Setting a trap here?
xDSL, where x = S/H, as a physical carrier (and set of modulation schemes)
is a tried and proven technoligy, often used today by telcos to carry T1s
over longer spans with less need for repeating equipment.
The model of xDSL internet service (differing from xDSL as a way to carry
T1s), on the other hand....
And the list of failed local xDSL providers gets longer. Luckily
we stayed out of it, and are still in business as are our customers.
Thats not a fair statement.
It's quite easy to stay in business offering xDSL services; charge more
than your competitors. Perhaps you won't get as many customers as your
competitors, but you will have a service offering that you can make money
off of.
It's what we did, and we still here and not in danger of going anywhere.
Hunter Pine:
> You are aware that a good percentage of the T1's you purchase nowadays are
> just a pair of bonded 768 dsl lines, right? The phone companies have been
> doing that for over 20 years to save on copper.Huh?
Just for starters: HDLC circuits run on different voltages, have timing
and a bunch of other characteristics that xDSL never heard of.
I am confused -- HDLC is a link-level protocol which has nothing to do
with voltages, and since you compare it to xDSL you can't have meant HDSL
instead. If you meant T1 instead (which can carry 24 DS0s of digitized
voice, PPP, or other protocols besides HDLC), remember that a POTS line
has very different characteristics than an optical signal, yet aside from
the last mile they are mostly carried over fiber, encapsulated in a T1
frame which is encapsulated in a T3 frame, which is encapsulated in OCx,
etc. Likewise, a point-to-point T1 doesn't have much in common with an
ATM PVC, yet you can carry a T1 across an arbitrarily complex ATM network
using circuit emulation. (Yes, I am talking about the US system here, and
I know elsewhere is different but a similar concept).
We are seeing BellSouth run 2 wire T1's, which have been working well so
far. Still not DSL (approx 900mhz over POTS). --Mike--
AFAIK, the 2-wire T1s are in fact carried over HDSL to the smartjack, and
the smartjack extracts the T1 -- I have two of these in my house, using
Pairgain (now ADC)'s HiGain Solitaire H2TU.R402 for T1 transport. The URL
of the frame describing the product line is at (minus any line breaks or
spaces added along the way):
This specific card is under HDSL2 RT Modules.
John A. Tamplin jat@jaet.org
770/436-5387 HOME 4116 Manson Ave
770/431-9459 FAX Smyrna, GA 30082-3723
> Why would anyone purchase dsl to run their business on. Let me guess,
the
> price was right.
I would call it a proven technology, but a very poor business model.
And xDSL is definately not for mission critical operations.
x is sometimes "H".
Are you sure you want to say HDSL is not for mission-critical operations?
Very well put. I do not think however that many cosider HDSL to be part to
the DSL family (mainlydue to the fact that it often uses two pairs instead
of one). I think if we are talking xDSL, HDSL is in most cases excluded
from the picture.
This post is long, but is not a rant.
Joe's post is pretty accurate. I worked for a DSL CLEC for almost three
years. Verizon is on the poorer side of ILEC performance, but the same
problems happen throughout the US.
DSL is certainly not an "unproven" technology. It's very reliable, if
we're talking hardware. In favorable circumstances, it is every bit as
reliable as DS-1. The vulnerabilities (in order) are:
1) ISP's who deploy DSL are on a very slim margin. They can't afford to
be "full service." That doesn't mean that the best DSL ISP's don't
provide better service than the mediocre or poor DS-1 ISP's, but don't
expect $500/month support for your $150/month line.
2) Data CLEC's who provide most of the lines for independent ISP's have a
challenging business model. Northpoint went down hard. That doesn't mean
that the others will go down hard, too, but they have the same kind of
risks. They needed lots of capital and got most of it through debt
financing.
3) ILEC's don't have a clue. Some of them are well-intentioned (although
I'm not sure Verizon is on that list), but their techs have years of
experience with dial tone. They don't know how to troubleshoot anything
but dial tone and DS-1 (which looks very different at the phone closet
than CLEC DSL). CLEC's deployed equipment that puts moderate voltage on
the line and no tone. ILEC techs are clueless. Note that all ILEC DSL IP
services run over lines with dial tone...
