Go DADDY forwarding + masking is HTTP redirections and URL Frame.
http://help.godaddy.com/article/422
If you want to make other ports than https or https to work, you need to make a CNAME in your DNS settings.
http://help.godaddy.com/article/680#cnames
Once you setup up a CNAME correctly, the answer to your question will be :
You can also use the dig command to check the TTL time about the records, you will see exactly when that record will expire and the new values fetched from the further queries.
(fake results)
dig www.domain.com
;; ANSWER SECTION:
www.domain.com. 3265 IN A 123.256.289.001
Now you know that from this example, the next fetch from the DNS servers specified in YOUR computer (normally your ISP servers) will be in 3265 seconds. (this is an exemple TTL, it is a countdown)
To be sure you configured it correctly, you can dig directly the NS servers.
dig NS domain.com
Check the ANSWER section
;; ANSWER SECTION:
domain.com. 60 IN NS ns1.exempledomain.com.
domain.com. 60 IN NS ns2.exempledomain.com.
Now try to query the ns server to check if your new settings are applied correctly.
dig @ns1.exempledomain.com www.domain.com
And check for a CNAME to account.dlinkddns.com
Hope this helps