in the following paragraphs , the present invention will be described in detail by way of example with reference to the attached drawings . while this invention is capable of embodiment in many different forms , there is shown in the drawings and will herein be described in detail specific embodiments , with the understanding that the present disclosure is to be considered as an example of the principles of the invention and not intended to limit the invention to the specific embodiments shown and described . that is , throughout this description , the embodiments and examples shown should be considered as exemplars , rather than as limitations on the present invention . descriptions of well known components , methods and / or processing techniques are omitted so as to not unnecessarily obscure the invention . as used herein , the “ present invention ” refers to any one of the embodiments of the invention described herein , and any equivalents . furthermore , reference to various feature ( s ) of the “ present invention ” throughout this document does not mean that all claimed embodiments or methods must include the referenced feature ( s ). fig1 is an illustration of a network implementation of a virtualization environment 100 constructed in accordance with the invention for virtualization system management such that resource utilization is highly leveraged . users at network computers 102 , 104 , 106 can communicate over a network 108 to gain access to system resources that are available through control center computers such as control center a 110 and control center b 112 . each of the control center computers 110 , 112 executes application software and thereby manages one or more virtual environments regardless of any underlying central processing unit ( cpu ) and regardless of any underlying operating system ( os ) or virtualization platform software . for example , a control center computer can manage resources and virtual assets that are powered by cpus from intel corporation of santa clara , calif . usa or from motorola , inc . of schaumberg , ill . usa , or other vendors . the physical resources and virtual assets can be managed from the control center computers whether the underlying os of the computers , resources , and assets is a windows - based os from microsoft corporation of redmond , wash . usa or a macintosh os from apple computer inc . of cupertino , calif . usa or others , and whether the virtualization environment is a platform by vmware , inc . of palo alto , calif . usa or international business machines corporation of armonk , n . y . usa or others . operating parameters of the virtualization system management can be specified and changed at the control center computers 110 , 112 through a user interface that is provided by the application software described herein executing at the respective control center computers 110 , 112 . the control center computers are represented in fig1 as physical devices rather than virtual assets . deployment of the control center on physical devices is typical , because otherwise a control center that is deployed on a virtual asset would leave the users with being dependent on their virtualization platform for configuration management and the like , in addition to the usual machine dependencies . in this description , physical devices such as computers , printers , routers , and other “ boxes ” will be referred to as resources , whereas virtual devices that exist only as software instantiations of equipment objects in a virtual environment will be referred to as virtual assets . the resource - asset dichotomy will be maintained throughout this discussion . the present invention provides automated management of network - based virtual environments through control center software that supports on - demand operation of one or more functions including ( 1 ) identification and management of enterprise resources and virtual assets , ( 2 ) provisioning of virtual assets in response to network workflow demands , ( 3 ) dynamic deployment ( routing ) of virtual assets across the network , ( 4 ) performance measurement and reporting of virtual assets and resources , and ( 5 ) planning and forecasting of resource demands and asset utilization . such operations are carried out without regard to the mix of otherwise proprietary processors , operating systems , virtualization platforms , application software , and protocols . these features and functions are provided in a modular fashion so that desired functions can be included in the system , and functions not desired can be excluded from the system . in any implementation in accordance with the present invention , the virtualization management system is transparent to the virtual environment being managed , in that the system can support multiple virtual environments with different protocols and operating specifications . thus , the disclosed system is platform - independent . fig1 shows that the users 102 , 104 , 106 can communicate with the control centers 110 , 112 through a network 108 , which can comprise a local area network , a wide area network , or through an extended network such as the internet , or any other network for communication among multiple computers . fig1 also indicates that the users can be connected directly to a control center computer , if desired , such as for the user 106 indicated as user 3 . each control center computer 110 , 112 that is equipped with the virtualization management application described herein will have management of one or more physical assets within a domain or other subnet arrangement associated with the respective control center . fig1 shows that control center a 110 manages multiple resources , two of which are shown : a first set of resources 120 and a second set of resources 122 . for ease of illustration , each set 120 , 122 may be considered in the context of a computer rack system containing multiple computer physical assets . it should be understood that additional physical resources can be managed by the control center a , but are not shown in fig1 for simplicity of illustration . the first set of resources 120 are illustrated as comprising two blade servers , indicated in fig1 as blade 1 and blade 2 . the second set of resources are illustrated as comprising two additional blade servers , blade n and blade n + 1 . thus , a number of different resources can be accommodated . it should be understood that the resources could comprise other devices or equipment , such as memory devices , printers , routers , and the like . it should also be understood that the blade servers themselves ( blade 1 , blade 2 , . . . , blade n , blade n + 1 , . . . ) can be configured to support a variety of virtual assets , including desktop computer environments , data storage , application servers , routers , and the like . fig1 shows that control center b 112 manages two sets of resources , illustrated as rack b 1 and rack b 2 . as with the control center a , it should be understood that the actual physical resources that make up rack b 1 130 and rack b 2 132 can comprise a variety of network - based computer equipment . fig2 is a schematic diagram that illustrates the application components for the virtualization management application of the control center computers 110 , 112 illustrated in fig1 . the components enable the control center computers to function according to the description herein to provide automatic , network - based virtualization management independently of underlying processors , operating systems , and virtual environments . fig2 shows the control center computer as including an asset manager 204 , a provisioning manager 206 , a dynamic application router 208 , an optimizer 210 , a performance manager 212 , and a capacity planning manager 214 . in addition , a virtual mapping engine 216 is included , for determining the physical resources and virtual assets with which the control center will communicate . the virtual mapping engine is programmed to discover the physical resources , such as the physical devices with which the control center is in network communications , and also the virtual resources , such as virtual servers , storage , desktops , and the like with which the control center has access . the virtual mapping engine 216 can be self - starting , such as being launched at