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How to measure UDP one-way latency?

General Discussion
Yunha Choi
2025-04-16
2025-05-16

  • Yunha Choi

    Yunha Choi - 2025-04-16

    Hello,
    I'm using iperf version 2.2.0 and want to measure the one-way latency of UDP packets.
    The time between the two hosts is synchronized.

    When I use the -e option on the server side, I see latency metrics. Are these RTT (Round-Trip Time) values?
    Also, when I use the --trip-times option on the client side, I get latency metrics as well.

    How can I get accurate one-way latency measurements?

     

    • Robert McMahon

      Robert McMahon - 2025-04-20

      Use --trip-times if the clocks are synchronized. 

      rjmcmahon@rpi5-34:~ $ iperf -s -i 1 -e -u
------------------------------------------------------------
Server listening on UDP port 5001 with pid 43853
Read buffer size: 1470 Byte 
UDP buffer size:  208 KByte (default)
------------------------------------------------------------
[  1] local 192.168.1.34%eth0 port 5001 connected with 192.168.1.35 port 51657 (trip-times) (peer 2.2.2-master) on 2025-04-20 14:47:46.856 (PDT)
[ ID] Interval        Transfer     Bandwidth        Jitter   Lost/Total  Latency avg/min/max/stdev PPS  Rx/inP  Read/Timeo/Trunc  NetPwr
[  1] 0.00-1.00 sec   129 KBytes  1.06 Mbits/sec   0.001 ms 0/90 (0%) 0.123/0.122/0.162/0.004 ms 91 pps 90/0(0) pkts 90/0/0 1077
[  1] 1.00-2.00 sec   128 KBytes  1.05 Mbits/sec   0.001 ms 0/89 (0%) 0.122/0.123/0.129/0.001 ms 45 pps 89/0(0) pkts 89/0/0 1069
[  1] 2.00-3.00 sec   128 KBytes  1.05 Mbits/sec   0.001 ms 0/89 (0%) 0.122/0.122/0.128/0.001 ms 89 pps 89/0(0) pkts 89/0/0 1073
[  1] 3.00-4.00 sec   128 KBytes  1.05 Mbits/sec   0.000 ms 0/89 (0%) 0.122/0.122/0.126/0.001 ms 89 pps 89/0(0) pkts 89/0/0 1075
[  1] 4.00-5.00 sec   128 KBytes  1.05 Mbits/sec   0.001 ms 0/89 (0%) 0.122/0.122/0.129/0.001 ms 89 pps 89/0(0) pkts 89/0/0 1075
[  1] 5.00-6.00 sec   128 KBytes  1.05 Mbits/sec   0.001 ms 0/89 (0%) 0.122/0.122/0.128/0.001 ms 89 pps 89/0(0) pkts 89/0/0 1071
[  1] 6.00-7.00 sec   129 KBytes  1.06 Mbits/sec   0.001 ms 0/90 (0%) 0.122/0.122/0.128/0.001 ms 90 pps 90/0(0) pkts 90/0/0 1080
[  1] 7.00-8.00 sec   128 KBytes  1.05 Mbits/sec   0.001 ms 0/89 (0%) 0.122/0.122/0.128/0.001 ms 89 pps 89/0(0) pkts 89/0/0 1069
[  1] 8.00-9.00 sec   128 KBytes  1.05 Mbits/sec   0.001 ms 0/89 (0%) 0.122/0.119/0.129/0.001 ms 89 pps 89/0(0) pkts 89/0/0 1070
[  1] 9.00-10.00 sec   128 KBytes  1.05 Mbits/sec   0.001 ms 0/89 (0%) 0.122/0.122/0.128/0.001 ms 89 pps 89/0(0) pkts 89/0/0 1070
[  1] 0.00-10.02 sec  1.25 MBytes  1.05 Mbits/sec   0.001 ms 0/894 (0%) 0.122/0.119/0.162/0.002 ms 81 pps 894/0(0) pkts 895/0/0 1075

