Latency and Loss in an IoT Gateway: A Discrete-Event Simulation of M/M/1, M/D/1 and M/M/1/K Queues

IoT gateways collect messages from many sensors and forward them to a network or a cloud service, and their queueing delay determines whether real-time requirements can be met. This paper simulates a single-server gateway with a service rate of 100 messages per second under Poisson arrivals and compares the simulated mean latency, the 99th percentile and the loss probability of a finite buffer with the analytical formulas for M/M/1, M/D/1 and M/M/1/K queues. The simulated mean latency agreed with theory within 2.5 % for utilisations from 0.1 to 0.95. The mean latency rose from 20 ms at utilisation 0.5 to 100 ms at 0.9 and 200 ms at 0.95, with a 99th-percentile latency of 480 ms at 0.9. Deterministic service halved the queueing delay compared with exponential service. A buffer of 20 messages lost 1.4 % of the messages at utilisation 0.9. The study assumes Poisson traffic, which is smoother than the bursty traffic of many real IoT deployments. This is a simulation study; all results are outputs of the deposited Python code with assumed parameters. Source code is attached.