A Lightweight SOAP over CoAP Transport Binding for Resource Constraint Networks

A huge momentum towards IP enabled Wireless Sensor Networks (WSN) appeared through the emerging 6LoWPAN protocols (i.e. IPv6 over Low power Wireless Personal Area Networks). By using existing cross domain open standards in contrast of proprietary solutions, technologies and deployments are not tailored too tight for specific applications. Nevertheless, 6LoWPAN is only the first step. Still efforts on higher layers on top of 6LoWPAN are an urgent need to provide the seamless connectivity and interaction of highly resource constrained devices with higher valued applications and services. This paper describes a new approach to bind SOAP to the emerging Constrained Application Protocol (CoAP) protocol. Thereby, CoAP provides a lightweight but reliable transport binding for SOAP. Compared to the widespread TCP based HTTP binding, round trip times can be reduced by 43% in an exemplary scenario because of the omitted expensive bidirectional TCP handshake mechanisms. Combined with dedicated XML compressors like EXI, SOAP based protocols become also applicable in WSNs.