Tips for a successful SDN migration

The prospect of transforming the traditional enterprise network into a new software-defined infrastructure can be a daunting one for many businesses, but the benefits are compelling and the risks can be minimised with proper planning.

In the software-defined network (SDN) model, the network is “programmable”. The data plane is decoupled from the control plane, and the control functions reside in the application layer instead of the network layer. This allows administrators to define how each device routes traffic across the network and control its operations from a single console. 

In the face of growing network complexity, this centralised control greatly simplifies management, improves visibility and security and boosts operational efficiencies. Instead of having to log in to each network device through a command-line interface to make changes, the software-managed control plane allows network-wide traffic flow to be adjusted easily to meet changing demands.

The network thus becomes much more agile and is able to align rapidly with business applications to drive innovation. At the same time, it is able to deliver the flexibility that users need to access applications and computing resources regardless of location, making SDN an important enabling technology for today’s cloud and mobile era.

The other important benefit of transitioning to a software-defined infrastructure is cost savings. By allowing network capabilities to be provisioned as software, SDN delivers significant savings by reducing the need for hardware procurement and lowering capital expenditure.

But a transition to any new network – in this case SDN – is invariably accompanied by concerns over possible outage, the proper functioning of monitoring and diagnostic tools, scalability and performance problems.

To mitigate such risks, the Open Networking Foundation (ONF) Migration Working Group has defined guidelines, systems and tools to facilitate and validate the steps required for a successful SDN migration. Below are some of the areas covered in their recommendations:

● Understand the impact of SDN migration

A good starting point in pre-migration planning is to study real-life migration use cases to gauge the challenges and understand the likely impact that an SDN transition may have on the network. ONF’s “Migration Use Cases and Methods”¹ document details some migration methods that can be applied, depending on the requirements of the target networks. It includes the description of target network core requirements, starting network migration requirements, phased migration requirements, and validation requirements to ensure a complete and successful network migration.

● Build up the necessary skillsets

The next step is to ensure that the enterprise has the skillsets required to build and operate an SDN. These encompass areas such as SDN architecture, design and interfaces, which are quite different from the skillsets required for traditional networks. A sound understanding of the OpenFlow protocol, SDN controllers, and how to configure devices to communicate with the controller will help ease the transition process.

● Document the existing network

The existing network must be very well understood and documented before the enterprise proceeds with SDN migration. Develop an accurate, comprehensive real-time inventory of physical and logical network resources with details about the type of network, the nature of existing equipment such as hardware or software switches and equipment, types of controls such as routing and switching protocols, interfaces and interdependencies.

● Design the target network

Specify the core architecture and service requirements for the target SDN deployment, including detailed information about the interfaces and devices that will be impacted throughout the transition process.

It is recommended that the enterprise plans for an end-to-end model² that incorporates the data centre, campus, branch, mobile networks and the cloud. After all, one of the biggest opportunities with SDN is the ability to quickly provision applications for use by workers in campus or branch offices and, increasingly, those who are working off their mobile devices, wherever they are located.

A second important consideration is support for open standards.³ In order to maximise the benefits of SDN, the network should be built on open standards supported by an open ecosystem. This allows the enterprise to select best-of-breed technologies where required and achieve cost efficiencies with a greater range of choices instead of being limited to the solutions offered by a single vendor. The use of open standards also enables the enterprise to leverage a broader ecosystem to drive innovation and to future-proof the infrastructure as technologies and standards continue to evolve.

● Take a step-by-step approach to migration

A key point to remember about SDN is that it does not force the enterprise to replace existing infrastructure. An SDN can co-exist with the traditional network in a hybrid configuration, for example, where an OpenFlow-enabled switch is deployed at the edge for application access, leaving the rest of the network intact.

This allows the enterprise to adopt an evolutionary approach to SDN and better manage risks by making the transition step by step, virtualising one network domain or service at a time to ensure a smooth pathway to full adoption.

● Define and execute post-migration acceptance procedures

It is important to test and validate the target network by defining and executing procedures for post-migration acceptance.  This can be done using the right software tools and metrics for each step of the transition. For example, network emulation and simulation tools can also be useful for predicting and validating network behaviour before and after real-world deployment.

As part of post-migration planning, it is also important to have a rollback strategy with detailed change logs, in case there is a need to return to a working pre-deployment configuration.

Given the inexorable march towards mobile and cloud, and the inability of legacy infrastructure to keep pace with the growing complexity and rising demand for agility, enterprises may soon be left with no choice but to take the SDN route. But it need not be a perilous journey. Careful pre-migration planning, a step-by-step transition and proper post-migration testing and validation will help ensure a smooth path to a software-defined infrastructure and all the benefits that this will unlock for the enterprise.

Speak to us to learn how to transition to a software-defined network.     

¹ Open Networking Foundation, Migration Use Cases and Methods.

^{2, 3} Transforming Network Infrastructure, Top 5 Considerations in Transitioning to Software-Defined Networking (SDN) for the Digital Workplace​​, 2018.