Virtual machine migration strategy in cloud computing

In a typical cloud based data centre, several physical machines (PM) host dozens of virtual machines (VM), which run various applications and services. VM load varies according to the different type of users' applications and traffic, and sometime this traffic may overwhelm VM's resources. Physical machines that host many VMs have limited capacity and if they are overloaded their performance might degrade or completely fail. A VM machine that hosts several different applications on a heavily loaded PM can be migrated to another under loaded PM in order to exploit the availability of the resources and to balance the load. In data centres, VMs exposed to huge amount of user traffic, if VM migration occurs on a network link that is overwhelmed with user traffic, then it will create a bottleneck if there's not enough bandwidth on the link to support the VM migration. Therefore, there is a clear need for mechanisms to control user traffic on both source and destination PMs in order to provide guaranteed bandwidth that needed for VM migration