The benefits of moving towards a virtualized environment have been well publicized – eliminating vendor dependence and product obsolescence, faster introduction of new products and services, and the creation of a flexible, user-driven, on-demand service delivery environment that enables network functions to be dynamically defined, deployed and reassigned to match and organizations scale, performance and capabilities requirement.

And these are just a very few examples of the many benefits.

Network operators are faced with unprecedented rate of change with respect to the growth of connected devices and associated traffic, consumption models and the surge in OTT services.

Furthermore, disruptive web-scale operators have changed the value proposition for the end customer – through lower prices, less stringent contractual obligations, self-service models as well as more choices and more ways to access their services.

The challenge facing operators is the need to protect existing network investments, while maximizing network value. To achieve this, network operators must transform how they operate and deploy their networks.

Transforming the Access Network

Until recently, much of the focus of SDN and NFV implementations has been on the core network. However, the time is right for this focus to also include the access network – a critical component towards the realization of next generation networks.

It is the access network that provides consumers with 24-hour, seven-days-a-week connectivity to the cloud and its wealth of content and applications, while supporting 99.999% uptime. Without the access network, consumers could not connect to the internet, stream their video, connect on social media, etc.

As such, network upgrades – such as upgrading technology to offer faster broadband speeds – must be implemented with little to no interruption to the end user.

The access network is also full of its own challenges. First of all, it is often a multi-technology distribution network with single points of aggregation such as the DSLAM or an OLT located at either the central office or at a remote terminal. It is characterized by vendor-proprietary specialized hardware. It is subject to extreme temperatures and harsh environments – unlike comfy climate-controlled data centers. And finally, it is characterized by non-redundant physical outside plant facilities (copper, coax and/or fiber optics).

The access network is also subject to regular upgrades as operators introduce new technology to offer end-users faster speeds and new services. In the copper world, these upgrades have gone from ADSL to VDSL to Vectoring to G.fast (and these does not include all the variants in between), while the fiber world has seen BPON, EPON, GPON, 10GEPON, XG-PON1 to NG-PON2.

And it is these upgrades that prove challenging, costly and cumbersome. Each technology upgrade is often associated with new equipment, new service definitions, lengthy testing cycles, new methods and procedures, as well as integration into the existing OSS/BSS. Essentially, both the vendor and the operator recreate the wheel each time there is a technology upgrade. (Remember OSMINE, anyone?)

In today’s hyper-competitive world, consumers are no longer willing to wait 12-18 months (the typical implementation timeframe for new technology) for new services and faster speeds.

Enter Software-Defined Access

While it is unlikely that the physical infrastructure of the access network will ever be virtualized, many of the benefits of virtualization technology developed for the data center can be brought into the access network to enable faster service upgrades and new feature delivery that can accelerate revenue growth and speed up time to market. 

Access network equipment vendors can leverage the principles of SDN and NFV by decoupling the hardware and software layers through hardware abstraction, and adopting an open source framework that uses SDN for automation and programmability. Decoupling the hardware development cycle from software development cycle, reduces both development and testing time and allows new services to be introduced without changing hardware.

Additionally, by offering fully programmable open application programming interfaces (APIs) enables multi-vendor network management systems and provides operators end-to-end control and the ability to program their own network applications and services. 

NFV can allow access node functions to be virtualized as VNFs and run in the cloud on commercial off-the-shelf hardware. These VNFs can be instantiated in parallel to physical network functions via service chaining – allowing operators to continue to leverage their existing network investment, but leveraging the centralized control and orchestration capabilities of SDN.

One of the greatest benefits of software-defined access (SDA) is that it is completely agnostic to the type of access network (copper, fiber, cable, etc.). Furthermore it could be used to provide a level of control similar to physical unbundling combined with the flexibility of deployment similar to bitstream unbundling in those networks where access network unbundling is prevalent or where retail and wholesale networks are separate.

Currently, operators are looking at SDA for next-generation access networks – primarily those supporting G.fast and NG-PON2. In both of these scenarios, these networks can implement virtualization technologies from the beginning, rather than taking a hybrid or overlay approach. By implementing open APIs and software frameworks at the beginning, operators can ensure a multi-vendor environment for these networks – which is virtually unheard of in the access network realm.

Standards for SDA in Early Stages

Standards work in this area remains in the early stages with the Broadband Forum with current focus on technical working document WT-358: Requirements for Support of SDN in Access Nodes. WT-358 will define the requirements necessary to support SDN-based implementations for access nodes including FTTdp, as well as identify gaps in current SDN protocols relative to the requirements identified and to communicate those gaps to the appropriate development organizations.  

Additionally, TR-301 specifies DPUs will be modeled in YANG and managed using NETCONF; while WT-355 is looking at YANG modules for FTTdp management.

SDA = Evolution Rather than Revolution

For most network operators, their approach towards SDA will be more evolutionary rather than revolutionary. By leveraging virtualization technologies, operators can experience immediate benefits such as increased automation and network programmability, as well as faster service activation and zero-touch provisioning.

Furthermore, SDA can benefit operators with faster innovation and new business models that can drive additional value out of the network. SDA can enable in-service upgrades and fault recovery on an automated basis without the need for extensive regression testing that is common with new software releases and silicon changes. And these are only a small examples of its benefits.

Software-defined access is a key step towards transforming the access network, reducing total cost of ownership, accelerating time to revenue and improving the overall quality of experience for the subscriber.