The classful qdiscs are:
ATM Map flows to virtual circuits of an underlying
asynchronous transfer mode device.
CBQ Class Based Queueing implements a rich linksharing
hierarchy of classes. It contains shaping elements as
well as prioritizing capabilities. Shaping is performed
using link idle time calculations based on average packet
size and underlying link bandwidth. The latter may be ill-
defined for some interfaces.
DRR The Deficit Round Robin Scheduler is a more flexible
replacement for Stochastic Fairness Queuing. Unlike SFQ,
there are no built-in queues -- you need to add classes
and then set up filters to classify packets accordingly.
This can be useful e.g. for using RED qdiscs with
different settings for particular traffic. There is no
default class -- if a packet cannot be classified, it is
dropped.
DSMARK Classify packets based on TOS field, change TOS field of
packets based on classification.
ETS The ETS qdisc is a queuing discipline that merges
functionality of PRIO and DRR qdiscs in one scheduler. ETS
makes it easy to configure a set of strict and bandwidth-
sharing bands to implement the transmission selection
described in 802.1Qaz.
HFSC Hierarchical Fair Service Curve guarantees precise
bandwidth and delay allocation for leaf classes and
allocates excess bandwidth fairly. Unlike HTB, it makes
use of packet dropping to achieve low delays which
interactive sessions benefit from.
HTB The Hierarchy Token Bucket implements a rich linksharing
hierarchy of classes with an emphasis on conforming to
existing practices. HTB facilitates guaranteeing bandwidth
to classes, while also allowing specification of upper
limits to inter-class sharing. It contains shaping
elements, based on TBF and can prioritize classes.
PRIO The PRIO qdisc is a non-shaping container for a
configurable number of classes which are dequeued in
order. This allows for easy prioritization of traffic,
where lower classes are only able to send if higher ones
have no packets available. To facilitate configuration,
Type Of Service bits are honored by default.
QFQ Quick Fair Queueing is an O(1) scheduler that provides
near-optimal guarantees, and is the first to achieve that
goal with a constant cost also with respect to the number
of groups and the packet length. The QFQ algorithm has no
loops, and uses very simple instructions and data
structures that lend themselves very well to a hardware
implementation.