control center start - up or at some other predetermined system event , or the virtual mapping engine can be initiated by a user via a command . as described further below , the illustrated embodiment of the control center 202 is configured in a modular fashion , such that the installation of the control center of the computers 110 , 112 in fig1 need not include every one of the modular components 204 - 214 illustrated in fig2 . rather , system requirements and user needs may be such that less than all of the control center components are installed on any one control center machine of the system . any installation of the control center , however , will include the virtual mapping engine 216 , so that the control center will be suitably informed of its environment . a more detailed description of the functionality for each of the modular components 204 - 214 is provided below . the asset manager 204 provides visibility and management of all global virtual assets available to the control center . this component provides a global view of all the resources used in a virtualized infrastructure along with a physical and logical topology view . thus , a user can view a global topology view and an inventory of virtual infrastructure from a central console . in addition , the component will support discovery and configuration of virtual resources , allow topology views for physical and logical infrastructure , provide inventory reports at local , remote , and global context , and simplify management of applications , hardware resources , virtual assets , and operating systems . the provisioning manager 206 provides an on - demand solution for provisioning of virtual assets for an automated workflow management . this component provides an automated solution allowing users to request and schedule their individual virtual asset needs and it management to prioritize and provision the required assets on demand . the component can be used to provide a portal for users &# 39 ; virtual asset requests showing available virtual assets , as well as a supervisor portal to prioritize needs and approve asset needs by time and priority , and also provides an it manager to provision the needed resources and keeping track of used and available assets , an automated workflow system for users and it to track needs and resources , supports the ability to keep mission critical application and assets to put them on line on demand for emergency and disaster recovery needs , and provides a repository of virtual machines supporting vmware , microsoft and xen virtual assets and their needed hardware components . the provisioning manager provides central management of global virtual machine images , provides an enterprise workflow system for adds , moves and changes in virtual infrastructure , and can be used to standardize and optimize virtual infrastructure use from lab to production environment , such as needed in different development testing scenarios . the dynamic application router 208 provides real time and dynamic routing of applications running on virtual infrastructure . with this component , users of the control center can move applications running on virtual assets by comparing application usage with business policy and drivers , and scheduling appropriate routing actions . this component can be used to move applications to different virtual assets as global business need changes , provide dynamic allocation of global virtual assets for workload optimization , enable zero down time in upgrading virtual environments , provide an optimizer for balancing resource and asset inventory against needs , a scheduler to auto schedule actions and provide reports , and provide alarms and triggers to notify users of out of balance inventory items . the component also provides an aggregated action library for all virtual infrastructure , performs zero downtime virtual asset maintenance and upgrades , ensures a high availability plan for mission critical applications running on virtual infrastructure , can compare business policy against real time asset usage and then make load balance changes , and can provide top 10 recommendations for solutions . the optimizer 210 component operates on the virtual assets of a physical resource to provide efficient configuration of the assets in accordance with a set of business rules . for example , the optimizer component may operate on a user desktop or on a server that manages a virtual environment so as to configure an efficient combination of applications and assets , such as virtual devices of the host machine . in this way , the optimizer provides a user with control over how virtual assets use the underlying physical resources . users can set business policies based on application criticality and can let the optimizer allocate appropriate physical resources in accordance with the business policies . the optimizer can allocate resources such as cpu , network , memory , hard disk , and the like in accordance with the business policies that have been set by the user . configuration of the business policies lets the user have a high degree of control over the allocation of resources . for example , users can set a maximum limit on how much each virtual asset can use the underlying physical resource . the performance manager component 212 provides availability and performance management for all virtual assets in the system . this component shows performance of virtual asset usage , provides key performance matrices and metrics , and identifies future potential bottlenecks . the component can be used to provide real time monitoring and viewing of all virtual assets usage , measure and trend performance and show it against plan , provide triggers , alerts , and alarms for key performance matrices and metrics , identify current and predicted bottlenecks , and provides a cross - platform solution . the capacity planning manager component 214 provides capacity planning , trending and forecasting based on usage and needs . this component provides capacity planning , trending and forecasting of virtual assets based on historical trends and future projected business needs . the component can be used to show used versus available capacity of virtual assets , trends capacity usage and compares it with thresholds , provides historical trend reports , provides forecasting of future needs , and provides alarms and triggers based on capacity usage and thresholds . fig3 is a schematic diagram that illustrates the configuration of an embodiment of a network computer device 300 constructed in accordance with the present invention to provide a virtualization environment that is managed by the control center described herein . the computer device is , therefore , a physical resource of the network 100 . for example , the computer device 300 can comprise a blade server , such as one of the blade servers 120 , 122 illustrated in fig1 . that is , the computer device 300 can comprise a desktop computer system , a laptop , a blade server , conventional server , or other computing machine that includes hardware components 302 . in fig3 , the hardware components are illustrated as including input / output facilities 304 ( such as keyboard , display , mouse , and printer facilities ), a central processor unit ( cpu ) 306 , memory 308 , mass storage 310 ( such as disk drives ), and a network interface card 312 for network communications . those skilled in the art will understand that not all of the hardware components shown are necessary for successful operation of the computer device 300 in the network 100 . the hardware components of the device 300 will depend on the system requirements and the function of the device within the network . the computer device 300 includes an application that provides a virtualization layer 322 that manages virtual assets 326 . thus , the computer comprises a host machine for the virtualization environment . in fig3 , the virtual assets are illustrated as two virtual computers , or machines , a first virtual machine 328 and a second virtual machine 330 . each virtual machine can include an operating system ( os ) for the virtual machine , computer applications programs executing on the virtual machine os , and virtual hardware assets for the virtual machine . in fig3 , the first virtual machine 328 is shown as including an application