tc qdisc
also: traffic control, queueing discipline, tc
A Linux command-line tool that manages Quality of Service (QoS) by configuring traffic control queuing disciplines to shape, prioritize, and rate-limit network traffic.
tc qdisc (traffic control queueing discipline) is part of the iproute2 package and allows you to control how the kernel queues and transmits network packets on an interface. It lets you implement traffic shaping, bandwidth limiting, packet prioritization, and packet dropping policies.
A qdisc is the algorithm the kernel uses to decide which packets to send first when the network interface cannot transmit them all immediately. Common qdiscs include pfifo_fast (default), htb (Hierarchical Token Bucket for complex rate limiting), and fq_codel (modern congestion control).
Example: tc qdisc add dev eth0 root tbf rate 10mbit burst 32kbit latency 400ms limits outgoing traffic on eth0 to 10 Mbps using the TBF (Token Bucket Filter) qdisc. Without such rules, a single application can consume all available bandwidth.