I am migrating the Solaris Server to a Linux based one. I was thinking about using the same DNS/URL for the Solaris box for the new Linux Server. It would help me as - Users don't have to make any changes and i just need to switch over to new Linux boxes once i am all set. I am not really aware of the concept of DNS/DNS porting I assume it is a sort of URL rewriting. Any material or assistance would be a great help.
With DNS you should be able to simply change the IP address the DNS record points to the IP address of the new server. This way you have both failback capabilities as well as testing abilities.
This is a pretty common requirement and standard practice.
Without more information on exactly what you're trying to do we can't tell you what the right solution is. I can however tell you with a high degree of confidence that setting up a complicated URL rewriting scheme is almost certainly the wrong solution.
Depending on how your site is structured your most likely strategy is to either take the Solaris box offline and replace it with the Linux box (give the Linux box the IP the Solaris box was using), or to perform a DNS swap like Brent suggests (bring the Linux box up on a new IP, and update DNS so your hostname points at the new IP).
The chief difference between the two options is that with a server swap (giving the Linux host the IP of the old Solaris host) your site will cut over "hard" (and there will be a brief outage window while you swap the IP).
Since you say you are
I also suggest picking up a copy of DNS and BIND at your earliest convenience and skimming through the chapters on how DNS works -- This is an invaluable reference.