SDN’s First Use Case Is the WAN, But Wither Management?

Considering how long Packet Design has been talking about the promise of SDN in the WAN, it was encouraging to see a Q&A in Network World last week on the subject. Editor John Dix interviewed Michael Elmore, IT Senior Director of the Enterprise Network Engineering Infrastructure Group at Cigna. Michael is also on the board of Open Network Users Group (ONUG).

Dix began the interview by asking why ONUG’s membership has voted the WAN as the top use case for SDN twice in a row now. In the context of the enterprise, Elmore replied that software defined WANs (SD-WANs) can reduce both capital and operational costs. He also said that they are easier to deploy than in the data center.

Elmore went on to discuss the limitations of today’s WANs (mainly the MPLS-based layer 3 VPN service offerings used by the Fortune 500) in terms of cost, scale, service quality, security, visibility, and agility/flexibility. He then outlined the benefits of SD-WANs in all those areas, saying that enterprises will be able to “take back control from service providers” while at the same time creating new market opportunities for those SPs.

When Dix asked how close the industry is to making this happen, Elmore said we are very close in terms of being able to deploy SDN-WANs. The drawbacks for enterprises may be “carrier proliferation” and vendor lock-in.

What he didn’t address much in the article is management. The rush to deploy SD-WANs because they are easy has negative consequences that enterprises and service providers need to consider. One consequence is that programmability takes the network operator out of the equation. With SDN, planning groups no longer get weeks and months to prepare for the rollout of a new application or service.

In addition, networking groups lose visibility with SDN. Traditional, manual management methods cannot provide the visibility needed to run a programmable network that automatically adapts to application demands. This is especially true across the dynamic, resource-constrained WAN where management is more complex than in the data center. Whether it is a network virtualization application for cloud operators, bandwidth-calendaring application for carriers, or indeed any SDN application, the moment the traffic hits the WAN, resources such as bandwidth become scarce.

The real-time network provisioning by the SDN controller and the successful monitoring and management of SDN applications requires always-current network models and traffic load profiles. Packet Design believes that the SDN architecture should be augmented with a Management and Orchestration Platform that checks whether the required resources are available. The goal is to verify if the network can handle the traffic demands of the application without impacting other applications and services adversely.

It is necessary to understand how the topology is changing and what commitments have been made in the network, so that when new requests come in via the SDN controller, network professionals can understand whether or not those can be met.

Another important element, which is key to viable SDN architecture and deployment, is the ability to predict the impact of change to network routing topologies and traffic flows. Unique Packet Design planning capabilities make it possible to simulate modifications to the network model and to flow records in real time and analyze their impact.

Packet Design also examines historical traffic profiles to determine if network load is likely to change significantly after the application request is satisfied (for example, the predictable increase in market data and trading traffic that occurs when stock markets open).

SDN holds great promise, but a rush to deploy it without consideration for how to manage it in the WAN could have dire consequences. We believe with our SDN management platform, which we are launching later this year, will provide the analytics and orchestration required for mainstream viability of software defined networking.