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In Wireless Multimedia Sensor Networks (WMSN), imaging and/or audio data must be delivered in time and respecting minimum reliability guarantees. While these objectives alone are usually conflicting, the resource constraints and error-prone nature of WMSN links increase the challenge even more, requiring special transport layer support such as the one offered by the Distributed Transport for Sensor Networks (DTSN) protocol. In DTSN, caching of packets at intermediate nodes contributes to significantly minimize the number of end-to-end retransmissions, but still requires packet blocks to be fully memorized at the source. In order to comply with the memory limitations of tiny nodes without compromising throughput in multi-layer data applications, a DTSN differentiated reliability extension is proposed, allowing the source to memorize only the most important packets (base layer), relying exclusively on caching to probabilistically recover the enhancement layer packets. Such extension is mainly useful to support multimedia services (e.g., imaging) and other incremental precision sensor applications. We integrated such an extension to DTSN. Extensive simulation results show that even when only a fraction of the data is stored at the source the protocol can still recover most of the enhancement data based on the caching mechanism.