The case for service assurance in carrier SDN

There are multiple reasons why moving to carrier Software Defined Network (SDN) make sense for telecom operators, which is evident in the high level of interest within the industry. After the initial excitement and early trials, the recent focus has shifted to technical and economic feasibility. But one key area that has so far been absent in most discussions is assurance. And it turns out that much of the promise of SDN/NFV actually depends on this missing piece.

On-demand and SDN

A key attribute of a software-defined network is its ability to make smart services placement decisions without human intervention. In other words, it places bandwidth where and when it is needed to meet the on-demand network needs of users and especially of cloud applications. This is critical when network resources are consumed and released on demand and traffic patterns can change in an instant.

Assurance and dynamic services

Carrier SDN enables the network to be this dynamic and responsive to user requirements, whether for consumers or enterprise. Automation is made according to pre-set policies. But in order to assure that these allocation decisions also optimize the health of services, the network has to have deep analytical capabilities. These capabilities provide assurance metrics that equip the network to make automated decisions that will meet established key performance indicators (KPI) on which customers rely.

Conventional assurance systems normally trigger manual corrective actions that are too slow for the rapid shifts of cloud-based applications. In contrast, the new virtualized network can make quick, automatic decisions to meet these dynamic shifts in network usage. However, in order to also assure the ongoing health of those dynamic services, assurance analytics have to be baked-in to the automated processes.

The issue of linking service placement and service assurance becomes more obvious when you think specifically about the nature of on-demand cloud services. 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. Each network service connection has specific requirements for bandwidth, latency and other metrics — all which have to be assured in the same dynamic timeframe as the service itself. Because Carrier SDN can instantiate services so quickly, assurance has to be equally as quick to assure the health and efficiency of the service.

Commercialized SDN

As we move out of the trial stage for carrier SDN, assurance becomes a critical component in commercializing SDN networks. As part of our Network Services Platform (NSP), we have introduced assurance capabilities into our Carrier SDN product. This enables service providers to ensure their SDN services are operational. It also ensures that requested constraints around latency and performance are always met, and the underlying network infrastructure is always running at peak efficiency.

How does this work? Technically speaking, the analytics, KPIs, and correlations that drive assurance graphical user interfaces (GUIs) and visualizations are integrated with the SDN controller. Thus 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 established and existing paths resized dynamically. This is all driven by KPIs, analysis and correlations from both the IP and optical layers, and from both physical and virtual domains. This is often referred to as closed-loop, or dynamic assurance.



Customer implementations

We have already implemented these dynamic assurance techniques with customers. One is delivering on-demand IP VPN services that are automatically provisioned across an IP/optical network. To ensure service health over time, they are leveraging the dynamic assurance capabilities of our Carrier SDN platform. They check link utilization and resize paths as necessary at the IP and/or optical layers 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.

In another example, China Telecom is leveraging network assurance to monitor congestion on multiple links/paths to and from datacenters. When congestion occurs, they dynamically remap these flows to secondary links to ensure that link efficiency and customer satisfaction remain high. When the congestion event is over, they redirect the flows back to the primary links.

The dynamic network arrives

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

For readers interested in more information on Carrier SDN, we have a video channel for the Nokia NSP featuring a number of videos that further explore the subject, including the key role of assurance.