Comcast Eyes Gradual Move to DOCSIS 3.0
CTO Werner Compares Move to Migrating from DOCSIS 1.0 to 1.1
By Todd Spangler -- Multichannel News, 7/2/2007 12:40:00 PM
Comcast hasn’t let the cat out of the bag about when -- or where -- it expects to launch “wideband” cable-modem service, with the promise of download speeds topping 100 megabits per second.
But chief technology officer Tony Werner is confident that upgrading Comcast’s networks to Data Over Cable Service Interface Specification 3.0 will proceed as a natural evolution of the existing cable-modem infrastructure.
“The good news is that when we go to 3.0, we’re backward-compatible with existing modems, so we don’t have to rip out any modems,” Werner said.
And, in Werner’s analysis, the headend side won’t require a forklift upgrade, either. Comcast typically has deployed chassis-based, integrated cable-modem-termination systems from vendors that include Motorola and Arris.
Upgrading CMTS gear to 3.0 will mostly be a software upgrade, although some systems will require additional hardware blades, Werner said, adding, “In my mind, this will be no harder than [migrating from] DOCSIS 1.0 to 1.1.”
Probably the hardest work, according to Werner, will be finding three additional 6-megahertz channels to get the four necessary to achieve 160-megabit-per-second downstream connections. The DOCSIS 3.0 specification allows equipment to bond several channels together to act as a single virtual pipe. “We have a pretty good plan for channel recovery, but we have a lot of things that want that bandwidth,” he said.
Werner said that for Comcast, there’s “no business-case decision” today for deploying modular CMTS gear -- which splits out functions into separate components -- as opposed to integrated CMTS gear. A modular CMTS is supposed to give operators more flexibility by separating DOCSIS processing from edge-quadrature-amplitude-modulation devices, allowing edge QAMs to be deployed and allocated separately from the CMTS core.
Comcast for now plans to keep integrated CMTS architectures in place, adding 3.0 where it’s needed. “We are buying CMTS blades and chassis on an ongoing basis,” Werner said. “We’re going to gradually evolve to a 3.0 footprint whether we like it or not.”
While DOCSIS 3.0 cable modems will be more expensive than 2.0 models, the additional cost will only be incurred “in the places you’re selling a new service,” Werner said. Plus, the bill of materials costs are declining as DOCSIS 3.0 silicon vendors like Broadcom and Texas Instruments ramp up production.
For CMTS gear, with the next wave of hardware, the cost per port comes down, Werner said, adding that a DOCSIS 3.0-compatible CMTS is “quite a bit less than half” the cost on a per-port basis of existing equipment.
Werner said Comcast is very close to initiating trials of DOCSIS 3.0 equipment. As for what services the operator will offer with the technology, he added, “We believe in having a very good high-speed premium service, but we’re not necessarily saying we want to offer 100 or 160 megabits [per second].”
Pricing, too, will depend on what competing service providers -- namely, Verizon Communications -- sell in a given area. “The market is reasonably rational,” he said. “We’re not going to be irrational.”
Factors Comcast will consider in deploying DOCSIS 3.0 in a market include the competitive nature of the market, what new business services it could offer and whether there’s an appetite for a premium Internet tier among consumers.
DOCSIS 3.0, besides providing much greater bandwidth capacity, also provides support for IPv6, the next-generation Internet-protocol-addressing scheme. IPv4, which is the widely used address space in use today, provides a more limited pool of available addresses -- about 4.3 billion -- compared with an astronomically large number of addresses with IPv6 (2 to the 128th power).
“The reality is that the world is running out of IPv4,” he said. “It’s a big, big deal to be able to move to IPv6.”