4) ILEC's can be obstructionist. This is mostly at the top and middle
management, but you see it in the line and lower management every once in
a while.
Here are some serious recommendations for DSL users (and network operators
who deploy DSL can take note):
1) Get it if it's right for you. Your budget will know if it's right.
2) Choose an ISP who cares and is able. That may mean that the price is
$500/month instead of $150 or $250/month, but you avoid the DS-1 costs of
$1500/month.
3) Have a contingency plan -- perhaps ISDN (shudder) or bonded 56k.
4) Have your access ISP host critical services (or another provider,
perhaps the one you've lined up for your contingency plan).
5) Get a line-shared DSL line. (That means that you get phone service
over the same copper pair.) The ILEC maintaining the copper knows how
to troubleshoot the pair.
Anyway, this entire stream is off topic and 90+% of us know it's not the
hardware.
-steve
Definitely my own views, not necessarily those of my current (or former!)
employer.
I don't think anyone is knocking dsl technology, just the expectation
> that you can run mission critical services with the level of service you
> get with dsl.
Yes, this has nothing whatsoever to do with technology. Just money. The
question of whether you feel like trusting your business to someone you're
giving $1500/month, or whether you feel like trusting your business to
someone you're giving $150/month. Or $29.95/month. TANSTAAFL. You get
what you pay for.
And in my own opinion, NANOG isn't the forum for whines from the
$29.95/month crowd. Of course, others seem to disagree.
-Bill
That is utter bullshit. Maybe they can't afford to colocate with Exodus but
there are definitely many places that a small business can EASILY afford to
colocate.
--Adam
Because...
-Dan
The DSL from work to home has been up 24/7 for about 4 years now without a
single interruption. Quite different from our PTP T1's which each go down
regularly.
-Dan
Randy Bush wrote:
they moved an entire customer segment, dsl, on short notice and in one day.
whew! shame there were glitches, but i'm impressed.
It's impressive, sure. But you and I both know that you can't rely on things
to go flawlessly, especially not when you're moving lots of customers. The
post-migration support has to be there.
If it makes anyone feel better, I don't think things would have been different
if T-1's were being moved, since CAIS was involved. Since attempting to
get in touch with them, I've not heard anything positive about the company.
Huh?
Just for starters: HDLC circuits run on different voltages, have timing
and a bunch of other characteristics that xDSL never heard of.
Except that youre wrong. (Ever heard of SDSL?)
We are seeing BellSouth run 2 wire T1's, which have been working well so
far. Still not DSL (approx 900mhz over POTS). --Mike--
I dont think US West has run a 2 wire T1 in 10 years, maybe longer...
-Dan
I have never had any line problems with my DSL connection. Never had to have
anyone come out and repair it and its never been down due to a line isssue
and we've had the connection since Jan 2000.
All of the issues have to due with mess-ups by PSINet or Covad. PSINet had
the wrong IP address information in their database and they sent that over
to CAIS when they transferred the account. Thats what started it all.
I have to say that I don't see where DSL is a flawed technology, just that
some of the players in the game are not very good at providing support.
Heh, I've had Verizon linemen yank HDSL-implemented T1 circuits because there was no dialtone. The ADSL from Verizon might actually be more reliable than their T1 service in areas where there's a shortage of pairs. After all, there WILL be a dialtone (assuming the ADSL is piggy-backing on a voice circuit) and the odds are they're not going to pull the circuit.
The xDSL standards folks probably should sacrifice a bit of bandwidth at the low end of the spectrum to generate an appropriate audio tone, letting the line workers know that the circuit IS in use. Clearly the absence of such has cost many folks a great deal of aggrevation, lost revenues, etc.
The interesting thing, is that this has absolutely nothing to do with
Technology, good or bad. It has to do with products. xDSL is normally
considered a product for the home or small business. It is supported and
priced that way. For most providers, that includes small, static IP blocks,
assigned out of the providers own space, in a systematic fashion.
The "T-1" product is usually something quite different, even if it is
provided over an HDSL line. This product usually includes BGP support,
greater flexibility for using your own address space, and the chance to talk
to engineers with greater clue. There is usually a big price difference.
