Balancing the migration of virtual network functions with replications in data centers

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 VNF placement problem requires solutions that often consider 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 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.

Maximizing Throughput of Delay-Sensitive NFV-Enabled Request Admissions via Virtualized Network Function Placement

“…As a result, the network resources may be overloaded and no future requests can be admitted. Several studies of NFV migrations primarily dealt with the development of migration mechanisms [4], [5], [9], [14], [21], [30], [35]. For example, the authors in [9] provided one of the earliest studies of vertical scaling of VNF instances with the objective of minimizing the sum of energy consumptions of network function instances and the re-configuration cost of network instances.…”

“…In [35], Xia et al studied the problem of migrating network functions such that the migration cost, defined as the aggregated transferring traffic rate during the migration progress, is minimized. Carpio et al [4], [5] recently tackled the NFV migration problem, by using replications in place of migrations, because of the adverse effects that migrations have on Quality of Service (QoS). They provided an Integer Linear Programming solution to the problem.…”

“…The profit setting reflects the costs associated with different scaling options defined in Eq. (5). Thus, the solution to the GAP instance, in terms of assignments of a subset of items to bins, corresponds to a solution in which as many as requests are admitted and the total operational cost of their admissions is minimized.…”

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

“…Because VNFs typically perform memory or I/O intensive operations, the intensity of their loads increases with the number of their flows. As in [4], we penalize the migration of a VNF in proportion to its utilization before the migration. The rationale behind this idea is to minimize the probability and impact of service disruption.…”

“…Authors in [3] characterized the migration cost by a penalty value. Carpio et al [4] considered the service disruption due to VNF migration as a cost. Tang et al [5] modeled the reconfiguration cost by the time that it takes to migrate a VNF instance and and Eramo et al [6] represented the reconfiguration cost by the revenue loss during the time that the VNF is unable to provide a service due to migration.…”