The answer to this operational dilemma is policies. This is one of the most compelling aspects of SDN, the ability to template services as policies. Policies are a higher level of abstraction by which a set of underlying virtual or physical network objects, flows and connections is pre-engineered and packaged as a single function more closely aligned to the intention of the person provisioning the service. This is especially helpful when the service provisioner may not understand the underlying network elements, but does know what effect they want to achieve.
For instance, a nightly backup service for a financial enterprise customer might be created as a policy specifying that latency is not important, but bandwidth cost is key and least-cost routing essential. A daytime service for the same company connecting the company’s trading floor with various securities and commodities exchanges where they have co-located their equipment might use a very different policy. For this policy, latency is critical, service up-time is key and cost is not an important parameter.
Where this approach shows its true power is when policies can also be engineered to be dynamic, that is, structured to include automated decision-making. For instance, if the trading floor’s real-time, low latency, premium bandwidth service encounters network congestion, the policy contains programming that instructs the underlying network to re-route the connection to back-up links and maintain specific QoS parameters. In this way, the service requirements are maintained because the software is network-aware and can dynamically provision and re-provision the service in a completely automated way in the background. The IT person who provisions the service doesn’t need to know any of this detail, neither when the service is fulfilled, nor during its operation.
Network awareness derives from assurance capabilities that can be built into carrier SDN. The analytics, KPIs and correlations that drive assurance can be integrated with the SDN controller so that they can trigger automatic changes to the network — for instance, in the example above, actions at the network layer to avoid network congestion. Flows can be redirected, new IP/optical paths 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.
What this means in practice is that assurance parameters are built into dynamic service policies. The analytics, KPIs and correlations are used to define the policy and establish the dynamic decisions and automated actions that will be driven by the policy. The “intentions” of the service provisioner are not only reflected in the creation of the service, but in the ongoing “assured” operations.
This automated, dynamic characteristic of policy-driven service fulfillment is important to meet the fluctuations characteristic of on-demand cloud-based services. Moreover, it is also essential for keeping operational overhead down using automation so that these services can be profitable for telecom operators. Somewhat as a welcome side effect, policy-driven service fulfillment also accelerates the time to market for new services, making service innovation not only possible but responsive to rapid shifts in market demands.
In summary, the cloud era imposes new requirement on network service providers. Their service fulfillment processes must evolve to become on-demand, agile and rapidly scalable. This requires moving to carrier SDN for the control of physical and virtual network resources. Network complexity needs to be simplified through a policy abstraction layer that provides fulfillment personal with a simplified language to accurately capture their intentions. This makes possible a highly agile, policy-driven provisioning system that automates service delivery using IP/MPLS, Carrier Ethernet and optical network resources.
Fully implemented, a policy-capable SDN will not only make on-demand operations possible, but also, profitable. By dynamically identifying the best available network resources to meet service requirements, carrier SDN will enable assured, network-aware, on-demand services ready for anything the cloud can throw at it.