iperf3 loses steam

[geraveoyomama]

Accepted connection from 10.0.0.1, port 51538
[  5] local 10.0.0.3 port 5201 connected to 10.0.0.1 port 40086
[ ID] Interval           Transfer     Bitrate
[  5]   0.00-1.00   sec   107 MBytes   898 Mbits/sec                  
[  5]   1.00-2.00   sec   106 MBytes   891 Mbits/sec                  
[  5]   2.00-3.00   sec   107 MBytes   900 Mbits/sec                  
[  5]   3.00-4.00   sec   107 MBytes   901 Mbits/sec                  
[  5]   4.00-5.00   sec  35.4 MBytes   297 Mbits/sec                  
[  5]   5.00-6.00   sec  0.00 Bytes  0.00 bits/sec                  
[  5]   6.00-7.00   sec  0.00 Bytes  0.00 bits/sec                  
[  5]   7.00-8.00   sec  0.00 Bytes  0.00 bits/sec                  
[  5]   8.00-9.00   sec  0.00 Bytes  0.00 bits/sec                  
[  5]   9.00-10.00  sec  0.00 Bytes  0.00 bits/sec                  
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval           Transfer     Bitrate
[  5]   0.00-10.00  sec   463 MBytes   389 Mbits/sec                  receiver

whilst this doesnt seem to affect real usecase and I can recreate this easily I do think it is noteworthy that iperf3 between two peers that are directly communicating drops off. Without nylon the bitrate is a bit faster (unsurprising) and doesnt drop off.

I'll do more investigation but until then here you go

[encodeous]

This looks interesting. Can you provide some more info?

Also, have you tried running iperf in UDP mode? i.e iperf3 -c 10.0.0.1 -u -b 1g (i guess your bandwidth is 1 gigabit)

Some helpful info would be:

1. What os you're running
2. Nylon version
3. Some more info about the network you are running this over (what's the MTU? bandwidth? latency?)

[geraveoyomama]

Yeah sorry it was 2AM.

1. Debian 13 with nothing special from the networking perspective (upgraded over time from Debian 11)
2. nylon version v0.3.3

• using ping, rtt min/avg/max/mdev = 0.053/0.122/0.279/0.060 ms
• mtu 1500 for the "real" device and mtu 1420 for the nylon device on both machines
• the two machines for testing are plugged into the same switch and nylon is directly connecting through the defined endpoints

Using iperf in UDP mode works as expected.

UPDATE: okay really weird. I did nothing through the night and now iperf3 tcp works the same as udp. I am going to investigate more but it seems to be some weird fluke...