Subject: [BEHAVE] IPvX-only meaningless?

From: Iljitsch van Beijnum <[email-masked]>
Date: Wed, 16 Sep 2009 15:48:43 +0200

Does it make sense to spend many cycles on exploring what IPv4-only or  
IPv6-only really means?

In order to be able to communicate over a certain protocol, both ends  
need to have:

1. a network stack that supports the protocol and is enabled
2. an address for the protocol
3. a route to the correspondent's address
4. the ability to find the correspondent's address

And that for both ends, so 8 yes/no combinations = 256 permutations  
per IP version.

(Note that 4 is usually the DNS but it can also be a BitTorrent  
tracker or a SIP server or something like that.)

In only very few circumstances all four are limited to one protocol.  
Does it make sense to single out that unusual case?

A more common case will be that some of the steps can handle a given  
protocol, but others can't.