Network Function Virtualization enables network slicing as a novel paradigm for service provisioning. With network slicing, Virtual Network Functions (VNFs) can be instantiated at different locations of the infrastructure, choosing their optimal placement based on parameters such as the requirements of the service or the resources available. One limitation of state-of-the-art technology for network slicing is the inability to re-evaluate orchestration decisions once the slice has been deployed, in case of changing service demands or network conditions.
In this paper, we present ACHO, a novel software framework that enables seamless re-orchestration of VNFs of any kind, including RAN and Core. With ACHO, VNFs and resources can be easily re-assigned to match, e.g., varying user demands or changes in the nodes’ load. ACHO uses lightweight mechanisms, such as splitting the engine of a VNF from the data it requires to perform its operation, in such a way that, when re-allocating a VNF, only the data is moved (a new engine is instantiated in the new location). We demonstrate the use of ACHO in a small scale testbed, showing that (i) the proposed re-orchestration is feasible, (ii) it results much faster than existing alternatives (especially for relocation), and (iii) the framework can be readily applied to existing VNFs after minimal changes to their implementation.