Put a scale on the path
The bandwidth-delay product estimates how much data must be in flight to fill a path. For a hypothetical 100 Mbps path with a 100 ms round trip, the product is 1.25 MB in decimal units. This is an estimate for a particular path, not a license to give every connection an arbitrarily large default allocation. Actual bottlenecks and RTT can change with the destination and time of day.
Know which transport you changed
Linux TCP congestion control applies to kernel TCP connections. A QUIC application typically implements its congestion controller in user space over UDP. Changing the kernel's TCP setting therefore does not, by itself, select that application's QUIC controller. Document the application version and its own configuration alongside the system setting.
Measure the tradeoff
An experiment should observe completion time, latency under load and resource use, not just peak throughput. Keep the server, destination, request size and connection count fixed. Save the previous settings and define the conditions for reverting them. A result that helps one long transfer may be unhelpful for many short interactive requests, and the difference should be visible in the workload you actually run.
At the terminal
sysctl net.ipv4.tcp_congestion_control
sysctl net.ipv4.tcp_rmem net.ipv4.tcp_wmem
tc qdisc show