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There is a lot of talk about software-defined networks (SDN) and network functions virtualization (NFV). But so far, the discussion has largely left out the access networks — mobile, broadband, and voice connections to the customer — which are crucial to building a full SDN and NFV platform. What exactly is required to build software-defined access (SD-Access)?

What good are SDN and NVF if they are incompatible with the technology that connects to the customer? Billions of customers worldwide require a connection to the first hop in the network, known as the last mile, which means that somewhere there is a piece of technology that must connect to the network from the customer premises, a device known as customer premises equipment (CPE).

To rapidly roll out new NFV services that can be controlled on an end-to-end basis, service providers need an open SD-Access platform that integrates with NFV. This platform needs to be open, flexible, and programmable, enabling configuration of the underlying access hardware to be made via software.

In existing NFV models, there are different views on how CPE fits into the system. In some models, CPE is commodity, open hardware based on standard server and chip technology. In other models, it's a hybrid, whereby specialized equipment is deployed but then made compatible with emerging SDN and NFV standards.

It’s unlikely that service providers are going to roll out an entirely new generation of commodity hardware to replace their extensive access networks. SD-Access will require an evolutionary platform that can manage both legacy and next-generation CPE and help move service providers toward an NFV model. This means taking the software-defined model from the core (SDN and NFV) to the access edge, so services can be connected end-to-end.

The appeal of a software-defined model is that it enables the dynamic update software and services on demand, independent of hardware. This same model needs to be adopted at the access layer, where proprietary hardware and operating systems need to be replaced with open systems with Application Protocol Interfaces (APIs).

The chart below outlines the requirements for the next-generation SD-Access platform.

Requirement Legacy Access Network Open SD-Access
Provisioning Requires Manual Provisioning Can Be Customer-provisioned
Operating System Proprietary Open with APIs
Management Proprietary and Monolithic Open and Distributed
Orchestration Manual and Hardware-based Automated and Software-based
Assurance & Visibility Requires Software Add-ons Built In
Underlay / Overlay Proprietary Underlay Underlay Integrated with Open Standards and APIs
Applications Built By the Provider Built By Provider and / or Third Parties

If these new technologies are adopted, here’s what an open SD-Access platform can deliver:

  • Service agility and flexibility in service deployment: Services and provisioning features can be updated and pushed out with software, rather than requiring hardware replacement
  • Network automation: By programming the network, carriers can build a more dynamic system that monitors conditions and can make prescribed changes, automatically.
  • Reduced capital expense (CAPEX)
  • Reduced operational expense (OPEX): Automated software updates and dynamic control software means less human OPEX (involvement in managing the network)

The gains in return on investment (ROI) here are clear: End-to-end network automation can reduce truck rolls, enable automated hardware configuration and customer provisioning, and faster time to market. Think of an access network that is more self-sufficient by taking care of itself.

There are additional benefits in the hardware area, as service providers consolidate services platforms and use cloud data centers to deliver the same services. The telco cloud can provide a new economy of scale.

Of course, we know there are challenges. Large service providers have discussed some of the key missing pieces. One of these is the integration with core information technology (IT) technology, including operations support system (OSS) and billing support systems (BSS). These systems provide the bridge between customer service requirements — provisioning, operations, monitoring and billing — and the implementation of network services that can fulfill the services.

An SD-Access platform will be key to this integration by providing compatibility with the access network and the new software-enabled telco core. It’s important that the access network adopts many of the data standards that are being used to integrate the OSS world with NFV, including NETCONF/YANG and many emerging APIs.

SD-Access will be a key piece to completing the SDN and NFV puzzle. It will require an integrated software platform that can adapt to quickly changing infrastructure needs – and work with a variety of access media.

R. Scott Raynovich has been a technology analyst and journalist for 20 years. He is the founder and principal analyst of Futuriom (, a technology analysis firm.