sibility and retainability [3GPP_KPIs, CELLULAR_QOS] in mobility environments-ha very different meanings as measured and reported by equipment from differ- ent vendors. Operating a network with such diversity necessitates tremendous investment in custom interfaces from OSSs to each of the different elements. But it also meant that the operations organi- zation had to build significant vendor and element-specific expertise within their teams, resulting in operational silos with dedicated teams focused on specific types of network elements. With traditional physical network elements, deploying new elements involves sending techni- cians to each and every site where a new network element is to be deployed. When hardware fails, technicians again have to be dispatched to the physical location of the hardware to repair or replace components (e.g., line cards) or entire network elements. When hardware is out of service, depend- ing on the resiliency options deployed, customers may also be out of service. Alternatively, the network may be operating in a simplex mode where a second similar failure could result in cus- tomer impact. Thus, rapid repair is imperative; technicians are either deployed on site 24 X 7, or are rushed to the location on demand. Spare hardware for each and every component has to be readily available for rapid deployment, thus requiring significant inventory lying idle across the network. The most fundamental operational transformation enabled by NFV may be the opportunity to reduce operational overhead by, using the industry phraseology, turning "pets into cattle." With physical network elements, each network element is akin to the family pet; it has to be lovingly cared for and highly managed. When it is "sick," it is tenderly nursed back to health. In contrast, efficiently scaling networks with the plethora of network functions that need to be supported means that different network functions need to look nearly identical and be treated accordingly, as with cattle. When a network function is "sick