Scale-Out Load Balancing with OpenFlow

When OpenFlow was still fresh and exciting, someone made quite a name for himself by proposing a global load-balancing solution that would install per-session OpenFlow entries in every core switch around the world. Clearly a great idea, mimicking the best experiences we had with ATM SVCs.

Meanwhile some people started using OpenFlow in real-life networks for coarse-grained load balancing that improves the scalability of stateful network services. For more details, watch the video recorded during the Real Life OpenFlow-based SDN Use Cases webinar.


  1. There are switches that can do consistent hashing, e.g. Broadcom:

    In this case, upon failure of a switch only 1/N of flows get rehashed ( i.e. the ones that were hashing to the failed LB ).

    In case of a web site, couldn't you simply use a set of HTTP redirect based load balancers?

    1. HTTP redirects don't give you high availability. If a particular back-end server fails, all clients redirected to it lose service.


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Ivan Pepelnjak, CCIE#1354 Emeritus, is an independent network architect. He has been designing and implementing large-scale data communications networks as well as teaching and writing books about advanced technologies since 1990. See his full profile, contact him or follow @ioshints on Twitter.