rjmcmahon@rpi5-35:~ $ iperf -c 192.168.1.34 -i 1 -e --trip-times -u
------------------------------------------------------------
Client connecting to 192.168.1.34, UDP port 5001 with pid 24142 (1/0 flows/load)
TOS defaults to 0x0 (dscp=0,ecn=0) (Nagle on)
Sending 1470 byte datagrams, IPG target: 0.00 us (kalman adjust)
UDP buffer size:  208 KByte (default)
------------------------------------------------------------
[  1] local 192.168.1.35%eth0 port 51657 connected with 192.168.1.34 port 5001 (trip-times) on 2025-04-20 14:47:46.855 (PDT)
[ ID] Interval        Transfer     Bandwidth      Write/Err/Timeo  PPS
[  1] 0.00-1.00 sec   129 KBytes  1.06 Mbits/sec  90/0/0      90 pps
[  1] 1.00-2.00 sec   128 KBytes  1.05 Mbits/sec  89/0/0      89 pps
[  1] 2.00-3.00 sec   128 KBytes  1.05 Mbits/sec  89/0/0      89 pps
[  1] 3.00-4.00 sec   128 KBytes  1.05 Mbits/sec  89/0/0      89 pps
[  1] 4.00-5.00 sec   128 KBytes  1.05 Mbits/sec  89/0/0      89 pps
[  1] 5.00-6.00 sec   128 KBytes  1.05 Mbits/sec  89/0/0      89 pps
[  1] 6.00-7.00 sec   129 KBytes  1.06 Mbits/sec  90/0/0      90 pps
[  1] 7.00-8.00 sec   128 KBytes  1.05 Mbits/sec  89/0/0      89 pps
[  1] 8.00-9.00 sec   128 KBytes  1.05 Mbits/sec  89/0/0      89 pps
[  1] 9.00-10.00 sec   128 KBytes  1.05 Mbits/sec  89/0/0      89 pps
[  1] 0.00-10.02 sec  1.25 MBytes  1.05 Mbits/sec  894/0/0      81 pps
[  1] Sent 895 datagrams
[  1] Server Report:
[ ID] Interval        Transfer     Bandwidth        Jitter   Lost/Total  Latency avg/min/max/stdev PPS  Rx/inP  Read/Timeo/Trunc  NetPwr
[  1] 0.00-10.02 sec  1.25 MBytes  1.05 Mbits/sec   0.000 ms 0/894 (0%) 0.122/0.119/0.162/0.002 ms 89 pps 89/0(0) pkts 0/0/0 1075

      Also supported are full histograms

      rjmcmahon@rpi5-34:~ $ iperf -s -i 1 -e -u --histograms=10u
------------------------------------------------------------
Server listening on UDP port 5001 with pid 43866
Read buffer size: 1470 Byte 
Enabled receive histograms bin-width=0.010 ms, bins=0 (clients should use --trip-times)
UDP buffer size:  208 KByte (default)
------------------------------------------------------------
[  1] local 192.168.1.34%eth0 port 5001 connected with 192.168.1.35 port 52920 (trip-times) (peer 2.2.2-master) on 2025-04-20 14:50:18.179 (PDT)
[ ID] Interval        Transfer     Bandwidth        Jitter   Lost/Total  Latency avg/min/max/stdev PPS  Rx/inP  Read/Timeo/Trunc  NetPwr
[  1] 0.00-1.00 sec   129 KBytes  1.06 Mbits/sec   0.001 ms 0/90 (0%) 0.122/0.122/0.161/0.004 ms 91 pps 90/0(0) pkts 90/0/0 1082
[  1] 0.00-1.00 sec T8-PDF: bin(w=10us):cnt(90)=13:89,17:1 (5.00/95.00/99.7%=13/13/17,Outliers=0,obl/obu=0/0) (0.161 ms/1745185818.179112)
[  1] 1.00-2.00 sec   128 KBytes  1.05 Mbits/sec   0.001 ms 0/89 (0%) 0.122/0.122/0.128/0.001 ms 45 pps 89/0(0) pkts 89/0/0 1075
[  1] 1.00-2.00 sec T8-PDF: bin(w=10us):cnt(89)=13:89 (5.00/95.00/99.7%=13/13/13,Outliers=0,obl/obu=0/0) (0.128 ms/1745185820.007306)
[  1] 2.00-3.00 sec   128 KBytes  1.05 Mbits/sec   0.001 ms 0/89 (0%) 0.122/0.122/0.126/0.001 ms 89 pps 89/0(0) pkts 89/0/0 1075
[  1] 2.00-3.00 sec T8-PDF: bin(w=10us):cnt(89)=13:89 (5.00/95.00/99.7%=13/13/13,Outliers=0,obl/obu=0/0) (0.126 ms/1745185820.455915)
[  1] 3.00-4.00 sec   128 KBytes  1.05 Mbits/sec   0.001 ms 0/89 (0%) 0.122/0.122/0.126/0.001 ms 89 pps 89/0(0) pkts 89/0/0 1076
[  1] 3.00-4.00 sec T8-PDF: bin(w=10us):cnt(89)=13:89 (5.00/95.00/99.7%=13/13/13,Outliers=0,obl/obu=0/0) (0.126 ms/1745185821.913893)
[  1] 4.00-5.00 sec   128 KBytes  1.05 Mbits/sec   0.001 ms 0/89 (0%) 0.122/0.122/0.127/0.001 ms 89 pps 89/0(0) pkts 89/0/0 1071
[  1] 4.00-5.00 sec T8-PDF: bin(w=10us):cnt(89)=13:89 (5.00/95.00/99.7%=13/13/13,Outliers=0,obl/obu=0/0) (0.127 ms/1745185822.441008)
[  1] 5.00-6.00 sec   128 KBytes  1.05 Mbits/sec   0.001 ms 0/89 (0%) 0.122/0.122/0.127/0.001 ms 89 pps 89/0(0) pkts 89/0/0 1068
[  1] 5.00-6.00 sec T8-PDF: bin(w=10us):cnt(89)=13:89 (5.00/95.00/99.7%=13/13/13,Outliers=0,obl/obu=0/0) (0.127 ms/1745185823.416732)
[  1] 6.00-7.00 sec   129 KBytes  1.06 Mbits/sec   0.001 ms 0/90 (0%) 0.123/0.122/0.127/0.001 ms 90 pps 90/0(0) pkts 90/0/0 1080
[  1] 6.00-7.00 sec T8-PDF: bin(w=10us):cnt(90)=13:90 (5.00/95.00/99.7%=13/13/13,Outliers=0,obl/obu=0/0) (0.127 ms/1745185824.459744)
[  1] 7.00-8.00 sec   128 KBytes  1.05 Mbits/sec   0.001 ms 0/89 (0%) 0.123/0.123/0.127/0.001 ms 89 pps 89/0(0) pkts 89/0/0 1066
[  1] 7.00-8.00 sec T8-PDF: bin(w=10us):cnt(89)=13:89 (5.00/95.00/99.7%=13/13/13,Outliers=0,obl/obu=0/0) (0.127 ms/1745185825.424256)
[  1] 8.00-9.00 sec   128 KBytes  1.05 Mbits/sec   0.001 ms 0/89 (0%) 0.123/0.123/0.127/0.001 ms 89 pps 89/0(0) pkts 89/0/0 1064
[  1] 8.00-9.00 sec T8-PDF: bin(w=10us):cnt(89)=13:89 (5.00/95.00/99.7%=13/13/13,Outliers=0,obl/obu=0/0) (0.127 ms/1745185826.422409)
[  1] 9.00-10.00 sec   128 KBytes  1.05 Mbits/sec   0.001 ms 0/89 (0%) 0.123/0.123/0.127/0.001 ms 89 pps 89/0(0) pkts 89/0/0 1066
[  1] 9.00-10.00 sec T8-PDF: bin(w=10us):cnt(89)=13:89 (5.00/95.00/99.7%=13/13/13,Outliers=0,obl/obu=0/0) (0.127 ms/1745185827.431782)
[  1] 0.00-10.02 sec  1.25 MBytes  1.05 Mbits/sec   0.001 ms 0/894 (0%) 0.122/0.122/0.161/0.002 ms 81 pps 894/0(0) pkts 895/0/0 1074
[  1] 0.00-10.02 sec T8(f)-PDF: bin(w=10us):cnt(894)=13:893,17:1 (5.00/95.00/99.7%=13/13/13,Outliers=0,obl/obu=0/0) (0.161 ms/1745185818.179112)

rjmcmahon@rpi5-35:~ $ iperf -c 192.168.1.34 -i 1 -e --trip-times -u
------------------------------------------------------------
Client connecting to 192.168.1.34, UDP port 5001 with pid 24152 (1/0 flows/load)
TOS defaults to 0x0 (dscp=0,ecn=0) (Nagle on)
Sending 1470 byte datagrams, IPG target: 0.00 us (kalman adjust)
UDP buffer size:  208 KByte (default)
------------------------------------------------------------
[  1] local 192.168.1.35%eth0 port 52920 connected with 192.168.1.34 port 5001 (trip-times) on 2025-04-20 14:50:18.178 (PDT)
[ ID] Interval        Transfer     Bandwidth      Write/Err/Timeo  PPS
[  1] 0.00-1.00 sec   129 KBytes  1.06 Mbits/sec  90/0/0      90 pps
[  1] 1.00-2.00 sec   128 KBytes  1.05 Mbits/sec  89/0/0      89 pps
[  1] 2.00-3.00 sec   128 KBytes  1.05 Mbits/sec  89/0/0      89 pps
[  1] 3.00-4.00 sec   128 KBytes  1.05 Mbits/sec  89/0/0      89 pps
[  1] 4.00-5.00 sec   128 KBytes  1.05 Mbits/sec  89/0/0      89 pps
[  1] 5.00-6.00 sec   128 KBytes  1.05 Mbits/sec  89/0/0      89 pps
[  1] 6.00-7.00 sec   129 KBytes  1.06 Mbits/sec  90/0/0      90 pps
[  1] 7.00-8.00 sec   128 KBytes  1.05 Mbits/sec  89/0/0      89 pps
[  1] 8.00-9.00 sec   128 KBytes  1.05 Mbits/sec  89/0/0      89 pps
[  1] 9.00-10.00 sec   128 KBytes  1.05 Mbits/sec  89/0/0      89 pps
[  1] 0.00-10.02 sec  1.25 MBytes  1.05 Mbits/sec  894/0/0      81 pps
[  1] Sent 895 datagrams
[  1] Server Report:
[ ID] Interval        Transfer     Bandwidth        Jitter   Lost/Total  Latency avg/min/max/stdev PPS  Rx/inP  Read/Timeo/Trunc

      PS. I'd recommend 2.2.1.

       

    • Robert McMahon

      Robert McMahon - 2025-04-20

      Use --trip-times if the clocks are synchronized. 

      rjmcmahon@rpi5-34:~ $ iperf -s -i 1 -e -u
------------------------------------------------------------
Server listening on UDP port 5001 with pid 43853
Read buffer size: 1470 Byte 
UDP buffer size:  208 KByte (default)
------------------------------------------------------------
[  1] local 192.168.1.34%eth0 port 5001 connected with 192.168.1.35 port 51657 (trip-times) (peer 2.2.2-master) on 2025-04-20 14:47:46.856 (PDT)
[ ID] Interval        Transfer     Bandwidth        Jitter   Lost/Total  Latency avg/min/max/stdev PPS  Rx/inP  Read/Timeo/Trunc  NetPwr
[  1] 0.00-1.00 sec   129 KBytes  1.06 Mbits/sec   0.001 ms 0/90 (0%) 0.123/0.122/0.162/0.004 ms 91 pps 90/0(0) pkts 90/0/0 1077
[  1] 1.00-2.00 sec   128 KBytes  1.05 Mbits/sec   0.001 ms 0/89 (0%) 0.122/0.123/0.129/0.001 ms 45 pps 89/0(0) pkts 89/0/0 1069
[  1] 2.00-3.00 sec   128 KBytes  1.05 Mbits/sec   0.001 ms 0/89 (0%) 0.122/0.122/0.128/0.001 ms 89 pps 89/0(0) pkts 89/0/0 1073
[  1] 3.00-4.00 sec   128 KBytes  1.05 Mbits/sec   0.000 ms 0/89 (0%) 0.122/0.122/0.126/0.001 ms 89 pps 89/0(0) pkts 89/0/0 1075
[  1] 4.00-5.00 sec   128 KBytes  1.05 Mbits/sec   0.001 ms 0/89 (0%) 0.122/0.122/0.129/0.001 ms 89 pps 89/0(0) pkts 89/0/0 1075
[  1] 5.00-6.00 sec   128 KBytes  1.05 Mbits/sec   0.001 ms 0/89 (0%) 0.122/0.122/0.128/0.001 ms 89 pps 89/0(0) pkts 89/0/0 1071
[  1] 6.00-7.00 sec   129 KBytes  1.06 Mbits/sec   0.001 ms 0/90 (0%) 0.122/0.122/0.128/0.001 ms 90 pps 90/0(0) pkts 90/0/0 1080
[  1] 7.00-8.00 sec   128 KBytes  1.05 Mbits/sec   0.001 ms 0/89 (0%) 0.122/0.122/0.128/0.001 ms 89 pps 89/0(0) pkts 89/0/0 1069
[  1] 8.00-9.00 sec   128 KBytes  1.05 Mbits/sec   0.001 ms 0/89 (0%) 0.122/0.119/0.129/0.001 ms 89 pps 89/0(0) pkts 89/0/0 1070
[  1] 9.00-10.00 sec   128 KBytes  1.05 Mbits/sec   0.001 ms 0/89 (0%) 0.122/0.122/0.128/0.001 ms 89 pps 89/0(0) pkts 89/0/0 1070
[  1] 0.00-10.02 sec  1.25 MBytes  1.05 Mbits/sec   0.001 ms 0/894 (0%) 0.122/0.119/0.162/0.002 ms 81 pps 894/0(0) pkts 895/0/0 1075

