Firewalls

The New Perimeter, Part 1: A Short History of the Firewall

The perimeter-based defense model — a centralized, physical firewall guarding a well-defined network edge — is effectively obsolete. As business operations move to hybrid, multi-cloud environments, the “network boundary” now stretches to wherever an authorized user or workload happens to be running. ...

The New Perimeter, Part 2: SASE, ZTNA, and Policy as Code

Part 1 traced the firewall from stateless packet filters through NGFWs — four generations, each one built to close the previous generation’s blind spot. This part covers what happened once there was no longer a single perimeter to defend at all. ...

The New Perimeter, Part 3: Two Fronts — AI for the Firewall, Firewalls for AI

Part 1 covered the firewall’s evolution through NGFWs, and Part 2 covered the shift to SASE and Zero Trust. This part is where AI enters the picture — and it enters from two directions at once. ...

The New Perimeter, Part 4: Building an AI Security Gateway

Part 3 covered the AI Security Gateway conceptually — inbound, RAG-context, and outbound protection for GenAI traffic. This part is the actual build: a working deployment using LiteLLM, an Apache 2.0 open-source AI gateway, with Redis for state tracking and rate limiting. ...

The New Perimeter, Part 5: Agentic Firewalls and Post-Quantum Cryptography

This series has traced the firewall from stateless packet filters (Part 1) through SASE and Zero Trust (Part 2), the two-front AI security problem (Part 3), and a working AI Gateway deployment (Part 4). This last part looks at where the architecture goes from here — two directions, moving on very different timelines. ...