Software Defined Networking (SDN) has brought a paradigmatic shift in the networking industry and has led to significant benefits in the data-center and enterprise network domains. The service provider networks that form the largest segment of networking industry, are now evaluating SDN technologies for adoption. In this paper, we present a SDN framework for service provider networks and report the first field trial of SDN in a tier-1 service provider domain. The proposed SDN framework is built using Carrier Ethernet and augmented with recently proposed Segment Routing paradigm manifested through Software Defined-Carrier Ethernet Switch Routers (SD-CESRs). Carrier Ethernet on account of its distinct, programmable control plane and Segment Routing through its source routing capabilities facilitates SDN implementation. The SD-CESRs are deployed in a tier-1 service provider network in the metropolis of Mumbai. The SDN framework is extended through specific APIs to enhance revenue bearing services portfolio of the service provider and performance results from the field are shown to validate the benefits of SDN adoption.