Call it Secure Access Service Edge (SASE), call it Secure Services Edge (SSE), call it Zero Trust Network Architecture (ZTNA), even call it the Service Edge — whatever the label, modern secure access looks nothing like the SSL/IPsec VPNs you’ve used for years. That’s because the application landscape has changed: apps live in multiple clouds, SaaS dominates, teams are distributed, and users expect fast, secure access from anywhere. VPNs were designed for a world where the data centre was the centre of everything. That world is gone.
From “castle and moat” to cloud-native access
Historically, enterprises kept most apps on-prem and routed remote users through a small number of VPN concentrators. That model tolerated wasteful backhaul, brittle firewall changes, and long change cycles because traffic and users were predictable. When remote work went mainstream, the limitations became obvious: VPN concentrators saturated, latency spiked, and IT teams were buried in firewall change tickets and routing problems.
SASE/SSE/ZTNA solve that by making access app-centric instead of network-centric. Instead of extending a user into your LAN (Layer-3 network extension), ZTNA authenticates and authorises each user-to-app session and only opens the exact access required. The heavy lifting is done in cloud PoPs close to the user or at app locations, reducing latency, avoiding backhaul, and enabling consistent policy enforcement across cloud, on-prem and branch.
What actually changes
- Performance — traffic to SaaS or cloud apps exits locally (closest PoP), not via an overloaded corporate gateway. That reduces latency and frees WAN circuits.
- Security — micro-segmentation and per-session access reduce lateral movement; policies are applied at the application layer, not by blunt network tunnels.
- Scale & resilience — providers run global PoPs and elastic control planes; you gain capacity without building a global VPN fabric.
- Operational simplicity — fewer firewall rule churns, fewer emergency change requests, and a centralised policy model that spans clouds and branches.
Why it matters in practice
SASE is not just “VPN in the cloud.” It’s a new architecture: orchestration + control plane + distributed enforcement. It transforms remote access from a brittle network extension into an auditable, programmable security service that aligns with modern app architectures and business needs.
Practical migration advice
Move in phases. Start with low-risk SaaS apps and pilot ZTNA connectors close to your cloud workloads. Run hybrid models during migration: keep legacy VPNs for stateful or non-cloudable apps while shifting web and SaaS traffic to SSE. Test legacy application behaviour (authentication, session stickiness, IP expectations) early — those are the usual blockers. Use PoVs to validate user experience, telemetry and failover behaviour before a full rollout.
How CACI Can Help You Transition to SASE and SSE
Making the move from legacy VPNs to modern secure access isn’t just a technology shift — it’s an architectural transformation. At CACI, we specialise in designing and deploying SASE and SSE solutions that fit your business model, application landscape and security posture. From initial assessments and phased migration planning to PoC validation and full-scale rollout, our experts ensure performance, resilience and compliance at every stage. Whether you need ZTNA for SaaS, hybrid models for legacy apps or global PoPs for distributed teams, we’ll help you build a secure access strategy that scales with your future.
Ready to start your transition? Get in touch with CACI today to discuss your secure access roadmap.