voipwelcome.com

[uhf]

So I would expect the URL would need to be tied to DNS servers at VOIPo.
I guess that means all resellers would be on one DNS server, and that would be a clue ...

Yes, and No.

Voipo would need to add your sip.yourdomain.com to their DNS, but you could use a CNAME record at ANY DNS provider you choose.

So at GoDaddy, you can use their DNS, point the A record to your IP at Hostgator, and a CNAME for sip at voipo. Alternatively, when you register the domain you can point it at Hostgators DNS servers, but have Hostgator add the CNAME record for you to point to Voipo.

I'm not a DNS expert by any means, so there may be a better way than this. A CNAME record will show the voipwelcome.com domain if a customer does a DNS lookup on your domain, so this isn't completely invisible.

[chpalmer]

I recall that Tim chose the voipwelcome name to set it apart from the Voipo name in anticipation for the reseller program.

[usa2k]

True, but it found other uses!