While OpenFlow has received a considerable amount of industry attention, it is worth mentioning that the idea of programmable networks and decoupled control plane (control logic) from data plane has been around for many years. The Open Signaling (OPENSIG) working group initiated a series of workshops in 1995 in order to make ATM, Internet, and mobile networks more open, extensible, and programmable. Motivated by these ideas, Internet Engineering Task Force (IETF) working group came up with General Switch Management Protocol (GSMP) to control a label switch. This group officially concluded and GSMPv3 was published in June 2002.

The active network initiative proposed the idea of a network infrastructure that would be programmable for customized services. However, the active network never gathered critical mass, mainly due to the practical security and performance concerns. Starting in 2004, the 4D project (http://www.cs.cmu.edu/~4D/) advocated a clean slate design that emphasized the separation between the routing decision logic and the protocols governing the interaction between network elements. The ideas in the 4D project provided direct inspiration for later works such as NOX (https://github.com/noxrepo/), which proposed an operating system for networks in the context of an OpenFlow-enabled network.

Later on, in 2006, the IETF Network Configuration Protocol (NETCONF) working group proposed NETCONF as a management protocol for modifying the configuration of network devices. The working group is currently active and the latest proposed standard was published in June 2011. The IETF Forwarding and Control Element Separation (ForCES) working group is leading a parallel approach to SDN. SDN and Open Networking Foundation share some common goals with ForCES. With ForCES, the internal network device architecture is redefined as the control element that is separated from the forwarding element, but the combined entity is still represented as a single network element to the outside world. The immediate predecessor to OpenFlow was Stanford's SANE/Ethane project (for more information, visit http://yuba.stanford.edu/sane/, and http://yuba.stanford.edu/ethane/), which, in 2006, defined a new network architecture for enterprise networks. Ethane's focus was on using a centralized controller to manage policy and security in a network.