Reference Guide

Figure 30. CoPP Implemented Versus CoPP Not Implemented
Configure Control Plane Policing
The S4820T can process a maximum of 4200 packets per second (PPS). Protocols that share a single
queue may experience flaps if one of the protocols receives a high rate of control traffic even though per
protocol CoPP is applied. This happens because queue-based rate limiting is applied first.
For example, border gateway protocol (BGP) and internet control message protocol (ICMP) share same
queue (Q6); Q6 has 400 PPS of bandwidth by default. The desired rate of ICMP is 100 PPS and the
remaining 300 PPS is assigned to BGP. If ICMP packets come at 400 PPS, BGP packets may be dropped
though ICMP packets are rate-limited to 100 PPS. You can solve this by increasing Q6 bandwidth to 700
PPS to allow both ICMP and BGP packets and then applying per-flow CoPP for ICMP and BGP packets.
The setting of this Q6 bandwidth is dependent on the incoming traffic for the set of protocols sharing the
same queue. If you are not aware of the incoming protocol traffic rate, you cannot set the required
queue rate limit value. You must complete queue bandwidth tuning carefully because the system cannot
open up to handle any rate, including traffic coming at the line rate.
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Control Plane Policing (CoPP)