Introducing the ALIAS Record | Hacker News Reader

Introducing the ALIAS Record

blog.dnsimple.com

45 pointsglenngillen11 comments

"We’re still working out some of the details of ALIAS records, but we do feel that they are a very useful addition to the records supported by DNSimple"

Guys, have you heard of writing an RFC? Other people might like this too, and have contributions to the detail.

It seems like this is a provisioning trick, rather than an actual DNS record. None of this "ALIAS" records ends up in a zone, or in a DNS packet; rather it is some option on a web interface that presumably never comes near the actual DNS because it is provisioned as something else.

I'm curious, if you point such an ALIAS to a service that dynamically returns different IP addresses based on location; what this service is going to do.

Right now it would resolve to the location of whichever of our name servers handled the request. Theoretically we could pass through the original requestor's IP address, but we don't right now.

Seems like that would make caching the results substantially harder on your side.

So, a small limitation is that this shouldn't be used in front of a geo dns. Fortunately, it's still a great choice for the other 99% of sites.

They should refer to this as a feature of their platform, not a record type.

This seems very similar to the Amazon Route 53 Alias record which I've found quite useful for pointing to ELB instances:

http://aws.amazon.com/route53/faqs/#Supported_DNS_record_typ...

The Amazon Alias record provided both the inspiration and the name. :-)

CNAMEs wont work for their use case, but it seems like DNAMEs might. However DNAMEs work at the (sub)domain level to alias a series of records, not just one.

We considered DNAME records, however a DNAME only redirects subdomains:

  Unlike a CNAME RR, a DNAME RR redirects DNS names subordinate to its owner name; the owner name of a DNAME is not redirected itself.

Thus for this to work for a second-level domain the redirection would have to occur at the top-level domain. In essence the behavior is not what is needed for this particular problem.

Dont PTR records already have this functionality

A domain could indeed have multiple PTR records and they can exist with other records for a name, however for PTR records to be used for the purpose of aliasing there would need to be some sort of additional processing in resolvers. If I were to write an RFC then PTR records might be a good place to start. Alternatively I think NAPTR records could be used as well.

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