1. Introduction to Linux Traffic Control

1.1. Target audience and assumptions about the reader

The target audience for this HOWTO is the network administrator or savvy home user who desires an introduction to the field of traffic control and an overview of the tools available under Linux for implementing traffic control.

I assume that the reader is comfortable with UNIX concepts and the command line and has a basic knowledge of IP networking. Users who wish to implement traffic control may require the ability to patch, compile and install a kernel or software package [1]. For users with newer kernels (2.4.20+, see also Section 5.1), however, the ability to install and use software may be all that is required.

Broadly speaking, this HOWTO was written with a sophisticated user in mind, perhaps one who has already had experience with traffic control under Linux. I assume that the reader may have no prior traffic control experience.

1.2. Conventions

This text was written in DocBook (version 4.2) with vim. All formatting has been applied by xsltproc based on DocBook XSL and LDP XSL stylesheets. Typeface formatting and display conventions are similar to most printed and electronically distributed technical documentation.

1.3. Recommended approach

I strongly recommend to the eager reader making a first foray into the discipline of traffic control, to become only casually familiar with the tc command line utility, before concentrating on tcng. The tcng software package defines an entire language for describing traffic control structures. At first, this language may seem daunting, but mastery of these basics will quickly provide the user with a much wider ability to employ (and deploy) traffic control configurations than the direct use of tc would afford.

Where possible, I'll try to prefer describing the behaviour of the Linux traffic control system in an abstract manner, although in many cases I'll need to supply the syntax of one or the other common systems for defining these structures. I may not supply examples in both the tcng language and the tc command line, so the wise user will have some familiarity with both.

1.4. Missing content, corrections and feedback

There is content yet missing from this HOWTO. In particular, the following items will be added at some point to this documentation.

• A description and diagram of GRED, WRR, PRIO and CBQ.

• A section of examples.

• A section detailing the classifiers.

• A section discussing the techniques for measuring traffic.

• A section covering meters.

• More details on tcng.

I welcome suggestions, corrections and feedback at <mabrown@securepipe.com>. All errors and omissions are strictly my fault. Although I have made every effort to verify the factual correctness of the content presented herein, I cannot accept any responsibility for actions taken under the influence of this documentation.