Joe,
I agree in the sense that NV is a means to create a VM. I disagree about the "shared substrate" part - it's the tunnels that define the virtualization in my definition; how devices are shared is not directly relevant (that's mechanism; see the end of this post).
Well, terms like "overlay" and "virtual network" are admittedly used by many people with different meanings. In my mind, a tunnel itself is also a sort of mechanism, and the notion of a tunnel alone doesn't help draw a meaningful distinction for me between (say) a virtual network and an overlay network.
The analogy to VM is useful here. There are many ways to achieve VM, but they do not all involve sharing physical memory
Yup, agreed. That gets at the distinction I would make between "memory virtualization" and "virtual memory". Memory virtualization would, to me, refer to the sharing of the physical memory (i.e., on a platform that supports virtualizing the physical memory so multiple virtual memories can share it), whereas virtual memory is the concept or abstraction or architecture as seen by a single process.
Asking what it means for "a substrate to support NV" is a different question than asking what VN or NV is, IMO.
Yup, I understood your viewpoint, and was intending to offer a different view that draws a distinction between the abstraction (of a virtual network) and an underlying system that can support or host multiple instances of that abstraction (i.e., network virtualization).
-- Jen
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