rjmcmahon@rpi5-35:~ $ iperf -c 192.168.1.34 -i 1 -e --trip-times -u
------------------------------------------------------------
Client connecting to 192.168.1.34, UDP port 5001 with pid 24142 (1/0 flows/load)
TOS defaults to 0x0 (dscp=0,ecn=0) (Nagle on)
Sending 1470 byte datagrams, IPG target: 0.00 us (kalman adjust)
UDP buffer size:  208 KByte (default)
------------------------------------------------------------
[  1] local 192.168.1.35%eth0 port 51657 connected with 192.168.1.34 port 5001 (trip-times) on 2025-04-20 14:47:46.855 (PDT)
[ ID] Interval        Transfer     Bandwidth      Write/Err/Timeo  PPS
[  1] 0.00-1.00 sec   129 KBytes  1.06 Mbits/sec  90/0/0      90 pps
[  1] 1.00-2.00 sec   128 KBytes  1.05 Mbits/sec  89/0/0      89 pps
[  1] 2.00-3.00 sec   128 KBytes  1.05 Mbits/sec  89/0/0      89 pps
[  1] 3.00-4.00 sec   128 KBytes  1.05 Mbits/sec  89/0/0      89 pps
[  1] 4.00-5.00 sec   128 KBytes  1.05 Mbits/sec  89/0/0      89 pps
[  1] 5.00-6.00 sec   128 KBytes  1.05 Mbits/sec  89/0/0      89 pps
[  1] 6.00-7.00 sec   129 KBytes  1.06 Mbits/sec  90/0/0      90 pps
[  1] 7.00-8.00 sec   128 KBytes  1.05 Mbits/sec  89/0/0      89 pps
[  1] 8.00-9.00 sec   128 KBytes  1.05 Mbits/sec  89/0/0      89 pps
[  1] 9.00-10.00 sec   128 KBytes  1.05 Mbits/sec  89/0/0      89 pps
[  1] 0.00-10.02 sec  1.25 MBytes  1.05 Mbits/sec  894/0/0      81 pps
[  1] Sent 895 datagrams
[  1] Server Report:
[ ID] Interval        Transfer     Bandwidth        Jitter   Lost/Total  Latency avg/min/max/stdev PPS  Rx/inP  Read/Timeo/Trunc  NetPwr
[  1] 0.00-10.02 sec  1.25 MBytes  1.05 Mbits/sec   0.000 ms 0/894 (0%) 0.122/0.119/0.162/0.002 ms 89 pps 89/0(0) pkts 0/0/0 1075

