Can I run a dns server with an ADSL connection(dynamic ip)?

I have an adsl connection with a dynamic ip address. I have a registered domain.
Can run a dns server and host my domain by myself so that
I connect to my registrar's server and update the IP address of my ns1.mydomain.com when ever my IP changes?

if not . why is it not possible ?
if possible. what are the disadvantages of hosting my domain
with this kind of connection?

Two more questions!

1) Where can I buy a static IP address?
my ISP does not provide static ip address.


2)where can i find a dns server to host my domain and I provide
me with the services or facilities of updating my IP for free?

Help.

>> I connect to my registrar's server and update the IP address of my ns1.mydomain.com when ever my IP changes?

Yes you can, but nobody on earth do silly thing like this.

>> what are the disadvantages of hosting my domain
with this kind of connection?

Depends on how dynamic your IP is. If it changes regularly even you haven't restarted your server, then as you know, 90% of the time people can't reach your site. Why so? Because the IP of your ns1.mydomain.com doesn't get updated immediately at root servers. By the time it gets updated, you might have another brand new dynamic IP.

As far as the answer to your two questions:
1) Just change ISP, preferably to SpeakEasy.net, if you really wanted to play this toy you have to pay for it.

2) The dynamic DNS services out there, be it free or non-free, ain't reliable either. 99.9% of them have misconfigured their DNS in some ways.