# Balancing the Migration of Virtual Network Functions with Replications in Data Centers

## TL;DR

This paper proposes a linear programming model to balance VNF replications and migrations in data centers, aiming to optimize server load, energy efficiency, and service quality in NFV environments.

## Contribution

It introduces a novel LP model that quantifies the trade-off between VNF replications and migrations to improve load balancing and QoS in data center networks.

## Key findings

- Replications reduce the number of migrations needed.
- Replications improve server load balancing.
- The model enhances QoS while optimizing resource use.

## Abstract

The Network Function Virtualization (NFV) paradigm is enabling flexibility, programmability and implementation of traditional network functions into generic hardware, in form of the so-called Virtual Network Functions (VNFs). Today, cloud service providers use Virtual Machines (VMs) for the instantiation of VNFs in the data center (DC) networks. To instantiate multiple VNFs in a typical scenario of Service Function Chains (SFCs), many important objectives need to be met simultaneously, such as server load balancing, energy efficiency and service execution time. The well-known \emph{VNF placement} problem requires solutions that often consider \emph{migration} of virtual machines (VMs) to meet this objectives. Ongoing efforts, for instance, are making a strong case for migrations to minimize energy consumption, while showing that attention needs to be paid to the Quality of Service (QoS) due to service interruptions caused by migrations. To balance the server allocation strategies and QoS, we propose using \emph{replications} of VNFs to reduce migrations in DC networks. We propose a Linear Programming (LP) model to study a trade-off between replications, which while beneficial to QoS require additional server resources, and migrations, which while beneficial to server load management can adversely impact the QoS. The results show that, for a given objective, the replications can reduce the number of migrations and can also enable a better server and data center network load balancing.