program “ app 1 ”, an application program “ app 2 ”, and two instances or copies of an application program “ app 3 ”. the second virtual machine 330 is shown with one instance of app 1 , one instance of app 3 , and single instances of applications app 4 and app 5 . as noted above , any one of the computer host machines , or boxes , of the network 100 can include a greater or lesser number of virtual machines . two virtual machines are shown in fig3 for purposes of illustration . likewise , a greater or lesser number of applications running on the virtual os can be provided . there is similar flexibility in the configuration ( type and number ) of os and hardware assets of each virtual machine . in accordance with the invention , a control center ( such as illustrated in fig2 ) manages the virtual assets of each computer host machine 300 for which the control center is responsible . to accomplish such functionality , the control center must communicate with the virtualization layer of the host machine . fig3 shows that a control agent 324 can be installed on the host machine 300 to facilitate such communication . the control agent 324 provides an interface between the hardware resources 302 of the host and the virtualization layer software 322 . the control agent 324 facilitates communication between the external control center components 204 - 214 ( fig2 ) and the virtualization layer 322 of the host machine , and provides a common interface to the variety of virtualization software that might be available on the host machine . for example , the virtualization layer may be provided by products from vmware , or xen , or microsoft , or ibm corporation , or other visualization platforms or emulation interfaces . in this way , the control agent acts as a universal adapter between the control center and the virtualization layer platforms of the host machines in the network . in some cases , it might be possible for the control center components ( fig2 ) to communicate directly with the virtualization layer 322 without need for a control agent 324 , in which case there will be no control agent 324 installed at the host machine . for example , if the asset manager component 204 can communicate directly with the virtualization layer using native interfaces of the virtualization layer , then the control agent 324 is not needed . this would likely be the case if , for example , the virtualization layer is provided by vmware , which includes controls needed for external communications . other virtualization software , such as provided by xen and microsoft , does not typically include such native controls and therefore a control agent 324 would be necessary . those skilled in the art will appreciate that such controls typically include actions such as “ move vm ”, “ migrate vm ”, “ clone vm ”, and the like , which support movement , migration , and cloning of virtual machines and which usually can be invoked programmatically by all virtualization platforms . it is these controls that may be implemented by the control agent 324 , in the absence of a native control in the virtualization platform . if the host machine does include a control agent 324 , then the control agent 324 will have components to facilitate communication between the control center and the virtualization layer 322 . in an alternative embodiment , the control agent 324 can be integrated into the control center itself , such that the control center can communicate directly with the virtualization layer 322 of the host machine , regardless of the virtualization middleware that is actually installed at the host machine . those skilled in the art will understand how to integrate the functionality of the control agent 324 described herein into the control center , without further explanation , in view of the description provided . fig4 is a schematic diagram that shows the construction of the control agent 324 with components for virtualization communication and management . these are the components that enable the control agent 324 of a host machine ( that is , the machine on which the control agent 324 is installed ) to communicate with the control center of an external network machine . fig4 shows that the control agent 324 includes a communication abstraction layer / adapter 402 . this component ensures that the control agent 324 can communicate with the hardware resources of the host machine , such as network communications devices , through which the control agent 324 can send and receive data with one of the external control centers 110 , 112 . in the control agent 324 , an action event receiver 404 receives notifications about incoming events for which a response or action is required . such notifications will typically involve , for example , changes in status of a virtual machine or requests for action or service . the control agent 324 also includes a server monitor 404 that checks for status of the virtual applications of the host machine , and also checks the status of the external control center with which it is communicating . as noted above , each host machine is associated , or managed , by a designated control center . the control agent 324 also includes an event dispatcher 408 , which initiates actions by the host machine in response to the incoming events received by the action event receiver 404 . a control center interface layer 414 provides a monitoring interface function , a management interface function , and a statistics interface function for data exchange between the control agent 324 and the associated control center . a virtual platform abstraction layer 416 permits communications between the host machine 302 resources and a set of multiple middleware adapters 418 , as described further below . in the server virtualization of the illustrated embodiment , the control agent 324 acts as a proxy between the control center 110 , 112 and server instances . the control agent manages the messaging between the control center and the actual vms . the control agent 324 will be created per host and per vm , as required . the control agent communicates with the control center through a communications protocol , such as the ws management catalog protocol specification , wherein the control agent 324 is implemented as a service and will have the set of virtual assets that it manages . other communications schemes can be used , as will be known to those skilled in the art . the vm &# 39 ; s and hosts are the available resources , as specified by the protocol . the control agent 324 is assigned a unique uri and will provide a selector to select a vm instance running within the server . the control agent 324 can create a vm using a resource configuration feature . the control agent 324 is responsible for a variety of tasks , including : collecting statistics from the vm &# 39 ; s and hosts ; monitoring the health of the vm &# 39 ; s and hosts ; generating alarms when the vm &# 39 ; s are out of balance ; monitoring the various events generated by the vm &# 39 ; s and sending an appropriate alert to the server ; communicating the vm / host status to the server ; performing management actions such as create a vm , suspend vm , stop vm , and move vm . the control agent 324 also supports communication between the abstraction layer 416 and different virtualization servers ( virtualization platforms ). the abstraction layer supports interfaces for monitoring , managing , and collecting statistics from the vms and hosts . the control center 110 , 112 can start the control agent 324 . the control agent 324 has its lifecycle independent of the control center and can handle reconnection with the control center , when it starts . the control agent 324 also controls and monitors the health of the host machine . the control agent 324 is responsible for mining the system performance statistics such as the network performance , memory usage , and the disk usage of the host and passing these statistics on to the control center . if a particular vm fails , the control agent 324 tries to restart the vm , or if that fails , sends out an alarm message to the virtual server . data constructs , such as communication objects , implement the communication protocols between the control agent 324 and the control center 110 , 112 . the communication protocol can be based on the ws catalog protocol , in