XNA Architecture in Summary
I just did an overview of the XNA framework together with its existing tools. So if you want a really overview of the technology, here's the deal. 
Do note that Network support is NOT available for the XBOX 360 from the XNA Framework at this point in time. However, for Windows, you could create networking features via the System.NET Namespace. The .NET Compact Framework in the XBOX is not the same as the one on your mobile phone. =)
Read the complete post at http://darrensim.com/blogs/techbits/archive/2007/04/20/xna-architecture-in-summary.aspx