To implement zonal design, the Naval Architect starts with the NCETL and chooses mission system packages to achieve the NCETL capabilities. These packages, or elements of the packages, are assigned to different zones of the ship. For the capabilities that are required to have zonal survivability, redundant packages, or redundant elements of the packages, must be assigned to different non-adjacent zones. This assignment of functions and associated equipment to different zones at the earliest stages of design is the key feature of zonal ship design.