Applications of Software-Defined Networking (SDN) to the Internet Routing hold great promises for supporting the ever-growing performance requirements of Internet applications. The inherent centralization of these SDN approaches on the Internet routing comes with the following concerns: 1) privacy , the operators are reluctant to share private routing information, 2) separation of responsibilities , the Internet eXchange Point (IXP) running the centralized controller is involved in the routing and forwarding at too many levels, and 3) scalability , the growing number of IP prefixes routed on the Internet (i.e., hundreds of thousands) pose extremely high requirements at both the control- and data-planes, e.g., several minutes for policy compilations and a large number of forwarding rules, in SDN. In this paper, we propose DeSI to apply SDN at IXPs by considering the above concerns. We break this centralization by devising an SDN-enabled IXP architecture in which each member connects to an SDN-enabled IXP through its SDN controller and SDN switches, thus tackling privacy, scalability, and separation of concerns issues. To spur adoption, we introduce an expressive, yet simple, language to configure the routing policies of the members. Our evaluation shows that DeSI needs n times fewer forwarding table entries for an IXP in which n is the number of IXP members. DeSI also gives the possibility of slowly migrating to the SDN-enabled IXPs.