In addition to controlling proxies from the Virtualize Server view, you can also create different proxy configurations in CTP. For instance, you can configure a component to have two available states: one with a proxy directing traffic to a virtual asset and one with a proxy directing traffic to the actual component. This is done by configuring "component instances" with the desired proxy settings (as well as virtual asset settings, data source settings, performance profiles, etc.).
Developers and testers interact with these component instances when creating "environment instances." An environment instance defines the a specific combination of component instances that should be provisioned for each test environment they need. For example, one instance might have component A set to "Virtual - Expected Response Times and Data" and component B set to "Virtual - Errors". Another instance might have component A set to "Virtual - Expected Data, Delayed Response" and component B set to "Actual Asset" 
Once the components are set to the desired states, users can simply click Provision once to execute all of the configuration actions associated with the given environment. This makes a particular combination of component instances "live." For more details on CTP, see Continuous Testing Platform.
