The Boston Diaries

The ongoing saga of a programmer who doesn't live in Boston, nor does he even like Boston, but yet named his weblog/journal “The Boston Diaries.”

Go figure.

Wednesday, May 01, 2002

A clarification on an interesting point

A friend of mine wrote in, having read what I wrote about DNS and asked for some clarifications. And yes, rereading what I wrote, I should probably pass on what I wrote back.


If someone typed this into their web browser:

… would they be redirected to:


I've never seen this work so I'm curious if that's how this is resolved by the nameserver.

It doesn't quite work that way. Normally, given a URL

a browser would extract out the host portion, and do a DNS A record lookup:

ip = dns_resolve(host,A_RR);

and if a port wasn't specified, use port 80 as a default:

connection = net_connection(ip,TCP,80);

Using the SRV record (which, to my knowledge, isn't used by any web browser that I know of currently), the code would look something like (for now, ignoring the priority codes and multiple servers issues):

srvinfo    = dns_resolve("_http._tcp" + host,SRV_RR);
ip         = dns_resolve(,A_RR);
connection = net_connection(ip,TCP,servinfo.port);


It's handled completely at the DNS level and no HTTP redirect is sent at all. Unfortuately, nothing much (except for some Microsoft products, and Kerberos installations oddly enough) use the SRV records, which means …

PS: I have 2 never-used-domains (XXXXXXXXXXXX and XXXXXXXXXXXXXXXX) that I'd like to point to my home unix box. Unfortunately, XXXXXXXX blocks all port 80 traffic … I'm on the hunt for a free dynamic DNS provider that will handle port forwarding or give me the ability to edit the DNS records manually … with the end result being that I want all traffic for these two domains to reach my home machine.

You can't use them for this. Sorry.

You can add the records if you want (I have) but don't expect anything to use them anytime soon.

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