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Technology Stocks : Novell (NOVL) dirt cheap, good buy? -- Ignore unavailable to you. Want to Upgrade?

To: SteveG who wrote (18355)	11/5/1997 11:45:00 PM
From: Jack Whitley	Respond to of 42771

(This is somewhat off topic, and my last post regarding this subject on this board. If you are not interested in xDSL, please skip.) <<While I agree that both bridge taps and load coils will be a stickly problem, a number of trials in the US have given surprisingly good results. I don't know how pervasive ADSL due to the line problems, but where it works, it'll be a plus to those willing to pay for the faster local loop connection................ and MAY be less hassle to install (depending on modem type used and things like whether a lifeline voice splitter is needed.">> Steve, What you stated above is somewhat addressed below - Review of DSL modems from four vendors By Jim Brown Network World, 11/3/97 Luck has more influence than solid planning on whether you'll hit pay dirt with Digital Subscriber Line (DSL) services. For openers, you've got to be in an area with a service provider that is knowledgeable and daring enough to deal with the offering. Then you have to cross your fingers and hope you'll get a pair of copper wires clean enough to carry the signal the short mile or two it's designed to travel. At least that's what we found in testing a DSL circuit supplied by HarvardNet, an Internet service provider and competitive local exchange carrier (CLEC) in Harvard, Mass. While we had little trouble getting the circuit installed within the promised two-week window, we met with varying levels of success in getting different vendors' DSL equipment to operate over the circuit. In fact, only two of the five products we examined worked over the line and both operated at less than 1M bit/sec - a far cry from the 7M bit/sec many DSL equipment vendors tout. The products that successfully shipped data over the line, Paradyne Corp.'s HotWire and Ascend Communications, Inc.'s DSLpipe, support rate adaptive DSL (RADSL), which enables the equipment to adjust its speed to account for line conditions. We never got a symmetric DSL (SDSL) unit for Ascend, asymetric DSL (ADSL) equipment from Amati Communications Corp. or a RADSL unit from PairGain Technologies, Inc. to work over the line............................................................ Unfortunately, there is no easy way to tell exactly what's causing a problem on the line when you encounter one. Just follow along with what happened to us. We ordered the line on Sept. 8 and it was installed on Sept. 22. The line connected our lab to a Bell Atlantic central office (CO) 1.8 miles away. That office was linked to a HarvardNet point of presence a few hundred feet from the CO. In other words, we were within DSL distance limits. With Ach's help, we installed the CO equipment component of each vendor's DSL product at the HarvardNet POP and tried to get it to communicate with the customer premises equipment (CPE) in our Framingham, Mass. lab. In addition to a DSL interface, the CO and CPE pieces of each vendor's product has a 10Base-T Ethernet port for connection to a hub on either side of the DSL link. This configuration sets up the DSL equipment to act as an Ethernet bridge or router, depending on the type of software each vendor provides. We tried PairGain's Megabit Modem CRA first and quickly ran into problems when it failed to connect using a default configuration. Using the management interface on PairGain's self-enclosed CO unit, which looks like a modem, we dropped the top speed the pair would try to connect at and adjusted the amount of noise the units would tolerate to the highest level permitted. Still, nothing. To ensure the DSL line would support a connection, we plugged an analog phone into each end and from our lab had a conversation with someone at the POP. HarvardNet asked Bell Atlantic to trace the circuit and make sure it was clean and all connections were tight. Despite checking several times over several weeks, we never heard back. Oddly, Ach says the PairGain units linked up at near top speed on another DSL line to a building a few hundred feet from ours. This further shows that dealing with DSL takes a little luck. After fiddling with some parameters on Paradyne's chassis-based HotWire CO unit, such as stepping down the maximum link speed it would establish, we finally got it to connect with the modem-like unit in our office lab. However, we had to settle for a much lower speed than the 1M bit/sec uplink and 2.5M bit/sec downlink speeds the HotWire units achieved in the VITALNet lab. Likewise, Ach said the HotWire products connected at higher speed over the DSL line to the building a few hundred feet from ours.............................................. Because of the line problems, our testing was inconclusive on whether Carrierless Amplitude and Phase Modulation (CAP) line encoding is any better than the competing Discrete Multi-Tone (DMT). CAP was developed by AT&T Paradyne and is now controlled by Globe Span Technologies, the sole producer of CAP chip sets. DMT is an emerging international standard that has won support from a number of chip makers. Of the five products we examined, only Amati's supported DMT. Overall, our experience with DSL shows you'll be taking shots in the dark in trying to get a good operational DSL link until the carriers - both the traditional local exchange and CLECs - reengineer their local loops to provide top-notch copper pairs or equipment providers design affordable products that can overcome the problems in existing lines. ..................................................................... While intersting, it is not ready for prime time. I do not see xDSL WIDELY available this year, the next, or the next, and by then, other technology will have passed it by. If you have to pull new wire, why not pull fiber ? jww