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Technology Stocks : LAST MILE TECHNOLOGIES - Let's Discuss Them Here -- Ignore unavailable to you. Want to Upgrade?

To: Raymond Duray who wrote (3139)	3/16/1999 11:26:00 PM
From: Raymond Duray	Read Replies (1) \| Respond to of 12823

Threaders, May I direct you attention to: data.com DSL Linked to Slowdown on T1 Circuits Is DSL hazardous to the health of corporate networks? At least one telecom engineer argues that it is: Steve Powell, a technical consultant who last year installed DSL circuits for Pacific Bell, argues that some types of the high-speed technology may actually slow performance on T1 and ISDN access lines. Powell also claims that competitive carriers eager to pick up market share are contributing to the problem. And he indicates that ILECs (incumbent local exchange carriers), whose lines are being used to roll out these services, don't have a clue as to the trouble in the making. "If all of the sudden your T1 doesn't work as well as it's supposed to, get your RBOC to check the loop. You may find out why," Powell says. Specifically, Powell points to ADSL (asymmetric digital subscriber line) encoded with CAP (carrierless amplitude phase modulation) as an accident waiting to happen. He says the encoding scheme can interfere with transmissions on other cables in the local-loop binder, causing bit errors that take a bite out of performance. He also notes that that this is the type of DSL being deployed by CLECs (competitive local exchange carriers) over incumbent carriers' local loops. He cites Covad Communications Co. (Santa Clara, Calif.), Northpoint Communications Inc. (San Francisco) and Rhythms Netconnections Inc. (Englewood, Colo.) as three primary offenders. Lou Pelosi, Covad's executive director of marketing, dismisses the potential problem, saying Covad and many other CLECs are chiefly deploying SDSL (symmetrical DSL). SDSL uses 2B1Q, an encoding scheme that doesn't cause spectral interference. And what do the ILECs (incumbent local exchange carriers) say? At least one--Pacific Bell (San Francisco)--says it hasn't seen any problems because of CAP products, comments Michael McLeland, vice president of business service operations. But Powell argues that the problems exist; the ILECs just don't realize the cause. That's because the interference hasn't show up in large amounts yet. For now, the ILECs just attribute slow performance to a bad circuit and change it. But Powell believes that in about a year, the amount of CAP deployed could be enough to start causing noticeable errors. At that point, the ILECs may stop CLECs from deploying CAP on their networks, relying on interconnection contracts that prohibit the use of non-standards-based gear. What about the ADSL being rolled out by the ILECs themselves? They typically use standards-based DMT (discrete multitone), which doesn't cause as much interference. So why aren't the CLECs using it? "It's a pain to deploy," explains Powell, adding that only 50 percent of copper loops support DMT, while 85 percent handle CAP. Also, CAP-based products came out one year before DMT products. "CLECs didn't want to wait," confirms Ron Young, vice-president of sales and marketing at Diamond Lane Communications Corp. (Petaluma, Calif.), which manufactures both types of DSL equipment