What type of WLAN attack is prevented with the use of a per-MPDU TKIP sequence...

TKIP (Temporal Key Integrity Protocol) was introduced with WPA to enhance WEP security. One of the security mechanisms used in TKIP is a per-MPDU (MAC Protocol Data Unit) sequence counter called the TSC (TKIP Sequence Counter). The TSC acts as a form of replay protection by assigning a unique sequence number to each transmitted frame. If a packet is received with a sequence number lower than or equal to a previously received number, it is discarded. This directly prevents replay attacks, where a malicious actor resends previously captured frames in an attempt to spoof the session or extract data.