Towards Consistent VNF Forwarding Graph Reconfiguration in Multi-domain Environments

Network Function Virtualization (NFV) enables running Virtualized Network Functions (VNF) on top of any generic, commercial off-the-shelf hardware. VNFs rely on the VNF-Forwarding Graph (VNF-FG) concept to describe and implement network topologies. VNF-FGs are provisioned and managed by appropriate orchestrators. In the multidomain approach, and for complex and sophisticated network topologies, VNF-FGs are managed by multiple orchestrators. Despite being a key task in the lifecycle of network services, the reconfiguration of VNF-FGs under multi-domain orchestration has not been thoroughly explored in the literature, focused mostly on the initial VNF-FG placement and embedding. Reconfiguration enables the providers to answer to unforeseen changes in the environment. However, such distributed orchestration might lead to inconsistencies, and thus partial or total failure of network services. In turn, such inconsistencies increase the cost for providers. This paper proposes the use of causal dependencies among orchestrators to provision consistent VNF-FG reconfiguration in distributed multi-domain environments under asynchronous communication channels. The proposed model is implemented and compared with the current ETSI VNF-FG reconfiguration algorithm. Results indicate that, with this proposal, the inconsistencies are reduced compared to the reconfiguration algorithm according to the ETSI standard for VNF-FGs in multi-domain orchestration.