The support for quality of service is available from linux kernel versions 2.1.90. However, the support is more comprehensive in the more recent kernels. This document is written with reference to the kernel version 2.2.1. This kernel also has support for differentiated services in the form of a patch, that can be downloaded from ftp://lrcftp.epfl.ch/pub/linux/diffserv/patches/ds-3.patch.gz. This patch needs to be applied in order to exercise all the QoS features supported in linux. The latest linux kernels can be downloaded from http://www.kernelnotes.org/.
Having discussed the configuration of the QoS support in linux, let us now discuss the details involved in the implementation of these features. The location of all the kernel related files referred to in the rest of this document are specified with respect to the /usr/src/linux directory.