John Chapman, Engineering Fellow and CTO of Cisco System’s Cable Access Business Unit, is a pioneer in broadband communications, having helped to define and write the original DOCSIS (Data Over Cable Service Specification) spec — which spawned the cable modem marketplace, and, consequently, the broadband explosion we’re living in right now. He’s currently leading the development of the DOCSIS 3.1 specification, which promises substantial throughput and speed gains for residential broadband consumers. In this Q&A, originally posted on the Cable Congress blog “Interview with John Chapman”, he characterizes the highlights of DOCSIS 3.1, why it matters, and current events.
Q. What does DOCSIS 3.1 mean to cable-delivered broadband, as opposed to fiber?
Chapman: Service providers are often under scrutiny in terms of their competitiveness, against fiber-to-the-premise architectures. DOCSIS 3.1 will go a long way in assuaging those misperceptions. It can make that hybrid fiber-coax plant perform as well as fiber, at a fraction of the price of a fiber upgrade. DOCSIS 3.1 is all about getting more bang for the buck – it’s a higher performing, lower cost technology.
Q. What is the biggest change coming, in DOCSIS 3.1? Read More »
Think back to the year 1997. Back then, Bill Clinton had just begun his second Presidential term. Princess Diana’s funeral was watched by 1.5 billion people. Internet Explorer version 4 was new. The Hale-Bopp comet made its closest approach to Earth – and the Data Over Cable Service Interface Specification (DOCSIS) was released publicly for the first time (March 1997), marking the beginning of the broadband revolution.
People often ask how many 6 MHz channels it takes to do an IP video offering over cable. The answer, of course, is “it depends,” but let’s be more specific: MSOs can create an IP video offering with as few as four 6 MHz channels. With eight, they can create a partial replacement of the traditional linear and on-demand video product line. Sixteen 6 MHz channels afford a full replacement of what’s on the MPEG plant today.
If that sounds like a lot, think about it another way. Today’s 860 MHz cable plant contains about 125 channels, including analog and digital. Between two and four channels are currently used to handle both broadband and voice over IP (VoIP) traffic. Viewed through that prism, 16 channels perhaps don’t seem like so much!
How much bandwidth is really needed to deliver VoIP depends on the nature of the service offering. Offering a full simulcast of the linear lineup costs more in bandwidth – some networks are already carried in dedicated analog, standard definition, and high definition bandwidth. By contrast, offering VoD content in IP is a variation on switched digital video, itself a bandwidth saving mechanism.
John Chapman, Cisco Fellow and CTO of Cisco’s Access, Transport and Technology group,
talks candidly in this short video about what it takes, in bandwidth and QoS, to launch a video over IP service.