View All Posts
View All Posts

Understanding Flexible MAC Architecture (FMA)

Discover the power of being able to deploy the DOCSIS MAC anywhere in the cable network as cable operators evolve the cable access network for a more digital, connected future.

March 14, 2022
7 - Minute Read
CableOS Sales Specialist

As operators deal with the ever-increasing bandwidth demand they face the need for significant changes in their network infrastructure. DOCSIS version upgrades may no longer be enough to meet new demands for faster broadband speeds. Operators now have more options to consider and decisions to make around network architecture:

  • DOCSIS 4.0, PON or both
  • FDX or ESD
  • Central or distributed architectures
  • Virtualization or Legacy buildouts
  • Edge cloud or deep edge cloud

The Flexible MAC Architecture (FMA) aims to align the industry and provide a framework to deploy a virtualized, agile, and scalable architecture that supports multiple access architectures.

This article will explain the need and benefits of FMA and the Harmonic MAC Anywhere capability. Both from a business and engineering perspective. We will also highlight the new MAC Anywhere Eco-system that brings vendor optionality and competition back to cable operators worldwide.


What is the Flexible MAC Architecture (FMA)?

The Flexible MAC Architecture is a recent specification for distributed access architecture (DAA) systems. The Flexible MAC Architecture is a standardized framework to deploy both Remote PHY (R-PHY) and Remote MACPHY (R-MACPHY). DAA enables FMA, we will explore more in this blog as to the different drivers operators have to deploy FMA.

The specification is designed to create greater optionality for cable operators that are facing challenges to update the network for the broadband market’s demand for bandwidth and high-speed connectivity.


Drivers for Flexible MAC Architecture

Optionality & Agility for DAA Deployment

FMA provides agility and flexibility when deploying distributed architectures like DAA.

The key driver for FMA was the desire to be able to combine the different distributed PHY options, to get to a single framework.

Some vendors have a focus on specific parts of FMA, such as R-PHY or R-MACPHY, Harmonic is one of the very few vendors with a full FMA in the works. From MAC-manager to R-MACPHY and R-PHY. This is the power of a virtualized Cloud Native software architecture.


Interoperability & No Vendor Lock-In

A key driver for FMA is the need to combine all the DAA deployment options to get to a single framework in a multi-vendor environment with the best possible interoperability.


Use Cases Demonstrating the Optionality in the Flexible MAC Architecture

Optionality leads to greater business agility so operators can make the most advantageous decisions based on their actual business needs. Here are a few examples where optionality for FMA could be important.


CAP and Grow Strategy for existing CCAP deployments

When deploying legacy CCAP solutions or even I-CMTS, deploying a vCMTS with R-PHY shelf devices retains the consistency from a solution architecture perspective. This may be important for operational reasons and often is an easier transition for organizations to deal with. In time the solution can add R-PHY nodes when the replacement for the Optical Nodes is due. Deploying R-MACPHY will be too much of an operational change for many of these operators.


Super Hub deployments

As operators have gone through mergers and acquisitions, there are operators that have both Super hub locations in dense metropolitan areas and de-centralized smaller hub site locations. When dealing with Super hub locations (hubs with a very high number of services groups) in large metropolitan areas it may be more cost efficient from a physical footprint, power and cooling perspective to use R-MACPHY. At the same time the areas with average sized hubs might be better served with vCMTS and R-PHY solutions. Hub site locations with a very low number of services groups might be using either R-MAPHY or R-PHY with the vCMTS located in the larger hubsites. Optionality is again of key importance providing flexibility to operators and MSOs to select the best fitting solution for their requirements.


Alternative Backhaul solutions

Use cases that include using backhaul solutions with distributed PHY devices other than Ethernet, for example fixed wireless access, Satellite or long fiber backhaul links. Different latency characteristics of the backhaul solution might drive different FMA options.


Ultra low Latency

Latency is often mentioned as a reason to try to reduce the distance between the MAC and the cable modem. Low Latency DOCSIS (LLD) is in fact the best tool to ensure low latency for FMA deployments. Yet in some specific use cases that require ultra-low latency and where the length of the backhaul network is extremely long R-MACPHY can provide a solution.

In the end the most important aspect to consider is that FMA allows operators to make decisions based on business requirements, and not on vendor imposed requirements.


What are the Deployment Options for Flexible MAC Architecture?

We have already mentioned the different remote devices in FMA : Remote MACPHY, Remote PHY. R-PHY and R-MACPHY were first introduced in DAA. DAA with R-PHY has seen accelerated adoption by many operators around the world. This architecture is currently the most widely deployed.

Harmonic’s DAA deployment footprint is leading the industry and gives operators the ability to enable FMA with no additional deployments. Harmonic’s CableOS cloud-native platform and network edge devices make FMA possible, right now.


How Does the Flexible MAC Architecture Solution Work?

A  DAA R-PHY device provides the PHY capabilities of a legacy I-CCAP (downstream and upstream PHY). The  DOCSIS MAC is hosted by a R-PHY Core. In the past, a legacy I-CCAP was reused as R-PHY-Core, but today most R-PHY deployments are using a virtual CMTS as R-PHY-Core.

R-PHY devices come in multiple flavors: a traditional field hardened device, optical node, and a hub-site based device (fixed or modular). Both allow the CMTS to transition to a virtual entity, eliminating purpose-built CMTS hardware.

