The state of IPv6 deployment

While IPv6 deployments are still anecdotal, there is a steady effort aimed at increasing adoption. The drive towards IPv6 is primarily fueled by the estimation that we will run out of IPv4 addresses around 2011. Several organizations are offering counters of when the dwindling supply of IPv4 addresses allocated to Regional Internet Registries (RIR) by the Internet Assigned Numbers Authority (IANA) will be exhausted. One tool is provided by Hurricane Electric (http://ipv6.he.net/statistics/). You see:

• Number of IPv4 addresses left
• Number of blocks of IPv4 addresses still not assigned to a RIR
• Number of Autonomous System Numbers (ASN) that run IPv6 (the size of the IPv6 Internet backbone)
• Number of Top Level Domains (TLD) that are operating on IPv6
• Number of domains that are IPv6 (I would say the number of web sites reachable via IPv6 out of the 10 millions top web sites as per Alexa)

Email and IPv6

But what about email? How many servers can receive email via IPv6? We took a sample of 500,000 domains. Unfortunately we cannot use the list from Alexa as they are web sites and not domains with mail servers. Instead, we sampled 500,000 email domains known to Genius.com and went to look for their MX records. For each MX record we checked if the host has an AAAA record (reachable via IPv6).

We used the simple program below against a csv file of domains:

<?php
$file=$argv[1];
$f=fopen($file,"r");
$buffer = fgets($f, 4096);
$i=1;
while (!feof($f)) {
    $buffer = fgets($f, 4096);
    $domain=substr($buffer,1,-2);
    echo $i."|".$domain."|";
 
    //look for MX record
    $mxhosts=array();
    $foundMX=getmxrr($domain,&amp;$mxhosts);
    if ($foundMX) {
        //loop through MX records
        $ipv6=false;
        foreach($mxhosts as $host) {
            if (checkdnsrr($host,"AAAA")) {
                $ipv6=true;
                break;
            }
        }
        if ($ipv6) {
            echo "IPv6";
        } else {
            echo "IPv4";
        }
    } else {
        echo "No MX found";
    }
    echo "\n";
    $i++;
}
fclose($f);
?>

Our results shows that 1.895% of the sampled domains have one or more MX records with at least one host on IPv6.

There are about 120 Millions domains registered under a generic Top Level Domains (gTLD), which are not registered with a country code Top Level Domains (ccTLD), as per RegistrarStats. We can expect the same amount for ccTLD domains, although it is difficult to assess as no ccTLD is required to provide statistics. A sampling of 500,000 domains is short, but fair. We know that all these domains are linked to email addresses.

How does it compare with web sites on IPv6? As per the stats of Hurricane Electric, there are 1.5 Millions web sites which are available via IPv6. On the Top 500 websites on Alexa, Hurricane Electric indicates 0.2% are available via IPv6.

It seems the deployment of IPv6 for email seems slightly better than for the web. Perhaps because with several MX per domains, it is easier to have at least one host on IPv6.