Network Service Reconfiguration in Hybrid Optical/Electrical Datacenter Networks

The hybrid optical/electrical datacenter networks (HOE-DCNs), which use both electrical Ethernet switches and optical cross-connects (OXCs) to interconnect top-of-rack (ToR) switches, have been considered as a scalable solution for the ever-increasing datacenter traffic. Meanwhile, the network services in an HOE-DCN generate various virtual network (VNT) requests, and their dynamic nature can degrade the optimality of their virtual network embedding (VNE) schemes as time goes on. Therefore, this paper studies how to realize cost-effective VNT reconfiguration (VNT-Recfg) in an HOE-DCN, such that its IT resource utilization can be balanced well. The problem has its unique difficulty because the topology of the substrate network (i.e., the HOE-DCN) can change in the VNT-Recfg due to the "1-to-1" connectivity of an OXC. We design the procedure of our VNT-Recfg to include two major algorithms, i.e., a selection algorithm to choose virtual machines (VMs) to migrate, and a reconfiguration algorithm to determine the reconfiguration schemes of VMs, virtual links (VLs), and the OXC. The selection algorithm is developed to maintain the IT balance degree, while the reconfiguration algorithm consists of two steps, 1) getting the VM migration schemes to re-balance the IT resource usage, and 2) calculating the reconfiguration schemes of related VLs and the OXC. For the first step, we formulate a mixed integer linear programming (MILP) model and design a time-efficient heuristic. We solve the second step with a novel algorithm that leverages both dynamic programming and a lightweight ILP.