The Architectural Refinement of μD3TN: Toward a Software-Defined DTN Protocol Stack

This paper provides a comprehensive overview of the $\boldsymbol{\mu}\mathbf{D}\mathbf{3}\mathbf{TN}$ project's development, detailing its transformation into a flexible and modular software implementation of the Delay-/Disruption-Tolerant Networking (DTN) Bundle Protocol. Originating from $\boldsymbol{\mu} \mathbf{PCN}$, designed for microcontrollers, $\boldsymbol{\mu}\mathbf{D}\mathbf{3}\mathbf{TN}$ has undergone significant architectural refinement to increase flexibility, compatibility, and performance across various DTN applications. Key developments include achieving platform independence, supporting multiple Bundle Protocol versions concurrently, introducing an abstract Convergence-Layer Adapter (CLA) interface, and developing the so called Application Agent Protocol (AAP) for interaction with the application layer. Additional enhancements, informed by field tests, include Bundle-in-Bundle Encapsulation and exploring a port to the Rust programming language, indicating the project's ongoing adaptation to practical needs. The paper also introduces the Generic Bundle Forwarding Interface and AAPv2, showcasing the latest innovations in the project. Moreover, it provides a comparison of $\boldsymbol{\mu}\mathbf{D}\mathbf{3}\mathbf{TN}^{\prime}\mathbf{s}$ architecture with the Interplanetary Overlay Network (ION) protocol stack, highlighting some general architectural principles at the foundation of DTN protocol implementations.