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MPLS stands for Multi-Protocol Label Switching. Basically, MPLS is a standard set up by the Internet Engineering Task Force (IETF).It is considered as a high performance telecommunication network. MPLS works between two layer 2 (link) and layer 3(Network) of the ISO/OSI model. In short, MPLS is a standard based technology used to accelerate the delivery of network packets over multiple protocols.

What are the Elements of MPLS?

Infographic Source – Visually


  1. Label: It is referred as a first length identificator of packet in the network.
  2. Forwarding Equivalence Class (FEC): It is used to delineate a set of packets with similar features which may be forwarded in a way that may be restricted to the same MPLS label.
  3. Label Switched Path (LSP): It is a path inside an MPLS network created by some protocol (Label Distribution Protocol, Resource Reservation Protocol – Traffic Engineering, BGP Extension.


  1. Label Switch Router (LSR): It is router located in the internal segment of the MPLS network. It reads the label, applies some services, and then forwards the packet to the next router.
  2. Label Edge Router (LER): It is located in the perimetrical zone of the MPLS network. In order to determine the FEC, it reads the packet header at the entrance and assigns a label to the packet. Moreover, it also removes the label for the outgoing packets.

How MPLS Works?

When an unlabeled packet enters the ingress router (LER), it needs to get on to an MPLS path, but the router first determines the FEC  for the required packet and then inserts one or more labels in the new MPLS header of the packet. The packet further reaches the next router (LSR) for the path. When the packet arrives at an egress router, then the router removes the label and directs the packet to the receiver.

Are you looking for a new type of a network infrastructure to accomplish a greater service quality? Well in that case MPLS can be the answer.

What is the difference between MPLS and Simple Routing/Switching?

In fact, a lot.

Usually ip packets consist of an extra header (the mpls header) while progressing through the mpls zone and all forwarding decisions are based on the mpls header, not the ip header. This allows making the forwarding decisions much differently from what one would expect from usual ip packet routing.

  • With MPLS, you can route the similar destination ip packets to different destinations, since the destined ip isn’t your decision point while you are there inside the mpls domain. In usual, it is done with MPLS based Layer-3 VPNs.
  • You can also choose different forwarding paths, without even depending on the usual ip-based routing protocols. You don’t need to look at your ip routing tables for making the routing decisions.
  • Moreover, you can also have conflicting ip addresses in various end points, and you can make a clear distinction between them.
  • If you want you can also get rid of all ip-based information collection. Without ever learning anything about their addresses, you can forward the packets.
  • Pre-defined and pre-set forwarding paths are possible when path circulation times become a burden. Hence, you can pre-set a path for the primary router, and if at all primary fails, the back will kick-in without even calculating anything- almost an immediate convergence. And this is the idea behind TE-based backup paths.

In Which Layer Does MPLS Works?

MPLS works at a layer in between the layer 2 (data link layer) and layer 3 (network layer), and therefore is often called as a ‘layer 2.5 protocol’.

Basically it was fabricated to provide a unified data-carrying service for both the circuit based clients and packet switching clients which give a datagram service model. It can be utilized to carry various types of traffic including the ip packets, native ATM, SONET, and the ETHERNET frames.

What is GMPLS?

Conceptually, GMPLS is similar to MPLS, but instead of using an explicit label to differentiate an LSP at each LSR, some of the physical properties of the received data stream are used to make out which LSP it belongs to.

Therefore, LSPs are implicitly labelled in a GMPLS network. GMPLS can also be used to establish LSPs for circuit traffic.

MPLS and GMPLS Signaling Protocols

What is the function of signaling protocol? Basically, it informs the switches along the route which labels and links to use for each LSP. Therefore, this information is used in order to program the switching fabric. Depending on the application, one of the three main signaling protocols is used for MPLS which are:

LDP is used for

  • MPLS transport where traffic engineering is not required
  • Some MPLS services, like the Pseudo wires

RSVP-TE is used for

  • MPLS transport where traffic engineering is required
  • All GMPLS Support
  • BGP which is a signaling protocol is used for certain MPLS services, like BGP/MPLS Layer 3 VPNs.

Moreover, if we ponder over the security, the MPLS VPN internet is much more secure than a regular internet connection; it is basically like a virtual leased line. However it runs no encryption.

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