Question about WCF Reliable Sessions

Question

One of the things that the Microsoft documentation says about enabling reliable sessions is that the service will be able to process messages in the order that they were received.

Does this mean that messages within a single session are processed in order? Or does it mean that all messages for all sessions within the service are processed in order?

I know that netTcpBinding is reliable already, without enabling reliable sessions. However, say you use something like WsDualHttpBinding without reliable sessions enabled... is it possible that if the client sends request A and then sends request B that the service might receive B before A? Or does it mean that if client A sends message A and client B sends message B, that I might process B before A?

Answer 1

The service might receive B before A, but reliable sessions will place the messages in a buffer and only process them in the order they were sent within the session. It will not gaurentee order between different sessions, only within the same session that is created by the client.