CableLabs and its MSO and vendor partners are developing a new approach for what was previously known as the "modular" implementation of the Converged Cable Access Platform (CCAP) after the original vision didn't spark enough interest from the vendor community.

The new work won't have any effect on how vendors develop a fully integrated CCAP, a super-dense device that combines cable modem termination system (CMTS) and edge QAM functions and which will help pave cable's way toward an all-IP infrastructure. But the notion of a modular version with a discrete Access Shelf (for the downstream and upstream PHY and MAC layer) and a Packet Shelf (for packet processing) tied together by an interoperability interface will no longer be pursued.

The original concept involved the development of an interface that would link an Access Shelf, to be made by edge QAM vendors, with a Packet Shelf, to be developed by routing vendors such as Alcatel-Lucent, Huawei Technologies Co. Ltd. and Juniper Networks Inc., among others.

"The need for a change in course became clear earlier in the year when edge QAM and router vendors evaluated what it would take for each to develop their products," says Jorge Salinger, Comcast Corp.'s vice president of access architecture. "The greatest difficulties were for Packet Shelf candidates to commit the necessary resources to develop their products and for edge QAM vendors to establish a path for success without dependencies," he adds. (See AlcaLu Undecided on Cable Gear Opportunity, Juniper Still Not in Love With CMAP and RGB Shelves CMAP Product Plans .)

New approach under development
For the past six months or so, MSOs and CableLabs have been pursuing a new approach that doesn't include the separation of Docsis functions originally envisioned in the Packet-to-Access-Shelf Interface (PASI) requirements. Instead, the new approach aims to help edge QAM suppliers, such as Harmonic Inc., BigBand Networks Inc. -- soon to become part of Arris Group Inc. -- and CommScope Inc. to develop CCAP devices without having to deal with as many of the routing protocols currently present in a CMTS, which is something that should reduce the complexity of the product.

The cable industry hasn't created a new name for what's in mind, but the resulting device "will be a full CCAP, just not including a few of the router functions. But it will be Layer-3 aware," says Salinger, noting that this will allow edge QAM vendors, in addition to the traditional CMTS suppliers that are making fully integrated CCAPs, to join the product ecosystem without the downsides of the previous approach.

And this will also make it possible for suppliers that make both CMTSs and edge QAMs, such as Motorola Mobility Inc., Arris and Cisco Systems Inc., to develop products that adhere to both CCAP operation modes.

Salinger estimates that the new specifications are about 50 percent complete, but declined to put a precise target date on their completion.

"It's a flexible process. I expect it in the first half of 2012," he says. "The completion of these specs will be done well in time for when this equipment will be implemented."

— Jeff Baumgartner, Site Editor, Light Reading Cable