• Azure Fabric Controller get commands from RDFE. • The RDFE acts as kind of router for request and traffic to and from the load balancer and Fabric Controller. • When you log in to Azure portal and ask for a new service say for example “Web Role” instance, the portal send this request first to RDFE. • The RDFE asks the Fabric Controller for the same, based on the parameters you set and your location, proximity etc. • The Fabric Controller scans the available nodes in the racks and looks for two nodes that do not share a Fault Domain. • This could be two racks next to each other as Fabric Controller considers network proximity and available connectivity as Factors in optimizing performance. • Azure is unlikely to pick nodes in two different facilities unless necessary or specified. • Once Fabric Controller found its nodes, then puts the role-defining files at the host. • The host OS creates the requested Virtual machines and three virtual Hard Drives, a stock VHD (D :\) for the OS Image, a resource VHD(C :\) for user temporary files (next available drive letter) and a Role VHD for role specific files. • The load balancers do nothing until the instance receives its first external HTTP Communication. • Only then is the instance routed to an external endpoint and live to network.

RDFE (Red Dog Front End), named after the pre-release code name for Microsoft Azure (Red Dog) is a highly available, Azure deployed application which feeds deployment instructions to the Fabric controller.