# What is a Wide Area Network (WAN)?

> A wide area network (WAN) is a physical or logical network that connects users, sites, data centers, cloud environments, or other networks across a broader geographic area than a local area network.

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## Content

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 role:** Carry communications between distributed locations and services when one local network cannot provide the required reach.
- **Architecture:** Identify underlays, overlays, routing boundaries, provider handoffs, internet exits, cloud on-ramps, and dependencies shared by supposedly diverse paths.
- **Resilience and performance:** Size links for normal and recovery demand, test failover, monitor latency and loss, and verify that backup paths meet application and operational requirements.
- **Security treatment:** Authenticate and encrypt sensitive communications when the transport is not trusted, restrict reachable services, and monitor ingress, egress, and management paths.
- **Important limitation:** A private circuit, carrier service, or contractual service level does not by itself provide confidentiality, endpoint trust, secure routing, or uninterrupted availability.

### Related terms

[Multiprotocol Label Switching (MPLS)](<https://yellowcube.eu/glossary/multiprotocol-label-switching/>) · [Software-defined wide area network (SD-WAN)](<https://yellowcube.eu/glossary/software-defined-wide-area-network/>) · [Virtual private network (VPN)](<https://yellowcube.eu/glossary/virtual-private-network/>) · [Secure access service edge (SASE)](<https://yellowcube.eu/glossary/secure-access-service-edge/>) · [Network latency](<https://yellowcube.eu/glossary/network-latency/>) · [Border Gateway Protocol (BGP)](<https://yellowcube.eu/glossary/border-gateway-protocol/>) · [WAN aggregation](<https://yellowcube.eu/glossary/wan-aggregation/>)

### Sources

[NIST glossary: Wide Area Network](https://csrc.nist.gov/glossary/term/wide_area_network) · [NIST SP 800-215: Guide to a Secure Enterprise Network Landscape](https://csrc.nist.gov/pubs/sp/800/215/final)

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