SOFTWARE DEFINED NETWORKS: OPENFLOW AND VIRTUAL NETWORK OVERLAYS
A briefdescription of the main trends in the development of Software-defined networks (SDN) is given. We compare the advantages and disadvantages of the most popular approaches: end-to-end OpenFlow and virtual network overlays. We are describing existing SDN solutions. Among them, architectural and hardware preferences of Juniper Networks, the Virtualized Services Platform (VSP) from Nuage Networks, an integrated VMware/Nicira solution NSX and Windows Network Virtualization from Microsoft. Most of them tend to implement SDN on the existing infrastructure without having to replace network equipment, maintaining existing services. Main functions of the systems are implemented in software virtual switches that are directly managed by the hypervisor. It is concluded that at the present time OpenFlow has practical application only as a control protocol for virtual switches and most solutions are based on the virtual network overlays.