* * * * *
                                        
                    A clarification on an interesting point
                                        
A friend of mine wrote in, having read what I wrote about DNS (Domain Name
Service) [1] 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: 
> > 
> > http://www.example.com 
> > 
> > … would they be redirected to: 
> > 
> > http://www1.example.com:8080 
> > 
> > ???? 
> > 
> > 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 (Uniform Resource
> Locator) 
> 
> http://www.example.com/ 
> 
> 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(srvinfo.host,A_RR);
> connection = net_connection(ip,TCP,servinfo.port);
> 
> 	> 
> It's handled completely at the DNS level and no HTTP (HyperText Transport
> Protocol) 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. 
> 

[1] gopher://gopher.conman.org/0Phlog:2002/04/20.3

Email Sean Conner at sean@conman.org

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