      Also supported are full histograms

      rjmcmahon@rpi5-34:~ $ iperf -s -i 1 -e -u --histograms=10u
------------------------------------------------------------
Server listening on UDP port 5001 with pid 43866
Read buffer size: 1470 Byte 
Enabled receive histograms bin-width=0.010 ms, bins=0 (clients should use --trip-times)
UDP buffer size:  208 KByte (default)
------------------------------------------------------------
[  1] local 192.168.1.34%eth0 port 5001 connected with 192.168.1.35 port 52920 (trip-times) (peer 2.2.2-master) on 2025-04-20 14:50:18.179 (PDT)
[ ID] Interval        Transfer     Bandwidth        Jitter   Lost/Total  Latency avg/min/max/stdev PPS  Rx/inP  Read/Timeo/Trunc  NetPwr
[  1] 0.00-1.00 sec   129 KBytes  1.06 Mbits/sec   0.001 ms 0/90 (0%) 0.122/0.122/0.161/0.004 ms 91 pps 90/0(0) pkts 90/0/0 1082
[  1] 0.00-1.00 sec T8-PDF: bin(w=10us):cnt(90)=13:89,17:1 (5.00/95.00/99.7%=13/13/17,Outliers=0,obl/obu=0/0) (0.161 ms/1745185818.179112)
[  1] 1.00-2.00 sec   128 KBytes  1.05 Mbits/sec   0.001 ms 0/89 (0%) 0.122/0.122/0.128/0.001 ms 45 pps 89/0(0) pkts 89/0/0 1075
[  1] 1.00-2.00 sec T8-PDF: bin(w=10us):cnt(89)=13:89 (5.00/95.00/99.7%=13/13/13,Outliers=0,obl/obu=0/0) (0.128 ms/1745185820.007306)
[  1] 2.00-3.00 sec   128 KBytes  1.05 Mbits/sec   0.001 ms 0/89 (0%) 0.122/0.122/0.126/0.001 ms 89 pps 89/0(0) pkts 89/0/0 1075
[  1] 2.00-3.00 sec T8-PDF: bin(w=10us):cnt(89)=13:89 (5.00/95.00/99.7%=13/13/13,Outliers=0,obl/obu=0/0) (0.126 ms/1745185820.455915)
[  1] 3.00-4.00 sec   128 KBytes  1.05 Mbits/sec   0.001 ms 0/89 (0%) 0.122/0.122/0.126/0.001 ms 89 pps 89/0(0) pkts 89/0/0 1076
[  1] 3.00-4.00 sec T8-PDF: bin(w=10us):cnt(89)=13:89 (5.00/95.00/99.7%=13/13/13,Outliers=0,obl/obu=0/0) (0.126 ms/1745185821.913893)
[  1] 4.00-5.00 sec   128 KBytes  1.05 Mbits/sec   0.001 ms 0/89 (0%) 0.122/0.122/0.127/0.001 ms 89 pps 89/0(0) pkts 89/0/0 1071
[  1] 4.00-5.00 sec T8-PDF: bin(w=10us):cnt(89)=13:89 (5.00/95.00/99.7%=13/13/13,Outliers=0,obl/obu=0/0) (0.127 ms/1745185822.441008)
[  1] 5.00-6.00 sec   128 KBytes  1.05 Mbits/sec   0.001 ms 0/89 (0%) 0.122/0.122/0.127/0.001 ms 89 pps 89/0(0) pkts 89/0/0 1068
[  1] 5.00-6.00 sec T8-PDF: bin(w=10us):cnt(89)=13:89 (5.00/95.00/99.7%=13/13/13,Outliers=0,obl/obu=0/0) (0.127 ms/1745185823.416732)
[  1] 6.00-7.00 sec   129 KBytes  1.06 Mbits/sec   0.001 ms 0/90 (0%) 0.123/0.122/0.127/0.001 ms 90 pps 90/0(0) pkts 90/0/0 1080
[  1] 6.00-7.00 sec T8-PDF: bin(w=10us):cnt(90)=13:90 (5.00/95.00/99.7%=13/13/13,Outliers=0,obl/obu=0/0) (0.127 ms/1745185824.459744)
[  1] 7.00-8.00 sec   128 KBytes  1.05 Mbits/sec   0.001 ms 0/89 (0%) 0.123/0.123/0.127/0.001 ms 89 pps 89/0(0) pkts 89/0/0 1066
[  1] 7.00-8.00 sec T8-PDF: bin(w=10us):cnt(89)=13:89 (5.00/95.00/99.7%=13/13/13,Outliers=0,obl/obu=0/0) (0.127 ms/1745185825.424256)
[  1] 8.00-9.00 sec   128 KBytes  1.05 Mbits/sec   0.001 ms 0/89 (0%) 0.123/0.123/0.127/0.001 ms 89 pps 89/0(0) pkts 89/0/0 1064
[  1] 8.00-9.00 sec T8-PDF: bin(w=10us):cnt(89)=13:89 (5.00/95.00/99.7%=13/13/13,Outliers=0,obl/obu=0/0) (0.127 ms/1745185826.422409)
[  1] 9.00-10.00 sec   128 KBytes  1.05 Mbits/sec   0.001 ms 0/89 (0%) 0.123/0.123/0.127/0.001 ms 89 pps 89/0(0) pkts 89/0/0 1066
[  1] 9.00-10.00 sec T8-PDF: bin(w=10us):cnt(89)=13:89 (5.00/95.00/99.7%=13/13/13,Outliers=0,obl/obu=0/0) (0.127 ms/1745185827.431782)
[  1] 0.00-10.02 sec  1.25 MBytes  1.05 Mbits/sec   0.001 ms 0/894 (0%) 0.122/0.122/0.161/0.002 ms 81 pps 894/0(0) pkts 895/0/0 1074
[  1] 0.00-10.02 sec T8(f)-PDF: bin(w=10us):cnt(894)=13:893,17:1 (5.00/95.00/99.7%=13/13/13,Outliers=0,obl/obu=0/0) (0.161 ms/1745185818.179112)

