....[ ].... Since I am upgrading from a DVD, should I disconnect the internet during the upgrade ?
....[ ]....
To the best of my knowledge, internet is required for the activation of your new installation to be enabled. This has been true of all prior installations of Windows since XP as well. I suppose you could do the install and then activate later. However, I don't see any advantage in that approach.
Here's an interesting anecdotal side note about activation. M$ uses telemetry constantly, on all versions of Windows, escalating with each new version.
I ran afoul of this, in the process of something I considered innocent, and well within "the point system", M$ assigns to hardware changes.
I installed a video card (GT-750 ti) in my heretofore IGP based computer (Intel i3 3225), while disconnected from the web. When I did hook back up to the web, M$ promptly deactivated my Win 7 install.
However, (having smartened up a bit), I left my i5 6600 rig, which was running off the IGP at the time, hooked to the web while installed a GtX-1050 ti, and heard absolutely noting from the douches in Redmond when I made the install.
As always your results, and other's opinions may vary.