The cable industry took another step toward its "10G" future this week with the release of a new set of specifications giving operators and their suppliers a common framework for disaggregated networks that will deliver multi-gigabit speeds and, eventually, lead them to fully virtualized access networks.

That new set of CableLabs specifications – called the Flexible MAC Architecture (FMA) – provides suppliers with the technical means to develop interoperable products. The specs will likewise provide cable operators with the ability to build and develop these next-gen access networks without worrying about getting locked into vendor-specific, proprietary technologies.

FMA should also put to rest a years-long technical and engineering debate over what path operators should take as they pivot from traditional, integrated Converged Cable Access Platforms (CCAPs) to more disaggregated and distributed forms of the access network. Until recently, that debate has centered on whether to go with remote PHY (whereby the PHY of the CCAP is deployed in a fiber node) or remote MACPHY (where both the PHY and the MAC processing are pushed out toward the edge).

"The biggest takeaway for FMA is flexibility," said Jon Schnoor, lead architect, wired technologies at CableLabs. "It allows the operator to choose when and how they implement and deploy CCAP functionality. It gives them choices of where to do it in the access network where it makes the most sense for them."

FMA also represents a complete disaggregation of the industry's broadly deployed integrated CCAP device. "We literally blew it up," said Schnoor, who also authored a blog post about the new specs.

Multi-phase approach
Although FMA will ultimately enable cable operators to deploy the MAC anywhere, phase I of the FMA project – as defined by this initial batch of specs – is focused on remote MACPHY, where the MAC and PHY are miniaturized and packed into a fiber node.

Further out, phase II will focus on specs for a remote MAC core, and phase III will set upon a full virtualization of the access network. The time frames for phase II and III are still to be decided, Schnoor said.

FMA building blocks
Back to FMA phase I. For that, CableLabs, Schnoor explains, has developed three key pieces that will work together: the MAC Manager, the Remote MACPHY Device (RMD) and an optional element called the PacketCable Aggregator.

Figure 1: (Source: CableLabs)

The MAC Manager relates to how operators will control the remote MAC, which used to reside in the central CCAP core but will instead be moved to Remote MACPHY Devices that are deployed further out on the network. To facilitate that, CableLabs has crafted a spec called the MAC Manager Interface, which takes data from the operator's OSS and BSS and translates it into Yang data models that, in turn, are shot down to the Remote MACPHY device.

The MAC Manager can be virtualized. "It's just software," Schnoor said.

The optional PacketCable Aggregator (supported by its own specified and interoperable interface) will help operators manage IP voice services that still rely on the industry's PacketCable backend specs. Managing PacketCable services properly will become an issue as operators disaggregate their networks and deploy about 10x the number of nodes they have out there today.

Boiled down, the PacketCable Aggregator will enable those PacketCable telephony systems to perform the necessary translations and make the overall system take on the appearance of a traditional CCAP deployment underpinned by much fewer nodes, as well as to ensure that the right node connects to the backend of the network.

How the Distributed CCAP Architecture (DCA) fits in
FMA, Schnoor explains, is also a "foundational piece" for the work being done around the Distributed CCAP Architecture (DCA) program.

And what, pray tell, is that? DCA, which initially focused on remote PHY, is all about the complete disaggregation of the DOCSIS network and the individual DOCSIS functions. Think of it as the HFC piece of the distributed network. DOCSIS 4.0, which will require a disaggregated node architecture (using remote PHY or the Flexible MAC Architecture), is part of that.

Update: CableLabs further clarified that DCA represents an HFC architecture toward virtualizing the DOCSIS technology. The first step was R-PHY by providing the ability to virtualize the CCAP Core and FMA completes that picture once the specs are finalized.

DCA is also a subset of a broader industry program called the Distributed Access Architecture (DAA), which, in addition to DOCSIS, factors in the use of PON and coherent optics in distributed access networks. (The CableLabs coherent optics specs released in 2018 pave the way for cable operators to bring coherent optics techniques traditionally used in long-haul networks to the cable access network.)

When taken together, these all fit in with a broader industry initiative centered on convergence and the adoption of an access-agnostic approach to the access network.

Meanwhile, FMA and DCA represent the first steps of virtualizing the DOCSIS access network, Schnoor says.

Ties to '10G'
FMA and DCA are also technology pillars for cable's broader aims around "10G" – a label being applied to access networks that will deliver up to 10 Gbit/s (at least in the downstream), along with enhanced security and low-latency services.

FMA and DCA help to create the "foundation" for 10G, at least with respect to HFC networks, Schnoor said. Cable operators aren't going to deliver multi-gigabit services on HFC without some type of disaggregated cable access architecture – whether that involves remote PHY or remote MACPHY or perhaps a mix of both – he adds.

How and when those pieces all come together will now rest on the vendors (and how quickly the cable operators prod them forward). As for CableLabs' role, the plan is to start "in-depth" FMA interoperability events sometime in 2021.

Cable engineers contacted by Light Reading about FMA believe that some early FMA prototypes should surface as early as the end of this year. They are looking at some initial use cases such as business service applications and serving multiple dwelling units (MDUs).

"It's quite a step forward," an engineering exec with a top North American cable operator said.

FMA is becoming particularly attractive to cable operators with diverse networks they've acquired over the years and through other forms of consolidation and as they get deeper into mobile backhaul and fixed wireless backhaul, said Jeff Heynen, senior research director, broadband access and home networking at Dell'Oro Group.

FMA also doesn't lock operators into a remote PHY or remote MACPHY approach, he notes. "Now you can, as things have evolved, become more accepting of a virtualized MAC and put it where it makes sense," Heynen said.

The new specs could generate more momentum for remote MACPHY as cable operators mull their next big moves on the access network.

"It will be interesting to see if, and how much, the new FMA specs spur the deployment of remote MACPHY by cable operators," said Alan Breznick, cable/video practice leader for Light Reading. "Up to now, the remote PHY option of DAA has clearly had the edge because it's simpler to do and the specs were already established for it. But this new move by CableLabs now puts remote MACPHY on what seems like an equal footing with remote PHY."

Jockeying for position
So, how will the vendors attack this and who is set to lead the way, at least early on?

Heynen gives Vecima Networks a slight edge at this juncture given its recent acquisition of Nokia's cable access network assets, which include remote MACPHY products and technologies pioneered by a startup called Gainspeed (Nokia acquired Gainspeed in 2016 and sold off the lot to Vecima earlier this year).

One cable operator exec agrees that Vecima has a "leg up" at the moment, though its initial architecture used a proprietary approach with FPGAs. However, new Broadcom silicon with the complete MAC and PHY integrated into one chip will open the field to others.

Other suppliers, including CommScope, Casa Systems and Cisco, will also be vying for this business with a virtual CCAP or remote MAC core driving a remote PHY device or a remote MACPHY device, Heynen said. Harmonic and its CableOS platform – already being adopted by Comcast and Vodafone – will also be in the mix.

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— Jeff Baumgartner, Senior Editor, Light Reading