Architectural Considerations for a Software-Defined Network

By: Steve Currie| - Leave a comment


IT architects make critical decisions throughout the development of a system in response to business drivers and requirements. With any journey, we begin with the end in mind.

The end of the software-defined networking (SDN) journey must satisfy specific organization needs. Oftentimes software-defined network targets the need to improve the overall networking, IT agility and responsiveness to changes in markets — while supporting associated applications at the same time. SDN is also used to improve network security through greater segmentation and isolation of critical data assets. The business drivers of agility and security are the foundation of most SDN deployments. The decisions involving network security deserve a more focused treatment, especially in light of heightened security risks and greater regulatory requirements.

SDN is an architecture to manage the control (network services) and forwarding (network infrastructure) planes of the network that is programmable through a logically centralized point. SDN virtualizes and abstracts the network services from the physical network infrastructure, and is then applied to data center, wide area, wireless and campus networks.

Here, we’ll explore some key decision points focusing on SDN in the data center, though the decisions can be adapted to other forms of SDN as well. To make effective decisions surrounding SDN in data centers, businesses must consider the following:


Improving agility and responsiveness requires a coordinated IT infrastructure, with compute, storage and network resources orchestrated and provisioned to enable applications to operate on them. Organizations need to devise their orchestration approach to inform their SDN solution decision and deployment. The decision to use OpenStack or a vendor-specific tool, for example, may place constraints on the SDN products and even limit the features of the orchestrated SDN products.


Similar considerations are required for the adoption of automated operations, which improve the efficiency and effectiveness of the infrastructure. A key attribute of SDN solutions are the application programmable interfaces (APIs) available for monitoring and responding to events in an automated fashion. The approach to automation should be consistent across all IT disciplines leveraging the skills and libraries of the whole organization.

Compute Endpoints

The data center endpoints are important in determining the SDN solution. The hypervisors used for Intel-based systems will affect the available solution choices. The decision whether to integrate non-Intel systems into the virtualized network — or rely on the edge services to access these often critical systems — is also an important consideration. Both approaches are valid depending on the rate of change, security, performance and capacity applications requirements.

Hybrid Cloud and the Software-Defined Network

The last decision we’ll explore is how the traditional on-premises data center will integrate with cloud services — that’s hybrid cloud. SDN offers the opportunity to extend virtual networking constructs from the traditional to the cloud regardless of the underlying physical network. The extended virtual network can enable consistent orchestration and holistic security approaches.

SDN architectural decisions flow from the organizational drivers. SDN, using orchestration and automation with the overall IT infrastructure and its cloud services, will deliver the desired benefits of greater organizational responsiveness to rapidly changing market conditions.

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About The Author

Steve Currie

Distinguished Engineer, IBM

Steve Currie, Distinguished Engineer, IBM Global Technology Services, has more than 25 years of experience in IT consulting. Currently, he is leading the qualification and adoption of software defined networking (SDN) technologies with IBM clients as a member of the GTS Technology Innovation and Automation team. Over his career, he has delivered leading edge IT services and solutions to solve pressing business issues for his clients. He has also managed Network Infrastructure and Mobility/Wireless consulting practices.

Articles by Steve Currie
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