NDT measures “bulk transport capacity”: the maximum date rate that TCP can reliably deliver data using the unreliable IP protocol over an end-to-end Internet path. TCP’s goal is to send data at exactly the optimal rate for the network, containing just the right mix of new data and retransmissions such that the receiver gets exactly one copy of everything. Since its creation, the TCP protocol has consistently made improvements to the way it accomplishes this task, consequently, NDT has also incrementally changed to reflect these improvements. The most recent improvements, including support for TCP BBR, are available in ndt7. On July 24th, we announced the start of migration of NDT clients to the latest protocol version. As of today, approximately 50% of clients are using ndt7. As the ndt7 measurements become the majority of the NDT dataset, the M-Lab team is considering what we do and do not know about whether and how changes to the NDT protocol have affected M-Lab’s longitudinal NDT dataset over time.
When the M-Lab platform was initially launched in 2009, the software and operating system running on our servers used the best available boot management, virtualization, and kernel-level measurement instrumentation available. In the years since M-Lab’s initial launch, the state of system administration has improved dramatically. In 2017, the M-Lab team began work to upgrade the platform to adopt modern and flexible system administration components. This post provides a roadmap of that work.