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Manpages PRIOSection: Linux (8)Updated: 16 December 2001 Index Return to Main Contents NAMEPRIO - Priority qdiscSYNOPSIStc qdisc ... dev dev ( parent classid | root) [ handle major: ] prio [ bands bands ] [ priomap band,band,band... ] [ estimator interval timeconstant ]DESCRIPTIONThe PRIO qdisc is a simple classful queueing discipline that contains an arbitrary number of classes of differing priority. The classes are dequeued in numerical descending order of priority. PRIO is a scheduler and never delays packets - it is a work-conserving qdisc, though the qdiscs contained in the classes may not be.Very useful for lowering latency when there is no need for slowing down traffic. ALGORITHMOn creation with 'tc qdisc add', a fixed number of bands is created. Each band is a class, although is not possible to add classes with 'tc qdisc add', the number of bands to be created must instead be specified on the commandline attaching PRIO to its root.When dequeueing, band 0 is tried first and only if it did not deliver a packet does PRIO try band 1, and so onwards. Maximum reliability packets should therefore go to band 0, minimum delay to band 1 and the rest to band 2. As the PRIO qdisc itself will have minor number 0, band 0 is actually major:1, band 1 is major:2, etc. For major, substitute the major number assigned to the qdisc on 'tc qdisc add' with the handle parameter. CLASSIFICATIONThree methods are available to PRIO to determine in which band a packet will be enqueued.
QDISC PARAMETERS
CLASSESPRIO classes cannot be configured further - they are automatically created when the PRIO qdisc is attached. Each class however can contain yet a further qdisc.BUGSLarge amounts of traffic in the lower bands can cause starvation of higher bands. Can be prevented by attaching a shaper (for example, tc-tbf(8) to these bands to make sure they cannot dominate the link.AUTHORSAlexey N. Kuznetsov, <kuznet@ms2.inr.ac.ru>, J Hadi Salim <hadi@cyberus.ca>. This manpage maintained by bert hubert <ahu@ds9a.nl>
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