Jennifer Rexford wrote:
Joe,If that's true, then why is the Internet not already a virtual net, e.g., supporting different transport protocols over IP? IP is shared by different transports. Similarly, ethernet supports different network protocols.
>
In that sense, I'd view the Internet as supporting overlay networks, in the generic sense that an overlay network running (say) on end hosts could have packets traversing an overlay link be delivered via the Internet.
I'm asking whether you then consider TCP and UDP overlays on IP. > But, the Internet does not support network virtualization in
that you cannot instantiate a virtual network *inside* the Internet, running *in parallel to* (as opposed to *on top of*) IP.
Ethernet supports Appletalk, Decnet, etc. - does that mean that ethernet supports network layer virtualization? that (as above) IP supports transport layer virtualization?
IMO, it's useful to distinguish virtualization from layering; the former ought to add a layer of indirection. That's what tunnels provide; perhaps that focuses too much on the mechanism, and we need to say "a network that supports address indirection"?
(I say "network" here because VLANs don't support network indirection; they support only link indirection; endpoints are not abstracted)
Joe
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