Multiprotocol Label Switching (MPLS)

Definition of Multiprotocol Label Switching (MPLS) in The Network Encyclopedia.

What is MPLS (Multiprotocol Label Switching)?

A proposed standard from the Internet Engineering Task Force (IETF) for a switching protocol for backbone routers in large TCP/IP internetworks such as the Internet.

How It Works

Multiprotocol Label Switching (MPLS) is an outgrowth of switching protocols such as Layer 3 switching, tag switching, and Internet Protocol (IP) switching. MPLS enables routers to exchange information about the common paths taken by IP packets with different addresses. Routers can identify these paths as label-switched paths (LSPs) and enable routers to perform more efficient lookups in the relatively small label-swapping table (LST) that they maintain, instead of having to perform slower lookups in large IP address tables.

MPLS is particularly useful in the Internet infrastructure, where core routers are often connected in fully meshed topologies using permanent virtual circuits (PVCs) through Asynchronous Transfer Mode (ATM) backbones. MPLS also supports quality of service (QoS), which makes IP more suitable for sending multimedia and other streamed information.


Label switching is also implemented in other technologies such as ATM and frame relay networks. MPLS proposes to bring the same traffic management features to IP internetworks, and MPLS-enabled routers will treat ATM and frame relay switches as peers within the label-switched IP internetwork.