SDN architectures

SDN Migration: Ensuring a Smooth Flight

Open SDN is widely accepted by the networking industry as the way to transform enterprise, data center, carrier and campus networks. Potential benefits for enterprises considering SDN migration include simplifying networks, reducing operating costs and tying networks more closely to business objectives.

For telecom service providers, the biggest potential benefit is the rapid introduction of new services. However, making the transition to SDN modifies the way that networks operate, demands new skills from network managers and offers no guarantee that things will run smoothly at the outset. A poorly planned transition can lead to network outages, impaired monitoring and fault management systems, or, most detrimental of all, stalled or failed migration.

A carefully considered, holistic approach to the transition will ensure a seamless migration of existing services (with zero or minimal disruption) and create greater overall business value for network users in terms of technical, operational, and ROI benefits.

Throwing out existing equipment is a non-starter. Rather, in order for operators to migrate to SDN, they need a sensible plan. To assist in this transition, the Migration Working Group at the Open Networking Foundation (ONF) has explored a variety of SDN use cases in order to develop a collection of methods, metrics, tools and best practices to help companies migrate to pure software-defined networks based on the OpenFlow protocol.

Some key questions that should be considered to guide the initial stages of the transition include:

  • What are my goals for migrating to open SDN?
  • What are the initial steps I should take to achieve my goals for SDN?
  • What are my migration options?
  • How have others performed the migration, and how different from their strategies is my current SDN migration plan?

Addressing these questions is fundamental to successful migration to SDN.

By examining real-world use cases of how other networks have successfully migrated to SDN, some key steps for migration have been identified, including:

  • Identifying and prioritizing core requirements of the target network: Not all requirements of the traditional starting network may be met, at least initially, by the target software-defined network.
  • Preparing the starting network for migration: The starting network might need to be moved to a clean intermediate standard state from which the rest of the migration can proceed.
  • Implementing a phased network migration: Migrating individual devices will necessitate device-specific drivers and methods.
  • Validating the results: Once migration is completed, the target network must be validated against a documented set of requirements or expectations.

Enabling new services is an important motivation for SDN migration. These services achieve end-to-end connectivity, overlay on top of virtual networks, span several network segments and cross multiple layers of networking technologies. There is value to be gained from examining use cases across different networks to better understand unique migration strategies, tools, and methods that could be specific to each service or network type, given the diversity in the network landscape.

Many operators have identified maintaining service continuity during the migration process as a top priority: It is critical to focus on service continuity with minimal disruption. Optimally, the consistency of OpenFlow protocol versions is maintained between SDN controllers and switches during the migration. Pre- and post-migration checklists that address specific applications will also help ensure a smooth migration.

Effective migration of traditional networks to OpenFlow-based SDN necessitates deliberate and thorough planning. Our findings and technical recommendations for real-world SDN migration can help facilitate this process.

— Dan Pitt, Executive Director, Open Networking Foundation

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