Brick-wall limiters use look-ahead to guarantee no digital overs by anticipating peaks before they arrive

A brick-wall limiter delays the signal a small amount (the book says about two milliseconds) so it can anticipate an upcoming transient peak and catch it before it gets by. Because there is no possibility of overshoot, the signal will not exceed a predetermined level and there will be no digital overs. Analog limiters cannot predict their input this way, which is why digital look-ahead limiters achieve louder, cleaner ceilings and are the standard final-stage mastering tool.

Examples

A digital limiter set as a brick-wall with ~2 ms look-ahead lets the engineer gain several dB of apparent level just by controlling the program peaks, with no overs.

Assessment

What technical feature enables a brick-wall limiter to catch peaks without overs, and roughly how long is the typical look-ahead delay?