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Re: [HSSG] fault signalling

The capabilities being discussed are as important for
maintenance and installation of services by experts as they
are for customer installers.  The
value of the higher bandwidth (and the costs of its not
being available) argue for more powerful maintenance
and installation techniques.  The physical links are also
very likely to be more sensitive to various forms of
degradation because they are operating with narrower 
margins than lower bandwidth links, requiring more
powerful techniques to verify proper behavior.


-----Original Message-----
From: Trowbridge, Stephen J (Steve)
Sent: Tuesday, September 18, 2007 12:13 PM
Subject: Re: [HSSG] fault signalling

I was just thinking about the reasonableness of your installation
scenario ...

If I order analog voice service from Qwest, Qwest sends somebody to my
house to verify the connectivity to their central office and turn up the
If I order cable modem service from Comcast (6 Mbit/s), Comcast sends
someone to my house to verify connectivity to their network, do
extensive checks on my cabling at home (how I have my splitters
configured, making sure that everything except the cable modem jack is
filtered so that I don't leak anything back into their Cable TV
distribution network, and that the service works).

Is it realistic to think that for a bleeding edge service at over 15,000
times the bandwidth of any service I have to my house, that this will
occur by letting the customer install and connect their own equipment
over an unverified run of dark fiber and I expect to turn up that
service from one end of the fiber at the service provider POP without
sending anyone to the customer premises?

-----Original Message-----
From: Mikael Abrahamsson [mailto:swmike@SWM.PP.SE] 
Sent: Tuesday, September 18, 2007 12:19 PM
Subject: Re: [HSSG] fault signalling

On Tue, 18 Sep 2007, Geoff Thompson wrote:

> Mikael-
> You need to be careful about the level of complexity that you are
asking for. 
> Each item can e a significant expense. After all, there is only one 
> important question that has to be answered for a single hop system. 
> That would be "Do I need to put a repairman at the other end of the
> The more important question in that context (when you lose a link) 
> usually becomes (a) do I need to send a repairman to the far end 
> equipment or do I need to send a cable crew to find a break and (b) 
> can I tell the difference between the two without going through the 
> step of sending a technician to the far equipment?
> In my view, it is perfectly reasonable to use test equipment on the 
> fiber to make determination (b). After all, the link is down so there 
> is no reason not to move the fiber to a piece of test equipment. If it

> is a WDM fiber, then you will hopefully know if the loss is all of the
wavelengths or some subset.

Let's try to give this another dimension. A common scenario for us is

We have equipment in two different data centers, at each side of a city.

Turnup of a patch involves at least three parties to do patching (each
end hosting provider, might involve our engineer at each end to do
patching, and then the dark fiber provider). The person responsible for
the turnup is in another country, trying to coordinate all this. Going
between the sites might involve a 2 hour drive in city traffic,
typically we only have a single engineer doing each end.

Now, if one end has too much attenuation due to dirty patch, this is
extremely helpful to know without doing that two hour drive. Yes, this
can be solved by doing one end first and so on, and it's typically done
so, but in some cases we'll discover that one party hasn't done their
part etc, and the remote end is done first.

So basically, there is real cost (man hours) that can be reduced in both
initial and maintenance phase by having proper management. We're today
paying the OC192 vs 10GE premium to accomplish this for DWDM, because
there it's extra helpful, but without DOM we might do the same even for
dark fiber (DOM does help quite a lot, at least when both ends are

Are there any calculations on cost for what I'm proposing, so it can be
put into perspective? I don't see us using 100GE without DOM anyway, so
the information I would like to have via OAM is actually available to
the unit in my scenario, what I'm asking is for a communication channel
where it can tell the other end what's going on.

Mikael Abrahamsson    email: