Greetings, I have been testing the T-Mobile Home Internet (4G/5G fixed wireless) service to a Linode VM via WireGuard.
The TMHI service uses CGNAT plus an additional NAT in their modem/gateway with a MTU of 1420, so WireGuard is configured with a 1340 MTU. Everything works, but I thought I would share some jitter results that readers here might find interesting. [gw-lan WGIP:10.4.1.1] -- [TMHI modem/gateway] -- 4G/5G/CGNAT -- [linode WGIP:10.4.1.10] gw-lan ~ # mtr -wn -c 30 -s 1340 10.4.1.10 ... HOST: gw-lan Loss% Snt Last Avg Best Wrst StDev 1.|-- 10.4.1.10 0.0% 30 88.7 88.9 77.2 99.2 5.4 Looks to be as expected, in the direction of the CGNAT, now the other direction, against the grain of the CGNAT ... linode ~ # mtr -wn -c 30 -s 1340 10.4.1.1 ... HOST: linode Loss% Snt Last Avg Best Wrst StDev 1.|-- 10.4.1.1 0.0% 30 206.1 243.5 73.8 393.9 97.9 Huge jitter, and is very reproducible. But no packet loss. Further investigation shows for low traffic rates (linode->gw-lan) the jitter over WireGuard is huge, here are some UDP iperf3 tests showing how the jitter goes down as the traffic rate is increased. linode ~ # iperf3 -c 10.4.1.1 -u -b 5k -t 30 ... [ ID] Interval Transfer Bitrate Jitter Lost/Total Datagrams [ 5] 0.00-30.25 sec 18.9 KBytes 5.11 Kbits/sec 68.428 ms 0/15 (0%) receiver linode ~ # iperf3 -c 10.4.1.1 -u -b 10k -t 30 ... [ ID] Interval Transfer Bitrate Jitter Lost/Total Datagrams [ 5] 0.00-30.30 sec 37.7 KBytes 10.2 Kbits/sec 82.411 ms 0/30 (0%) receiver linode ~ # iperf3 -c 10.4.1.1 -u -b 50k -t 30 ... [ ID] Interval Transfer Bitrate Jitter Lost/Total Datagrams [ 5] 0.00-30.14 sec 184 KBytes 49.9 Kbits/sec 7.532 ms 0/146 (0%) receiver linode ~ # iperf3 -c 10.4.1.1 -u -b 100k -t 30 ... [ ID] Interval Transfer Bitrate Jitter Lost/Total Datagrams [ 5] 0.00-30.10 sec 367 KBytes 100 Kbits/sec 4.182 ms 0/292 (0%) receiver linode ~ # iperf3 -c 10.4.1.1 -u -b 500k -t 30 ... [ ID] Interval Transfer Bitrate Jitter Lost/Total Datagrams [ 5] 0.00-30.11 sec 1.79 MBytes 498 Kbits/sec 1.308 ms 0/1456 (0%) receiver So using VoIP a higher bitrate CODEC is actually better w.r.t jitter. Hope others find this interesting. Lonnie