What does MSL stand for in TCP and why is it used in TIME_WAIT calculations?

• A. Maximum Segment Lifetime
• B. Maximum Segment Length
• C. Managed Segment Latency
• D. Multi-Segment Link

Answer: (A)

Maximum Segment Lifetime is the maximum time a TCP segment could exist in the network before being discarded. This value is used to compute the TIME_WAIT duration, which is typically 2 × MSL. The reason for this two-times multiplier is to ensure that any late-arriving or duplicate segments from the old connection cannot be mistaken for part of a new connection using the same endpoints. Since network delays and retransmissions can cause old segments to linger, waiting for twice the MSL provides a safe window for those segments to die off before a new connection starts. The exact MSL is an estimate and can vary by implementation (often around 30 seconds), so TIME_WAIT is commonly around 60 seconds, though some environments may choose different values.