Cisco Systems Inc. (Nasdaq: CSCO) and Texas Instruments Inc. (NYSE: TXN) are the first, but apparently not the only, vendor pair to successfully demonstrate interoperable Docsis 3.0 upstream channel bonding at CableLabs ' Louisville, Colo.-based R&D house.

The lab demo, conducted in July, teamed Cisco's flagship cable modem termination system (CMTS), the uBR10012, with TI's Puma 5 Docsis 3.0 modem chipset and reference design, which was introduced in May at the 2007 Cable Show. (See TI Chips In.)

For Cisco's part, the upstream channel bonding was handled in the core CMTS chassis via the company's uBR10-MC5X20S/U/H Cable Interface Line Card, which contains 20 upstream ports, according to Paul Yesnosky, Cisco's senior product line manager for CMTS products.

The CMTS, he explains, can then address a key challenge of upstream channel bonding: taking in fragments from multiple upstream channels and reassembling everything back to its original order.

Upstream channel bonding is just one feature of Docsis 3.0. The platform, designed to offer shared speeds in excess of 100 Mbit/s, also bonds downstream channels and supports IPv6 and IP multicast applications. Deployments and trials involving pre-Docsis 3.0 equipment have been largely limited to downstream channel bonding.

"The upstream test was one of the final pieces that had to be put into place to show some major progress on Docsis 3.0," Yesnosky says.

A CableLabs spokesman confirmed that TI and Cisco were the first to demonstrate upstream interoperability, but he added that other CMTS vendors have also achieved it. The spokesman would not say who else has joined the CableLabs 3.0 upstream interop club, but the most likely candidate is Casa Systems Inc. , a next-gen CMTS startup based in Andover, Md.

Although Cisco has shown upstream Docsis 3.0 channel bonding in tandem with TI, the company still expects to submit the uBR10012 CMTS for "Bronze" qualification this October when CableLabs launches Certification Wave 56, the first Wave that will officially test CMTSs and modems for Docsis 3.0 qualification and certification.

To push the CMTS qualification needle, CableLabs announced a tiered CMTS testing plan in April, allowing vendors to submit products for "Bronze," "Silver," or "Full." (See CableLabs Accelerates Docsis 3.0 Testing .)

CableLabs has not publicly disclosed which features are included in each tier, but people familiar with the process say Full will include the whole spec, while Bronze will support downstream channel bonding and IPv6; and Silver will introduce upstream channel bonding and the spec's Advanced Encryption System (AES). (See Go for the Bronze! )

Among CMTS vendors, Casa is believed to be one -- and possibly the only one -- that expects to go for Full Docsis 3.0 CMTS qualification right out of the blocks. Casa president and CEO Jerry Guo confirmed in an email that his company has demonstrated upstream channel bonding in a lab setting, but he wasn't ready to disclose its plans for Wave 56.

Although CMTS vendors don't have to incorporate the whole spec yet just to gain a piece of Docsis 3.0 qualification, the tiered approach won't go on in perpetuity. It's said that Bronze and Silver testing will sunset on March 2009. After that, all CMTS vendors will have to shoot for Full qualification. Cable modem vendors must test against the full specs starting with Wave 56.

Conexant Systems Inc. (Nasdaq: CNXT) and Broadcom Corp. (Nasdaq: BRCM) are also developing Docsis 3.0 CPE chipsets. Other than confirming that Cisco is working with all Docsis chipset vendors, Yesnosky declined to say how far along Cisco was with each of them or what their respective plans are for Wave 56.

— Jeff Baumgartner, Site Editor, Cable Digital News