- Is there a way already in place to make use of IPv6 as a routable protocol?
- Is it possible to buy private IP addresses for IPv6 yet and if so who sells them?
- Would there be any performance advantage or reduction in latency from having a network based on IPv6?
- Many software vendors tell you to disable the IPv6 capability of your NIC in order to prevent problems with their software. Does use of IPv6 somehow confuse systems also using IPv4?
Yes, but your network infrastructure has to support it, meaning your Operating System, your router and your ISP. The NIC is irrelevant in this case, you can send IPv6 with a modem or a pigeon.
Your ISP should sell them, ask them (SuperUser is not a place for shopping recommendations). Many US-based ISP's don't offer IPv6 support and/or addresses to their residential clients. If your ISP does not offer IPv6 addresses, you can still get multiple free IPv6 addresses that map to your existing IPv4 address. A couple of the larger tunnel brokers are Hurricane Electric and SixXS.
Not really, although IPv6 has a slightly larger overhead the header to payload ratio is still too small.
If that is true, disable their software. IPv6 is a standard that anyone who claims their software can make use of the Internet has to support. And as said above you'd have to disable it in your OS.
No, IPv4 and IPv6 use totally different stacks in the operating system and their headers are distinguished by their version number. If there is a node on the network whose software cannot handle IPv6 the packets have to be packed inside an IPv4 packet. But this is something you do not have to worry about.
Yes. You either need a ISP which supports this or you will need to tunnel. In the past it was rare to get IPv6 via your ISP, but now that IPv4 addresses really start to run out ISPs finally seem to support it.
On the other hand, you might just be lucky with your ISP. Mine started supporting it since late 1998.
Basically the same as with IPv4 ranges. Ask your ISP to allocate some of them for you.
Note that IPv6 address space is much larger. You probably get a large range allocated for you allowing you to to connect supply just about anything you can think of with an unique IP number.
No performance advantage is likely, though it depends on what you compare it with:
Their software is broken.
No. IPv6 and IPv4 (and other protocols) can happily coexist on the same network, and even on the same NIC.
There have been some problems with wrongly configured networks. E.g. where a DNS would happily return a 'yes, we do have a IPv6 address!' while no service was listening on IPv6. Many systems then gave up after trying the IPv6 address without falling back to IPv4.
I've been using IPv6 since 2006, when all there was to see was a dancing turtle*, so I can tell you it is very much live on the Internet today. Major websites such as Google and Facebook are already live with IPv6 and if you have IPv6 connectivity from your ISP then you will already connect to them using IPv6. The last time I looked, my home router told me that a quarter of the traffic to/from my house was over IPv6.
June 6, 2012 was designated World IPv6 Launch Day, where ISPs, network equipment manufacturers and web site operators committed to deploy IPv6.
To obtain IPv6 connectivity at home, contact your ISP and ask them when they plan to deploy native dual stack IPv6. If the answer is anything but "We already did" and you still want to experiment with IPv6, you can obtain temporary service from an IPv6 tunnel broker such as SixXS or Hurricane Electric. (I use both of these for places I can't yet get native dual stack.)
When you obtain IPv6 service as a residential customer, you typically will be granted between a /56 and /64 subnet, which provides billions of times the amount of address space of the current IPv4 internet - just for your house. It would be virtually impossible for you to use your entire allocation. Even so, business customers can typically obtain additional addresses; I could have a /48 just for the asking if I had even the slightest reason to get such a block.
A typical business will typically have somewhere between a /48 and a /56 depending on the complexity of their internal network. ISPs will have much larger blocks; US cable ISP Comcast has a /31 and a /28, for instance, from which it delegates blocks to its IPv6 customers, and probably more blocks I don't know about.
Whether you experience improved latency or performance depends in large part on where you connect to and what you do when you connect there. For the most part your performance should be virtually identical, give or take a millisecond or two. I know of a few degenerate cases where my IPv6 route dramatically outperforms my IPv4 route (we're talking 120ms round trip on IPv4 and 90ms on IPv6), but none of the reverse.
As for software telling you to disable IPv6, some antique software may still not support IPv6 or may malfunction when IPv6 is deployed, or even simply on an IPv6-capable computer. This of course is a bug with that software, and the software vendor should provide an update (if they're still even in business, which is questionable if any such software is still doing that in 2012). IPv6 has been an RFC for 15 years now, and so there's very little excuse for any current software to lack support for it.
(*The turtle only dances if you connect with IPv6.)