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#1 2023-07-26 10:05:52

train__wreck
Member
Registered: 2020-08-23
Posts: 32

IPerf3 retries

Hello, I have recently done a test between 2 Arch desktop PCs using IPerf3. The machines both have gigabit ethernet adapters, a Realtek R8125 in one and an Intel PRO/1000 MT in the other, with 2 gigabit switches in between. I notice retries during the test:

Connecting to host 172.16.16.23, port 5201
[  5] local 172.16.16.10 port 55062 connected to 172.16.16.23 port 5201
[ ID] Interval           Transfer     Bitrate         Retr  Cwnd
[  5]   0.00-1.00   sec   113 MBytes   951 Mbits/sec   27    140 KBytes       
[  5]   1.00-2.00   sec   112 MBytes   939 Mbits/sec   27    133 KBytes       
[  5]   2.00-3.00   sec   112 MBytes   937 Mbits/sec   24    202 KBytes       
[  5]   3.00-4.00   sec   112 MBytes   939 Mbits/sec   27    201 KBytes       
[  5]   4.00-5.00   sec   112 MBytes   942 Mbits/sec   27    191 KBytes       
[  5]   5.00-6.00   sec   112 MBytes   938 Mbits/sec   27    208 KBytes       
[  5]   6.00-7.00   sec   112 MBytes   938 Mbits/sec   27    136 KBytes       
[  5]   7.00-8.00   sec   112 MBytes   940 Mbits/sec   27    136 KBytes       
[  5]   8.00-9.00   sec   112 MBytes   939 Mbits/sec   27    136 KBytes       
[  5]   9.00-10.00  sec   112 MBytes   939 Mbits/sec   24    192 KBytes       
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval           Transfer     Bitrate         Retr
[  5]   0.00-10.00  sec  1.09 GBytes   940 Mbits/sec  264             sender
[  5]   0.00-10.00  sec  1.09 GBytes   939 Mbits/sec                  receiver

iperf Done.

The amount of retries is pretty much the same every time I run the test. Apparently retries are dropped packets? I have left a continuous ping overnight between the machines and the next morning it had 0% loss. I do not notice any other issues with the network. I tried different cabling but it did not change anything.  Is this worth investigating further? Thanks.

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#3 2023-07-27 04:47:50

train__wreck
Member
Registered: 2020-08-23
Posts: 32

Re: IPerf3 retries

I am using the r8169 module. I dug out an old Intel PRO1000 PCIe adapter and tried using it instead of the Realtek, the IPerf retries are still there in identical numbers.

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#4 2023-07-27 06:44:18

seth
Member
Registered: 2012-09-03
Posts: 52,269

Re: IPerf3 retries

Is your only concern the retransmits (not "retries")?
Cable, maybe the switch.

You can also try https://wiki.archlinux.org/title/Networ … eue_length
Carefully or you can just ramp it up to the "default" of 9000, but as pointed out it must be supported by all devices.
"ping" sends significatly smaller packages at a very low rate, so there's no stress on the infrastructure at all.

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