What Is MPLS? Definition and Operation
·1 min read·148 words
MPLS (Multi-Protocol Label Switching) is a forwarding technique based on short labels (20 bits) instead of a full IP routing lookup. ISPs use it for L3/L2 VPNs, Traffic Engineering, and contractually guaranteed QoS. It remains dominant among carriers in 2026.
How It Works
- Label switching instead of hop-by-hop IP routing
- LSP (Label-Switched Path): a pre-established path
- LDP, RSVP-TE, or Segment Routing for label distribution
- Encapsulation: a label is added between the L2 header and IP
Use Cases
- L3VPN: one VRF per customer for multi-tenant isolation
- L2VPN: point-to-point or multipoint Ethernet emulation
- Traffic Engineering: explicit LSPs with reserved bandwidth
- Fast Reroute (FRR): failover in <50ms
MPLS vs SD-WAN
- MPLS: contractually guaranteed QoS and SLA, but expensive
- SD-WAN: Internet-based, best-effort, and 5-10× less expensive
- Trend: migration from MPLS to SD-WAN and hybrid architectures
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