1.ASP.NET sessions are initiated by server
while WCF sessions are initiated by WCF Client.
2.ASP.NET sessions data can be accessed in unordered way
but In WCF session Messages delivered during a session
are processed in the order in which they are received.
3.ASP.NET has a general data storage mechanism for session
but In WCF there is no such data storage.
Below is a sample WCF class with Required Session Mode
public interface ICalculatorSession