This paper formally models and studies latency-insensitive systems (LISs) through max-plus algebra. We introduce state traces to model behaviors of LISs and obtain a formally proved performance upper bound achievable by latency-insensitive design. An implementation of the latency-insensitive protocol that can provide robust communication through back-pressure is also proposed. The intrinsic performance of the proposed implementation is acquired based on state traces. It is also proved that the proposed implementation can always reach the best performance achievable by latency-insensitive design.