Traffic & Rule Configuration
Bandwidth Composition & Overhead
Detailed Packet Analysis
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Cloud Firewall Capacity & Overhead Estimator
Understanding Cloud Firewall Capacity and Overhead
When designing cloud network architecture, engineers often focus solely on Bandwidth (Mbps/Gbps), neglecting the critical metrics that actually determine firewall performance: Packets Per Second (PPS) and Protocol Overhead. This calculator provides a comprehensive analysis of how your specific traffic patterns, encryption methods, and inspection rules impact the actual effective throughput (Goodput) and the processing load on your cloud firewalls.
The Importance of PPS (Packets Per Second)
Network appliances, including Cloud Firewalls (NGFW) and Load Balancers, are bound by CPU interrupt limits. A 10Gbps link saturated with small packets (e.g., DNS queries or VoIP) generates a massive number of packets per second, which can overwhelm the device's control plane long before the bandwidth limit is reached.
The formula for calculating PPS is:
Why it matters: If your estimated PPS exceeds the vendor's datasheet limit, you will experience packet drops and latency, even if your dashboard shows low bandwidth utilization.
Calculating Protocol Overhead
Every packet carries "tax" in the form of headers. When you add VPN tunnels (IPSec) or encryption (TLS), this tax increases, reducing the space available for your actual data.
Header Breakdown:
- Ethernet: 14 Bytes
- IPv4 Header: 20 Bytes
- TCP Header: 20 Bytes
- IPSec (ESP + Tunnel): ~50-80 Bytes
The Efficiency Ratio is calculated as:
Firewall Inspection Depth and Latency
Not all firewall rules are created equal. The depth of inspection dramatically affects latency:
- Stateless (L3/L4 ACLs): Lowest latency, simply checks IP/Port.
- Stateful Inspection: Tracks connection state (SYN/ACK/FIN), requiring memory and CPU.
- DPI (Deep Packet Inspection): Analyzes the payload (L7) for signatures, heavily taxing the CPU.
- SSL Decryption: The most resource-intensive task, decrypting traffic to inspect it and then re-encrypting it.
Use this calculator to right-size your cloud instances and anticipate network bottlenecks before deployment.