Technical data
4. Packages
DSCP* Differentiated Services Code Point
DSCP is a marking according to RFC 2474. This process has replaced TOS
marking mostly since 1998.
Filters on DSCP-classes can be configured as follows:
QOS_FILTER_x_OPTION='DSCPef'
QOS_FILTER_x_OPTION='DSCPcs3'
Please note that DSCP is in capital letters while the class is lower case.
The following classes can be used:
af11-af13, af21-af23, af31-af33, af41-af43, cs1-cs7, ef und be (Standard)
4.18.2. Examples
How do we configure OPT_QoS in detail? This will be shown below for some use cases:
• Example 1: targets at spreading bandwidth between 3 clients.
• Example 2: targets at spreading bandwidth between 2 clients and on the clients between
one port and the rest of the traffic on this client.
• Example 3: targets at learning the general structures of working with QoS.
• Example 4: a configuration for preferring ACK packets in order to keep downstream high
even if upstream is overloaded.
Example 1
Spreading bandwidth between 3 clients.
Four classes are created (see QOS_CLASS_N) with the following speeds (see QOS_CLASS_x_-
MINBANDWIDTH / QOS_CLASS_x_MINBANDWIDTH). They are subclasses of class 0 (see QOS_CLASS_-
x_PARENT) and therefore are bound directly to the interface for “up” res. “down” (see QOS_-
CLASS_x_DIRECTION).
The fourth class is only for visitors and gets lesser bandwidth. By QOS_INTERNET_DEFAULT_-
DOWN=’4’ all traffic not filtered is queued to the forth “guest” class. Because we seldom have
visitors and the bandwidth is the same for the other 3 classes clients get 1/3 of the overall
bandwidth (256Kibit/s each).
This configuration is only a beginning. It has to be specified how traffic is regulated by the
classes.
We use two filters to assign traffic to the classes. We create 3 filters, one for each of
the 3 clients (see QOS_FILTER_N a.s.o.) and attach a filter to each class (see QOS_FILTER_x_-
CLASS). By specifying QOS_FILTER_x_IP_INTERN, QOS_FILTER_x_IP_INTERN, QOS_FILTER_x_PORT,
QOS_FILTER_x_PORT and QOS_FILTER_x_OPTION it can be defined what rules apply to each class.
Let’s call the interface 0, the 3 classes 1, 2 and 3 and the 3 filters F1, F2 and F3. The
scenario looks like this image 4.7.
Configuration looks like this:
Three client PCs filtered by IP with 1/3 bandwidth each if visitors are absent:
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