High CPU utilization coupled with a high rate of new sessions per second, despite relatively low overall bandwidth, is a strong indicator that the firewall is spending a disproportionate amount of time processing the first packet of many sessions, which occurs on the slow path. The slow path is CPU-intensive because it involves App-ID lookup, policy matching, session creation, NAT/routing decisions, and security profile assignment. - Option A: Long-lived, established sessions are primarily handled by the fast path after the initial setup. While security profiles add some overhead, the core processing of established flow is hardware-accelerated, not CPU bound for simple forwarding. - Option B: While NAT involves slow path processing for the first packet (or connections requiring dynamic NAT allocation), established sessions with NAT are handled efficiently by the fast path using the created session state. - Option C (Correct): A large volume of short-lived connections, especially if they vary widely in destination and application, means the firewall must process the first packet of each connection individually on the slow path. This puts a heavy load on the CPU for session setup, even if the data transferred within each session is small. This is a classic scenario causing high 'sessions per second' and thus high slow-path CPU load. - Option D: Established UDP sessions, once identified by App-ID and allowed by policy, are also typically handled efficiently by the fast path (or hardware session acceleration), similar to TCP established sessions. - Option E: Policies allowing traffic with no security profiles still require App-ID identification and policy lookup for the first packet, putting it on the slow path for session creation. However, this processing is generally less intensive than processing requiring deep inspection, and the bottleneck described points to the volume of new sessions overwhelming the CPU's ability to perform the initial setup, which is exacerbated by complex policies or varied traffic, but fundamentally driven by the 'new session' rate.