The deployment types to consider are as follows:
•
New Installation
–Greenfield—Completely new installation of the Cisco Unified Communications system, using no existing equipment.
–Legacy—New installation of the Cisco Unified Communications system combined with existing legacy equipment, such as TDM PBXs and third-party adjuncts, which may require long-term co-existence and integration or eventual migration to the new installation.
–Brownfield—Existing Cisco Unified Communications system, which requires an upgrade and migration from a previous system release to the current system release.
•Single-Stage Upgrade
–Using existing hardware—All components in the network start at the base release set and all components can be upgraded to the target release set within a single maintenance window.
–Using new hardware (flash-cut or shrink-and-grow)—A parallel network should be built using new hardware and pre-staged with configuration to support the existing production network.
•Multistage System Upgrade
–Using existing hardware (hybrid system)—The components in individual sites can be upgraded from the base release set to the target release set in stages, during separate maintenance windows.
•Multisite Migration with Independent Site Upgrade
–Using an hybrid network with interworking release sets—Components are upgraded on a site-by-site basis during separate maintenance windows. At the completion of each maintenance window, a hybrid network exists within the multiple sites that have components operating on the base release set; or components that are operating on the target release set; or components that are a hybrid system as described in Multistage System Upgrade.
For more information about deployment types, see the System Installation and Upgrade for IP Telephony: Cisco Unified Communications System 
.