SD-WAN - Control Plane

Fabric Discovery & Control: Facilitates fabric discovery and distributes control plane information, data plane policies, and application-aware routing policies to WAN Edge routers.

Policy Implementation: Executes control plane policies (e.g., service chaining, multitopology, multihop).

Simplicity & Resilience: Drastically reduces control plane complexity and is highly resilient.

OMP Protocol: SD-WAN Controllers run the Overlay Management Protocol (OMP) with each other and with WAN Edge routers to facilitate fabric discovery.

Data Plane Establishment: Controllers and WAN Edge routers distribute essential data to establish direct data plane connectivity between WAN Edge routers.

Shared Data Types: This distributed information includes LAN-side reachability, transport-side IP addressing, IPsec encryption keys, site identifiers, and other details.

Route Reflector Model: WAN Edge routers send all control updates to an SD-WAN Controller, which reflects them to all remote sites.

No Direct Control Channels: Because of this centralized model, every router learns about all tunnel endpoints and user prefixes without needing direct control channels between each other.

Policy Distribution: Controllers distribute data plane and application-aware routing policies to WAN Edge routers for local enforcement.

Control Plane Policies: Policies affecting control plane info are enforced directly on the controllers. They influence traffic flow across the fabric and implement:

• Service chaining (e.g., inserting firewalls in the data path).

• Topologies (e.g., hub-and-spoke, partial-mesh, full-mesh).

Solving n^2 Complexity: Centralization eliminates the high control plane load traditionally needed for large IPsec networks, solving the n^2 complexity issue.

Scalability & Resiliency: The controller deployment model ensures horizontal scaling and high availability.

Deployment Options:

• Geographically Dispersed: Often placed in separate physical data centers to prevent total control plane failure.

• Cisco Cloud Service: Redundantly hosted in the Cisco cloud.

• On-Premises: Deployed by the customer, who must then provide the infrastructure resiliency.