MPLS, or Multiprotocol Label Switching, is a networking technique that directs data through a network using short path labels rather than long network addresses, avoiding the need for each router to look up a packet's destination in a routing table. By forwarding traffic based on labels along predetermined paths, MPLS makes routing faster and more predictable. It is called "multiprotocol" because it works with many underlying protocols, and it has been widely used by carriers and large enterprises to build reliable wide-area networks.

How does MPLS work?

In traditional IP routing, every router along a path independently examines each packet's destination address and consults its routing table to decide where to send it next, a repeated lookup at every hop. MPLS avoids this. When a packet enters the MPLS network, the first router (the ingress, or label edge router) classifies it and attaches a label. From then on, the interior routers (label switch routers) forward the packet by reading only its label and swapping it for the next one along a predetermined path called a label-switched path (LSP). The final router (the egress) removes the label and delivers the packet.

Because the interior routers act only on simple labels rather than performing full address lookups, forwarding is fast and follows a controlled, predictable route. MPLS is sometimes described as operating at "Layer 2.5," because it sits between the traditional data-link layer (Layer 2) and network layer (Layer 3).

What are the benefits of MPLS?

MPLS offers several advantages that made it the backbone of enterprise wide-area networking for years. It is protocol-independent, working over Ethernet, ATM, and other technologies. It is highly scalable, supporting very large networks. It allows traffic engineering: administrators can define paths and prioritise important traffic, such as voice and video, over less time-sensitive traffic like email, to meet service-level agreements. And its label-switched paths are isolated from one another, giving a level of privacy and security comparable to a VPN, which made MPLS popular for reliably connecting branch offices to central data centres.

What are the drawbacks of MPLS?

MPLS also has real limitations, which have grown more significant with the shift to cloud. Provisioning a new MPLS connection is slow and can take weeks or months, and it is often expensive, particularly as bandwidth demands rise. It was designed for a world where applications lived in a central data centre, so it handles cloud traffic poorly: sending cloud-bound traffic through a central site for inspection, called backhauling, adds latency and hurts the performance of cloud and SaaS applications. As organisations became more distributed and more cloud-dependent, these drawbacks pushed many toward newer alternatives.

MPLS vs. SD-WAN

Software-Defined Wide Area Networking (SD-WAN) emerged as a flexible alternative to, or complement for, MPLS. Rather than relying on a single dedicated MPLS circuit, SD-WAN can combine multiple connection types, MPLS, broadband internet, and cellular, into one virtual network, choosing the best path for each application in real time. It secures traffic with encryption across all links, adapts automatically when a link degrades or fails, and can send trusted cloud traffic directly to the internet instead of backhauling it, improving cloud performance. SD-WAN is also centrally managed and can be provisioned quickly. Many organisations now use SD-WAN either to replace MPLS or to run alongside it, keeping MPLS for the traffic that benefits from its guaranteed paths while offloading other traffic to cheaper, more flexible links.