I went through few online study material of SDN and come to the point that it is going to make huge major in up coming years. There are so many operators and users who want to comes out from these vendor-locked devices. Now and days there are so many open source communities who are creating software for programmable devices.
If I take example of telecom network such as LTE, most of the deployments are vendor-locked such as Nokia EPC, Ericsson EPC, Cisco, Juniper EPC and switches and so on. These big players are running networking technologies.
To reduce CAPEX/OPEX and time to market for new services, now operators are heading towards open source hardware and switches. Replacing existing devices with the new devices will take time but at least each operator can gradually replacing.
SDN provides programmable switching and routing things. Based on type of service, SDN controller can change rules in switches and routers. Big players are going to loose on their existing black-box devices since open source approach is being backed by big software giants such as google.