use by vmware . other suitable protocols will occur to those skilled in the art , in view of this description . managing / monitoring control agents 324 ; triggering business rules in the case of alarm messages ; launching / moving applications to different virtual machines based on the vm work load ( the server makes the decisions and the request is sent to the control agent 324 to perform the operation ; balancing workload across different hosts / vm &# 39 ; s ; performing scheduled events ; re - initiating a control agent 324 in case of a failure ; aggregating the performance statistics across all the control agents 324 ; providing management api &# 39 ; s for the control center console ( user interface ) with which an administrator can monitor / manage individual host machines ( physical devices ) and vms . the control center includes the following functional components to perform the above - mentioned responsibilities : an event receiver that receives messages from the control agent 324 and passes them on to an action manager . the event receiver is also responsible for generating a timeout event that will be triggered if no ping / alarm / report status messages are received after a configured period of time ; a host monitor that sends out heartbeat messages s to the control agent 324 ( similar to a ping ) to ensure that the host is available . when a host monitor detects that a host is not available , it will provide the host manager with that information ; host states , which include two distinct states , from the point view of other machines managed by the server : either offline , in which the host is not a fully active member of the virtualization infrastructure , wherein the host and vms deployed may or may not be running ; and online , in which the host is a fully active member of the virtualization infrastructure , wherein the host maintains heartbeats , mines system performance statistical data , and can own and run control agents 324 ; a host manager that is responsible for controlling host machines with control agents 324 . for each host , the host manager will launch one control agent 324 . when a host monitor detects that a host is not available , the host manager tries to send a double - check ping message to the suspected unavailable host . if that host does not respond , the host manager will first try to launch a new control agent 324 process over that host before changing the host state to indicate it as ‘ offline ’ and implementing fail - over of its vm &# 39 ; s to other hosts ; a scheduler that is responsible for scheduling applications based on a business policy . the scheduler generates a set of actions to be performed based on certain business rules and the business policy . the actions are passed on to an action manager . the action manager is responsible for executing the actions ; an action manager that receives actions from the event receiver , host manager , and the scheduler . the choice of host for performing actions such as createvm , movevm is made by a load balancer process . the action manager submits a list of hosts and vm actions to the load balancer process . the load balancer , based on certain business rules and also the load on the hosts , maps the vms to the host machines . the operation of the components described above can be better understood with reference to fig5 , which illustrates the operation of the control center and control agent 324 . the operation of fig5 begins with a halt condition of a vm , for example “ vm 1 ”, which generates an event message that is sent to an event receiver of the control center . this condition is represented by the diagram box numbered 502 . next , at box 504 , the control agent attempts to restart vm 1 . in this example , the restart fails , and therefore the control agent 324 sends a message to the corresponding server monitor ( box 506 ). that is , a condition is detected by the control agent 324 and , once detected , the control agent 324 will attempt to rectify the condition . if that attempt fails , then the control agent 324 informs the control center with an event message and the control center processes the event with the event receiver . at box 508 , the control agent 324 message is received at an event receiver , and business rules are executed to determine the available hosts for supporting the type of virtual machine that has failed . at box 510 , the load balancing procedure identifies a host machine from the list of available hosts . next , at box 512 , the event dispatcher sends the failure event message to the control agent 324 of the selected host machine . lastly , the action event receiver of the selected host machine receives the event message and performs the action ( startup vm ) to restore the failed virtual machine . returning to the description of fig4 , the control center interface layer 414 enables the control agent 324 to communicate with the associated control center to provide the control center with information about the status of the host machine ( monitoring function ), receive instructions and commands from the control center ( management ), and report on operational information ( statistics ). thus , the interface layer extends these three functional areas involving administration , monitoring , and performance statistics . the administration aspect of the control agent 324 provides all the methods that are required for managing a virtual server , such as the gsx / esx server platform from vmware , and the virtual machines under its supervision . all methods related to starting , stopping , cloning , and moving a virtual machine are managed through the administration interface . the monitoring aspect of the control agent 324 provides methods to check virtual machine status and review heartbeat information for a virtual machine . the monitoring interface includes methods to get the statistical information and compare it with specified thresholds and generate action events . the control agent 324 operation includes a “ getallevents ” method that validates each threshold value and generates the necessary action events . the statistical aspect of the control agent 324 collects the statistical information . the methods used by the control agent in these duties are responsible for obtaining performance statistics for cpu performance , disk performance , memory performance , and network performance . those skilled in the art will understand the various performance metrics by which such performance is typically judged . the control agent 324 operation therefore includes methods such as getcpuperfstats , getdiskperfstats , getmemoryperfstats and getnetworkperfstats , which are responsible for returning corresponding specific statistical objects such as cpustats , diskstats , memorystats , and networkstats . these methods are supported for a variety of servers , such as esx servers , and some servers will require the control agent 324 to make system calls to obtain the information , such as for gsx servers . as noted above , the virtual platform abstraction layer 416 of the control agent 324 includes a set of multiple middleware adapters 418 . the middleware adapters communicate with the virtualization environments of the host machine 302 . these virtualization environments are shown in fig4 as including platforms by vmware 420 , xen 422 , microsoft 424 , ibm 426 , and also emulation solutions 428 . it should be understood that these depicted platforms are for purpose of illustration only ; additional or alternative virtualization platforms can also be accommodated . to provide an abstraction layer over a variety of virtualization servers such as from vmware , xen , and microsoft , the abstraction layer 416 of the control agent 324 provides a common api access for the virtualization servers . to do so , the control agent 324 includes components in accordance with the virtualization platform and communication management protocol , components such as : a communication object layer that manages services management events and translates to corresponding method calls , in accordance with the communication management protocol in use for the virtualization platform , such as jms events and in the case of the vmware virtualization platform ; an agent interface comprising a generic interface that supports at least three interfaces