A fine-grained network traffic analysis with Millisampler

Introduced Millisampler, a lightweight, fine-grained network traffic characterization tool. Millisampler uses an eBPF-based tc filter to collect time series data on ingress/egress traffic volumes, active flows, ECN marks, and retransmissions at configurable timescales (100us, 1ms, 10ms). It employs per-CPU variables to avoid locks and samples periodically to minimize overhead, storing data locally for on-demand analysis. Millisampler has been instrumental in debugging network performance issues, such as synchronized traffic bursts and NIC driver bugs, and in characterizing traffic patterns for service performance optimization.