Can a simple line-card replacement do the DSL trick?

The folks at DSL equipment start-up Catena Networks all carry the company slogan, "Everyone Wants Broadband," superimposed against the company logo on the back of their business cards.

So you might think Catena would have a comprehensive roadmap for bringing lots of varieties of DSL to the crazy quilt of telco last-mile architectures found in central office, digital loop carrier and remote-terminal facilities all across this great land of ours.

Well, it does.

But Catena also has an initial product that's designed to get itself out of the gate without making service-provider customers and end users wait for the usual uncertain "phases" on a "roadmap" (or "marketecture," to use the old derisive term). Catena this week announced the availability of a product with a remarkably specific, if limited, function: a line-card replacement for old-fashioned, but widely deployed, Lucent digital loop carrier systems called the SLC Series 5, or SLC-5.

The Catena product, called the CNX-5, replaces a two-port line card on these Lucent remote terminals with an upgrade providing two ports of POTS and two ports of ADSL. The Lucent SLC-5 systems, serving somewhere between 20 million and 30 million households, can have, say, 96 slots for a total of 192 phone lines. For as many of those slots as the telco wants, a technician simply slides out the original line cards with notched white levers, and installs the Catena CNX-5 cards with red levers. Now the carrier can now provide both a POTS line and ADSL line where before there was only one phone line.

What could be simpler? Well, of course there's a little more to it than that. The SLC-5 chassis also has to be retrofitted with an accompanying ATM multiplexer card. And the telco is supposed to obtain the CatenaView Element Management System to enable remote configuration of the new line cards. That helps reduce the number of truck rolls to these remote-terminal sites, which after all are more likely to be found the farther away from central offices you get.

Catena's approach, based on key improvements in processing and silicon, provides a way out of the crushing dilemmas service providers face in bringing their old loop-extension gear into the broadband age.

Right now telcos have to consider alternatives ranging from bolt-on mini Remote Access Multiplexer (mini-RAM) systems to remote DSLAMs, all presenting huge space, expense and regulatory (think CLEC collocation) challenges. Catena's simple card-for-card upgrade eliminates the need for POTS splitters, cross-connects, external cabling and additional pads and cabinets. And they haven't forgotten about the all-important backhaul. The CNX-5 upgrade provides T-1 and T-3 links plus the option of 4xT-1 via standards-based inverse multiplexing over ATM.

Note that Catena's approach doesn't provide a place for voice over DSL. Catena executives I spoke with this week at the ComNet trade show think users want to keep their regular phone lines and get DSL for data, not a bad way to look at it especially since VoDSL right now loses some key lifeline functions. But you can probably see some other limitations of the initial Catena offering: It only provides ADSL, and it only works in communities where a telco once installed a digital loop carrier system from Lucent (or AT&T in olden days).

But don't worry, this start-up with $105 million of funding iis more ambitious than that. Which brings us back to that roadmap, which envisions a complete overhaul of the old digital loop carrier architecture with a fully packetized, voice/data approach Catena calls "broadband loop carrier." That'll be the subject of another newsletter, so stay tuned. Or for a sneak peak, head to Catena's Web site at www.catena.com.

This story, "Can a simple line-card replacement do the DSL trick?" was originally published by Network World.

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