Reprovisioning for Latency-aware Dynamic Service Chaining in Metro Networks

To support newly emerging and highly dynamic 5G services, optical metro networks must be capable of provisioning services on the fly. Network function virtualization (NFV) is leveraged to fulfill these dynamic service demands by placing virtual network functions (VNFs) in NFV-capable network nodes and chaining them together (service chaining). In addition, new 5G service chains often have bandwidth requirements with subwavelength granularity, making traffic grooming essential for efficient network resource utilization. However, the latency requirement for these services will not allow one to always perform traffic grooming, as grooming operations add non-negligible latency to traffic, and this might lead to poor utilization and high service blocking. Thus, it is important to investigate dynamic solutions to increase network utilization and decrease service blocking. One approach to achieve this goal is to reprovision service chains (SCs) to use network resources as efficiently as possible. Reprovisioning consists of tearing down a service chain and reallocating its resources, typically with the intent to make room for new chains that would be otherwise rejected. While traditional reprovisioning entailed only routing reassignment, reprovisioning of SCs entails both rerouting traffic and/or relocating VNFs, hence originating new research problems. In this paper, we propose new heuristic algorithms to reprovision SCs whenever a service cannot be provisioned. We provide two different approaches to perform reprovisioning, i.e., bandwidth and location. While bandwidth reprovisioning consists of modifying only bandwidth assignment of SCs, location reprovisioning considers the possibility of changing the nodes each SC is mapped to. We also considered two different optical network architectures. Results obtained on realistic network topology and services show that location reprovisioning allows us to achieve up to 28% improvement in terms of the number of SCs we are able to provision in the network.