DSL without breaking your backbone

Many local exchange carriers, from giant Bells to small-town independent telcos, are coming under pressure to do something about their remote neighborhood terminals that extend ordinary voice lines but block DSL signals.

It’s not that there aren’t ways to retrofit these remote terminals – also known as traditional digital loop carrier (DLC) systems – that serve a full 30 per cent to 40 per cent of the population. Plenty of vendors, including the big equipment players and specialized firms, are offering DSL-compatible next-generation DLCs for retrofitting or new construction.

However, local carriers face trunking issues from the remote terminals back to the central office. U.S.-based SBC’s remote-terminal DSL upgrade, known as Project Pronto, is slated to use fiber to the terminal with OC-3 links, in an announced US$6 billion project. Carriers with less than $6 billion on hand – in other words, everyone else given the growing telecom financial crunch – need to look at more conservative options.

That’s why a low-key announcement this past Monday from two independent vendors with remarkably similar names but different functions should not go unnoticed. California DLC vendor Advanced Fibre Communications (AFC) announced it would resell access-aggregation gear from Virginia Advanced Switching Communications (ASC) under an OEM arrangement. Their joint goal is to create an end-to-end, remote terminal-to-central office access upgrade for the economy-minded service provider in the DSL age.

Under one scenario, AFC’s AccessMax line of multiservice loop-extension equipment will feed neighborhood DSL (or other) traffic over nothing more than ordinary copper-based T-1 trunks back to a central office equipped with ASC’s A-1240 pizza-box access aggregator. The A-1240 – or whatever AFC winds up calling it under the OEM agreement – offers 24 ports of T-1 equivalents but also is equipped for frame relay and ATM, including both protocols’ inverse-multiplexing standards. That way, the carrier can determine the precise amount of trunking needed as end users’ bandwidth demands grow.

This is important because remote terminals only serve a relatively small community and many carriers have found that DSL traffic is slow to ramp up at first from any given neighborhood. “You want to keep the cost profile as low as possible,” ASC’s Larry Kraft told me this week. But if the service provider’s DSL offering takes off, the carrier shouldn’t be caught unprepared. ASC’s MultiStream software allows the carrier to redefine traffic needs port by port, and ASC’s support for the inverse-muxing standards – inverse multiplexing over ATM and multilink frame relay -means the carrier has NxT-1 options instead of the immediate leap to T-3. ASC’s boxes also are stackable, and the company also offers the chassis-based A-4000 for larger installations.