tcpdiag.com

This is the cloud-hosted variant of tcpdiag with a web frontend. It generates data flows between the server and the web browser. Meanwhile, tcpdiag runs on the server and streams the captured diagnostics to the web browser. If there is a proxy between the server and the web browser, the diagnostics describe the flow between the server and the proxy.

This tool is intended to provide hands-on experience with congestion control algorithms (CCAs) and as a measurement tool for your Internet connection. In general, the results depend on both the CCAs and the Internet connection, so these goals are intertwined.

Selects the address family for the data flow. This choice can make a difference when IPv4 traffic passes a NAT gateway or because of differences in WAN routing.
Sets a server-side, kernel-level rate limit for the data flow, using the SO_MAX_PACING_RATE socket option. This setting is useful to test an uncongested link, for example.
Sets an additional downstream (one-way) RTT delay for the data flow, using the TCP_TX_DELAY socket option. This setting can be used to evaluate the RTT-dependence of CCAs.
CUBIC is the default CCA of the Linux kernel.
bbr1 from Google's BBRv3 kernel
bbr from Google's BBRv3 kernel
LoLa is a delay-based CCA provided by the KIT.
Start a flow uploading data. In this case, the client chooses the CCA and TCP diagnostics are captured on the receiver side, so they are less meaningful. For example, the congestion window and retransmissions cannot be determined correctly.
or

Start Remote Flow

Remote flows transfer data from the cloud server to some HTTP client, possibly on another host. The diagnostics are shown in this web browser.

Use this command to start a flow:

curl -o /dev/null ''

Feel free to use http instead of https. The rate limit can be set by appending &rate=100000, for example. The CCA can be set by appending &alg=bbr for example.