In september 2015, I published an article on LinkedIn about IPv6 because ARIN announced that they have exhausted their IPv4 address space! I think that we will, finally, see a lot of enterprise adopting IPv6.
The North American organization is now only able to deliver very small chunk of IPv4 addresses for help in transitioning from IPv4 to IPv6.
First of all, IPv6 is not a new protocol. IETF is working on this since 1990s.
IPv4 is (was?) 32 bit address space, with a lot of unusable IP addresses (Test, Multicast, Reserved for ?Future Use?, Network address, Subnetting, …). The theoretical maximum number of addresses is 2^32 (4294967296). In IPv6, the maximum number of addresses is 2^128 (340282366920938463463374607431768211456 or 3,4*10^39).
Most modern systems are able to run dual stack (IPv4 and IPv6), as are most modern application.
While IPv6 is still IP in the payload and the general behaviour, the way to use, route and allocate addresses is totally different than IPv4.
First of all, about address allocation. The system administrator should be able to forget everything he knows about IPv4 address allocation. In IPv6, you NEVER subnet in less than /64 networks (I wrote NEVER, this is NEVER). This is the most difficult part for Net and Sys admins. They must learn a new way of thinking. The idea behind this is to give a public IP address to all connected devices (nice for IoT).
The general routing protocol between the ISP is still BGPv4, but if you were using OSPFv2 for internal routing, you’ll have to use OSPFv3, right now.
The way the headers are organised in IPv6 reduce routers load.
Quality of servvice as Security were also built from the beginning in the protocol. In fact, IPSEC was defined for IPv6.
There are working, standardised discovery and autoconfiguration protocols to help the administrator to set-up his basic IPv6 Network.
So a tight integration with your DNS will be mandatory as 128 bits of IP addresses makes impossible to learn/remember all your important devices IP addresses like you (probably) did with IPv4. Therefore, a good working DNS infrastructure will be needed.
If I see that there is an interest in this short introduction, I’ll give a more detailed introduction on the working internals of IPv6 for SYS and NET admins!
You can also find a lot of information on http://ipv6actnow.com.