--- /dev/null
+Scope
+-----
+
+| This document describes the user requirements on the smooth upgrade
+ function of the NFVI and VIM with respect to the upgrades of the OPNFV
+ platform from one version to another. Smooth upgrade means that the
+ upgrade results in no service outage for the end-users. This requires
+ that the process of the upgrade is automatically carried out by a tool
+ (code name: Escalator) with pre-configured data. The upgrade process
+ includes preparation, validation, execution, monitoring and
+ conclusion.
+| ==[MT] While it is good to have a tool for the entire upgrade process,
+ but it is a challenging task, so maybe we shouldn't require automation
+ for the entire process right away. Automation is essential at
+ execution.==
+| ==[hujie] Maybe we can analysis information flows of the upgrade tool,
+ abstract the basic / essential actions from the tool (or tools), and
+ map them to a command set of NFVI / VIM's interfaces.==
+
+The requirements are defined in a stepwise approach, i.e. in the first
+phase focusing on the upgrade of the VIM then widening the scope to the
+NFVI.
+
+The requirements may apply to different NFV functions (NFVI, or VIM, or
+both of them) . They will be classified in the Appendix of this
+document.
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