| Virtualization is a proven software technology that is rapidly changing the face of IT, but also fundamentally change people's calculations. Use of virtualization technology, the physical machine can run multiple virtual machines, thus realized the sharing of computer resources. The physical machine on the same virtual machine can run different operating systems and multiple applications.Virtual machine technology is designed to improve the utilization of physical resources safely and effectively, to support multiple independent virtual machines(which is also known as client operating system, called VM as followed) running over one operating system, to shield heterogeneous underlying hardware, to achieve disaster protection and tolerance intrusion protection, to deploy a virtual cluster dynamicly, to assist software testing, to meet different computing resources need for customization.The rise of virtual machine and virtual cluster technology effectively solve the dependency problem of High Performance Computing Environment to hardware platform. It provides a new way to solve the problem of dynamic management such as load balancing, fault-tolerant intrusion tolerance and energy management in calculating the environment. As a basis for achieving these goals, the technology of virtual machine live migration has become a hotspot in this field. At the present stage, some popular open source and commercial virtualization platform such as Xen, KVM and VMware provide the function of virtual machine live migration. But these virtualization platforms only support virtual machine live migration in the LAN, not WAN.Virtual Machine Migration is that we migrate a virtual machine instance from a host( source host) to another host(destination host),and it need restore the virtual machine instance's running state to before migration. In order to achieve this goal, it should copy the virtual machine instance's running state from source host to destination host, and then restore the virtual machine running on the destination host. Virtual Machine Live Migration is that during the procedure of virtual machine migration, downtime of virtual machine is so short that services on the virtual machine can always response to a user's request to ensure transparency of virtual machine environment to the user.At the present stage, virtual machine migration regularly confines to the LAN. Many mature programs such as Xen, VMware are based on NFS to achieve sharing of virtual machine image file. Migration means migrating CPU and memory status. Such as these migration programs can solve the problem of virtual machine's dynamic management in the LAN. After migration in the LAN, virtual machine's IP address don't need change, virtual machine could communicate with external network according to the same way. Realization means is that destination nodes broadcast an unsolicited ARP reply after migration to notify other nodes the binding of IP address and MAC address. But there are two problems, one is that ARP reply doesn't apply to WAN, the other problem is during the downtime of virtual machine migration there are a small number of data packets lost.There are some network connectivity solutions of virtual machine live migration between different subnet. proposed a network connectivity solution that keep source virtual machine running and IP address unchanged during virtual machine migrating and after migration finished; after destination virtual machine migrated to another network, it should configure new IP address and network configuration, and then start virtual machine. When new service starts to run, it uses new IP address. Source virtual machine and destination virtual machine should running together, after service on the source virtual machine is done, stop the virtual machine. From now on, all future service is running on the destination virtual machine. This solution's shortage is that after virtual machine migration, it should change virtual machine's network configuration lack of transparent to virtual machine.Virtual machine migration in the WAN should keep all protocol states with its IP address, it's similar to that mobile nodes roam with the same IP address, so in our research we can reference to mobile IP technology. Mobile IP key technologies include Agent Search,Address Translation,Tunneling. Based on existing technology, we should resolve two key problems; the first is that removing the dependency of data communication to former network; the second problem is that designing efficient message forwarding protocol and mechanism.With the development of virtual computing environment, quantity of single LAN managing hosts and network environment will limit the scalability of virtual computing environment; on the other hand, how to share virtual computing resources among some managing domains will become a hot research question. The research of virtual machine migration under cross-domain virtual networks becomes a hotspot in this field.This research will use network communication technologies such as IP Tunneling; overlay network and virtualization technology to study virtual machine migration under cross-domain virtual networks. We should realize transparent and reliable virtual machine live migration in the WAN. First of all, we should resolve the consistency problem of communication address before and after migration, in other words, the migration virtual machine in the other network still use original IP address communicate with the application on the other virtual machine. Secondly, in order to support parallel computing, we should ensure there are not any message lost and shuffle during the procedure of virtual machine migration. The current research work only focus on reduce the application's Downtime; it's not virtual machine Live migration in the strict sense.This paper proposes a novel approach of virtual machine live migration in cross-domain Virtual Networks. A Virtual Network routing protocol is presented to support cross-domain communication between VMs. A VM Migration Protocol controlling the migration process is designed to enable dynamic management of virtual infrastructure. We implement a prototype based on a typical virtualization tool, Xen. VM Live migration method presented in this work enables dynamic virtual infrastructures extending to wide-area network. |
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