It can use infrastructure operated by the organization, telecommunications providers, internet service providers, or a combination of them.
WAN connectivity may run over leased circuits, carrier Ethernet, Multiprotocol Label Switching, broadband internet, cellular, microwave, or satellite links. Virtual private networks and software-defined WAN overlays can combine or protect these underlays. Design choices affect path diversity, latency, bandwidth, failure behavior, routing control, observability, and provider dependence.
Key points
Primary roleCarry communications between distributed locations and services when one local network cannot provide the required reach.
ArchitectureIdentify underlays, overlays, routing boundaries, provider handoffs, internet exits, cloud on-ramps, and dependencies shared by supposedly diverse paths.
Resilience and performanceSize links for normal and recovery demand, test failover, monitor latency and loss, and verify that backup paths meet application and operational requirements.
Security treatmentAuthenticate and encrypt sensitive communications when the transport is not trusted, restrict reachable services, and monitor ingress, egress, and management paths.
Important limitationA private circuit, carrier service, or contractual service level does not by itself provide confidentiality, endpoint trust, secure routing, or uninterrupted availability.