DSL Prime: Trials Continue

Tests of DSL chips continue as vendors fight for an advantage.

by Dave Burstein of DSL Prime and Future of TV [March 10, 2005]

Centillium asks "ADSL2+ or VDSL2?"
For 3,000 to 6,000 feet, is the added performance worth the price?
Without a doubt, the 50 to 100 Mbps speeds of VDSL are the best option under 2,000 feet. But carriers who want to minimize investment are looking at 2,000 to 6,000 feet away, using field boxes already in place. Faraj Aalei of Centillium believes the actual performance of VDSL2 in the field will be little better than his new Pharos generation of ADSL2++ for those middle distances. The Ikanos target price for CO chips is $25, while ADSL2+ is going for a quarter of that price.

The new Pharos chip has scored an important win with Dasan, the Siemens company in Korea. Siemens needs an IP-DSLAM, and Dasan's units have always had top of the line capabilities. That gives Centillium hope of a major customer outside their Japanese niche.

DSL Prime's position is to ask all involved for more data, and to remain skeptical until volume field shipments prove who is right. I chose to put the Ikanos data in a headline because a third party (SBC) recently reported favorable testing as well. That story should have included the fact the testing was with 24, not 26-gauge wire. There was no deception from Ikanos, just my mistake not asking that question.

A respected engineer offers, "A word of caution about VDSL2 results. VDSL reaches high enough into the frequency spectrum to be self-FEXT (far-end crosstalk) limited. The only meaningful results are ones that are derived with the use of real distribution cable binder groups loaded up with multiple operating VDSL pairs. Make sure that the spectacular numbers that people are reporting are measured in that way. Otherwise, the results may be optimistic." The Ikanos data included simulated interferers, helpful but not the same as field data.

Likely non-standard deployments
The best guess is that a VDSL2 preliminary standard will be agreed in May, early enough that SBC will be able to pay lip service to standards. However, there are several features, including advanced coding, still in dispute and unlikely to make it into the standard, several participants tell me. A carrier doing HD video, such as SBC, needs every bit of performance possible, which will tempt them into "non-standard" choices.

One result may be a rapidly evolving standard, with a VDSL2+ coming quickly because the same carriers rushing VDSL to agreement want the higher throughput. The downside is higher prices (acceptable) and no option to switch chipmakers (totally unacceptable to major carrier outside Asia previously, but possibly that is changing).

Entrisphere Comes Out of the Closet
Inferno, Plan 9 and now ya do-everything
The elegant Pathstar, designed by Entrisphere's Phil Winterbottom, was once the future of Lucent. It was the ultimate voice and data switch and promised to deliver all the dreams of the marketing department. Lucent's many struggles resulted in discouraging early field trials, and ultimately Lucent bought Telica for a soft switch to have a product with some of the capabilities.

Winterbottom and Unix legend Ken Thompson had already left, and with millions of venture capital created Entrisphere. Mark Floyd joined them later as CEO, bored with a life of unlimited golf although he stayed with Siemens for a while after selling Efficient to them. The combined reputations gave them entree to every major bid in the U.S., including a dark horse shot at the Verizon fiber PON bid. Don McCullough of Entrisphere tells me their interoperability with several vendors' home units was welcomed by telcos reluctant to choose proprietary systems.

After several years, the company is now opening the curtains that literally surrounded their SUPERCOMM booth. Despite the stealth cover, TDS, a million line U.S. carrier, has been using Entrisphere's BLM 1500 to serve customers for nine months. McCullough believes Entrisphere has more checklist items for carriers than anyone else, but recognizes intense competition.

McCullogh's customers are sometimes buying just DSL and voice today, not fiber, and McCullough believes that requirement is keeping the price of this kind of equipment very attractive. "With Entrisphere, they can just change blades and offer fiber when they choose." They currently feature BPON, because "that's what customers are asking for," but McCullogh agreed with me a clear path to GPON or GEPON is absolutely required today. Calix, announcing a BPON card, sees the coming shift as well, "With 200 Gbps of backplane capacity, the Calix C7 is uniquely positioned to facilitate the migration from BPON to GPON and active optical approaches"

Winterbottom re-engineered the "Plan 9 From Bell Labs" operating system that was not Unix, although they shared many of the same parents. According to the Plan 9 FAQ, the name was chosen from an Ed Wood movie "in the Bell Labs tradition of selecting names that make marketeers wince." The symbol of the system is white bunny Glenda. Bunnies are faster, more (re)productive, and more cuddly than Linux penguins. Despite that, Linux is more popular, partially because Lucent did not release Plan 9 as open source until far too late. A related Winterbottom project, Inferno, has theoretical advantages over Java and also coulda been a contenda. The team is pictured here.

Copyright 2005 Dave Burstein.
The DSL Prime Newsletter is reprinted with permission.

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