---

   tc    ( 8 )

---

CLASSLESS QDISCS

The classless qdiscs are:

choke CHOKe (CHOose and Keep for responsive flows, CHOose and Kill for unresponsive flows) is a classless qdisc designed to both identify and penalize flows that monopolize the queue. CHOKe is a variation of RED, and the configuration is similar to RED.

codel CoDel (pronounced "coddle") is an adaptive "no-knobs" active queue management algorithm (AQM) scheme that was developed to address the shortcomings of RED and its variants.

[p|b]fifo Simplest usable qdisc, pure First In, First Out behaviour. Limited in packets or in bytes.

fq Fair Queue Scheduler realises TCP pacing and scales to millions of concurrent flows per qdisc.

fq_codel Fair Queuing Controlled Delay is queuing discipline that combines Fair Queuing with the CoDel AQM scheme. FQ_Codel uses a stochastic model to classify incoming packets into different flows and is used to provide a fair share of the bandwidth to all the flows using the queue. Each such flow is managed by the CoDel queuing discipline. Reordering within a flow is avoided since Codel internally uses a FIFO queue.

fq_pie FQ-PIE (Flow Queuing with Proportional Integral controller Enhanced) is a queuing discipline that combines Flow Queuing with the PIE AQM scheme. FQ-PIE uses a Jenkins hash function to classify incoming packets into different flows and is used to provide a fair share of the bandwidth to all the flows using the qdisc. Each such flow is managed by the PIE algorithm.

gred Generalized Random Early Detection combines multiple RED queues in order to achieve multiple drop priorities. This is required to realize Assured Forwarding (RFC 2597).

hhf Heavy-Hitter Filter differentiates between small flows and the opposite, heavy-hitters. The goal is to catch the heavy-hitters and move them to a separate queue with less priority so that bulk traffic does not affect the latency of critical traffic.

ingress This is a special qdisc as it applies to incoming traffic on an interface, allowing for it to be filtered and policed.

mqprio The Multiqueue Priority Qdisc is a simple queuing discipline that allows mapping traffic flows to hardware queue ranges using priorities and a configurable priority to traffic class mapping. A traffic class in this context is a set of contiguous qdisc classes which map 1:1 to a set of hardware exposed queues.

multiq Multiqueue is a qdisc optimized for devices with multiple Tx queues. It has been added for hardware that wishes to avoid head-of-line blocking. It will cycle though the bands and verify that the hardware queue associated with the band is not stopped prior to dequeuing a packet.

netem Network Emulator is an enhancement of the Linux traffic control facilities that allow to add delay, packet loss, duplication and more other characteristics to packets outgoing from a selected network interface.

pfifo_fast Standard qdisc for 'Advanced Router' enabled kernels. Consists of a three-band queue which honors Type of Service flags, as well as the priority that may be assigned to a packet.

pie Proportional Integral controller-Enhanced (PIE) is a control theoretic active queue management scheme. It is based on the proportional integral controller but aims to control delay.

red Random Early Detection simulates physical congestion by randomly dropping packets when nearing configured bandwidth allocation. Well suited to very large bandwidth applications.

rr Round-Robin qdisc with support for multiqueue network devices. Removed from Linux since kernel version 2.6.27.

sfb Stochastic Fair Blue is a classless qdisc to manage congestion based on packet loss and link utilization history while trying to prevent non-responsive flows (i.e. flows that do not react to congestion marking or dropped packets) from impacting performance of responsive flows. Unlike RED, where the marking probability has to be configured, BLUE tries to determine the ideal marking probability automatically.

sfq Stochastic Fairness Queueing reorders queued traffic so each 'session' gets to send a packet in turn.

tbf The Token Bucket Filter is suited for slowing traffic down to a precisely configured rate. Scales well to large bandwidths.