Cost efficient and performance guaranteed virtual network embedding in multicast fat-tree DCNs

Most of today´s data center networks (DCNs) adopt a multi-rooted tree structure called fat-tree, which delivers large bisection bandwidth through rich path multiplicity. In fat-tree DCNs, core switch modules play an important role in providing nonblocking capability, and form a significant part of network cost simultaneously. Reducing core switches while simultaneously guaranteeing performance has been a constant challenge. For example, multicast is an essential communication pattern in cloud services which needs to be supported efficiently. In this paper, we propose virtual network embedding schemes to deal with this problem. In the first scheme, we place the virtual machines (VMs) of a multicast-capable virtual network (MVN) as compact as possible, without any disturbance to existing traffic. In the second scheme, we manage to keep VMs in an even more compact way to reduce cost by allowing a small degree of VM migration. Both schemes are guaranteed to support any multicast communications within MVNs, and simultaneously achieve significant cost saving in terms of core switches, compared to currently best known result. Moreover, we show that our schemes incur only a small overhead in terms of migrations. Finally, we evaluate the performance of proposed schemes and validate the theoretical analysis through extensive simulations.