I was looking at some issues streaming some data, which led me to run speedtest-cli on my NS instance which is connected directly to my cable modem. Running this a number of times, it was averaging a download speed of around 85 Mbps, which is less than half what my ISP is supposed to provide.
Remembering an issue I had when running Zentyal, where the Traffic Shaping module was throttling my downloads, I checked the same settings on NS. This by default was enabled, but I had no rules configured. I changed the setting to disabled, but this made no difference to my download speed.
Connecting a spare laptop, directly to the cable modem, I am able to get over 200 Mbps, as promised by my ISP. So NS is definitely throttling the downloads.
Any ideas where to look/investigate further as to what’s causing this.