Challenges for Inter Virtual Machine Communication by Carl Gebhardt and Allan Tomlinson Abstract: Past research in virtualisation technology has mainly focused on increasing isolation of co-resident virtual machines. At the same time network intensive applications, such as web services or database applications are being consolidated onto a single physical platform. The isolation properties of virtualisation, however, demand a strict separation of the shared resources. Co-resident virtual machines are therefore forced to fallback to inefficient network emulation for communication. Many inter virtual machine communication methods proposed recently, introduced shared memory, customised libraries or APIs. This is not only unpractical but can also undermine a system's integrity; moreover transparency and live migration is commonly neglected. Therefore in this paper we discuss the challenges and requirements for inter virtual machine communication and examine available solutions proposed by academia and industry. We also discuss how the current evolution of virtualisation and modern CPUs pose new challenges for inter virtual machine communication. Finally, we consider the possibility of utilising previously unused CPU capabilities to accommodate an inter virtual machine communication mechanism.