How to test suspect network?

[Richard Cooke]

I am sorry if this is answered elsewhere, I did some digging before posting this and did not find anything.

I have a friend that's an accountant, they use Quick Books - which is notorious for its network load. They are getting occasional connection lost errors between their laptops and the QB data server.

The server connects to a TP link gigabit hub (unmanaged), which connects to their ISP supplied router/modem/WiFI access point.

My suspicion is the ISP's router has a problem with the volume of data routing through it between the server and the WiFI laptops.

I am looking for a way to figure out how much data the wifi can handle, and how reliable the connection is.

So far, I have tried the example tests in the man page. And they get the occasional TCP write (or read) failure). That is, I ran in -s mode on the data server. And -c mode on the laptops. I have tried one at a time, and all 3 laptops at the same time. I think I see a significant drop in bandwidth when multiple laptops are testing, I suppose that suggests the WiFi device has a limited bandwidth and/or unable to handle multiple clients at the same time. Given QB's propensity for high data usage, that could be the problem.

Thanks in advance,
Richard

[Robert McMahon]

You might want to try --burst-size and burst-period. Then monitor the xfer time on the server. Run the iperf server on the same computer as the QB server.

rjmcmahon@fedora:~/Code/crosscompile/iperf2-code$ iperf -c 192.168.1.35 --burst-size 4M --burst-period 15 -e -i 15 -t 60
------------------------------------------------------------
Client connecting to 192.168.1.35, TCP port 5001 with pid 357559 (1/0 flows/load)
Write buffer size: 131072 Byte  Burst size: 4194304 Byte
Bursting: 4.00 MByte every 15.000 second(s)
TCP congestion control using cubic
TOS defaults to 0x0 (dscp=0,ecn=0) (Nagle on)
TCP window size: 85.3 KByte (default)
------------------------------------------------------------
[  1] local 192.168.1.103%enp4s0 port 38596 connected with 192.168.1.35 port 5001 (icwnd/mss/irtt=14/1448/170) (ct=0.22 ms) on 2024-06-14 09:22:06.562 (PDT)
^[[O[ ID] Interval        Transfer    Bandwidth       Write/Err  Rtry     InF(pkts)/Cwnd(pkts)/RTT(var)        NetPwr
[  1] 0.00-15.00 sec  4.00 MBytes  2.24 Mbits/sec  33/0         0        0K(0)/345K(244)/2581(90) us  108
[  1] 15.00-30.00 sec  4.00 MBytes  2.24 Mbits/sec  32/0         0        0K(0)/451K(319)/3528(228) us  79.26
[  1] 30.00-45.00 sec  4.00 MBytes  2.24 Mbits/sec  32/0         0        0K(0)/524K(371)/4005(100) us  69.82
[  1] 45.00-60.00 sec  4.00 MBytes  2.24 Mbits/sec  32/0         1        1K(1)/178K(126)/2657(135) us  105
[  1] 0.00-60.01 sec  16.0 MBytes  2.24 Mbits/sec  129/0         1        0K(0)/178K(126)/3349(1487) us  83.48


root@raspberrypi5:/usr/local/src/iperf2-code# iperf -s -e
------------------------------------------------------------
Server listening on TCP port 5001 with pid 18991
Read buffer size:  128 KByte (Dist bin width=16.0 KByte)
TCP congestion control default cubic
TCP window size: 85.3 KByte (default)
------------------------------------------------------------
[  1] local 192.168.1.35%eth0 port 5001 connected with 192.168.1.103 port 38596 (burst-period=15.00s) (peer 2.2.1) (icwnd/mss/irtt=14/1448/155) on 2024-06-14 09:22:06.567 (PDT)
[ ID] Burst (start-end)  Transfer     Bandwidth       XferTime  (DC%)     Reads=Dist          NetPwr
[  1] 0.00-0.04 sec  4.00 MBytes   942 Mbits/sec  35.619 ms (0.24%)    617=617:0:0:0:0:0:0:0 3306
[  1] 15.00-15.04 sec  4.00 MBytes   909 Mbits/sec  36.905 ms (0.25%)    618=618:0:0:0:0:0:0:0 3080
[  1] 30.00-30.04 sec  4.00 MBytes   886 Mbits/sec  37.852 ms (0.25%)    626=626:0:0:0:0:0:0:0 2927
[  1] 45.00-45.04 sec  4.00 MBytes   876 Mbits/sec  38.325 ms (0.26%)    553=549:0:0:0:0:0:0:4 2856
[  1] 0.00-60.00 sec  16.0 MBytes  2.24 Mbits/sec  37.175/35.619/38.325/1.194 ms  2414=2410:0:0:0:0:0:0:4