Mobile Web Service Communication Over UDP

A Web service based middleware for mobile applications is a promising platform to accelerate the application development for mobile systems. Currently, the Web service protocol stack is using by default the simple object access protocol (SOAP) on top of HTTP. Since HTTP is using TCP, the round-trip time of a Web service call in mobile networks is high due to the connection establishment of TCP (three-way- handshake) and the congestion and error control mechanisms (slow-start phase). Some applications do not require delivery guarantees of TCP. For these applications an unreliable transport of SOAP messages over the user datagram protocol (UDP) is a natural choice. If an application needs a reliable transport of SOAP messages a lightweight ARQ mechanism on top of UDP is the better choice than using HTTP over a mobile link. The session management of HTTP is substituted by introducing Web services addressing properties within the SOAP header. This paper will present the architecture and the realization of an unreliable and reliable UDP SOAP binding for a mobile Web service based middleware, which consumes Web services (client) and provides Web Services (server). Both bindings will map two basic MEP to UDP services. The reliable binding encapsulates a selective-repeat (explicit request) ARQ protocol on top of UDP which ensures even the transmission of SOAP messages over several datagrams. Some use cases and examples motivate the work and stress the importance according to the mobile middleware. A comparison of method invocation latencies of the reliable UDP binding and the HTTP binding illustrate the performance enhancements.