WS-* specifications and WCF
To create robust distributed service with WCF it is very essential to understand WS-* specifications.
List of Web service specifications - http://en.wikipedia.org/wiki/List_of_Web_service_specifications
In .NET this supports as Web Services Enhancements (WSE). http://en.wikipedia.org/wiki/Web_Services_Enhancements
The Web Service Specifications is to provide interoperable protocols for Security, Reliable Messaging, and Transactions http://msdn.microsoft.com/en-us/library/ms951274.aspx
Windows Communication Foundation (WCF) implements a number of Web services protocols. http://msdn.microsoft.com/en-us/library/ms734776.aspx
The article for WCF implementation of the WS-ReliableMessaging http://msdn.microsoft.com/en-us/library/aa480191.aspx is very nice.