IETF recently announced the publication of RFC 7050 – “Discovery of the IPv6 Prefix Used for IPv6 Address Synthesis”. This is an interesting RFC that will help service providers transition their customers to an IPv6 only network. I’m happy to have been contributing with minor suggestions to the authors around how the DNS pieces of the RFC should work.
RFC 7050 is really an extension to the initial DNS64 RFC (RFC 6147). If you are unfamiliar with the original RFC and DNS64 here is a quick recap:
We are running out of IPv4 addresses in the world. Service providers, especially in the wireless industry, are looking at ways of providing users with IPv6 only networks so that they still can grow their customer base. However, they still need these new customers to be able to IPv4 sites.
RFC 6147 describes a way of doing this by adding intelligence into the DNS to trick the endpoint into believing that everything is accessible via IPv6. To work properly, this trick relies on a DNS64 prefix that is configured into the DNS by the service provider.
DNS64 works very well with most applications and web sites but some applications and websites utilize hardcoded IPv4 addresses that bypass the DNS, and therefore bypass the DNS64 trick. These sites, therefore, cannot be reached from an IPv6 only network. One would hope that the owners of such applications and website would rewrite them to use domain names rather than hardcoded IP addresses, but this is not happening quickly enough. This is where the new RFC 7050 comes in.
Instead of just dropping those IPv4 only requests the idea behind RFC 7050 is that the endpoint should do its own translation. To do so the endpoint will need the magic DNS64 prefix. RFC 7050 describes a way of obtaining this prefix by doing some intelligent DNS probes. IANA has added a special record ‘ipv4only.arpa’ into the global DNS. The endpoint can do a lookup of this record, and by doing so, the endpoint can determine the DNS64 prefix and start translating IPv4 hardcoded addresses itself.
RFC 7050 is mostly for wireless services providers and it will require cooperation from handset manufacturers to be effective. I hope the handset manufactures will implement support for RFC 7050 in their software so that we all can migrate into IPv6 as soon as possible.