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The future of cable broadband networks will largely be software-driven, as operators look for ways to address the ongoing bandwidth explosion seen among their residential and enterprise subscribers.
Traditional cable suppliers, including Casa Systems and Harmonic, joined cable upstarts ADTRAN, Calix, and Nokia to introduce new DOCSIS and FTTH hardware platforms with a heavy emphasis on software-defined control planes at the SCTE Cable-Tex Expo, held in Philadelphia.
Cable operators and their CMTS vendors have for years prided themselves on the tight integration of hardware platforms and software to provide high QoS levels for broadband services. This integration has served them well in helping to quickly and economically expand their broadband service offerings, including a continuous cycle of speed upgrades, as well as digital voice and other adjunct services.
But the tight coupling of hardware and software is quickly being viewed as a limiting factor for operators who are faced with a future that calls for a minimum of 1Gbps of downstream throughput for every broadband subscriber. Even today’s generation of CCAP-capable platforms from ARRIS, Cisco, and Casa Systems will be hard-pressed to evolve to match those performance levels without a fundamental decoupling of underlying software from hardware platforms and a dramatic architectural change in HFC access networks.
The architectural change is coming in the form of remote PHY (R-PHY) and remote MACPHY (R-MACPHY) architectures, where the core elements of the CMTS are pushed deeper into HFC networks in order to reduce service group sizes, reduce the RF domain, and reduce space constraints in existing headend and hub sites.
Distributed access architectures have been addressed at previous SCTE conferences. What was new this year was the emphasis on software-based control, data, and management planes to help distributed access architectures scale to support the massive growth expected in new service groups. Today, service group sizes average 500 homes passed, with each service group being supported by a single optical node. A single CCAP chassis can generally support up to 512 individual optical nodes, or 256,000 homes passed.
But with bandwidth demands increasing, operators want to reduce their service group sizes to 50 or over the next decade, resulting in the need for 10x more optical nodes. Cable operators, however, do not have the space in their headends or hub sites, however, to purchase and install 10x more CCAP chassis. Hence, the need to push the PHY and potentially the MAC capabilities closer to subscribers. Bandwidth can be increased to each service group without having to scale the headend-based CCAP platform linearly.
So, to mitigate those issues and to ensure operators can scale their DOCSIS MAC and PHY domains from a control and data plane perspective, vendors are virtualizing these capabilities in software, allowing operators to potentially move away from the dedicated hardware platforms of today which rely on proprietary implementations of ASICs (Application-specific integrated circuits) and FPGAs (Field-programmable gate arrays) to commercial servers running standard Intel processors.
In addition to improving scale and the overall economics of deploying broadband, virtualizing the control and data planes on standard servers allows operators to deliver services much faster than from dedicated hardware like a CMTS. Typical control plane services that can now be hosted in the cloud include VPNs and MPLS tunneling. Data plane services include parental control, WAN acceleration, and NAT services. Virtualization allows these services to be deployed network-wide and not on a system-by-system basis, which is how services have historically been provisioned.
Virtualization also opens up the potential for cable operators to offer new services, including subscriber-specific CDNs where content and bandwidth preferences can be stored on the network and optimized on a per-subscriber basis.
Finally, in a world where the functions of the CCAP and the access network, in general, are virtualized and contained in an open operating system, cable operators can standardize on this OS across all their network platforms, including wireless and WiFi infrastructure.