Enterprise GPON / Zhone Questions

Wed Dec 12 20:09:03 UTC 2018

On Wed, Dec 12, 2018 at 7:51 PM William Herrin <bill at herrin.us> wrote:

> On Tue, Dec 11, 2018 at 10:47 PM Baldur Norddahl
> <baldur.norddahl at gmail.com> wrote:
> > Compared to the traditional approach, you will only have one centralized
> > GPON switch to manage. All the small ONT switches are managed through
> > this. Complaints about the interface is vendor specific. Because there
> is only
> > one centralized switch, it would be fairly cheap to switch vendor. Much
> cheaper
> > than to rewire with copper in any case.
>
> Except you won't have one central GPON switch because LANs change
> incrementally.
>

In my experience, a PON network is extremely flexible. Our FTTH network is
ever expanding and there is no master plan. Whenever people in existing
areas decide to buy our product or whenever people in a new area decides to
take a vote to get us in their area, the network will expand as needed.
Often we will discover that we could not make a planed crossing because of
something in the ground, but we can just change plans and do it another
place. We have a competitor that decided to use p2p (point to point
ethernet over fiber) instead and I have watched how they are struggling
because they had to plan everything from the outset, and we didn't. The
reason being that we use very little fiber for our backbone and can afford
to change plans constantly. They need to backhaul hundreds or thousands of
fiber strands to the central point, where they have the switches.

>
> That throwback in office 412 with the fax machine? Can't simply buy
> him a pots line. You get to futz with fax over the converged phone
> system.
>

GPON is actually ATM and will provide hard realtime bandwidth guarantees.
ISDN delivery over GPON is part of the standard. You will reserve 2x64
Kbit/s channels and GPON guarantees that will always be 100% available with
no dropped frames and no jitter. You can do fax, modems, anything that the
public phone service will carry over ATM.

I have not personally tried this out as fax and modems are completely dead
in my part of the world and nobody cares. But I have had a ONT (from Zhone
no less) with ISDN ports (not POTS) and thought they are crazy.

>
> Speaking of the converged phone system, you're now committed to VoIP
> on a VLAN. When you decide you want to switch to a physically
> separated network for the phones, well, that's too bad because your
> cabling infrastructure doesn't make that possible.
>

Nothing stops you from deploying two independent GPON networks, one for
ISDN service and the other for data service. Typically the drop cables will
be at least 2 fibers (GPON runs on a single fiber) so you would not need to
change anything. In my example the backbone would need a maximum of 7
fibers. With a duplicated GPON network, that would be 14 fibers in the
backbone.

Personally I think duplicated networks are silly. But who am I to decide?

>
> The AV lab gets screwed. You're running the coax they need through the
> noisy electrical riser because you didn't build dedicated comms risers
> and closets. Naturally nobody checked with them so you don't yet
> realize they can't do what they need to do with video over IP
> equipment.
>

Fiber will transmit anything that goes on coax as analog signals. Typically
on 1550 nm. The converters are dead cheap and are purely analog devices.

This is how we deliver TV on a FTTH GPON network. GPON uses 1310 nm for
upstream data, 1490 for downstream data and 1550 nm for analog TV. When I
say analog TV that is really DVB digital signal these days, but the
equipment does not know any of that and just transmits it as an analog
signal. Many GPON ONT for residential use come with a coax TV out port that
can be turned on and off remotely, so the ISP can control TV delivery. Some
also have build in filters that can be remote controlled, so you can have
multiple TV packages using the usual system of filtering frequencies on the
coax.

>
> And what will you do in 5 years when they want the computer lab in 204
> upgraded to 100Gig? Maybe run some fiber all the way back to the
> campus head end because as expensive as that is, it's still cheaper
> than replacing the OLT with 100-gig capable equipment and then
> replacing all the ONTs in the building because oops, there's no 100
> gig OLT compatible with the old ONTs and you'd have to take the
> building down for a week to forklift-upgrade the whole mess.
>

One advantage of a fiber to the desktop solution is that you have fiber to
every room. You just move a drop cable from the splitter and to a pair of
backbone fibers. With this you can get a dedicated connection from any room
to any other room including back to your data center. Yes you will have
extra dark fibers available, anything else would be stupid.

>
> Folks have advised Nick rip it out now because they foresee the
> slow-motion train wreck on its way. That may be extreme, but certainly
> he should take immediate action to preserve his options. For example,
> I would demand the creation of comms closets and risers before the
> building opened and I'd threaten to quit if they weren't. At least
> then the inevitable modifications can be structured and planned
> instead of turning in to an ad-hoc mess.
>

This is out of line IMHO. Hopefully they did add in extra conduits so you
could do some special cable runs (including some copper and coax), if
needed. But if they did not, it would be the responsibility of management,
not yours. It also has nothing to do with fiber nor GPON. Plenty of copper
builds have a severe lack of space for future proving.

If they did the fiber build in the recommended way, there will be ducts
prepared for fiber blowing, so one quickly can add more fiber cabling.

I find it silly to threaten to quit if they wont make closets, that are
then going to be empty.

Regards,

Baldur
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