The rapid increase of memory, computational capacity and network virtualization leads to higher and higher demands on network resources and infrastructure. Traditional network structures were designed for static-consuming manual administration and can no longer cope with the system environment of modern data centers. With Software Defined Networking (SDN), in addition to the OpenFlow protocol, a flexible network architecture that meets modern requirements can be achieved. The centralized control provided by such architecture opens the door to dynamic routing and load balancing algorithms that could not have been achieved using traditional network architectures. All these applications and algorithms mainly depend on the previous knowledge of the network topology and the topology updates. The aim of this thesis is to design and implement a generic topology discovery service that can instantly notify applications about topology changes and is applicable on any Software-defined Network (SDN) controller that uses OpenFlow protocol to communicate with its network. The designed topology discovery service is based mainly on OpenFlow protocol and partially on Link Layer Discovery Protocol (LLDP) to discover all different nodes in the whole network. The SDN controller used to implement and test the topology discovery service is The Floodlight Open SDN controller. The implementation was tested first on Mininet virtual network simulator, then tested on the actual SDN testbed available at The Institute of Parallele and Distributed Systems (IPVS), Universität Stuttgart.