Dynamic resource allocation in hybrid optical–electrical datacenter networks

• Joint problem of bandwidth allocation and VM-placement in optical-electrical DC.
• Challenges: (i) limited reachability due to the size of the optical switch in the datacenter netework, (ii) dynamic creation of optical paths lead to the creation of constrained optical network topology.
• The problem is formulated as nonlinear optimization problem, that is NP-hard in nature.
• Input requests from users are abstracted as virtual networks, where a single node in a virtual network is a cluster of VMs, and an edge connecting two nodes is the bandwidth demand between the two clusters of VMs.
• Three algorithms are developed for embedding input virtual networks on hybrid datacenter network, and their performances are evaluated using simulations.

A promising development in the design of datacenters is the hybrid network architecture consisting of both optical and electrical elements, in which end-to-end traffic can be routed through either an electrical path or an optical path. The core optical switch is used to dynamically create optical paths between pairs of electrical edge-switches in such a datacenter network. In this context, the joint problem of bandwidth allocation and VM-placement poses new and different challenges not addressed yet in hybrid datacenter. In particular, we foresee two issues: (i) the number of edge-switches that can be simultaneously reached using optical paths from an edge-switch is limited by the size of the optical switch, (ii) the dynamic creation of optical paths can potentially establish a constrained optical network topology leading to poor performance. In this work, we abstract the requests of tenants as virtual networks, and study the problem of embedding virtual networks on a hybrid datacenter. We formulate the problem as a non-linear optimization problem and analyze its complexity. We develop and analyse three algorithms for embedding dynamically arriving virtual network demands on a hybrid optical–electrical datacenter. Through simulations, we demonstrate the effectiveness of not only exploiting the already established optical paths, but also of using electrical network in embedding requests of virtual networks.