improving dynamic DNS

[Tom Metro]

While using dynamic DNS for a non-critical project where I was 
monitoring the accessibility of the system connected via the dynamic IP, 
I noticed that the system went offline, then a while later came back. 
But after further investigation determined that it hadn't came back, it 
was just that the IP got assigned to another customer at the ISP, and 
the dynamic DNS never got updated because the system was down.

This is of course completely expected, but got me thinking that there 
really ought to be a better mechanism for handling dynamic DNS. One 
option might be having the dynamic DNS provider periodically expire the 
IP address and retarget the host name to some unroutable address if it 
hasn't heard from the host. (Like a watchdog timer.)

Another option might have the dynamic DNS provider use some protocol to 
periodically query the host on the dynamic IP address and ask it for 
some secrete token that was established when the IP address was set. If 
the provider fails to get the right token back, it again updates the DNS 
to point to an unroutable address.

For this project I happen to be using DynDNS. As far as I can see it 
doesn't support anything like the above. Does anything know of a dynamic 
DNS provider that does?

I remember a long time ago when I was using a mail server on a dial-up 
connection. I didn't use dynamic DNS or otherwise make my IP address 
public. For my mail, I used ETRN to trigger mail to be sent from my 
ISP's MX to the local server. One day right after I connected I received 
a pile of mail for some other domain (this is back before anti-relay 
rules were common), who apparently was using dynamic DNS and had a 
public MX record pointing to their dynamically connected host. A pretty 
risky thing to do...

  -Tom

-- 
Tom Metro
Venture Logic, Newton, MA, USA
"Enterprise solutions through open source."
Professional Profile: http://tmetro.venturelogic.com/