Why is this question important? Several reasons, all of which derive from the fact that there isn't any standardized definition to those concepts:
- It is very important to establish meaningful, context-specific metrics for performance for your network. The metrics will depend on the nature and use of the network, the users, the business processes it supports and the types of applications involved.
- A common vocabulary needs to extend from the technical people all the way up to the CIO, out to the applications and support people and into the service level agreements that are in use with customers. That vocabulary needs to be based on metrics that are effective and can be assessed against and validated.
So I applaud your effort to define those terms. When I talk with customers about network performance, my first question is often, "What metrics do you use?" Their ability to answer tells me if/how they have been thinking about network performance.
There are of course relatively generic text-book meanings for these words, but I don't find them useful – they typically can't be applied to measurements for lack of access to the requisite data or lack of applicability to the meaningful outcomes (user productivity and business process optimization).