Highly available SDN control of flexi-grid networks with network function virtualization-enabled replication

New trends and emerging requirements have driven the development of extensions to the path computation element (PCE) architecture beyond the computation of a set of constrained routes and associated resources between endpoints, given a network topology. Such extensions involve the use of a PCE for the control of network services, in which deploying a PCE as a centralized network controller facilitates the adoption of software-defined networking (SDN) principles while allowing a progressive migration of already existing deployments. A key requirement for the adoption of centralized control solutions is the ability to deploy a resilient, secure, dynamically configurable, adaptive, and highly available (virtualized) infrastructure supporting end-to-end services, including critical and vertical ones. Part of this infrastructure is the control plane functional elements (e.g., controllers), and the use of network function virtualization (NFV) is a enabler for the high availability of such elements while additionally reducing OPEX and CAPEX. NFV provides a feature-complete framework for the replication of software components that is a straightforward and commonly adopted approach to address the aforementioned requirement, but it implies the need for timely synchronization of databases between replicas. In this paper we present, implement, and validate an architecture for PCE and SDN control high availability, combining the virtualization of the control function by means of dynamic replication and the timely synchronization of their internal state using the PCEP and BGP-LS protocols. We experimentally validate the approach with a testbed, including a GMPLS/PCE control plane, and a replica management system implemented following the ETSI NFV framework, using the OpenStack cloud management software.