including administration , monitoring , and statistics , and uses a factory pattern to create an agent object specific to vmware , xen or microsoft , or whatever the virtualization platform as desired ; a virtualization platform agent , such as a vmware agent as an implementation class for an agent interface that is specific to vmware platforms , and which uses jni to call the com layer on ms platform and uses jpl on linux and solaris ; a jni dll comprising an atl dll that wraps the vmcom object , wherein the com functionality is exposed as method calls that can be accessed through jni ; vmcom interfaces , such as vmserverctl , vmctl , iconnectparams ; a vmiqagent that is designed to be a web service with certain exposed methods , which for applicable communication management protocols may comprise a jms client application that produces / subscribes to certain sets of events for the required communication protocols . on startup , the vmiqagent will use the agent factory class to create the vmware agent object . the information about the virtualization server can be maintained as a part of the agent configuration file , which will only maintain the virtualization server name , such that the details of the server , such as whether it is a gsx server or esx server , will be obtained by querying the server itself . for example , the control agent 324 may include a “ vmwareagentimpl ” class for implementation of a control agent 324 interface to vmware systems . this implementation class makes calls to classes called “ vmserverctl ” and “ vmctl ”, wherein the vmserverctl class includes methods related to the gsx and esx servers . the vmserverctl class is implemented as a singleton class . there would be only one instance of the server object . this discussion assumes that there will be only one server per host ( gsx server or esx server ). a host will not have the virtual machines of multiple virtualization servers ( such as vmware , xen , and microsoft ). the server object will maintain a map of the vmname - to - vmctl objects . the lookup will be on vmnames . the user can give the same name to multiple virtual machines on a server . currently , vmware does support duplicate names . the vmctl and vmserverctl classes invoke the com / perl interfaces of vmware using jni wrapper and jpl , respectively . the jniwrapper is a dll file which exposes methods from the vmcom object . the operations of the control center and control agent 324 to manage the virtual environment will support various use cases , or operating scenarios , including creation and startup of virtual machines ( vms ). such operations are described as follows for a vmware environment ( corresponding operations for other virtualization environments will be known to those skilled in the art , in view of this description ): 1 . in order to create a vm on a particular host , the vm manager first copies the “ vmdk ” file and the “ vmx ” file to the host machine using ssh and then send an event to the host . 2 . the event message contains the following information vm name — name of the vm to be created vmtemplateinfo — template details include type of server , location of the vmx and . vmdk files . 3 . the event is received by the control agent 324 . 4 . createvm method is invoked by passing the vmname and the template info 5 . vmwareagentimpl class then modifies the display name to the vmname and the vmdk file reference in the vmx file . 6 . vmwareagentimpl class then checks for an existing vm with the same name and checks to see if the configuration file is the same . if not , then registers the vm with the gsx / esx server . startvm 1 . vm manager sends an event to the vmiqagent on a particular host to start a vm . the message contains the vmname . 2 . the vmiqagent receives the message and then calls the vmwareagentimpl &# 39 ; s startvm method . 3 . vmwareagentimpl looks up the vmctl object corresponding to the vmname in the vmmap 4 . calls a startvm method of the vmctl object by passing the vmx file name . 5 . the startvm method returns a task handle . 6 . the task status is monitored by the vmwareagentimpl 7 . the vmcom object returns a task handle . if the task state is completed then the completed status is returned to the manager . 8 . the vmwareagentimpl class monitors the task status . 9 . if the task status is vm_question , then a new event is raised to the vm manager with the questioninfo as the message . 10 . the event is received by the vmmanager — either through an autoresponse or a manual process an answer is sent back to the vmiqagent 11 . control agent 324 receives the message — message has a reference to the vmname , task id and the answer . 12 . vmwareagentimpl then calls answervm method of the vmcom object to set the answer . 13 . procedure is repeated till the task status is set to completed . 1 . createvirtualdisk 2 . changepermissions 3 . consolidate_vm 4 . snapshot_vm 5 . revert_vm 6 . enable / disable host 7 . configure cpu , configure disk , configure memory , configure host , configure network . fig6 is a representation of the virtualization environment that can be managed using a computer with the control center application described herein , such as the control center a 110 and the control center b 112 illustrated in fig1 . fig6 is a schematic diagram that illustrates the various levels of virtualization that can be reached and managed with the control centers . in fig6 , multiple end users 602 , 604 , 606 can access physical resources and virtual assets of the host computer 300 . fig6 shows a conceptualized depiction of the access as the multiple users being accommodated through multiple virtual desktops , or user interfaces , through a desktop virtualization layer 608 . the desktop virtualization layer presents the users with a collection of virtual assets available to the users as they communicate over the network ( see the system configuration illustrated in fig1 ). the assets can include multiple applications of the host machine , depicted as “ app 1 ” 610 , “ app 2 ” 612 , and “ app 3 ” 614 for purposes of illustration . the applications may include word processing , email , web browsers , servers , and the like . the applications can be supported by middleware software through an application virtualization layer 616 . the middleware applications are represented by “ mw 1 ” 618 , “ mw 2 ” 620 , “ mw 3 ” 622 . the middleware applications 618 , 620 , 622 can access data stores through a storage virtualization layer 624 . the data stores are represented in fig6 by databases 626 , 628 , 630 indicated as db 1 , db 2 , and db 3 , respectively . in accordance with the invention , the control center application can perform configuration management and forecasting services for the host computer and the available virtual assets through each of the various virtualization layers 608 , 616 , 624 . fig7 is a screen shot of a control center display produced by the user interface of the control center computers 110 , 112 of fig1 . that is , the control center virtualization management application provides a user interface that includes a display such as illustrated in fig7 . the “ virtual manager ” program window shows a list of applications in a left window pane corresponding to a virtual environment for the specified host machine , which is illustrated as “ xpro2005 ” in the left window pane . the control center display shows that the xpro2005 computer includes three applications , which are operating systems , as shown in the detail pane on the right side of the display . the three operating systems are illustrated in fig7 as “ windows xp professional ”, “ suse linux enterprise server ”, and “ windows 2000 advanced server ”. other operating systems can be supported by the control center . the setting pane on the right side , below the os listing pane , shows the user interface feature for setting operating parameters of the control center . the priority of the virtual machine under management ( vm priority ) can be set with a display slider from low priority to high priority . a high priority setting means that the vm will have a high probability of being instantiated on the host machine under management . a low priority setting means that the vm is a likely candidate for deletion from the virtualization of the host machine if resource utilization is great and if other