The Cable Intersection Point

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A Deep Disaggregated Fiber Future —

Cable providers are in a bandwidth arms race as residential and business subscribers want more capacity at lower prices. Consumers need HBO Now and Netflix at 4K resolution to feed large-screen TVs in the living room while business subscribers desire speed for a Cloud-based applications world providing everything from basic PBX dial tone to specialized vertical services through a monthly subscription.

MSO competitors in the bandwidth race today include local “phone” companies busy pulling fiber to provide gigabit services, while the wireless world is starting to deliver gigabit speeds via LTE today and promising multi-gigabit speeds through 5G in the near future.

Existing MSO infrastructure and networks built in the days when DOCSIS was king are becoming hard pressed to keep up, with legacy architectures burdened with scaling challenges, including increased power consumption and avoiding bottlenecks as bandwidth requirements increase. The 10 Gigabit (and beyond) network future is clearly fiber, but simply deploying fiber or new DOCSIS technologies (DOCSIS 3.1 or FDX) results in increased head-end congestion, even with the newest Cable Modem Termination System (CMTS) and Converged Cable Access Platform (CCAP) equipment deployed. Building a bigger head-end doesn’t scale as speeds increase, with both power and physical space for hardware becoming concerns.

Plotting a sound and future-ready migration path from legacy DOCSIS technologies to advanced DOCSIS or fiber technologies means moving away from the traditional DOCSIS-based, head-end-centric network and to one that is open, distributed and scalable. A distributed architecture is the solution to centralized head-end congestion, with virtualization as a key benefit. MSOs are moving to Fiber Deep Architecture, pushing fiber as far to the edge as possible to take advantage of the improved performance and smaller service groups.

Fiber Deep effectively moves the muscle of the network out of the head-end and closer to the customer, giving smaller numbers of customers significantly more bandwidth from hundreds of megabits to multiple gigabits. Such an increase in capacity means customers can use existing and future bandwidth-rich services for their benefit.

Using 10G Ethernet Passive Optical Network (10G-EPON), DOCSIS 3.1, and FDX, as a baseline for fiber deep deployments and upgrades provides a high-speed framework to deploy distributed access architectures (DAA) that scale to deliver the bandwidth needed in a multi-gigabit world expected to support services such as 4K video today and emerging ones like virtual/augmented reality. A common network build can support a mixture of residential, business, and infrastructure backhaul, and support service expansion more rapidly than alternative point-to-point fiber architectures. Further, next-generation 10G-EPON technologies and DOCSIS technologies have the capacity to double the useful life of an operator’s fiber and coax networks investment.

Centralized CMTS and CCAP functions choking the head-end in a traditional MSO architecture can be distributed and virtualized in a fiber deep strategy, disaggregation of CMTS and CCAP out of the head-end and moving it closer to the customer using fiber enables higher modulation using DOCSIS and higher speeds. It also eliminates a lot of dedicated, proprietary hardware at the central office that consumes both space and power, reducing operational costs. Replacements in a DAA network include the virtual Converged Cable Access Platform (vCCAP), Remote PHY, Remote MAC / PHY, and Remote Optical Line Terminal (R-OLT).

SDN and NFV
Software defined access (SD-Access) architectures built on top of DAA provide additional cost and flexibility benefits for cable operators. Leveraging the ongoing evolution of open standards, software defined networking (SDN) and network function virtualization (NFV), operators can build and operate modular, component-based, multi-vendor network architectures that can easily scale to add services through a bandwidth-rich environment.

SDN and NFV trace their origins back to data center networks, with the same technologies now being applied to telecom and MSO networks. Adding services and optimizing network performance can essentially be done in real time with SDN/NFV, instead of having to use dedicated and proprietary vendor-centric hardware for each function. Functions once embedded in centralized hardware are now performed as tasks operating on commercial off-the-shelf (COTS) server hardware within a data center. Instead of having a dedicated box per function, multiple functions can be run on a single server or a resource intensive function can be distributed across multiple servers, with the ability to scale up and down based upon need. Using SDN/NFV also provides cost savings to operators through consolidating functions on commercially “white box” hardware instead of proprietary equipment requiring floor space and power.

With SDN/NFV, the legacy of pricy and proprietary Layer 3 router and switch hardware becomes anyone’s “white box” with open standards software providing programming and scalable infrastructure at a significant cost reduction. Operators also gain a simplified network, automation and lower operational costs in managing their fiber access networks.

Automation is an underappreciated feature of SD-Access networks. Established tools and supplemental scripting when needed drastically reduces service provisioning times, human error, and IT complexity, while enabling the customers self-service capabilities if desired.

By leveraging open systems, MSOs can build networks based on their specific network topology and service requirements, selecting the customer premises equipment (CPE), middleware, and access platforms that best meet their needs. New customers and new services are easily added through a plug-and-play model using open interfaces, while the MSO is not locked into a specific vendor solution with all of its proprietary burdens.

SD-Access enables network flexibility and agility to scale in a multi-Gigabit world, supporting thousands of Remote Physical Layer (R-PHY) or Remote Media Access Control/Physical Layer (R-MAC/PHY) devices in the network. SDN-based systems provide the management and service orchestration necessary to rapidly deploy and support R-PHY and R-MAC/PHY devices.

Using a standalone fiber or coax aggregation architecture combined with a non-blocking leaf-spine fabric and aggregation switching, service providers get a multi-Gigabit scalable network access architecture from day one. Leaf-spine switching networks of this type have full meshed connectivity to spine switches.

Within this architecture, programmable network elements can scale horizontally. As the number of Ethernet aggregation ports in an SD-Access network grows over time, leaf and spine switches can be added as needed, with meshed connectivity staying in place. Leaf and spine switching functions are sized to accommodate growth and can be easily upgraded when needed.

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About Author

Hossam Salib is VP Cable & Wireless Strategy, ADTRAN. He is an expert in copper technologies with a background in system and silicon development. Most recently he was VP Access Technology Strategy at Comcast. He joined Comcast in 2013 from Positron, which acquired Aktino in 2009. Hossam co-founded Aktino in 2003. There, he led the Positron/Aktino Team defining and building the industry’s first 4/8 Pair Bonded ADSL2/VDSL2 products with Vectoring and MIMO. For more information, please visit http://adtran.com/sd-access or http://adtran.com/fiber-deep.

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