# What is Multiprotocol Label Switching (MPLS)?

> Multiprotocol Label Switching (MPLS) is a forwarding architecture in which network devices assign packets to a forwarding equivalence class and use short labels to direct them across an MPLS domain.

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## Content

An ingress label-switching router pushes a label, intermediate routers swap labels according to forwarding state, and an egress router removes the label or forwards the packet onward.

The resulting label-switched path can support engineered forwarding, service separation, and traffic classes across a provider or enterprise backbone. Labels have meaning within their defined context rather than serving as globally meaningful addresses. MPLS can carry different network-layer protocols and underpin services described as Layer 2 or Layer 3 virtual private networks.

### Key points

- **Forwarding:** Use the active label and local forwarding entry to select the next hop and perform a push, swap, or pop operation on the label stack.
- **Service design:** Define route separation, path selection, restoration, quality-of-service treatment, and handoff responsibilities for each service rather than inferring them from “MPLS.”
- **Operations:** Protect management and control planes, monitor label-switched paths and provider boundaries, test failover, and understand whether nominally diverse circuits share infrastructure.
- **Important limitation:** MPLS does not inherently encrypt or authenticate customer traffic. Route separation inside a managed provider network is not equivalent to cryptographic protection, and misconfiguration or provider compromise can cross an intended boundary.

### Related terms

[Wide area network (WAN)](<https://yellowcube.eu/glossary/wide-area-network/>) · [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/>) · [Quality of service (QoS)](<https://yellowcube.eu/glossary/quality-of-service/>) · [Network latency](<https://yellowcube.eu/glossary/network-latency/>)

### Sources

[RFC 3031: Multiprotocol Label Switching Architecture](https://www.rfc-editor.org/info/rfc3031) · [RFC 3032: MPLS Label Stack Encoding](https://www.rfc-editor.org/info/rfc3032) · [RFC 4364: BGP/MPLS IP Virtual Private Networks](https://www.rfc-editor.org/info/rfc4364) · [RFC 4664: Framework for Layer 2 Virtual Private Networks](https://www.rfc-editor.org/info/rfc4664/)

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