udt2

udt2 is a software library and protocol designed to enable high-performance data transfer over UDP networks. It is described by its maintainers as a second-generation evolution of the UDP-based Data Transfer (UDT) protocol, with a focus on reliability, scalability, and efficiency in wide-area and high-bandwidth environments.

The project emerged to address limitations of earlier UDT implementations, aiming to improve congestion control, portability, and integration into scientific and data-intensive applications. udt2 provides a reliable transport service on top of UDP, combining ordered delivery with congestion-controlled throughput. It implements streaming and file-transfer modes and supports different topologies, including client–server and peer-to-peer configurations.

Technical design emphasizes asynchronous I/O, tunable performance parameters, and a lightweight API intended for C++ programs, with bindings available for other languages in some distributions. The reference implementation is compact, cross-platform, and focused on predictable behavior under varying network conditions.

Usage and ecosystem: udt2 is used in academic research, data-transfer testbeds, and some high-performance computing workflows where UDP-based reliability and tunable throughput are advantageous. It exists alongside other high-performance transfer protocols and is often evaluated in experiments comparing throughput, latency, and loss resilience.

Limitations: as with other UDP-based systems, network devices and firewalls can impede connectivity, and performance is sensitive to tuning and end-host configuration. Documentation and community activity vary by release.