Why we have to change application layer in IPv6 if this is a layered architecture?

Question

If TCP/IP is a proper layered architecture why do we need to change all the applications in the application layer in order to change a bottom layer protocol IP from version 4 to version 6?

Answer 1

If the application is well-developed and really layered then it should not have to change. Unfortunately many applications use lower-layer details like IP addresses for access control, logging etc. In many cases understandable, but it does indeed break the layered architecture...

The basics are covered in http://www.stipv6.nl/whitepaper-ip-aspecten-software

And don't forget things like input validation with regular expressions and user interfaces that only handle IPv4 notation (providing four input boxes for the address or automatically inserting dots at certain places etc).

Answer 2

We wouldn't have to change if people would use the getaddrinfo() and getnameinfo() functions.

But as their usage needs 3 more lines of code, people did not use it before.

Meanwhile, they slowly start doing so...

Answer 3

I Think application layer softwares in general doesn't care about IP layer, but however for security reasons some applications need to deal with IP layer (i.e. Access lists at Web servers), this why we need to upgrade software in order to handle IPv6.