A little Microsoft humor...

[Ben Scott]

Lloyd Kvam <python at venix.com>  wrote:
>> So far as I know, T1 connections use DSL between the central office
>> and your premises.

  Eh.  This implies that "DSL" actually means something specific.  It
generally doesn't.  There are a bunch of "flavors" of DSL, and they
don't all work the same way.  Further, there is often disagreement
over what the "flavors" are, so terms are not always equivalent across
markets.  (It's similar to how terms like "SCSI-3" gets applied to
connectors, cables, speeds, and other things, with no consistency,
because "SCSI-3" is just a standards document that covers all of that.
 The terminology gets abused.)

  There are some flavors of DSL that re-use older equipment in new
ways.  In particular, the line cards for both ISDN and T1.  Line cards
just transmit bits; they don't really "interpret" much.  So there are
DSL flavors which use ISDN or T1 line cards.  The defunct Vitts called
these "SDSL" (symmetric DSL) and "HDSL" (high-speed DSL),
respectively.  I don't know if Verizon even offers these services.  I
know that most asymmetric DSL being delivered by Verizon in this area
is a 1-pair (2-wire) system, while a T1 is a 2-pair (4-wire) system,
so the Verizon ADSL I've seen is not the same thing as a T1.

On 5/20/07, Bill McGonigle <bill at bfccomputing.com> wrote:
> That brings up an interesting scheme - I've been told more than once
> that even if you can't get DSL in your area you can always order a T1
> anywhere.  If they're being provisioned on DSL lines these days, I
> wonder if I could order a T1, have them fix the induction coil
> problems on our backhaul to get it out here, then cancel the T1.

  There are multiple factors in play.  DSL is usually offered as a
low-price, consumer product, while DS1s are usually higher price,
business class products.  Businesses are willing to pay a lot more, so
the telcos are willing to do a lot more.

  When line quality is bad, T1 installation will often involve running
a brand new copper pair (or reconditioning existing pairs) the entire
distance from the CO to the demarc.  This is typically billed per foot
and can run into the five figures if you're sufficiently far out in
the woods.

  T1 also allows for extenders (in-line amplifiers).  If they reach
the distance limit, they install an extender on the pole.  They'll run
a separate power pair if needed.  This is also expensive, and -- more
significantly -- just not done for consumer DSL.

  So even assuming you didn't get hit with an early cancellation fee,
you'd likely end up with a line that was still not useful for DSL, due
to the distance limits mentioned above.  There's also the fact that
the telco could probably just say, "That's a T1 line, not a DSL pair.
Even if we *could* run DSL over it, we're not going to.  It was
installed for a T1, and we're not going to let it be used for anything
else but."

-- Ben