+Backup
+ The term refers to making a copy of the system persistent data to a storage,
+ so that it can be used to restore the system or a given part of it to the same
+ state as it was when the backup was created. Restoring from backup will lose
+ volatile states like CPU and memory content. Changes made to the system from
+ the moment the backup was created to the moment it is used to restore the
+ (sub)system are also lost in the restoration process.
+
+Carrier Grade
+ The refers to a system, or a hardware or software component that is extremely
+ reliable, well tested and proven in its capabilities. Carrier grade systems are
+ tested and engineered to meet or exceed "five nines" high availability standards,
+ and provide very fast fault recovery through redundancy (normally less than 50
+ milliseconds). Sometimes, Carrier grade is also referred as Carrier Class.
+
+Downgrade
+ The term refers to an upgrade operation in which an earlier version of the
+ software is restored through the upgrade procedure. Compared to rollback,
+ Downgrade is normally initiated with Operator, and it is allowed to select any
+ earlier version, providing the compatibility of the versions is met or upgrade
+ strategies are allowed (whether service outage or data lost can be tolerant.)