R-MACPHY is an option that is an evolution from the legacy distributed CMTS, based on the SARF C-DOCSIS specification, that came to market in 2013 and was mostly used in China. It is in essence an R-PHY device with the DOCSIS MAC embedded in it, running on a compute module. It does not require any external MAC engine, yet it does utilize a MAC-Manager for virtual management and provisioning, the management plane.

The PTP timing for synchronization is mandatory for R-PHY, some operators looking at deploying R-MACPHY are considering deploying the optional PTP timing for R-MACPHY as well. The third option in FMA is the Remote MAC Core, this is an extension of the R-MACPHY as the compute module on the RMC can run a full instance of a virtual CMTS and can act as RPHY Core. This means it can support multiple R-PHY devices.


Why Is Optionality Key?

R-MACPHY has unique benefits for deployments where latency is incurred due to long distances between the datacenters and node location. R-MACPHY also prevents some of the tromboning of traffic since there is no centralized CCAP. The R-MACPHY approach may also be of benefit for deployments using larger “super hubs” or centralized datacenters.

Remote PHY is a technology that provides a less complex remote device yet has more solution components. R-PHY deployments allow for a broader Remote PHY Device vendor landscape, since the R-PHY device does not contain any MAC software and is thus less complicated to develop and bring to market.

R-PHY is a solution that is also aligned with the edge cloud proposition. This includes the hardware and software infrastructure used by the vCMTS which can be used by other applications, thus optimizing resource efficiencies.

Optionality provides operators with the capability to use any, or all of the three FMA options, to align with any specific business requirements and use cases operators need to handle. The decision to deploy R-PHY, R-MACPHY or a Remote MAC Core needs to be driven by a specific customer business outcome, not by the product portfolio choices a vendor has made.

Some vendors are not able to provide optionality to their customers as they may only have R-PHY or R-MACPHY products, thereby limiting the operator’s choice to a specific option of FMA. That is contradicting FMA and is not the intent of FMA.

Optionality not only provides the operators with the flexibility and agility FMA intended to provide, but optionality also fosters innovation and competition between vendors. Which is essential to industry growth as whole.


The Role of the DOCSIS MAC

We have discussed the different FMA options: Remote PHY, Remote MACPHY and the Remote MAC Core, yet the most critical piece of FMA is the DOCSIS MAC. The DOCSIS MAC is used by all three FMA options.  

The MAC is the most critical part of any DOCSIS solution and defines the network behavior. It’s responsible for the DOCSIS control and data plane and dictates the behavior of the cable modem. The DOCSIS MAC handles quality of service and prioritization of specific traffic types, and is also the driving factor behind functionalities such as spectrum management.

In short, the DOCSIS MAC is directly responsible for the customer experience. All three FMA options have one thing in common, the DOCSIS MAC.  The MAC for R-PHY is housed in a vCMTS, the MAC for a R-MACPHY and RMC is running in the compute module in the remote device.

MAC Anywhere Delivers on Optionality

Harmonic has the most widely deployed and the most feature rich DOCSIS MAC for R-PHY. Our CableOS cloud-native core platform leverages a containerized software architecture to host our DOCSIS MAC anywhere, on any FMA device, or any vendors FMA device.

The Harmonic MAC Anywhere capability fosters network consistency and utilizes a feature-rich and field proven MAC that can be used by all R-PHY, R-MACPHY and RMC devices, ensuring a superior user experience.

Harmonic CableOS Solution Brief FMA

Being able to deploy the MAC anywhere is a vital element of the DOCSIS solution and the most important piece of any FMA solution. The MAC is responsible for the quality of experience of the subscriber. A failing or badly performing MAC has an immediate impact on end- user experience. The MAC anywhere capability brings optionality to the cable operator. With CableOS, operators can use R-PHY, R-MACPHY and RMC in the network while retaining feature functionality and interoperability.  Operators can continue to work with their incumbent node vendors, avoiding disruption and stranded assets by enabling them to use the DOCSIS MAC anywhere on their R-MACPHY edge devices.


Get Ready for FMA Today

Harmonic is one of the very few vendors with a full FMA in the works, from MAC-manager to R-MACPHY and R-PHY. This is the power of a virtualized cloud-native software architecture that CableOS provides as the market leader in virtualized CMTS. Contact Harmonic today to learn more about our virtualized cable access and broadband solutions and stay tuned for the next blog on FMA to learn more about the MAC Anywhere Ecosystem.

As we advance toward a more connected future, multiple pathways emerge for operators looking to take the next step on the path to 10G broadband. DOCSIS 4.0 is moving to its next phase in testing, and FMA continues to spark interest, especially for operators looking to leverage their existing distributed access architectures.

Harmonic is the recognized market leader for both virtualized CMTS and DAA. Its CableOS solution is able to support both Remote PHY and Remote MAC-PHY, providing operators the ability to deploy services with the utmost architectural flexibility. The MAC Anywhere approach uses the same CableOS containerized MAC in both central and distributed architectures and offers a field-proven, feature-rich, scalable and agile solution for FMA.

CableOS delivers on the promise of 10G as a sustainable foundation for FMA and brings edge cloud capabilities to operators worldwide. Contact us to start a discussion on how you can leverage MAC Anywhere with the CableOS solution for FMA.
Daniel is a long time cable industry executive living in Belgium with his wife and four kids. At Harmonic, Daniel is leading the Liberty Global team. He has previously worked in different roles at some of the major vendors in the industry such as Casa Systems and Cisco. Daniel has been involved in DOCSIS as of the start of the journey in 1998.

Subscribe to our blog

Don't miss out! Keep up to date with the latest by subscribing to email notifications.
No thanks, I am not interested