Contributed By John Chapman, Chief Technology Officer, Cisco Cable Access Business Unit, and Engineering Fellow
Earlier this year, as part of CableLabs’ “Innovation Showcase,” in Atlanta, we showed how DOCSIS 3.0-based technologies can gracefully and powerfully scale, if operators were to continue increasing the number of digital channels they place into a DOCSIS bond.
The question we were endeavoring to answer was this: Is DOCSIS dead, or does it have another 15+ years of life in it? The answer is clearly the latter. Why? Because the classification and QoS features in backbone routers (like our recently announced ASR 9000 System) are architected for massive speed, in terms of packets-per-second - and those features will migrate down into cable CMTS gear.
The demo for CableLabs focused on our 3G60 CMTS cards, which bonded 48 downstream channels and 12 upstream channels, using 256 QAM in the downstream, and 64-QAM in the upstream. The result was a 1.6 Gbps downstream pipe, and 300 Mbps upstream. But that was back in February. The bond size was generous, but still partial. When you consider the full spectrum capacity of cable television systems - from 54 MHz to 1 GHz, downstream, and from 5 MHz to 42 MHz upstream - clearly, there’s a lot more breathing room for wideband IP services.
The math goes like this: 134 digital, 6 MHz channels downstream, modulated with 256 QAM, yields a total potential throughput of over 5 Gigabits per second of capacity. Upstream, with advanced modulation, as much as 500 Mbps. Of course, this assumes that all of those channels are available for bonding (meaning they’re not used by anything else), and that’s a function of the long-term migration to IP. But it’s a powerful endorsement for full-spectrum bonding, as a catalyst for abundant levels of IP.
Those of you at this morning’s keynote session, at the Cable Show in Chicago, saw the power of DOCSIS during Comcast CEO Brian Roberts’ demonstration of a 1 Gbps down / 300 Mbps upstream link over a live production network. As someone who watched Brian demonstrate the speed differences between dial-up phone modems and cable modems a dozen years ago, and again of “regular” cable modems vs. DOCSIS 3.0-based cable modems, just a few years ago, it was fun and gratifying to see this next leapfrog in capabilities: From DOCSIS 3.0 to whatever we’ll call this uber-amount of brute-force IP capacity.
In short, it means that yes, DOCSIS does continue to scale -- in a big way, and for a long time.