QoS shaper
QoS mechanism: smooth out traffic by buffering and delaying instead of dropping. Output rate capped at target — bursts handled through queue. Better for TCP bursty traffic than policer.
Distinct from policer: shaper buffers (queue size config), introduces latency but minimizes drops. Classic use: WAN link (limited uplink) → shape egress to 90% of link rate to avoid provider policing. Token-bucket algorithm also used, but exceed action is buffer instead of drop. Linux tc HTB is standard shaper. Buffer-bloat warning: large shaper queues + bad algorithm = catastrophic latency. CAKE/fq_codel combine shaping with smart queueing → low latency + bandwidth utilization.