<a href="http://msdn.microsoft.com/Longhorn/understanding/books/rector/default.aspx?pull=/library/en-us/dnintlong/html/longhornch06.asp">Introducing Longhorn for Developers: Chapter 6: Communication</a>. Interesting read there. Also, <a href="http://msdn.microsoft.com/Longhorn/understanding/books/rector/default.aspx">the book is here, Introducing Longhorn for Developers</a>, not fully though. upto chapter 6, 7 comming soon.