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#1 2021-07-18 17:47:06

LyCC
Member
Registered: 2012-09-05
Posts: 127

[Solved] SSH transfer rate way too slow over WiFi

Hi everyone,

I have an interesting question - the situation is as follows: multiple PCs in the network, some over ethernet cable, some over wifi (N150).
Focusing on two (any two, doesn't matter), transferring files, small, large (also doesn't matter):
PC 1: cable connected
PC 2: wifi connected. The signal isn't particularly grate,  but a speed test shows constant ~50-60mbps / sec down and ~80-90mbps upload (wifi connection info states 120mbit/sec connection speed).
The issue: file transfer over SSH is at best 1.76 mbyte / sec (what i seen), but averages at about ~ 1000 kbyte / sec. With a large number of smaller files even worse (somewhere around 600-700kbyte/sec).
Now, here's the interesting part, when I plug an ethernet cable into the same PC 2 it achieves the full gigabit transfer speed (about ~105mbyte/sec).
Of course the CPU isn't overloaded or anything like that. Any ideas what causes this issue and if/how can this be overcome? I seen this on a couple of other networks too,
totally different setups and equipment.

edit: using "mc" for the transfer, connection is also initiated via mc.

Any idea is welcomed,
Thank you.

Last edited by LyCC (2021-07-20 09:24:55)

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#2 2021-07-18 20:28:33

seth
Member
Registered: 2012-09-03
Posts: 23,367

Re: [Solved] SSH transfer rate way too slow over WiFi

Is it ssh or the LAN? (I assume you ran the speed test w/ some webservice?)
How does eg. ftp or http between the same systems behave?
What if you cut out mc and transfer w/ sftp?

Are wifi and ethernet in the same subnet?
How does wifi to wifi behave?

Since "plug an ethernet cable" apparently automatically switches the NIC, how do you manage the connections?
Networkmanager?
Does its scanning and esp. mac randomization get in the way?

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#3 2021-07-19 08:21:50

LyCC
Member
Registered: 2012-09-05
Posts: 127

Re: [Solved] SSH transfer rate way too slow over WiFi

Thank you for the reply.

So a perf3 test on Wi-Fi:

Connecting to host 192.168.1.10, port 5201
[  5] local 192.168.1.41 port 45370 connected to 192.168.1.10 port 5201
[ ID] Interval           Transfer     Bitrate         Retr  Cwnd
[  5]   0.00-1.00   sec  6.16 MBytes  51.6 Mbits/sec    0    232 KBytes       
[  5]   1.00-2.00   sec  6.09 MBytes  51.1 Mbits/sec    0    246 KBytes       
[  5]   2.00-3.00   sec  5.22 MBytes  43.8 Mbits/sec    0    246 KBytes       
[  5]   3.00-4.00   sec  5.65 MBytes  47.4 Mbits/sec    0    291 KBytes       
[  5]   4.00-5.00   sec  5.03 MBytes  42.2 Mbits/sec    0    291 KBytes       
[  5]   5.00-6.00   sec  5.65 MBytes  47.4 Mbits/sec    0    291 KBytes       
[  5]   6.00-7.00   sec  5.59 MBytes  46.9 Mbits/sec    0    291 KBytes       
[  5]   7.00-8.00   sec  6.21 MBytes  52.1 Mbits/sec    0    291 KBytes       
[  5]   8.00-9.00   sec  5.59 MBytes  46.9 Mbits/sec    0    291 KBytes       
[  5]   9.00-10.00  sec  6.21 MBytes  52.1 Mbits/sec    0    291 KBytes       
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval           Transfer     Bitrate         Retr
[  5]   0.00-10.00  sec  57.4 MBytes  48.2 Mbits/sec    0             sender
[  5]   0.00-10.02  sec  55.9 MBytes  46.8 Mbits/sec                  receiver

On HTTP I get 4.6 - 5.2MB/s. Sadly on SSH (same file), only 1.1MB/s.

During iperf test, the latency climbs to over 100ms, is maybe ssh way too sensitive to latency?

I am running NetworkManager.

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#4 2021-07-19 11:21:22

seth
Member
Registered: 2012-09-03
Posts: 23,367

Re: [Solved] SSH transfer rate way too slow over WiFi

seth wrote:

What if you cut out mc and transfer w/ sftp?

Also try playing w/ the -B and -R parameters.

seth wrote:

Does its scanning and esp. mac randomization get in the way?

Check your journal whether there're network drops during the ssh transfer.

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#5 2021-07-20 09:24:31

LyCC
Member
Registered: 2012-09-05
Posts: 127

Re: [Solved] SSH transfer rate way too slow over WiFi

Ok, thank you. Nothing in the logs.

scp -r user@192.168.1.10:/tmp/a/a /tmp/a/a
user@192.168.1.10's password: 
a                                             100%  102MB   4.8MB/s   00:21

I did another experiment after this, moved the wifi stick with an sub extension cord closer to the router so I get a better signal,
then the transfer with mc also improved. Seems it's acting up when the wifi signal is at the low-end.

Thank you Seth.

Last edited by LyCC (2021-07-20 09:25:30)

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