is
> > > cheap
> > > enough in brand new builds) to simply home run every home and
> > > maintain
> > > that.
> >
> > That's my fundamental design assumption, and you're the first person to
> > throw a flag on it. I'm hearing $700 per passing and $600 per sub; those
> > seem sustainable numbers for a 30 year service life amortization.
> >
> > I'm not yet 100% clear if that's layer 1 only or layer 2 agg as
> > well.
>
> OK, think about it like this. The most efficient topology to provide both
> coverage and resiliency is a ring with nodes (shelves) from which end users
> are connected. That ring (usually Gig or 10Gig Ethernet today) needs to be
> connected to a central location so you can interconnect to other providers
> (your ISP customers) and/or to connect to the Internet if the city is
> also going to provide direct L3 services. If you instead push down a L1
> path then the most expensive pieces of gear in the access network (the FTTx
> shelves) have to be replicated by everyone who wants to offer
> services.

In short, you're saying I *must* have a ring with active equipment 
scattered around it, and I *cannot* home run each property.

No one else is saying that, and you don't appear to justify it later
in this email:

> This bad not just from the initial cost perspective but because people
> and companies that identify themselves as ISPs seldom know anything beyond
> Ethernet and IP and then only in a few manufacturers (mainly Cisco and
> Juniper). They are most certainly not comfortable working with Calix,
> Adtran, and the rest of the carrier (formerly telco) equipment
> manufacturers. 

Well, ok, but those people who are not comfortable handling access gear
like the Calix will be L2 clients, anyway, taking a groomed 802.1q handoff
from my Calix/whatever core, so they won't *have* to care.

L1 access will be there a) cause it has to be anyway, to keep active
equipment out of the outside plant, b) for people who really want PtP,
and 3) for ISPs large enough to want to do it themselves, if any show 
up (they admittedly might not; we're only 6k households).

>                 To make matters more complicated in cases of problems
> you don't have a good demarcation of responsibility. What do you do as the
> L1 provider when one of your ISP partners tells you one of his customers
> can't connect or stay connected to that ISP's gear? Whose responsible in
> that case?

Well that's an interesting question, but I don't see that it's not 
orthogonal to the issue you raised earlier.

> What happens when your tech goes out with an OTDR (
> http://en.wikipedia.org/wiki/Optical_time-domain_reflectometer) meter
> and says the connection is fine but your ISP insists its your problem?

On an L1 connection, you mean?  I'll do what people always do; I'll work
the ticket; at that level, this stuff's relatively digital, no?

> > You're talking about what I'm calling L2 clients. If layer 2 falls
> > over it's my fault, and believe me, I'll know about it.
>
> What I'm telling you is that you can't reliably have L1 clients in
> shared model. 

You're telling me that, but you're not giving me good reasons *why* you
think so.

>        You can of course lease someone a dark fiber from point A to point
> B, but that's not a traditional way of partnering with ISPs and in any
> case will only be feasible for a small number of connections since you
> (probably) can't afford to home run each location in your network.

Well, I'll have to see on that, won't I?  That's my next practicality 
checkpoint; fiber passing costs.

> > > The long and short of it is lots of people have tried to L1
> > > sharing and its
> > > not economical and nothing I've seen here or elsewhere changes
> > > that.
> >
> > You just changed gears again, no?
> >
> > I'm not trying to share L1 *drops*. I'm trying to make it possible
> > to share *the entire L1 deployment between providers*, a drop at a
> > time.

> That's what I'm trying to tell you can't do. Its more expensive in
> both the initial and long term costs.

I can see 'initial', maybe, but if I reduce the utility of the field 
network by putting active equipment in it, then I've already raised the
OPEX, substantially, as well as reducing the intrinsic value of that 
network.

Cheers,
-- jra
-- 
Jay R. Ashworth                  Baylink                       jra () baylink com
Designer                     The Things I Think                       RFC 2100
Ashworth & Associates     http://baylink.pitas.com         2000 Land Rover DII
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