The packets that are destined for the CPU are prioritized based on the application. Some of the applications that are prioritized are Layer 2 data packets used for MAC learning (a copy of which is sent to CPU for MAC learning), EFM, CFM/Y.1731, STP, LACP, ICMP, TWAMP, and so on. A set of queues are used to queue packets to the CPU. The number of queues varies per 7210 SAS platform:
The 7210 SAS-D has 21 queues.
The 7210 SAS-Dxp has 8 queues.
The packets destined for the CPU are classified internally and are put into the correct queue. These packets are rate-limited to prevent DoS attacks. The software programs the classification entries to identify these packets and assigns appropriate bandwidth and priority to them. It is not configurable by the user.