Lamport timestamps are the simplest useful logical clock. Each process keeps one integer counter, and that counter moves forward on local events, sends, and receives.

The guarantee is narrow but important: if event A could have caused event B, then L(A) < L(B). That one-way property is enough for many ordering problems, but the reverse does not hold. A smaller Lamport timestamp does not prove A caused B.

This chapter covers the Lamport algorithm, the clock condition, total ordering with a tie-breaker, and where Lamport timestamps help and fall short.