WCF supports specifications defined by WS-* specifications. WS-* specifications are defined together by Microsoft, IBM, SUN and many other big companies so that they can expose there service through a common protocol. WCF supports all specifications defined we will understand them one by one. Messaging (WS-Addressing):- SOAP is the fundamental protocol for web services. WS-Addressing defines some extra additions to SOAP headers which makes SOAP free from underlying transport protocol. One of the good things about Message transmission is MTOM, also termed as Message Transmission Optimization Mechanism. They optimize transmission format for SOAP messages in XML-Binary formant using XML optimized packaging (XOP). Because the data will sent in binary and optimized format it will give us huge performance gain. Security (WS-Security, WS-Trust and WS-SecureConversation):- All the three WS- define authentication, security, data integrity and privacy features for a service. Reliability (WS-ReliableMessaging):- This specification ensures end-to-end communication when we want SOAP messages to be traversed to and fro many times. Transactions (WS-Coordination and WS-AtomicTransaction):- These two specifications enables transaction with SOAP messages. Metadata (WS-Policy and WS-Metadataexchange):- WSDL is a implementation of WS-MetadataExchange protocol. WS-Policy defines more dynamic features of a service which can not be expressed by WSDL. We have stressed on the WS-* specification as it’s a specification which a service has to follow to be compatible with other languages. Because WCF follows WS-* specifications other languages like JAVA , C++ can also exploit features like Messaging , Security , Reliability and transactions written in C# or VB.NET. This is the biggest achievement of WCF to integrate the above features with other languages. Note: - During interview the interviewer expects that you know what WS-* specification are supported by WCF and its advantages with respect to interacting with other languages.