SD-WAN Architecture

Overlay vs Underlay

• Underlay: The physical network infrastructure (Internet, MPLS, LTE) that provides basic connectivity.
• Overlay: The logical, virtualized network built on top of the underlay using IPsec or other tunneling protocols.

Vendor Architectures

Cisco SD-WAN (Viptela)

• vManage: The management plane (NMS).
• vSmart: The control plane (brain).
• vEdge / cEdge: The data plane (routers).
• vBond: The orchestration plane.

FortiGate SD-WAN

Integrates SD-WAN functionality directly into the Next-Generation Firewall (NGFW), offering a security-driven networking approach without separate control and data plane appliances in standard deployments.