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Comment by andy_ppp | Hacker News Reader

Domain names and IP addresses are interchangeable almost everywhere else right? There already is a standard here and the spec is breaking it, not the other way around.

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Not really when it comes to dns. You cant put a domain name in an A record or an ip address in a CNAME.

And that causes problems too right?

Does it? I've never heard anyone complain

Because most dns server software doesn’t accept it. There is no reason to put an IP address in a CNAME record, it’s not easier or more convenient, you just need to change the CNAME record type to ‘IN A’.

That's how I feel. Specific records should not specify if its a domain name or an IP. They both should be accepted.

So an A record should also hold domain names? Or IPv6 addresses?

In DNS, there is actually a single record type that should hold a physical address, for each supported protocol address. We have A records for IPv4, and AAAA records for IPv6. Anything else should be a domain name.

Adding both IPv4 and IPv6 support to every other record type would be a waste.

Note: ignoring other protocol addresses above to keep it focused on what is currently is large scale use.

DNS records are statically typed. An “A” record can only contain an IPv4 address, just like a variable of type “int” in the C programming language only can contain an integer. An MX record, just like CNAME, SRV, and others, can only contain a domain name, not an IP address of any kind. You can input a domain name which looks like an IPv4 address, but this is simply a syntax overlap; it happens to be that the normal textual representation of IPv4 addresses are also valid syntax for an unrelated domain name. Tellingly, the syntax for IPv6 addresses does not overlap with domain names, so you cannot make this error with IPv6 addresses.

I don't think you appreciate how old DNS is or why it uses the data structures it does.

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