Virtualization of servers and networks is a key technique to resolve the conflict between the increasing demands on computing power and the high cost of hardware in data centers. In order to map virtualnetworks to physical infrastructure efficiently, designers have to make careful decisions on the allocation of limited resources, which makes network embedding in data centers a very important problem. In this paper, we tackle the network embedding problem in fat-tree data centers. To meet the requirements of instant parallel data transfer between multiple computing units, we propose a model of multicast-capable virtual networks (Mons). We then design three virtual machine (VM) placement schemes with different features for embedding MVNs into fat-tree DCNs, named Most-Vacant-Fit (MVF), Most-Compact-First (MCF) and Mixed-Bidirectional-Fill (MBF).
All these VM placement schemes guarantee the no blocking multicast capability of each MVN while simultaneously achieving significant saving on the cost of network hardware. In addition, each VM placement scheme also has its unique features. The MVF scheme has zero interference to existing computing tasks in data centers, the MCF scheme leads to the greatest cost saving, the MBF scheme simultaneously possesses the merits of MVF and MCF, and it provides an adjustable parameter allowing cloud providers to achieve preferred balance between the cost and the overhead. Finally, we compare the performance and overhead of these VM placement schemes, and present simulation results to validate our theoretical results.