Date Added: May 2011
Virtualization is a key technology that powers cloud computing platforms such as Amazon EC2. Virtual Machine (VM) consolidation, where multiple VMs share a physical host, has seen rapid adoption in practice with increasingly large number of VMs per machine and per CPU core. The authors' investigations, however, suggest that the increasing degree of VMconsolidation has serious negative effects on the VMs' TCP transport performance. As multiple VMs share a given CPU, the scheduling latencies, which can be in the order of tens of milliseconds, substantially increase the typically sub-millisecond Round-Trip Times (RTTs) for TCP connections in a datacenter, causing significant degradation in throughput.