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It's been a while in coming, but the next commercial evolution of cable modem technology is poised to encompass a potentially killer product offering: IP telephony.
Those who oversee the the evolving Data Over Cable Service Interface Specification (DOCSIS) protocol are ushering in the standard's next generation of platforms and services as the cable industry nears 3 million high-speed Internet subscribers.
Building upon the best-effort scheme of DOCSIS 1.0, DOCSIS 1.1 includes key network technologies--dynamic Quality of Service, packet fragmentation and beefed-up security--letting cable operators offer sophisticated data and voice services over a managed IP network.
Last month, DOCSIS 1.1-based gear--cable modems and cable modem termination systems (CMTSes)--were put to the test for the first time by Cable Television Laboratories Inc. during its 16th DOCSIS certification wave. As expected, no DOCSIS 1.1 equipment passed CableLabs' scrutiny. CableLabs announced that it will be extending each of the four certification waves next year to accommodate the more complex 1.1 tests.
In its quest to ordain both cable modems and CMTSes as interoperable and conforming to DOCSIS, CableLabs has certified about 100 modems from more than three dozen companies as DOCSIS 1.0-compliant. It has qualified CMTSes from eight vendors as DOCSIS 1.0 compliant.
No one knows when the arduous CableLabs testing process will yield DOCSIS 1.1 certified and qualified equipment, but the industry is ready to embrace the new protocol. "Just as we were very aggressive with DOCSIS 1.0, we are in the same mindset with 1.1," says Luisa Murcia, vice president for high-speed data services with AT&T Broadband. "It's critical for our ability to provide multiple tiers of service in the network," said Murcia.
"DOCSIS 1.1 enables packet-based services," says Rouzbeh Yassini, executive consultant to CableLabs and the head of the DOCSIS project. Reaching beyond best-effort packet delivery, which was defined by the first iteration of DOCSIS, DOCSIS 1.1 is "really triggered by our desire as an industry to do voice-over-IP (VoIP)," says Doug Semon, principle Internet architect of Time Warner Cable.
"You really can't roll (VoIP) it out in scale without 1.1," says Steve Craddock, vice president of new media development for Comcast Cable Communications.
Yet voice places a different set of requirements upon a network than what can be accomplished through best-effort packet delivery. Voice calls must be free from latency and jitter that can break up a call. Consequently, the dynamic QoS provisions of DOCSIS 1.1 allow an operator to identify different streams--such as a voice stream--and treat it differently through service identifiers or SIDs. In this way, for example, a 911 call can be identified as the highest priority type of stream. When a user makes a 911 call under such a configuration, the voice stream will receive top priority over other traffic flows.
By "painting packets different colors" with service identifiers, cable operators, using the DOCSIS 1.1 protocol, can guarantee high-speed or low-speed "tiers" of service, much in the same way phone companies sell Frame Relay and DSL service.
Adding even greater flexibility, dynamic QoS lets operators change stream management on the fly, said Craddock. Theoretically, a subscriber surfing the Web can initiate a conference call by requesting that the priority of packets be changed to let the call go through with a higher SID.
The other key engineering aspect of 1.1, is packet fragmentation, which allows for the delivery of so-called "isochronous" services, such as voice, which doesn't tolerate any delay in packet arrival. Isochronous transmission means packets arrive at a very regular Interval, even at very low data rates," says Semon, thus allowing voice traffic and data traffic to co-exist on the same network. E-mail traffic, for example, is not as dependent as voice on arriving at its destination at the same time as other packets in the stream.
MSOs will implement DOCSIS 1.1 gear, when it becomes available (generally expected to be the middle of next year), differently based on marketing and business plans. The possibilities are vast. With the added network intelligence that DOCSIS 1.1 provides, choice of service and service provider become possible, Murcia pointed out that. For example, a user may subscribe to a particular Internet Service Provider's Internet access service, another provider's pay-per-use audio service, and still another provider's gaming service.
Yassini projects that three types of customer premise products will emerge using DOCSIS 1.1: standalone cable modems with RJ-11 and Ethernet jacks for both VoIP and Internet-over-cable services; products targeted to the small office, home office market allowing for multiple IP voice and data lines; and eventually futuristic Internet appliances, such as Web tablets and refrigerators, that will be wired in a home network for Internet connectivity and voice services.
While regular best-effort data services will remain a big part of operators' data services, DOCSIS 1.1, offers the flexibility to deliver business class conferencing, streaming media and other services "over a multitude of platforms and devices, not just the TV and not just the PC," says Craddock.
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