[lug] DSL Technical ?'s
Harris, James
James_Harris at maxtor.com
Tue Sep 4 18:16:52 MDT 2001
Thanks for describing all of this to such length. I sure got a lot of
techincal crud out of a it and I'd be willing to bet other's did too.
Jim
> -----Original Message-----
> From: Timothy Klein [mailto:teece at silverklein.net]
> Sent: Saturday, September 01, 2001 00:13
> To: lug at lug.boulder.co.us
> Subject: Re: [lug] DSL Technical ?'s
>
>
> Jeremy,
>
> I think you are running primarily into a business decision on
> Qwest's part. The technology is sure there, but Qwest has
> decided it is not cost efective to supply DSL to just anyone
> who asks. They are picky about who they will supply to.
>
> Now, at the lengths you are mentioning for your line, there
> is a high possibility that you are not on a copper pair at
> all, but rather a "pair gain" pair. This means that your
> line first rides to a central distribution point (Cross Box)
> as a digital signal on some kind of T1-type carrier ( that
> might be conditioned copper, or fiber). Usually 96 virtual
> "pairs" are put onto a few actual copper pairs (can't
> remember the number, something like 4 pairs) by using a
> digital signal rather than the plain old low frequency analog
> pots signal. At the cross box, these digitial signals are
> converted back the to the analog signal that your phone line
> expects, and then another, much shorter segment of copper
> connects your house to the cross box. DSL will not work over
> one of these pair gain arrangments, as it basically tries to
> do the same thing as the pair gain is already doing: put a
> higher frequence digital signal on the line. Now IDSL is
> just an ISDN line, that behaves like a DSL. The speed you
> were getting on your SDSL is only slightly faster than ISDN,
> so I would not be at all surprised if you were on some kind
> of ISDN-type arrangement, eg, the DSL was working through a
> pair gain system.
>
> Which companies will choose to offer you DSL is largely based
> on econimics, non techicalities, though. Any one *could*
> offer you some kind of high speed net access, the question is
> do they *chose* to. Does the company think it is a good
> business decision to do so? Covad, Rythyms, Jato and the
> like were hungry for customers, and thus willing to deploy
> whatever technology they could to get a customer. Qwest is
> an entrenched monopoly, so they can afford to be much pickier
> about which customer's the choose to serve.
>
> So, to summarize, DSL needs a clean copper pair, less than
> 18K long, with less than a few thousand feet of bridge tap,
> and no loid coils.
>
> An ISDN line needs either the above, OR a pair gain pair.
> There are a couple of variety of DSL's that are really just
> ISDN type services that will work this way.
>
> The other new piece to the puzzle is the now deploying
> 'Remote DSLAMS'. This is how DSL will be offered at the full
> speeds when the customer is served by pair gain. It moves
> the DSLAM to a box out next to the cross box. Thus your pots
> signal goes to the CO on one channel, and you DSL goes to the
> ATM network on another.
>
> Any way, I'm babbling. I know a lot about this stuff, as I
> work with these issues all day at a telecom.
>
> If you were interested, you could email me off list, and I
> could tell you exactly what your situation was if you were
> willing to give me the phone number or address involved.
>
> HTH
>
> Tim
>
> * Jeremy Hinegardner (jeremy at mlug.missouri.edu) wrote:
> > Hi all,
> >
> > Some background info:
> >
> > I have a few ?'s for the sage's of DSL. As of recently I
> > had a Rhythms 192kbps SDSL line to my home. Since Rhythms has
> > basically gone belly-up my ISP (Megapath) is going the motions to
> > switch me over to Covad. But it seems that Covad is unable
> to provide
> > SDSL service to me and they are installing an IDSL line.
> >
> > I called Qwest and they say they are unable to provide me
> > DSL service at all. But according to their documetation
> > http://www.qwest.com/disclosures/netdisclosure459/co_data.html
> > my CO (BLDRCOMA) has RADSL equip installed.
> >
> > I've checked the distances, estimates vary from 15500' to
> > 16500' and both fall well within the range of Qwest's
> > maximum for ADSL (17500').
> >
> > So now for my questions:
> >
> > 1. Why can't Qwest provide any DSL service? Is it because (a)
> > They don't provide SDSL service at all and don't have the
> > equipment at the CO? or (b) bridges/tap/etc on my line
> > to prevent ADSL from working?
> >
> > Part of this question is why cannot Qwest just use the
> > existing copper pair that is in place for my SDSL and
> > treat it as a phone line to run ADSL over? Both types
> > can run over the same line configuration right? I mean
> > I basically have an additional phone line at my house
> > when they installed the SDSL circuit right? It just
> > happens to plug into Rhythms' DSLAM instead of Qwest's.
> >
> > An additional interesting note on this one is I was
> > originally with Jato last fall (which also went out of
> > business) and from what they said, my SDSL circuit was
> > actually installed by Qwest.
> >
> > 2. Why can't Covad provide SDSL service to me. They do
> > provide SDSL service. Is it because they just don't
> > take SDSL service to 16000'? And if that is the case
> > What is the technical reason why? If Rhythms was able
> > to provide a satisfactory SDSL service to 16000' why
> > is Covad unable to? They are both in the same CO right?
> >
> > 3. I know there are several ISP's who are on this list and
> > I would like to know if any of them would be willing to
> > try an experiment. Basically the Homebrew SDSL option
> > talked about at http://www.odessaoffice.com/sdsl.htm
> >
> > I've tried getting these answers (1 and 2) from a few other sources
> > but with no avail. I really appreciate the level of information
> > available on this list and I hope you guys can help me out.
> >
> > Thanks,
> >
> > -jeremy
> >
> > ============================================================
> > Jeremy Hinegardner jeremy at mlug.missouri.edu
> > _______________________________________________
> > Web Page: http://lug.boulder.co.us
> > Mailing List: http://lists.lug.boulder.co.us/mailman/listinfo/lug
> ==============================================
> == Timothy Klein || teece at silverklein.net ==
> == ---------------------------------------- ==
> == "Hello, World" 17 Errors, 31 Warnings... ==
> ==============================================
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