wide area network (WAN) for research, test and engineering missions. DREN is a high-speed, high-capacity, low-latency, low-jitter nationwide computer network in support of the DoD's High Performance Computing, Science and Technology, Test and Evaluation and Acquisition Engineering communities. DREN connects scientists and engineers with the HPCMP's geographically dispersed high performance computing (HPC) sites, including the five DoD Supercomputing Resource Centers (DSRCs). DREN is installed at more than 210 DoD sites including research laboratories, test centers, universities, and industrial locations throughout the United States (including Hawaii and Alaska). The fourth generation DREN network (DREN 4) is provided under a commercial services contract awarded to Verizon in 2021. DREN has been awarded in the past to Lumen (DREN 3), Verizon (DREN 2), and AT&T (DREN 1). DREN service providers typically build DREN as a virtual private network overlay on their commercial network infrastructure. Capabilities provided by DREN 4 include digital data transfer speeds ranging from 1 Gbit/s through 100 Gbit/s. DREN 4 is an IPv6 network, with support for legacy IPv4. The HPCMP is currently in the process of building out DREN 4 which will ultimately replace DREN 3 when fully tested in 2022. The two networks will run in parallel for about one year while the 210 sites are transitioned from DREN 3 to DREN 4. In 2003, DREN was designated the Department of Defense's first IPv6 network by the Assistant Secretary of Defense for Networks & Information Integration. Since that time, DREN has been a pioneer within the DoD and US Federal Government for IPv6 deployment, running both IPv4/IPv6 dual stack and IPv6-only networks. DREN provides an extensive IPv6 Knowledge Base containing best practices and lessons learned, available at no charge on the HPCMP website. Other research networks of interest: CANARIE DANTE Energy Sciences Network High Performance Wireless Research and Education Network Internet2 Network NASA Research and Engineering Network Software Applications In addition to supercomputers and the national wide area research network, the HPCMP funds software applications that help the DoD achieve its research objectives by ensuring that important DoD applications run effectively on the large-scale supercomputers it deploys. HPC Software Applications Institutes HPC Software Applications Institutes, or HSAIs, are cross-disciplinary projects funded by the HPCMP but executed in the DoD labs. The HSAI program both develops tools to solve important computational problems facing the DoD and build organic HPC expertise within the department. User Productivity Enhancement and Training (PET)