IPv6 and the DNS: missed opportunities

▼ A few days ago I ran into this blog post from 2012: Deprecate, Deprecate, Deprecate, which lists a bunch of IPv6 stuff that's been "deprecated" by the IETF. That means: we changed our minds about this protocol or feature, stop using it.

The list (the blog post obviously has more information):

• IPv4-compatible IPv6 Addresses. Status: Deprecated.
• Site-Local Addresses. Status: Deprecated.
• The 6bone. Status: Deprecated.
• ipv6.exe (Windows XP). Status: Deprecated.
• NAT-PT and NAPT-PT. Status: Deprecated.
• The Type 0 Routing Header. Status: Deprecated.
• Your valid yet older SLAAC IPv6 addresses. Status: Valid (but deprecated).

But what, no IPv6/DNS-related deprecations?

Perhaps the most annoying one of those was the change from ip6.int to ip6.arpa. Originally, the idea was to have reverse mapping of IPv6 addresses under the ip6.int domain name. So for instance, the IPv6 address of this server is 2a01:7c8:aaaa:1fb::2. In the reverse DNS that would then become the following, with a PTR record pointing to the server's name:

2.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.b.f.1.0.a.a.a.a.8.c.7.0.1.0.a.2.ip6.int

Then, around 2003/2005 they decided to change this to:

2.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.b.f.1.0.a.a.a.a.8.c.7.0.1.0.a.2.ip6.arpa

Which of course led to the situation where you'd get inconsistent results for years as people made the change at various times. So annoying, especially because it's just a cosmetic change, but an invisible one!

There were also some more substantial IPv6/DNS-related deprecations: A6 records and bitlabels. The idea behind those is that IPv6 should make it simple to renumber. For this purpose, a system was designed where a DNS record wouldn't hold the entire IPv6 address, but parts of it. So if you move a bunch of systems to a different subnet, you just change the record that has these subnet bits, and all the other partial address records remain the same. Unfortunately, this proved too ambitious. Not only did we move to AAAA records, which are four times as big as A records, only four times as big, but support for A6 records and bitlabels was swiftly removed from BIND. This actually caused me some trouble as the zone file with my A6/bitlabel experiments in it suddenly wasn't recognized by other servers anymore.

Moral of the story: measure twice, cut once.

Permalink - posted 2020-01-13

Time to turn off IPv4 (just a little)

▼ Another month, and we'll be living in the 2020s. And yet, 70% of the internet is still IPv4-only. (I'll be writing a story looking back on IPv6 progress the past decade in January.) So I thought: maybe I should draw a line in the sand and turn off IPv4 for my website. But then how will those 70% find me, and all the links to older content will be dead to much of the internet.

So instead, I decided to host some of the images on my old website muada.com and the new home of my blog illjitsch.com on an IPv6-only domain name. This means that browsers running on a system with only IPv4 connectivity will find that they can't load the image at the top of this page. There's no tricks involved: the browser encounters a cold hard error.

However, I didn't want to have a broken image show up on the page, because people might just think it's my HTML skills that are the problem, rather than them being stuck in the past IP-version wise. So the browser is instructed that when it can't load the image, it should load another. That has a nice big warning in neon colors. I also use an image map to let people click on the word "IPv6" to get to a page that explains what's going on. If javascript is turned off, there's just a line of text saying there is no IPv6 connectivity.

Note that browsers will cache images, so you may still see the correct skyline image even if you currently don't have IPv6 connectivity.

This is the HTML code. You can click on the images to try if they load manually.

<img src="http://images.iljitsch.com/images/skylinedenhaag2.jpg" width=1920 height=180 style="max-width: 1920px" alt="Image couldn't load - you don't seem to have IPv6 connectivity" onerror="this.onerror=null;this.src='/images/warn-img-no-ipv6.png';" usemap="#nov6link">

<map name="nov6link" id="nov6link">
  <area shape="rect" coords="425,110,500,150" title="Click here for an explanation" href="http://iljitsch.com/ipv6-warning.php" />
</map>

I hope that more people will do the same so people start to actually notice that they're behind the times by having just IPv4 connectivity.

Permalink - posted 2019-12-03 - 🇳🇱 Nederlandse versie