MPLS (Multiprotocol Label Switching)
MPLS is a networking technology that directs data using labels instead of IP routing, enabling predictable performance and traffic prioritization across WANs.
What is MPLS?
Multiprotocol Label Switching (MPLS) is a packet-forwarding technology used in wide area networks to route traffic based on short labels rather than traditional IP address lookups. Labels are assigned at network entry points and used by intermediate routers to forward packets efficiently along predefined paths.
MPLS is commonly provided by carriers as a private WAN service for enterprises.
Why MPLS matters
MPLS is valued because it:
- Provides predictable latency and performance
- Supports traffic prioritization (QoS) for critical apps
- Offers high reliability with carrier SLAs
- Enables segmentation between sites
- Scales well for multi-site enterprises
It has long been the standard for mission-critical WAN connectivity.
How MPLS works (simplified)
An MPLS flow typically works as follows:
- Traffic enters the MPLS network at an ingress router
- A label is applied to the packet
- Intermediate routers forward packets using the label
- The label is removed at the egress router
- Traffic exits to the destination network
This label-based forwarding reduces routing complexity in the core.
MPLS and Quality of Service (QoS)
MPLS natively supports QoS, allowing carriers to:
- Classify traffic (voice, video, data)
- Prioritize latency-sensitive applications
- Guarantee bandwidth and jitter targets
- Enforce service-level agreements (SLAs)
This is a key reason MPLS is used for voice and real-time workloads.
MPLS vs Internet-based WAN
| Aspect | MPLS | Internet WAN |
|---|---|---|
| Predictability | High | Variable |
| QoS | Strong | Limited |
| Cost | Higher | Lower |
| Flexibility | Lower | Higher |
| Cloud access | Indirect | Native |
MPLS trades flexibility and cost for stability and guarantees.
MPLS and security
Security considerations include:
- MPLS provides traffic isolation, not encryption
- Data is separated from public internet traffic
- Encryption (IPsec) may still be required for compliance
- Trust is placed in the service provider's network
MPLS is often combined with additional security controls.
MPLS in modern networks
Many organizations are evolving from MPLS to:
- Hybrid WANs (MPLS + internet)
- SD-WAN overlays for dynamic routing
- Cloud-first architectures
MPLS is still widely used, but often as part of a broader strategy.
Typical MPLS use cases
MPLS is commonly used for:
- Connecting branch offices to data centers
- Supporting VoIP and unified communications
- Running latency-sensitive enterprise applications
- Environments requiring strong SLAs
- Legacy WAN architectures
Limitations of MPLS
MPLS has drawbacks:
- Higher cost compared to internet links
- Longer provisioning times
- Less agility for cloud and SaaS traffic
- Dependence on carrier infrastructure
These factors drive adoption of SD-WAN alternatives.
Common misconceptions
- "MPLS encrypts traffic by default"
- "MPLS is obsolete everywhere"
- "MPLS is faster than fiber internet"
- "MPLS cannot be combined with SD-WAN"