For most people it is not obvious, what the change from IPv4 to IPv6 really means. It is actually very simple. IP addresses are like phone numbers.
A long time ago, there was only one telephone in one village. The number range was much smaller that times then it is now. Today every person got at least one mobile, a land line, a fax line. To have enough telephone numbers, the range of numbers has been expanded. Exactly the same happens with IPv6. In theorie, you only get a much bigger number range.
Because IP was developed a long time ago, it is an old protocol. Of course there have been some changes over the time, but IPv6 also contains some improvements over IPv4.
If you look how computer communication works, it mainly consists of 4 layers:
- Link Layer
- Network Layer
- Transport Layer
- Application Layer
The Link Layer is the physical connection. Basically the cable. Or you could compare it with a road.
The Network Layer is responsible for the addressing. Compare it with the Post. If I send a letter to Fantasy Road 22 in Houston, Texas, I handover the letter to the postoffice. They know how to handle the letter and where to send it. Somewhen the letter arrives in Houston. I do not have to know where Houston is. The Post is doing it for me. Or the Network Layer.
While the Network Layer is only in charge to address the devices, the Transport Layer addresses the indvidual services. Services are identified using ports. In the Fantasy Road 22 in Houston you got multiple appartements. In every appartment you have multiple persons. The Transport Layer defines now the person, who gets the letter, Mr. Miller.
The top layer is the Application Layer. The application layer defines the kind of information which is exchanged. Is the letter an invoice or an order? In the network environment it defines the kind of traffic: DNS, SMTP, SSH, HTTP …
Changing IPv4 to IPv6 only changes the Network Layer. All other 3 layers remain the same. Of course there are small changes in the Transport and in the Application Layer, but the real change only affects one layer.