  The widespread use of cloud computing services is expected to deteriorate a
Quality of Service and toincrease the power consumption of ICT devices, since
the distance to a server becomes longer than before. Migration of virtual
machines over a wide area can solve many problems such as load balancing and
power saving in cloud computing environments.
  This paper proposes to dynamically apply WAN accelerator within the network
when a virtual machine is moved to a distant center, in order to prevent the
degradation in performance after live migration of virtual machines over a wide
area. mSCTP-based data transfer using different TCP connections before and
after migration is proposed in order to use a currently available WAN
accelerator. This paper does not consider the performance degradation of live
migration itself. Then, this paper proposes to reduce the power consumption of
ICT devices, which consists of installing WAN accelerators as part of cloud
resources actively and increasing the packet transfer rate of communication
link temporarily. It is demonstrated that the power consumption with WAN
accelerator could be reduced to one-tenth of that without WAN accelerator.
