IPerf3 UDP test requires TCP ports to be opened in firewall as well

[MightyChee]

Trying with udp test, I deployed iperf in azure vm (windows 10), i had the following networking Inbound port rules and the test failed, Iperf client was unable to connect to Iperf Server.

server command: Iperf3.exe -s -i 1 -p 5201 -f KBytes

But as soon as i changed the TCP port setting as below, then the test went ok.

Anyone know why UDP test need the same UDP port number to be opened in TCP port setting as well?

Thank you

[davidBar-On]

Hi, the control interface between the server and client is always over TCP, even if the test itself is UDP.

[MightyChee]

Hi, thank you for replying.

Is that mean Iperf works like Twamp which it has control phase (tcp) and test phase (udp/tcp depending on the protocol chosen)?

[davidBar-On]

Is that mean Iperf works like Twamp which it has control phase (tcp) and test phase (udp/tcp depending on the protocol chosen)?

I am not familiar with Twmap, but by briefly reading this explanation it seems that the answer is yes, when only two entities are used as shown in Figure 2. The iperf3-control and the TWAMP-control interfaces have similar usages. Note that these interfaces are used throughout the test and not only to start a test - the Twamp description say "TWAMP-Control - Initiates, starts, and ends test sessions".