Chapter 10. Traffic Shaping

Table of Contents

10.1. Graphs and Shapers
10.1.1. Graphs
10.1.2. Shapers

The FB2500 includes traffic shaping functionality that allows you to control the speed of specific traffic flows through the FB2500. The FB2500 also provides graphing functionality, allowing specific traffic flows to be plotted on a graph image (PNG format) that the FB2500 generates. Within the FB2500, traffic shaping and graphing are closely associated, and this is reflected in how you configure traffic shaping - in order to be able to perform traffic shaping, you must first graph the traffic flow.

10.1. Graphs and Shapers

10.1.1. Graphs

Several objects in the FB2500's configuration allow you to specify the name of a graph, by setting the value of the graph attribute. This causes the traffic flow that is associated with that object (a firewall rule, an interface, or whatever the attribute is attached to) to be recorded on a graph with the specified name. For connections that have a defined state, such as a PPP link, the graph will also show the link state history. Other information, such as packet loss and latency may also be displayed, depending on whether it can be provided by the type of object you are graphing.

For example, the XML snippet below shows the graph attribute being set on an interface. As soon as you have set a graph attribute (and saved the configuration), a new graph with the specified name will be created.

 <interface name="LAN"
            port="LAN"
            graph="LAN">
       

The graph is viewable directly (as a PNG image) from the FB2500 via the web User Interface - to view a graph, click the "PNG" item in the "Graphs" menu. This will display all the graphs that are currently configured - it is not currently possible to show a single graph within the web User Interface environment.

Note

You may find images shown for graph names that are no longer specified anywhere in the configuration. Over time, these graphs will disappear automatically.

Alternatively, the underlying graph data is available in XML format, again via the FB2500's built-in HTTP server. The XML version of the data can be viewed in the web User Interface by clicking the "XML" item in the "Graphs" menu, and then clicking on the name of the graph you're interested in.

Both directions of traffic flow are recorded, and are colour-coded on the PNG image generated by the FB2500. The directions are labelled "tx" and "rx", but the exact meaning of these will depend on what type of object the graph was referenced from - for example, on a graph for an interface, "tx" will be traffic leaving the FB2500, and "rx" will be traffic arriving at the FB2500.

Each data point on a graph corresponds to a 100 second interval ; where a data point is showing a traffic rate, the rate is an average over that interval. For each named graph, the FB2500 stores data for the last 24 hours.

Note

Specifying a graph does not itself cause any traffic shaping to occur, but is a pre-requisite to specifying how the associated traffic flow should be shaped.

10.1.2. Shapers

Once you have graphed a (possibly bi-directional) traffic flow, you can then also define speed restrictions on those flows. These can be simple "Tx" and "Rx" speed limits or more complex settings allowing maximum average speeds over time.

You define the speed controls associated with the graphed traffic flow(s) by creating a shaper top-level object. To create or edit a shaper object in the web User Interface, first click on the "Shape" category icon. To create a new object, click the "Add" link. To edit an existing object, click the appropriate "Edit" link instead.

The shaper object specifies the parameters (primarily traffic rates) to use in the traffic shaping process, and the shaper is associated with the appropriate existing graph by specifying the name attribute of the shaper object to be the same as the name of the graph.