AD and OD integration

To all. I am sure questions about Mac integration to an AD domain might have been asked a million times here but since this is my first and fairly new to Macs, I just need to get the right "Mac" answers and trying to understand the differences between the options available to go ahead with this project ([b]If someone could confirm my statements that ends with a question mark, much appreciated[/b]). As far as I have read, these are the options I understand that are available for adding macs to a windows domain: - To use the built-in active directory that comes with Mac OS X ([b]I do not need to setup an OD server, correct? The mac clients are only joined to the domain and the purpose is served?[/b] ) - To use the method commonly known as the "Golden Triangle" - [b]I am guessing this method is used if we need to manage policies on our Macs, same as using Group Policy for windows?[/b] ([b]And for this, I need to setup an OD server, correct?[/b]) [i]*If we were planning on setting up an Apple Update Server for all the macs, we would still need to have the ability to manage policies on Macs?[/i] - I have been reading suggestions by others to use third-party tools such as Likewise Open. - [b]Could someone tell me why exactly would we need to use such a tool?[/b] I figured from their website such a tool can be used for centralized management of policies & others such as from an AD MMC. [b]But my confusion is do I "really" need to use such a third-party tool?[/b] Thanks in advance!