Why? DSL is a mass market product, and folks want to package it in a certain
way. T-1 is a business product, and you're paying for better service. It's
as simple as that. Don't fall all over the technical details in this case,
as this hinges on folks using a Home/SOHO product for mission critical
business stuff. You might save some money in the short run, but it's a poor
investment.
- Daniel Golding
[I don't know that I agree that this is off-topic...]
Steve Schaefer wrote:
1) ISP's who deploy DSL are on a very slim margin. They can't afford to
be "full service." That doesn't mean that the best DSL ISP's don't
provide better service than the mediocre or poor DS-1 ISP's, but don't
expect $500/month support for your $150/month line.2) Data CLEC's who provide most of the lines for independent ISP's have a
challenging business model. Northpoint went down hard. That doesn't mean
that the others will go down hard, too, but they have the same kind of
risks. They needed lots of capital and got most of it through debt
financing.
Well, wasn't the big problem that the DLECs were having trouble turning
around orders, and as a result ended up not getting paid by the ISPs?
3) ILEC's don't have a clue. Some of them are well-intentioned
Which ILECs? I've dealt extensively with Ameritech, although not
recently. The owner of Cleveland's largest local ISP lives (and offers service)
in Verizon territory (former GTE North) and has lots of "wonderful" things
to say about both Verizon and Ameritech. Ameritech was fair-to-middling
until being bought by SBC, and they rolled downhill rapidly after that - the only
positive thing they are doing is the Project Pronto rollout. I can't say
anything about Qwest or Bellsouth, as I've never dealt with them.
than CLEC DSL). CLEC's deployed equipment that puts moderate voltage on
the line and no tone. ILEC techs are clueless. Note that all ILEC DSL IP
ervices run over lines with dial tone...
Here in Cleveland, Ameritech offers only ADSL. I am not sure they even
know what SDSL is. 
They will, however, be happy to sell you 1.5x256 ADSL
for $175 a month!
as for relibility, I cant tell you the number of times a Verizon tech,
would be out to install a phone line and steal one of our dsl lines cuase
it did not have a tone.
As a (serious) question, why not stick a tone on it? How much
can an oscillator at the CO plus some trivial passive low pass
filters (one set per line), cost? (Or, if you aren't the DLEC,
stick it at cust prem). Just don't use the trace tone... (translation
to US terminology may be required)
John Tamplin:
the smartjack extracts the T1 -- I have two of these in my house, using
Pairgain (now ADC)'s HiGain Solitaire H2TU.R402 for T1 transport. The URL
of the frame describing the product line is at (minus any line breaks or
spaces added along the way):
http://www6.adc.com/ecom/wps?lineid=OND2737&group=T1%2BTransport%252FHiGain&EXPAND=OND50995&L=EC_List_Group_Index.html&R=WPS_Out_Hierarchy.html&ID=OND50995
This specific card is under HDSL2 RT Modules.
Thats the units we have on the wall for some recent T1 installs as well.
So far working very well.. Yes, it is HDSL, It's not 2 x 786K sDSL or
whatever as stated in the original posted email that I responded to.
Whats funny is I got 2 private emails from BellSouth engineering types
that did not know they were being installed in this region.
That was my mistake Mike. HDSL is NOT two SDSL lines by definition. It's
just two circuits running symmetric 768k DSL (not SDSL) bonded to form a
single1.5mb line.
My fault for using SDSL (where S is the initial for symmetric) instead of
symmetric DSL lines. They are two different things in this case.
Sorry for the confusion I started, please resume your regularly scheduled
nanog ranting. 
And thanks for the nitpicking Mike.
Hunter Pine
Vice President, Network Operations
hunter@compuhelp.com
CompuHelp Technologies
11 Lispenard Street
New York, NY 10013
212-995-2955 x21
http://www.compuhelp.com
Which doesn't solve the problem of high-speed access to their own
equipment.
Umm, no. HDSL rides a single pair, and provides more than 1.5Mb.
John A. Tamplin jat@jaet.org
770/436-5387 HOME 4116 Manson Ave
770/431-9459 FAX Smyrna, GA 30082-3723