Having conducted a comparative analysis of the SSL inspection engines across Fortinet's hardware and cloud-native SASE offerings, I've arrived at a conclusion that may be contentious: the deep packet inspection and SSL decryption/re-encryption workflows executed on FortiGate hardware (specifically, models with dedicated SPUs) demonstrate superior efficacy and predictability compared to the current implementation within FortiSASE.
My assessment is based on several key operational dimensions where material differences are observable:
* **Inspection Depth and Context Awareness:** The hardware-based inspection, particularly with ASIC-offloaded sessions, maintains a more comprehensive state table and application control context throughout the decryption-inspection-re-encryption pipeline. In FortiSASE, while functional, I've observed more conservative handling of certain persistent, encrypted web socket connections, leading to either a fallback to certificate inspection only or a session bypass that would have been fully inspected on-premises.
* **Latency and Performance Predictability:** The performance penalty for SSL inspection in FortiSASE is inherently variable, dependent on the user's proximity to the cloud PoP and the current multi-tenant load. With hardware, the throughput and latency added by the inspection process are constants defined by the data sheet, allowing for precise capacity planning. For latency-sensitive internal applications accessed remotely, this variance can be problematic.
* **Troubleshooting and Log Fidelity:** The centralized FortiAnalyzer logs for a hardware FortiGate provide an uninterrupted, sequential view of the SSL inspection process. In FortiSASE's distributed cloud model, correlating events from the client connector, the cloud inspection node, and the web filtering service sometimes requires stitching together disparate log streams, which can obfuscate the root cause of an inspection failure.
Consider a simplified workflow comparison for an HTTPS request to a non-categorized domain:
**FortiGate Hardware Flow (Ideal)**
```
1. Session SYN received on physical interface.
2. SSL handshake intercepted; FortiGate presents its CA cert.
3. Session is offloaded to SPU for symmetric decryption.
4. Full packet payload inspected by IPS, Application Control, and Web Filter engines in a single pass.
5. Cleartext verdict logged under a single session ID.
6. Traffic re-encrypted and forwarded.
```
**FortiSASE Cloud Flow (Observed)**
```
1. Client connector establishes secure tunnel to nearest PoP.
2. PoP gateway terminates tunnel, initiates SSL inspection.
3. Decrypted stream is potentially routed to different logical services (AV, IPS, Filtering) which may reside in separate software containers.
4. Log events are generated by each microservice (Client Connector, Gateway, Web Filter).
5. Re-encrypted traffic is sent to origin server.
```
The architectural shift from an integrated, hardware-accelerated data plane to a disaggregated, software-defined cloud service introduces inherent trade-offs. The cloud version gains elasticity and ubiquitous coverage but, in its current iteration, sacrifices some of the deterministic inspection rigor and consolidated telemetry of its physical counterpart.
I am interested in whether others have performed similar data flow mappings or encountered specific scenarios where the cloud inspection behavior diverged from expected on-premises behavior, particularly concerning custom or complex web applications.
Agreed on the hardware being more predictable. You didn't mention the real kicker: the inspection penalty in SASE is a variable cost. Your bandwidth bill gets hit with those decryption cycles. On-prem, you paid your capex and the power is mostly fixed. The TCO model flips entirely when you push heavy inspection to their cloud.