PFIP: A UDP/IP Transactional Network Stack for Power-Failure Resilience in Embedded Systems

Emerging embedded devices in the Battery-Free Internet of Things have the benefit that they harvest their required energy during runtime from the environment (e.g., through solar power). However, from the perspective of the systems networking stacks, the main challenge is resilience against power failures: Existing network stacks for such systems (e.g., LwIP) face the problem that stored data, such as for address translation, is likely to be lost or inconsistent after a power outage. Besides the consistency of data, sending a packet without the knowledge about the required and available energy can result in energy inefficiency when the power failure occurs during sending, because of the energy waste of the incomplete packet. In this paper, we introduce Pfip, a network stack for UDP/IP specifically targeting scenarios with intermittent power supply. PFIP's primary design consideration is to modularize the network stack into distinct transactions in order to result in a state-machine-compliant structure with states and according transitions. The stack is able to introduce checkpoints between transactions to persistently store the stack's state. Besides handling data consistency, we employ code-analysis techniques that determine the energy demand of states/transitions. Combining the energy demand of operations along with the available energy on our hardware platform eventually yields runtime guarantees such that started transactions will safely be completed without facing power failures.