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Campus Networks

SDN Hybrid Mode: Connecting the Dots

by Simon Pollard on ‎06-10-2014 05:00 PM - last edited on ‎10-23-2014 03:14 PM by (3,230 Views)

Combining all the elements of a modern IT infrastructure can often feel like solving a technological dot-to-dot puzzle; there aren’t any visible relationships between all the points that must be interconnected but when they are joined up they form a coherent picture. Every IT professional is painfully aware that the reality is somewhat different; the relationship between the different components – network nodes, servers, storage and applications – runs deeper than mere connections; we must carefully configure each element to ensure that it works in harmony with the others but the challenge is that this needs to be done so that all eventualities are met which often results in compromises. What works perfectly at 10am on a Tuesday morning might not be ideal on a busy Friday afternoon. Software Defined Networking (SDN) offers the promise of real-time dynamic changes to all the key elements in response to the demand and load at any moment in time.


SDN delivers three key benefits;


  • Automated Real-Time Provisioning: Each user-to-application connection can be fine-tuned to optimize the use of resources while ensuring that the user’s Quality of Experience is maintained.
  • Orchestration: End-to-end visibility and control of all resources ensuring that they all work in concert.
  • Diagnostics: Monitoring systems can correlate information from every element in the service chain to provide a complete view of the data-path from application to user device.

The challenge we face is that there is not a direct path to full SDN OpenFlow control of every connection and every aspect of the IT infrastructure; before we get there we will need networks that can seamlessly mix OpenFlow and traditional routing and switching control mechanisms. Hybrid-Mode implementations operate with a “split-brain” that combines traditional forwarding with OpenFlow control giving us the ability to mix traffic directed by either method not only on the same device but also on the same port or VLAN. For more details on Hybrid-Mode SDN implementations take a look at this dedicated blog post by Norival Figueira.


As applications and services become available that can exploit the benefits of OpenFlow it makes sense to phase them into production networks. However, many legacy functions that cannot be easily migrated and these will continue to need to use traditional solutions based on current routing and switching technologies. Furthermore, OpenFlow is still evolving and the creation of totally SDN driven networks is highly unlikely in the foreseeable future thus a strong Hybrid-Mode implementation is vital to the adoption of SDN and its viability in the coming years, just as with the journey from IPv4 to IPv6 we must provide a seamless migration by supporting the new technologies without abandoning the old ones. Backwards compatibility is not an option, it’s a mandatory requirement.


Brocade is committed to Hybrid-Mode support on all the devices on which OpenFlow is being implemented from the MLX core router to the ICX range of campus switches. For more information go to or read the Software-Defined Networking in the Campus Network white paper and take a look at the presentation on campus SDN which we recently delivered at the Aruba Airheads event.