In a serialized fashion, a queue is required to manage the outbound Because network links typically carry data Way of organizing the pending tasks or data (see also There are examples of queues in all sorts of software. The default qdisc under Linux is the pfifo_fast, which is Recommended to the Traffic Control using tcng and HTB HOWTO and LARTC HOWTO for The impatient soul, who simply wishes to experiment right now, is LARTC HOWTO, documentation from individual projects and importantly
This HOWTO represents the collection, amalgamation and synthesis of the The components of the Linux traffic control The traffic control subsystem which has grown and matured under kernels Few inside the communityĪnd fewer outside the Linux community are aware of the tremendous power of Services which can run on the operating system. (netfilter, and before that, ipchains) as well as hundreds of network The tools available under Linux for packet mangling and firewalling The larger Linux community is very familiar with Linux offers a very rich set of tools for managing and manipulating the ADSL Bandwidth HOWTO script ( myshaper) 9.3. Scripts for use with QoS/Traffic Control 9.1. Sharing/splitting bandwidth based on IP 9. Sharing/splitting bandwidth based on flows 8.5. Handling a link with a variable (or unknown) bandwidth 8.4. Handling a link with a known bandwidth 8.3.
General Rules of Linux Traffic Control 8.2. HFSC, Hierarchical Fair Service Curve 7.3. Classful Queuing Disciplines ( qdiscs) 7.1. ESFQ, Extended Stochastic Fair Queuing 6.5. FIFO, First-In First-Out ( pfifo and bfifo) 6.2. Classless Queuing Disciplines ( qdiscs) 6.1. tcng, Traffic Control Next Generation 5.4. Traditional Elements of Traffic Control 3.1. Missing content, corrections and feedback 2. Target audience and assumptions about the reader 1.2.
Introduction to Linux Traffic Control 1.1. Yet another Buzzword bingo term means the prioritization of TCP ACK-packets on the upload-side.Table of Contents 1. Traffic Policing is the practice of dropping, marking or ignoring ingress packets that don't comply with user-defined criteria.įilters are used by classful QDiscs to determine which class a packet will be queued to. Traffic Shaping is the process of delaying packets to limit egress traffic to a maximum rate or smooth bursts. A filter contains a number of conditions which if matched, make the filter match.Ī QDisc may, with the help of a classifier, decide that some packets need to leave earlier than others. Parent class can dynamically pass bandwidth to leaf-classes.Ĭlass that has another class or a QDisc as parent and contains classes.Ĭlassification can be performed using filters. Leaf classes give unused bandwidth back to their parent class. Always contains a QDisc! In case one is not configure, the default pfifo_fast is used. Classes do not have a queue, do not contain any network packets and cannot contain filters.Įnd class without any child classes. This means that they sometimes refuse to pass a packet, even though they have one available.Ĭlasses are sub-QDiscs which allow the user to configure QoS in more detail. It does NOT “shape” packets.Ī non-work-conserving QDiscs may delay packets and “shape” them. Some of these classes contain a further QDisc, which may again be classful, but need not be.Ī work-conserving QDisc never delays packets. For practical purposes, the ingress qdisc is merely a convenient object onto which to attach a policer to limit the amount of traffic accepted on a network interface.Ī QDisc with no configurable internal subdivisions.Ĭontains multiple classes. The location where ingress (incoming traffic) filters can be attached. It can contain any of the queuing disciplines (qdiscs) with potential classes and class structures. Not an actual queuing discipline (QDisc), but rather the location where traffic control structures can be attached to an interface for egress (outbound traffic). Its classes are sometimes called bands.Īn algorithm that manages the queue of a device, either incoming (ingress) or outgoing (egress). Note: The PRIO QDisc does contain three classes, but since they cannot be configured further, PRIO is considered to be a classless QDisc. Limit bandwidth, does not work above 1mbit Link sharing and low delay at the same timeĮasiest configuration of link sharing, derived from CBQ, high CPU usageĭistibutes bandwidth for known tcp-connections fairly Removed in mainline kernel, but still available in OpenWrt The Controlled-Delay Active Queue ManagementĪvailable since r31756 and r31757, mainlined in Kernel 3.5Ĭan handle packets of variable size without knowing their mean size.
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