vms have a higher priority setting . the virtualization parameters that can be set for the virtualization environment through the user interface of fig7 include settings for operation of cpu , memory , hard disk , and network . the installed control center application provides a network - based , intelligent orchestration engine for automatic management of virtual assets across multiple computer virtualization platforms around a network . the exact management functions that can be performed by the control center will depend on the number of components selected for installation on the control center computer . the full complement of components are illustrated in fig2 and were described above . the illustrated embodiment described herein is constructed with a modular approach , so that users can select desired components and can leave out the rest . the following description of operating feature details assumes a full installation of all the fig2 control center components , except where noted , and the full installation will be referred to as the “ application ” except where a particular component is singled out for description or mention . it should be understood that installing any one of the fig2 components will provide a user interface that includes the control center , albeit with functionality in accordance with the installed components . the control center application provides a centralized repository for virtual infrastructure configuration change management with an audit trail for it compliance requirements . in accordance with the application , macro - level policies are defined based on business needs . these are implemented as application criticality rules ( acrs ), described further below . the control center operates as a virtual controller that can mediate between physical server , network , applications ; and storage resources . such mediation can occur based on a combination of portable , application - provided as well as user - defined , knowledge blocks ( kbs ). the control center can also provide adaptive application routing ( aar ) for virtual assets based on the acrs . with the knowledge blocks , the control center can take intelligent actions based on the kbs when any of the acrs are violated . the acrs allow a user to specify business rules for controlling priority settings for applications . for example , in a system with a set of five application app 1 , app 2 , app 3 , app 4 , and app 5 , one of the rules could specify that , each morning from 6 : 00 am to 10 : 00 am , the five applications will have priorities set as follows : app 1 has high priority , app 2 has low priority , app 3 has medium priority , app 4 has low priority , and app 5 has high priority . if preferred , the control center can provide a priority setting that is numerical , such as a range of integral numbers between 0 ( zero ) and 10 ( ten ). other priority range indicators can be used as desired , such as colors or other indexes . if traffic to an application is detected as being above a threshold level , another business rule could specify a dynamic response , that the priority for the corresponding application can be adjusted higher . conversely , action could be specified to reduce priority if traffic is detected as abnormally low . another business rule could be set for prospective action , for example , such that a particular application is given an increased priority according to time of day . control center management of virtual assets and mediation between physical resources in conjunction with the acrs provides a robust load balancing functionality with the ability to distribute server load among potential host machines , and determine when and how to increase or decrease the number of vm &# 39 ; s to improve overall system throughput . for purposes of the load balancing function , load can be calculated on a server by following several alternative criteria , or parameters . one parameter can be cpu run queue length , which returns the load as the average number of processes in the operating system ( os ) run queue over a specific time period in seconds , normalized over the number of processors . another parameter is cpu utilization , which returns the load as the cpu usage percentage . other suitable parameters can include network performance ( traffic throughput ), disk performance , which can be measured by the number of bytes read and / or written in a specific time period in seconds , and memory performance , mainly by the ratio of the active memory used as compared with total managed memory . if desired , a weighted formula can be used for computing the load on a particular host based on these parameters . with such parameters available , the load balancing strategy can be implemented with two different strategies : static load balancing and dynamic load balancing . static load balancing is similar to having a pre - defined set of minimum and maximum number of vm &# 39 ; s that can run on a given host . the dynamic load balancing approach suggests that , based on the current and the future load on a host , a decision is made as to which vm should run on which host . once a set of hosts are identified , then the load balancer processing can pick a particular host , by a round - robin or a weighted round - robin method . the load balancer processing would first try to assign the high priority vm &# 39 ; s to hosts with minimum load . the control center also provides an interface to the installed configuration management application , which operates in conjunction with observed real - time events on the network . this is achieved through a four - step process that includes ( 1 ) monitor , discover and alert tasks , ( 2 ) applying user - guided fix automation tasks , ( 3 ) automatically applying basic kbs , and automatically applying more complex kbs and user - defined kbs . in addition , the control center provides a mechanism to centrally schedule resource re - allocation in response to defined business events . fig8 and the following drawing fig . s illustrate the automatic virtualization management in accordance with an embodiment of the invention in the context of managing a collection of virtual assets comprising application servers , but it should be understood that the control center virtualization management application being described can also be used to manage other virtual assets , such as user desktops ( user interfaces ), data storage such as database arrays and attached storage , and network traffic devices such as routers and switches . fig8 is a screen shot of the physical view display page of the user interface , accessed from the control center computers 110 , 112 of fig1 . fig8 shows that the physical view display enables a user to visualize resource utilization relationships . for example , fig8 graphically illustrates two subnets attached to the control center computer , indicated as net 1 and net 2 . this illustrated arrangement is analogous to control center b of fig1 , which shows rack b 1 and rack b 2 under management of control center b . thus , rack b 1 could correspond to net 1 and rack b 2 could correspond to net 2 . alternatively , net 1 and net 2 could correspond to other types of network subdivisions . for example , net 1 and net 2 could relate to geographical divisions of the network , or could correspond to departmental groupings or subnet groupings . in fig8 , net 1 is shown as a virtual environment that includes server 1 and server 2 , each of which manages a vnet 1 and a vnet 2 , respectively . operating on vnet 1 are an instance of app 1 , an instance of app 2 , and an instance of app 3 . under server 2 , the operating applications include one instance of app 1 , an instance of app 4 , and an instance of app 5 . thus , vnet 1 and vnet 2 are virtual networks that are deployed within server 1 and server 2 . this view shows the application topology within the virtual infrastructure , and shows which virtual asset is running on what physical resource ( dependency ) and how they are interconnected via virtual networks and physical networks . the knowledge block feature can be used to specify analysis rules that can detect application performance degradation . in response to such detection , an alert can be sent over the network , such as an alert message being sent to a network administrator . after an alert message has been sent , the configuration management application can wait for an administrative action , or the application can be set up so as to execute an automatic action . for example , in response to a “ crash ” of a virtual machine , the application can find the last known “ good ” vm image from a repository and can deploy that image to the affected machine . in response to overtaxed applications , the application can deploy a new application instance , and can add new application instance information into a network load balancer to indicate the new instance is available and should be considered as part of the “ available application pool ”. in addition , the application can remove a degrading application from the available application pool , or can move a degrading application vm from a group of production servers to a debug server pool . other functions that can be performed by the application in accordance with knowledge blocks include the capture of log files from the degrading application vm , the capture of archive logs and sending of email alert messages to an administrator with the archive log location , and the halting of a degrading application vm and removal of it from the debug server pool . fig9 is an illustration of a control center display that shows a topology view of the virtual environment under management . fig9 shows physical resources and virtual assets such as depicted in fig8 , but illustrates particular user interface features of the control center software . thus , fig9 shows three physical servers , representing networks , indicated by network addresses 255 . 101 . 0 . 0 , 255 . 102 . 0 . 0 , and 255 . 103 . 0 . 0 . machine 1 and machine 2 , which are physical resources , are shown connected to the 255 . 101 . 0 . 0 server , and machine 3 , another physical resource device , is shown connected to the 255 . 102 . 0 . 0 server . various network management operations can be carried out with a drag - and - drop user interface , represented by the icons arrayed along the left side of the display window . for the objects in the large window pane , these operations represent moving display objects , connecting objects , and creating instances of objects such as networks , storage , routers , hubs , and the like . fig1 is an illustration of the fig9 topology view showing machine 3 expanded . the expanded ( level 1 ) view shows that machine 3 is installed with virtual server applications that include “ ssb server ”, “ oracle with mail ”, and “ ss2000 with mail ”. these virtual assets are connected so as to comprise a virtual network connected to the 255 . 101 . 0 . 0 server . the menu choices cpu , mem , net , and i / o in the level 1 window for machine 3 indicate that additional configuration details for these respective characteristics of machine 3 are available in a level 2 display ( not illustrated ) by selection of the corresponding display icons . fig1 is a block diagram representation of a server virtualization configuration management scheme that can be implemented from a computer such as the control center computers 110 , 112 illustrated in fig1 . fig1 depicts the virtualization management 1102 of the network computer system 100 ( fig1 ) as comprising an association or mapping between the actual physical resources , such as a collection of computer hardware machines 1104 , to a collection of virtual machine assets 1106 , or applications , in accordance with a set of application critical rules 1108 . in a typical system , for example , two physical machines might be sufficient to deploy forty virtual machines , each of which can be assigned a different application to operate and thereby provide services to network users . the configuration of the virtual machines 1106 and their corresponding operational applications will be governed by the set of rules 1108 . thus , if a rule specifies that a particular application has a high priority at a particular time of day , then a respective one of the control center computers 110 , 112 ( fig1 ) will adjust the deployment of applications among the virtual machines 1106 under its management at the appropriate times . the server virtualization implementation described thus far can be used to control and manage a complete virtualization environment , including assets such as storage assets , virtual routers , and virtual desktops . such configurations are depicted in fig1 , fig1 , and fig1 . fig1 is a block diagram representation of how storage in physical servers can be allocated by the virtual server using the system management of the present invention . fig1 depicts the configuration management 1202 of the network computer system 100 ( fig1 ) as comprising an association or mapping between actual physical resources comprising a collection of disk drives or storage devices 1204 to a collection of logical units 1206 , such as network virtual storage drives , in accordance with a set of application critical rules 1208 . that is , the storage servers ( physical resources comprising disks ) are mapped to virtual assets ( logical units ). in a typical system , for example , two physical machines ( cpus with attached data devices ) might be sufficient to implement forty logical units , each of which can be assigned a different network drive assignment , such as drive c :, or d :, or e :, and so forth , to operate and thereby provide data storage for network users . the configuration of the logical units 1206 and their corresponding virtual drives will be governed by the set of rules 1208 . thus , if a rule specifies that a particular network drive should have a capacity of 50 gb while a particular application is running , to act as temporary storage for the application , then the configuration management application 110 , 112 will adjust the data capacity configuration of the logical unit 1206 to provide the desired capacity , and will load the desired data , for the appropriate operational conditions . fig1 is a block diagram representation a network router virtualization configuration that can be managed through a virtual server that is managed from a control center computer 110 , 112 such as illustrated in fig1 . fig1 depicts the configuration management 1302 of the network computer system 100 ( fig1 ) for a collection of actual physical resources comprising a collection of processing devices for network path control , such as programmable machines or computers otherwise configurable through a virtualization layer to provide control of network paths , such as devices that can operate as routers 1304 . the devices 1304 are associated with or mapped to assigned network paths 1306 , such as virtual private network ( vpn ) devices , or secure routers . the mapping is in accordance with a set of application critical rules 1308 . in a typical system , for example , two physical machines ( cpus with attached network communications abilities ) might be sufficient to implement a set of forty vpn servers , each of which can be assigned to different network paths or addresses . the configuration of the network path devices 1306 and their corresponding routing operations will be governed by the set of rules 1308 . thus , if a rule specifies that a particular vpn router 1306 should handle traffic for a particular address , then the control center virtualization management application will adjust the network path assignment of the vpn router 1306 to provide the desired assignment . fig1 is a block diagram representation of a desktop computer virtualization configuration that can be managed through a virtual server that is managed from a control center such as illustrated in fig1 . fig1 depicts the configuration management scheme 1402 of the network computer system 100 ( fig1 ) as comprising an association or mapping between actual physical resources comprising a collection of computers or other processing devices 1404 to a collection of installed virtual asset applications 1406 , such as virtual machine applications including word processing , email , spreadsheet , and web browser , in accordance with a set of application critical rules 1408 . in a typical system , for example , a collection of physical computing machines 1404 ( processing devices such as desktops , laptops , and pdas ) might be sufficient to implement forty virtual user interfaces , each of which can