There’s a high level of interest within the industry for carrier software-defined networking (SDN) and multiple reasons why moving to carrier SDN makes sense for telecom operators. Recently the focus has been on technical and economic feasibility with a number of promising trials. Yet the topic of service assurance has been mostly absent in industry discussions despite the fact that much of the commercial promise of SDN/network functions virtualization (NFV) may depend on this so-far missing piece.

Software-defined networks have many powerful capabilities. The most important may be their ability to make smart service placement decisions when dynamically provisioning a service for cloud applications. A SDN network can automatically make bandwidth available when and where it is needed in order to meet the requirements of specific cloud applications. In the unpredictable cloud environment, where network resources are consumed and released on demand, and traffic patterns can change in an instant, this intelligent allocation of resources is critical.

Being this dynamic and responsive to user requirements is only half of the story, however. Dynamic allocation needs to be supplemented by assurance capabilities that ensure network and service health over time. The ability to make automated, corrective changes to the network — assurance — is different than simply dynamically responding to service requests. In commercial deployments, carrier SDN will have to leverage analytics, key performance indicators (KPIs), and other assurance metrics to ensure overall network and services reliability. Assurance in traditional networks involved time-intensive manual corrective actions, whereas in the new virtualized network, assurance has to be baked-in to ensure that the automatic decisions being made can happen quickly enough to make a difference.

On-demand cloud services change many of the key characteristics and needs of the network. This isn’t about nailing up T1/E1 leased lines for years. Services are automated to the point that they are negotiated, nailed up, torn down, and billed — potentially in hours or days. And each of these network service connections has specific requirements for bandwidth, latency, and other metrics. In this rapidly changing environment, networks have to take corrective action themselves — guided by policies and data triggers — rather than wait for the operator to assess a problem and take manual corrective actions. Just as SDN automation enables intelligent service instantiation, SDN assurance intelligently delivers service health and efficiency for the duration of the service.

As the trial stage for carrier SDN shifts to commercial deployment, it is critical that assurance is a critical component of vendors’ solutions. Having assurance capabilities will enable service providers to ensure their SDN services are operational and requested constraints around latency and performance are always met, and the underlying network infrastructure is always running at peak efficiency.

How should this work? Technically speaking, the analytics, KPIs, and correlations that drive assurance can be integrated with the SDN controller so that they can drive dynamic changes to the network — for instance, triggering actions at the network layer to avoid network congestion. This provides optimal flexibility so that flows can be redirected, new IP/optical paths are established, and existing IP/optical paths can be resized dynamically – all driven by KPIs, analysis, and correlations from both the IP and optical layers as well as physical and virtual domains. This is often referred to as closed-loop, or dynamic assurance.

There have already been some successful implementations of these dynamic assurance techniques with operators. One global operator is currently delivering dynamic, on-demand IP VPN services that are automatically provisioned across an IP/optical network. To ensure service health over time the operator is leveraging dynamic assurance capabilities to check link utilization and resize paths as necessary at the IP and/or optical layers, in this case, by adding an Ethernet link to a link aggregation group (LAG). On a commercial front, this is built into their service description to the customer.

Another tier one operator in Asia-Pacific is leveraging dynamic network assurance by checking congestion on multiple links/paths to and from data centers. It dynamically remaps these flows to secondary links when congestion occurs. This ensures that link efficiency and customer satisfaction remain high. When the congestion event is over, it redirects the flows back to the primary links.

Integrating assurance into our carrier SDN deployments is a critical step in the journey to a new dynamic network paradigm. Without it, operators will not have the level of trust in these technologies to offer guaranteed performance levels to their customers. Further, as we move deeper into the dynamic provisioning of services as nearly instantaneous on-demand transactions, assurance is the missing link in carrier SDN. It will allow service providers to offer truly reliable, as well as dynamic, on-demand services for pay-as-you-grow enterprises and cloud operators.