Instead of relying on network-level transport to convey routing information, a message utilizing WS-Addressing may contain its own dispatch metadata in a standardized SOAP header.
The network-level transport is only responsible for delivering that message to a dispatcher capable of reading the WS-Addressing metadata.
WS-Addressing supports the use of asynchronous interactions by specifying a common SOAP header (wsa:ReplyTo) that contains the endpoint reference (EPR) to which the response is to be sent.
The service provider transmits the response message over a separate connection to the wsa:ReplyTo endpoint.
An endpoint reference (EPR) is an XML structure encapsulating information useful for addressing a message to a Web service.