provide a collection of installed applications 1406 . the configuration of the installed applications 1406 will be governed by the set of rules 1408 . thus , if a rule specifies that a particular user interface should include word processing and a web browser during specified times of day , but then delete the browser application at other times of day , then the control center virtualization management application will adjust the deployed applications of the logical unit 1406 to provide the desired user interface , for the appropriate operational ( time - of - day ) conditions . although fig1 describes the virtualization management of virtual assets in the context of virtual machines or servers , as noted above , the control center application 202 ( fig2 ) described herein also can be used for management of other network virtual assets , such as virtual storage devices , network path devices , and user interfaces ( desktops ). fig1 is an illustration of a storage virtualization configuration that can be managed in accordance with the present invention . those skilled in the art will recognize that fig1 is similar to the illustration of fig8 except for depicting storage devices and virtual storage assets ( logical units , or luns ) in place of servers and virtual applications , respectively . thus , corresponding details of the discussion above for the server virtualization may be applied to the storage virtualization depicted in fig1 , which those skilled in the art will understand in view of this description . similarly , the present invention can be used in conjunction with other corresponding virtualizations , such as routers and desktops . fig1 is a flow diagram that illustrates operation of the computer installed with the control center application 110 , 112 such as illustrated in fig1 . when the application is launched , generally on boot up of the computer , the application will first perform a monitor and inventory operation 1602 that will determine the collection of virtual assets available to the computer . the monitor and inventory operation involves the control center application communicating with the virtualization platform software to determine a pool of available resource and asset inventory , including user interface inventory ( such as installed applications ), network servers , network storage devices , network routers and switches , and the like , all accessible from the host machine . as noted above , such communications are facilitated in appropriate situations by the presence of a control agent in each host machine . the control agent can provide the necessary communications facilities for communications between the host machine and the associated control center computer . after the control center determines the collection of available virtualization assets , the next operation is for the application to apply the application rules 1604 . these include the application critical rules such as illustrated above in fig1 - 14 and any rules defined by the user in knowledge blocks or imported as knowledge blocks . the next operation is for the control center application to enforce the rules 1606 . for example , the rules may specify the number of application servers of a particular type that are deployed at given times of the day , or in response to detected network traffic conditions . other discretionary operations may then continue . fig1 is a flow diagram that illustrates operation of knowledge block processing for the control center computer such as illustrated in fig1 . in the first operation , the group of rules can be created 1702 . these rules can include rules that are default rules common to all implementations of the application , and can also include rules that the user has fashioned for particular purposes using the rule editor . in the next operation , knowledge block rules can optionally be imported or exported 1704 . in the last knowledge block processing operation , the rules are applied 1706 . as noted above , application of the rules can result in automatic configuration changes that the control center application implements through an interface with the virtualization layer software . other processing can then take place . fig1 is a flow diagram that illustrates operation of the control center computers 110 , 112 illustrated in fig1 . in the first operation , real - time performance metrics are obtained 1802 . such metrics include utilization rate for each of the virtual assets , such as virtual network servers , virtual routers , virtual storage , and the like . such metrics are also used in the load balancing function , as described above . next , the control center application checks for any automatic configuration changes that are called for 1804 . for example , one of the rules might specify a specific mix of virtual servers at a given time of day . depending on the time of day , then , the application might instantiate more or fewer virtual servers , as specified by the rule ( kb ). if configuration changes are called for , an affirmative outcome at the decision box 1804 , then the control center issues commands to the virtualization layer software to implement the desired configuration changes 1806 . those skilled in the art will understand how to implement such configuration changes without further explanation , given the description herein . if no configuration changes are called for , a negative outcome at the decision box 1804 , then the control center next checks to determine if any of the acrs or knowledge block rules have been violated by any system configuration settings or performance metrics , as indicated by the decision box 1808 . if there has been a rules violation , an affirmative outcome at the decision box , then the application reports the violation 1810 . the report can take the form of an alert email message generated by the control center application that is sent to a network administrator or other predetermined email mailing address . after the alert email message has been sent 1810 , the control center issues commands to the virtualization layer software to implement the desired configuration changes 1812 . those skilled in the art will understand how to implement such configuration changes without further explanation , given the description herein . operation then returns to determining real - time system performance metrics 1802 and the loop repeats for as long as the control center application is executing . if there was no rules violation , a negative outcome at the decision box 1808 , then no configuration change is carried out and , instead , operation returns to determining the performance metrics and the loop repeats itself . in this way , the control center provides automatic virtualization management for computer network systems that include network virtual assets . a wide range of installation enhancements can be implemented , including business ( application critical ) rules , import and export of rules , and administrator alert messages . the present invention has been described above in terms of presently preferred embodiments so that an understanding of the present invention can be conveyed . one skilled in the art will appreciate that the present invention can be practiced by other than the above - described embodiments , which are presented in this description for purposes of illustration and not of limitation . the specification and drawings are not intended to limit the exclusionary scope of this patent document . it is noted that various equivalents for the particular embodiments discussed in this description may practice the invention as well . that is , while the present invention has been described in conjunction with specific embodiments , it is evident that many alternatives , modifications , permutations and variations will become apparent to those of ordinary skill in the art in light of the foregoing description . accordingly , it is intended that the present invention embrace all such alternatives , modifications and variations as fall within the scope of the appended claims . the fact that a product , process or method exhibits differences from one or more of the above - described exemplary embodiments does not mean that the product or process is outside the scope ( literal scope and / or other legally - recognized scope ) of the following claims .