Most of today's cloud applications are delivered by Cloud Service Providers (CSPs) on top of a physical network managed by one or multiple Infrastructure Providers (InPs). This new way of delivering services is impacting InPs' revenues, as InPs are only responsible for transporting data to users. Network Function Virtualization (NFV) was proposed to help InPs gain more flexibility in provisioning new services over their networks, hence achieving lower capital and operational costs, keeping stable revenue margins, and resisting the competition of CSPs (e.g., the "Over-The-Top"players). NFV aims at moving from the traditional approach of network functions running over dedicated hardware (e.g., firewall, NAT, etc.) into virtualized software modules running on top of Commercial Off The Shelf (COTS) equipment. However, deploying NFV in an operational network requires addressing two fundamental problems. The first consists on determining the locations where Virtual Network Functions (VNFs) will be hosted (i.e., VNF placement) and the second on how to properly steer network traffic to traverse the required VNFs in the right order (i.e, routing), thus provisioning network services in the form of Service Function Chains (SFCs). In this work we try to solve both problems focusing our analysis on a metro-regional scenario, where link bandwidth and COTS node processing capacity is inherently limited and where the current trend consists on moving towards a Fixed and Mobile Convergence (FMC) network infrastructure. We propose and compare different heuristic strategies for SFC provisioning, characterized by latency and/or capacity awareness (i.e., able to best exploit latency of links and/or processing capacity of COTS nodes for an effective placement of VNFs) and by the adoption of a load balancing policy for traffic routing, with
Optical metro networks are currently evolving in response to the new requirements of emerging 5G services. Network Function Virtualization (NFV) is being leveraged as a platform to dynamically provision these services on top of Virtual Network Functions (VNFs), and central offices in metro areas are being upgraded to host processing units that can host the needed to provision services with stringent-latency and highbandwidth requirements closer to users (i.e., edge computing). By concatenating these VNFs in a specific order and route traffic among them, operators generate a so-called "Service Chain"(SC). Considering the fact that, new 5G services have bandwidth requirements typically with sub-wavelength granularity, traffic grooming is required to achieve efficient network resources utilization. Since grooming affects the end-to-end latency of provisioned services, we investigate how to perform latencyaware traffic grooming, and we propose an algorithm for dynamic SC provisioning, that considers the latency requirements of each SC to decide about if grooming shall be allowed at intermediate network nodes. Our proposed algorithm tries to minimize the blocked bandwidth as well as number of nodes to host VNFs in the network (NFV-nodes) considering the nodes computational capacity, links bandwidth and end-to-end latency constraints. Results obtained from numerical evaluation show that, our algorithm is able to reduce the number of NFV-nodes up to 50%, while keeping amount of blocked bandwidth below a specific threshold.
Network Function Virtualization (NFV) has changed the way operators can provision network services. Decoupling network functions from dedicated hardware and running them on software, on top of commodity servers and switches, not only helps operators have more flexible and easy-to-manage networks, but also reduces their capital and operational expenditures. This is especially true for incoming 5G services, characterized by ultra-low latency, high reliability and bandwidth requirements. To satisfy these challenging requirements, multi-layer optical networks based on Optical Transport Network (OTN) over wavelength division multiplexing (WDM) are being deployed in the metro segment to support 5G services. In addition, the possibility to equip metro nodes with computing capabilities, enabled by new paradigms such as CORD (Central Office Re-architected as a Datacenter) is being exploited. In this scenario, an efficient placement of Virtual Network Functions (VNFs) for Service Chain (SC) provisioning within the metro network is needed, and different VNF placement strategies can lead to different costs for network operators. In this paper we analyze the impact of different VNF placement strategies on the optical metro network cost, considering specific Service Level Agreement (SLA) requirements, expressed in terms of service blocking probability. We provide a cost model which takes into consideration both capital and operational expenditures. Through extensive numerical results, we quantify the impact of using a cost-effective VNF placement strategy in decreasing network cost while meeting the desired SLA performance.
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