Datacenter federations are able to manage appropriately the green energy resources available in each datacenter (DC) thanks to their geographically distributed infrastructure, thus reducing energy expenditure. Scheduling algorithms can perform virtual machine migration, transferring a huge amount of raw data from one DC to another to minimize operational costs and ensuring a certain Quality of Experience (QoE). Optical connections can be used to provide connectivity services of enough capacity so as to perform those migrations. In particular, elastic optical networks can provide connections with multi-granular bitrate, which can be adapted on demand. DC resource managers can request optical connections and control their capacity. However, that scheme involves the resource managers to implement algorithms and interfaces to deal with network specifics and complexity. To solve that issue, in this paper we propose carrier software defined network (SDN) to perform network-driven transfer mode for inter-DC operations; inter-DC connectivity is requested in terms of volume of data and completion time. We analyze cost savings when each connectivity model is applied in a DC federation. For the sake of a compelling analysis, exhaustive simulation experiments are carried out considering realistic scenarios. Results show that the network-driven model can save up to 20% of energy costs and more than 30% of communication costs in the evaluated scenarios.