RTS Threshold is used to enable/disable RTS/CTS mechanism in NetSim. RTS/CTS is enabled if RTS Threshold value is set less than or equal to the MAC frame size. RTS-CTS is disabled if RTS Threshold value is set greater than the MAC frame size.
For eg:
For an application layer packet of size 1460 running UDP, the frame size at MAC will be 1488 bytes (1460 bytes + 8 bytes (UDP overhead) + 20 bytes (IP overhead)), RTS/CTS will be enabled if RTS Threshold is set to a value less than or equal to 1488.
Please see section 8.4 (in v13.2, or the appropriate section in any other version) of the User Manual to know more about the packet trace. Studying the packet trace is a good way to observe the simulation evolution and understand the protocol working. The trace file will also show you RTS-CTS-DATA-ACK flows in 802.11.
Related articles:
1. how-do-i-configure-802-11-simulation-for-rts-cts-to-work-
2. Modeling Interference in NetSim WiFi (WLAN 802.11): https://support.tetcos.com/a/solutions/articles/14000139111