Impact of virtual bridging on virtual machine placement in data center networking

The increasing adoption of virtualization techniques has recently favored the emergence of useful switching functions at the hypervisor level, commonly referred to as virtual bridging. In the context of data center network (DCN) consolidations, for VMs colocated in the same virtualization server, virtual bridging becomes very useful to offload inter-VM traffic from access and aggregation switches, at the expense of an additional computing load. DCN consolidations typically chase traffic engineering (TE) and energy efficiency (EE) objectives, and both should be affected by virtual bridging, but it is not intuitive to assert whether virtual bridging acts positively or negatively with respect to TE and EE that should also depend on the DCN topology and forwarding techniques. In this paper, we bring additional understanding about the impact of virtual bridging on DCN consolidations. First, we present a repeated matching heuristic for the generic multi-objective DCN optimization problem, with possible multipath and virtual bridging capabilities, accounting for both TE and EE objectives. Second, we assess the impact of virtual bridging on TE and EE in DeN consolidations. Extensive simulations show us that enabling virtual bridging has a negative impact when EE is the goal and multipath forwarding is adopted, while it leads to important gains, halving the maximum link utilization, when TE is the DeN consolidation goal.