rjmcmahon@rpi5-35:~ $ iperf -c 192.168.1.34 -i 1 -e --trip-times -u
------------------------------------------------------------
Client connecting to 192.168.1.34, UDP port 5001 with pid 24152 (1/0 flows/load)
TOS defaults to 0x0 (dscp=0,ecn=0) (Nagle on)
Sending 1470 byte datagrams, IPG target: 0.00 us (kalman adjust)
UDP buffer size:  208 KByte (default)
------------------------------------------------------------
[  1] local 192.168.1.35%eth0 port 52920 connected with 192.168.1.34 port 5001 (trip-times) on 2025-04-20 14:50:18.178 (PDT)
[ ID] Interval        Transfer     Bandwidth      Write/Err/Timeo  PPS
[  1] 0.00-1.00 sec   129 KBytes  1.06 Mbits/sec  90/0/0      90 pps
[  1] 1.00-2.00 sec   128 KBytes  1.05 Mbits/sec  89/0/0      89 pps
[  1] 2.00-3.00 sec   128 KBytes  1.05 Mbits/sec  89/0/0      89 pps
[  1] 3.00-4.00 sec   128 KBytes  1.05 Mbits/sec  89/0/0      89 pps
[  1] 4.00-5.00 sec   128 KBytes  1.05 Mbits/sec  89/0/0      89 pps
[  1] 5.00-6.00 sec   128 KBytes  1.05 Mbits/sec  89/0/0      89 pps
[  1] 6.00-7.00 sec   129 KBytes  1.06 Mbits/sec  90/0/0      90 pps
[  1] 7.00-8.00 sec   128 KBytes  1.05 Mbits/sec  89/0/0      89 pps
[  1] 8.00-9.00 sec   128 KBytes  1.05 Mbits/sec  89/0/0      89 pps
[  1] 9.00-10.00 sec   128 KBytes  1.05 Mbits/sec  89/0/0      89 pps
[  1] 0.00-10.02 sec  1.25 MBytes  1.05 Mbits/sec  894/0/0      81 pps
[  1] Sent 895 datagrams
[  1] Server Report:
[ ID] Interval        Transfer     Bandwidth        Jitter   Lost/Total  Latency avg/min/max/stdev PPS  Rx/inP  Read/Timeo/Trunc

      PS. I'd recommend 2.2.1.

       

  • Yunha Choi

    Yunha Choi - 2025-05-16

    Thanks for your reply.
    When I run iperf -s -u -e --histograms, and iperf -u --trip-times -e the result shows:

    [ ID] Interval        Transfer     Bandwidth        Jitter   Lost/Total  Latency avg/min/max/stdev PPS  Rx/inP  Read/Timeo/Trunc  NetPwr
[  1] 0.00-15.00 sec   562 MBytes   315 Mbits/sec   0.030 ms 51/401246 (0.013%) 0.236/0.174/1.132/0.066 ms -0 pps 401195/6(0) pkts 401196/0/0 166335
[  1] 0.00-15.00 sec T8(f)-PDF: bin(w=100us):cnt(401194)=2:81670,3:307775,4:5088,5:1025,6:1039,7:1775,8:1690,9:942,10:167,11:20,12:3 (5.00/95.00/99.7%u=0/0) (1.132 ms/1747374314.450849)

    I noticed that the bin width is shown as 100 μs, but according to the manual, the default bin width is supposed to be 1 ms. Which one is correct?
    Also, why is the PPS value shown as -0?

     

    • Yunha Choi

      Yunha Choi - 2025-05-16

      Oh, I can check this in the server header output.

      Server listening on UDP port 5001 with pid 43577
Read buffer size: 1.44 KByte (Dist bin width= 183 Byte)
Enabled receive histograms bin-width=0.100 ms, bins=10000 (clients should use --trip-times)
UDP buffer size:  208 KByte (default)
       

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