Traffic policing

Traffic policing

The FortiGate unit begins to process traffic as it arrives (ingress) and departs (egress) on an interface. In later phases of the network processing, such as enforcing maximum bandwidth use on sessions handled by a security policy, if the current rate for the destination interface or traffic regulated by that security policy is too high, the FortiGate unit may drop the packet. Time spent on prior processing, such as web filtering, decryption or IPS, is often wasted on packets that are not forwarded. This applies to VLAN interfaces and physical interfaces.

You can prevent this wasted effort on ingress by configuring the FortiGate unit to preemptively drop excess packets when they are received at the source interface, before most other traffic processing is performed:

config system interface edit <interface_name>

set inbandwidth <rate_int>

next end

where <rate_int> is the bandwidth limit in Kb/s. Excess packets will be dropped. If inbandwidth is 0, the rate is not limited.

A similar command is available that can be performed on egress as well using the CLI commands:

config system interface edit <interface_name>

set outbandwidth <rate_int>

next end

 

As with ingress, setting the rate to 0 (zero) sets the rate to unlimited.

Rate limiting traffic accepted by the interface enables you to restrict incoming traffic to rates that, while no longer the full capacity of the interface, at the traffic shaping point in the processing are more likely to result in acceptable rates of outgoing traffic per destination interface or all security policies. This conserves FortiGate processing resources for those packets that are more likely to be viable completely to the point of egress.

Excessive traffic policing can degrade network performance rather than improve it. For more details on factors that affect traffic policing, see Important considerations on page 2473.


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