Multi Protocol Label Switching

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Multi-Protocol Label Switching (MPLS) is a mechanism that when added to a routed IP network enables packets to be switched in hardware at high speed. It’s thought to be a Layer 2 technology, although in many circles it’s called Layer 2 and a half since it mostly functions between the Data-Link Layer and the Network Layer of the OSI Reference Model.

Lots of vendors had similar but proprietary technologies which became the foundation for MPLS, for instance, Cisco had Tag Switching and IBM had a comparable technology called ARIS (Aggregate Route-Based IP Switching). In 1997 a working group was formed under the advice of the IETF (Internet Engineering Task Force), and eventually, the title MPLS was determined upon.

MPLS label 

An MPLS label is a brief 32-bit identifier that’s used to switch packets in an MPLS domain. When used with ATM (Asynchronous Transfer Mode) the tag replaces the VPI/VCI, and a similar scenario happens when MPLS is used with some other Data-Link Layer technology like X.25 and Frame Relay. A relay is a very useful device for¬†MPLS label as well as other communication networks.

The original idea of MPLS was to combine the intelligence of Layer 3 Routing with the rate of Layer two Switching so as to deliver a high throughput of Layer 3 packets.

The technology is maturing and packet flows using the exact same FEC (Forward Equivalence Class) can be changed across specific paths to pay for that packet flow the proper Quality of Service.

Let us take a look at some of the terminology:

An LSP (Label Switched Path) is a route set up across a network from the entrance point called the ingress to the exit stage called the egress.

The path is defined in forwarding tables held at the switching devices, together with the patch being a collection of jumps across the tag switched domain.

Any information that adheres to an exact match algorithm performed upon the IP header data, called a Forward Equivalence Class will be dispersed throughout the LSP.

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