What Does 'MPLS (Multiprotocol Label Switching)' Mean?

Marvin Kaufman author Marvin Kaufman
What is MPLS (Multiprotocol Label Switching)?
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MPLS (Multiprotocol Label Switching) is a protocol for speeding up and shaping network traffic flow. It operates at an OSI Model layer that is generally considered to lie between traditional routing based on IP addresses (Layer 3) and traditional data-link layer switching (Layer 2).

The MPLS protocol defines a method to assign short, fixed-length labels to network packets in order to route them more efficiently through a network. Once packets are assigned a label, they are forwarded based on the label, rather than having to perform a routing lookup for each packet. This allows for faster and more efficient routing and also enables the creation of virtual private networks (VPNs) and traffic engineering (TE) on a large scale.

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MPLS is a mechanism for forwarding packets in a network using short, fixed-length labels rather than the longer, variable-length addresses used in traditional IP routing. In an MPLS network, packets are assigned a label at the ingress to the network and then forwarded through the network based on the label, without performing a routing lookup for each packet.

This makes possible faster and more efficient forwarding of packets, as well as the ability to create virtual private networks (VPNs) and perform traffic engineering (TE) on a large scale.

Multiprotocol Label Switching can be used in conjunction with any network layer protocol, although it is most commonly used with IP. MPLS is used to forward packets in a Layer 2 Tunneling Protocol (L2TP) VPN or a Virtual Private LAN Service (VPLS) network.

MPLS networks are composed of a series of Label Switch Routers (LSRs) and Label Edge Routers (LERs). LSRs are routers that are capable of forwarding packets based on the label, and LERs are routers that attach a label to a packet when it enters the MPLS network and remove the label when the packet leaves the MPLS network.

One of the key benefits of MPLS is that it offers the possibility for the creation of virtual private networks (VPNs). These VPNs facilitate the secure, private exchange of data between sites, even over a public infrastructure such as the Internet. MPLS VPNs can be used to create a number of different types of VPNs, including:

  • Provider-provisioned VPNs (PPVPNs), which are VPNs that are created and maintained by a service provider.
  • Customer-provisioned VPNs (CPVPNs), which are VPNs that are created and maintained by the customer.

MPLS also enables the use of traffic engineering (TE) on a large scale. TE allows network administrators to control the path that packets take through the network, with the aim of optimizing network performance and ensuring that the network is being used efficiently. This is achieved by manipulating the labels assigned to packets for the purpose of steering them along specific paths through the network.

It is also worth mentioning that MPLS is not just a single protocol but rather a set of protocols and technologies, which include: Label Distribution Protocol (LDP), Resource Reservation Protocol (RSVP), Constraint-Based Routing LDP (CR-LDP), and Label Distribution Protocol (BGP-LS).

MPLS is widely used on service provider networks, data center interconnections, and enterprise networks as well as in mobile networks, specifically in 5G systems, to handle packet forwarding as well as traffic engineering.