Traffic Policing Behaviors

Traffic policing is the process of monitoring network traffic for compliance with a traffic policy and then enforcing that policy.

• Policing actions are applicable only to data traffic.
• When a Layer 2 control protocol is not enabled on an interface, packets are dropped at ingress and are subject to ingress policing.
• If the configured CBS value is less than 2*(default MTU) value, then 2*(default MTU) is programmed as the committed burst size (CBS) in the hardware. For example, you configure CBS at 2000 bytes and the default MTU on an interface is 1548 bytes. When a policy map is applied on this interface, the CBS programmed in the hardware is 2*MTU (3096 bytes). If you update the MTU value, the CBS value is not updated.
• When the CBS and excess burst size (EBS) values are not configured, the values are derived from the committed information rate (CIR) and excess information rate (EIR), respectively. The burst size calculation is as follows:
  

  Burst size (CBS or EBS) = (1.2 × information rate (CIR or EIR)) ÷ 8 

• The underlying architecture of SLX 9740 supports the burst size only upto 256MegaBytes, Any higher Burst size configuration will result in Operational Burst size of 256MegaBytes.
• You are responsible for configuring configure rate limit threshold values on an interface based on interface speed. No validation is performed for user-configured values against the interface speed.
• Because CIR is a mandatory policing attribute, you cannot delete the CIR parameter. However, you can delete the CIR attribute by using the no police command in policy-map-class sub-mode.
• Packet drops caused by any action other than the ACL are included in the policing counter.
• Layer 3 control packets are policed at the egress side.
• When you attempt to bind the policer with a configured CIR or EIR value that is less than minimum supported CIR of the platform, the operational CIR or EIR value becomes zero and you receive a syslog notification on the console.
• The minimum CIR/EIR in SLX 9150, SLX 9250 and SLX 9740 platforms is 1000 bits/sec.
• The minimum cir/eir in SLX 9540 is 22000 bits/sec. On SLX 9640 minimum cir/eir is 26000 bits/sec.
• Unknown-unicast storm control does not rate limit the VLL or P2P traffic in the default TCAM profile.
• When an ingress service policy is bound on a port channel that has multiple member ports, then all port-channel member ports that belong to the same chip-core are governed by the same policy. The configured rate is per chip-core. For example:
  • A service policy with a CIR or EIR value of 10 Gpbs is applied on port channel 10. Port channel 10 has member ports 1/1 and 1/3 that belong to chip 1-core 0. So the total rate-limit value for the port channel is 10 Gpbs.
  • A service policy with a CIR or EIR value of 10 GPBS is applied on port channel 10. Port channel ten has member ports 1/6 and 1/13 that belong to chip 1-core 0, and chip 1-core 1. So the total rate-limit value of the port channel is 2*10, or 20 Gpbs.
  • A service policy with a CIR or EIR value of 10 GPBS is applied on port channel 10. Port channel ten has member ports 1/10 and 3/10 that belong to chip 1-core x, and chip 3-core x. So the total rate-limit value of the port channel is 2*10, or 20 Gpbs.