Proxy-Enabled Multi-Transport Connectivity

MTCL (Multi-Transport Communication Library) is a C++ header-only library that unifies heterogeneous transports, such as MPI, UCX, TCP, and MQTT, under a single connection-oriented API for point-to-point (Pt2Pt) and collective communication. This paper advances MTCL along four directions. First, we introduce a lightweight Proxy layer that brokers multi-cluster connectivity across NATs and firewalls via configurable pools, enabling cross-site deployments. Second, we extend the library with an asynchronous Pt2Pt API that enables overlap and pipelining. Third, we present a comprehensive experimental study across multiple transports and networks, with emphasis on collectives. Finally, we demonstrate the library's usability with a simple cross-silo case study, showing how the Proxy and unified API streamline orchestration while maintaining predictable performance. Together, these contributions move MTCL beyond its initial release and position it as a practical building block for multi-protocol distributed applications spanning edge, cloud, and HPC.