Documentation change only: add iPerf instructions to NETWORK.md.
@@ -16,3 +16,4 @@ This document describes the network arrangements of the automated test system.
- When moving a KMTronic Ethernet-based relay box onto the network, reset it and first connect it to a PC/laptop where you have disabled Wifi and \[temporarily\] hard-coded the laptop's Ethernet interface to 192.168.1.1; open a browser to 192.168.1.199 and configure the box to do DHCP, then on the router add a static address for it (take a photo of the Ethernet MAC address and then type it in) before connecting the KMTronic to the network.
- When moving a MiniCircuits Ethernet-based RF switch onto the network, you _may_ need to first connect it to a laptop via USB and talk to it using [their application](https://www.minicircuits.com/softwaredownload/rfswitchcontroller.html) to configure it before connecting it to the network.
- When moving a Nutaq network simulator onto the network, these things have a plethora of Ethernet connections in them: plug the network into the first of the two Ethernet ports on the front panel, then on the router move the assigned IP address to the correct static address and reboot the Nutaq box (the separate LTE application running on the Nutaq will be confused otherwise; you could possibly restart the application but if you have it starting on boot it is simpler to just reboot). Repeat for the second Ethernet port on the front panel (e.g. assigned to the next-up IP address) so that they are both moved in case you ever plug into the wrong one.
+- It is, of course, important that the connection between this network and the publicly-visible test server that is used out on the internet is rock solid; tests will fail randomly otherwise. Hence you may wish to set up something like [iPerf](https://github.com/esnet/iperf) to monitor the connection between, say the Jenkins machine and that machine. If your publicly-visible test server is Ubuntu then you can install iPerf with `sudo apt install iperf3`, or on Centos 8 with `sudo yum install iperf3`; make sure you have the port you are going to use (default 5201) is open on the server machine and its network (for both TCP and UDP) then start an iperf server on the publicly-visible test server as a [systemd service](https://gist.github.com/auipga/64be019018ef311deba2211ced316f5e) that runs at boot in the usual way. On the client side, do the same but this time with the parameters to iPerf being `-t 0 -b 100k -u -c ubxlib-test-system.redirectme.net`: this will do a UDP test every second, at a nice low bandwidth of 100 kbits/s, forever. You can now check the network status for uplink packet loss from the server-side by examining the log with something like `sudo systemctl status iperf` or, for a liveish view, `sudo journalctl -u iperf.service -f`. The important numbers are on the end: the jitter in milliseconds and the lost/total packets each second.
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