Underlying any messaging system is the transport or wire protocol that governs the serialization of the message as it is sent across a wire and the interpretation of the message bits when it gets to the other side. Although SOAP messages can be sent using any number of protocols, the SOAP specification defines only the binding with HTTP. SOAP uses the HTTP request/response message model. It provides SOAP request parameters in an HTTP request and SOAP response parameters in an HTTP response. The HTTP binding has the advantage of allowing SOAP messages to go through firewalls.