FireBrick FB6402, Руководство пользователя

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Traffic Shaping
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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.
10.1.3. Ad hoc shapers
You can define a
shaper
object and set the speed controls for that shaper, and then define the
graph
attribute
on something, e.g. an interface, to apply that shaper to the interface.
It is also possible, in most cases, to simply set a
speed
attribute on some object. This creates an un-named
shaper (so no graph) which has the specified speed for egress (tx). This is unique to that object unlike named
shapers which are shared between all objects using the same named shaper.
It is also possible to set
graph
and
speed
attributes to create a named shaper with the specified speed, without
having to create a separate
shaper
object.
If you set a graph attribute without a speed attribute or creating a shaper object then that simply creates
a graph without traffic shaping. Multiple objects can share the same graph.
Graphs can sometimes be created automatically and may have speeds applied.
10.1.4. Long term shapers
If defining a shaper using the
shaper
object there are a number of extra options which allow a long term
shaper to be defined. A long term shaper is one that changes the actual speed applied dynamlically to ensure
a long term usage level that is within a defined setting.
The key parameters for the long term shaper are the target speed (e.g.
tx
), the minimum speed (e.g.
tx-min
)
and maximum speed (e.g.
tx-max
). The target speed is what is normally used if nothing else is set, but if a
min and max are set then the shaper will actually use the max speed normally.
However, if the usage exceeds the target speed then this is considered to be bursting and this continues until
the average speed since the bursting started drops below the target speed.
When bursting, a time is intially allowed with no change of speed (e.g. tx-min-burst ) and after that the
speed drops. This can be automatic, or using a rate of drop per hour (e.g. tx-step ). The rate will drop down
to the defined minimum speed.
Once the average, since bursting started, drops below the target and the restrictions are lifted, returning to the
maximum speed. If the minimum speed is below the target speed then this will happen eventually even if the
link is used solidly at the maximum it is allowed. If the minimum is at the target or higher then the usage will
have to drop below the target for a time before the average speed drops low enough to restore full speed.
The overall effect of this means that you can burst up to a specified maximum, but ultimately you cannot transfer
more than if the target speed had been applied the whole time.
10.2. Multiple shapers
A packet that passes through the FB6000 can pass through multiple shapers, for example