- What about the other end? It's all well and good that you have enough IPv4 address space (for now, see next point), but what about the other system I'm trying to communicate with? In other parts of the world ISPs aren't so lucky. The European and Asia-Pacific regions are already out of addresses, and ISPs in those areas are carefully conserving what little IPv4 space they have left.
- Growing pains. While you may have "a very healthy inventory of IPv4 addresses available" (Michael Tate, TWCBC Account Consultant, East Region, 22 Apr 2013) at present, this will not continue to be the case... unless you don't plan on growing your customer base any further. Deployments of IPv6 alongside IPv4 should already be underway, if not complete, to ensure there has been adequate testing not only on the part of the ISP but at all the customer sites. Deploying IPv6 "only ... in instances where IPv4 addresses are completely out" (@TWC_Help, Twitter DM, 10 Mar 2014) puts everyone at a disadvantage.
- The whole Internet. I touched on this in a previous post with regard to content providers, but the same call should go out to the ISPs. Why do I want to subscribe to an ISP that isn't giving me access to all of the Internet?
I pick on TWC here because they are my ISP and I've had the most direct experience with them. My impression is that other ISPs are behaving in a similar fashion. I hope we can all get moving before this migration gets any costlier.