Date: Tue, 19 Mar 96 17:07:17 MET From: Greg Lehey <lehey.pad@sni.de> To: alk@Think.COM (Tony Kimball) Cc: hackers@freebsd.org (FreeBSD hackers), isdn@muc.ditec.de (Distribution List; FreeBSD ISDN) Subject: Re: ADSL Message-ID: <199603191609.RAA20723@nixpbe.pdb.sni.de> In-Reply-To: <199603191542.JAA10395@compound>; from "Tony Kimball" at Mar 19, 96 9:42 am
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Humpty Dumpty writes: > > From: Greg Lehey <lehey.pad@sni.de> > > What is ADSL? This is the first time I've heard of it. Are the > speeds you mention without compression? > > Asymmetric Digital Subscriber Line. See Dan Kegel's page at > http://www.alumni.caltech.edu/~dank/isdn/adsl.html Thanks. Interesting stuff. I had heard of this, but I didn't know the name. >> ISDN is obsolete. > > Is ADSL available everywhere? Does every ISP who supports ISDN also > support ADSL? Can you use it for telephones and faxes? If not, you > can't make that claim. > > ADSL is available everywhere, because all it takes is a pair of wires. > If your ISP won't support ADSL, you will be needing a new ISP. > Yes, you can use the same line for POTS and Fax. This is a rather naive approach. Your pair of wires need to be connected to something. Over here, the only copper wire pair you're likely to see coming in to your house belongs to the phone company. What you connect to it depends on what they have connected at the other end. Over here, it's ISDN (128 kb/s or 2.048 MB/s). Are you saying you can use the same line at the same time for POTS and Fax? How does that work? > There is not a great deal of correlation between technical obsolescence > and market share, and I can say what I like because words mean what > I tell them to mean:) Agreed on both points (see above). DOS is an excellent proof of the first claim. > ISDN was obsolete before it ever got started. How long will people be > willing to pay for a 115kb link once commodity 2nd-gen ADSL modems > give them a link at 1-8Mb for the same price? First, ISDN BRI is 128 kb/s, not 115. Second, it's obvious that, under those circumstances, the prices will change. > No, a factor of 10-80 in performance, the opportunity for real > videoconferencing and VOD is just too much weight for ISDN to bear. I don't see that factor out there. The Web page you point me to talks about downlink speeds between 384 kb/s and 4 Mb/s, and uplink speeds between 64 kb/s and "10 times that much". That's hardly any faster than regular ISDN. On top of that, there are a lot of disadvantages that I can see: from the Web page, it would seem as if every "modem" manufacturer is doing his own thing. This means that I might be able to set up a point to point link with one ISP, but doesn's seem to be a way to connect to multiple, unrelated sites. ISDN *does* give you that advantage, even today. > PairGain modems come out in June, and the Willtel CAP offering comes > out in October. You may argue about the relative obsolescence of > ISDN today, but come Christmas time, any further arguments will be > silly. OK, let's have a bet about it. Don't get me wrong, I'm not a rabid ISDN fanatic, even if you might get that impression from my postings. Show me something viable, and I'll go for it. But from what I've seen so far, I don't think that ADSL will go very far. I don't really see a big technical difference from ISDN PRI: I'd guess that this is a marketing ploy designed to fit specific data transmission needs only, while making it unsuitable for phone calls (which require symmetric data rates). It's more likely to lead to something else, maybe ATM. I consider it extremely unlikely that it will find much following in mainland Europe. Greg
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