On the Cost-Optimality Trade-off for Service Function Chain Reconfiguration

Abstract

Optimal placement of Virtual Network Functions (VNFs) in virtualized data centers enhances the overall performance of Service Function Chains (SFCs) and decreases the operational costs for mobile network operators. Maintaining an optimal placement of VNFs under changing load requires a dynamic reconfiguration that includes adding or removing VNF instances, changing the resource allocation of VNFs, and rerouting corresponding service flows. However, such reconfiguration may lead to notable service disruptions and impose additional overhead on the VNF infrastructure, especially when reconfiguration entails state or VNF migration. On the other hand, not changing the existing placement may lead to high operational costs. In this paper, we investigate the trade-off between the reconfiguration of SFCs and the optimality of the resulting placement and service flow (re)routing. We model different reconfiguration costs related to the migration of stateful VNFs and solve a joint optimization problem that aims to minimize both the total cost of the VNF placement and the reconfiguration cost necessary for repairing a suboptimal placement. Numerical results show that a small number of reconfiguration operations can significantly reduce the operational cost of the VNF infrastructure; however, too much reconfiguration may not pay off should heavy costs be involved.

Service Function Chain Placement in Distributed Scenarios: A Systematic Review

“…For instance, if a SFC placement strategy takes into account only the costs regarding the network bandwidth, the costs related to the node resource consumption can be high, or the placement solution can result in a high VNF migration cost [62]. In addition, minimizing the operational costs of SFCs can conflict with other metrics, such as performance and resiliency [77].…”

Be Scalable and Rescue My Slices During Reconfiguration

“…The authors formulate an ILP and a column generation model in order to jointly optimize the deployment of the SFCs of new users and the readjustment of the SFCs already provisioned in the network while considering the trade-off between resource consumption and operational overhead. [13] studies the trade-off between the reconfiguration of SFCs and the optimality of the reconfigured routing and placement solution.…”

Reconfiguration Aware Orchestration for Network Function Virtualization With Time-Varied Workload in Virtualized Datacenters

“…Most of the works in literature have used migration as a reconfiguration solution. For instance [16] have used an optimal formulation that can reduce the migration overhead while achieving a sub-optimal VNF placement solution and [22] have shown how VNF instances can be migrated with least overhead. Similarly [14] have used a candidate migration…”

“…This will impact the SLA for the end user as many SFC requests will not be processed. In the literature, there are research studies that have used reconfiguration solutions either to reduce energy consumption [15] or reduce some reconfiguration cost [14], [16]. However none of the works attempted to address the trade-off between them.…”