[Serusers] nathelper, rtpproxy and mediaproxy: What should I use?

[Alberto Cruz]

Hi everybody, I'm a ser newbie and I really confused about all the ser 
information that is published at the different WEB sites. I began to 
read some of them and it is quite difficult for me (my software 
development background is really poor) to understand it.
I would like to know which are the main differences between nathelper, 
rtpproxy and mediaproxy (I'm talking about features) ?
I want to deploy a IP Telephony solution over the Internet and most of 
the end users are going to be behind a NAT or a Firewall with DYNAMIC 
Public IP addresses. Which module or program fits better for it?
Where can I find the most complete or detailed information about SER 
configurations? Is there a book that we can order?

Thanks a lot I really apprecitte your time to answer my questions.

Regards

Alberto Cruz