Master Thesis: Externalize State between Processes

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About this opportunity: 

Radio Access Networks (RANs) consist of functions with stringent requirements for performance, availability, and resilience. These functions run on modern multicore architectures in embedded and cloud environments, where the ability to recover from failures is fundamental.

Multiple instances of the same RAN function may be deployed to improve resilience. An instance may be restarted, upgraded, or temporarily unavailable while another continues providing the service. RAN functions may also be partitioned by cells, users, bearers, or other traffic domains, with each instance maintaining state for the network and traffic it handles.

When state is kept only in an individual process, restarting that process may require the state to be reconstructed or may cause service interruption. Externalizing some or all state allows another process to access or restore it, potentially improving resilience and reducing the impact of restarts. However, this introduces challenges related to performance, consistency, synchronization, memory management, traffic migration, and implementation complexity.

This thesis will investigate state externalization between separate processes and evaluate methods for implementing it in a high-performance RAN packet-processing context. One method of particular interest is the DPDK multi-process model, which allows multiple processes to use shared DPDK resources such as memory, rings, mempools, and message-passing mechanisms. The thesis will assess this model’s suitability and limitations for sharing or externalizing state between RAN function processes.

The thesis will consider two processes providing the same RAN function and handling a common traffic domain. An externalized state mechanism will allow one process to access, update, or restore state maintained by the other process or by a shared state component. The processes may either operate active-active for all traffic, or one may be active while the other is a cold standby. If the active process restarts, the standby becomes active and continues handling the same traffic.

The thesis will investigate and compare suitable state-externalization methods, potentially including shared memory, inter-process messaging, state replication, and the DPDK multi-process model. The DPDK approach should be implemented or evaluated as one candidate method.The investigation should address the technical feasibility and operational consequences of the selected approaches, including: