Some of the major applications in which Multi Protocol Label Switching can be used include traffic engineering and dictating the path through which traffic passes in a network. When it was first conceived, MPLS was not supposed to depend on Layer 2 though today it is attracting a lot of attention because it can provide much better means of using the IP network in respect of a backbone such as a WAN that is ATM based.
Today, Multi Protocol Label Switching is undergoing new developments and it has already managed to gain widespread approval and was for long also considered as being one of the most crucial developments in networks in the nineties. In essence, this technology allows for generating a short label that is of a fixed length and which can represent in a sort of shorthand manner the header of any IP packet.
It can be likened to the ZIP code that is used to represent a home or street as well as city in your normal address. However, in the Multi Protocol Label Switching, the label will be used to allow for improved decision making concerning the forwarding of the packet.
An IP packet will need to include a field that must be present in the header and which will hold the packets address. This address indicates the intended destination of the packet. In the traditional manner in which a network works, the address information will be stored in each and every router along the path through which the packet travels over a network. Such a method is referred to as hop by hop.
However, in the Multi Protocol Label Switching method, the IP packet has to be given the different labels which are done by the first device on the network. This device is known as the edge router which does the job of analyzing the IP header content of the packet and then it gives the packet a proper label which is used for encapsulating the packet.
This method is not only different than normal network routing but is also much more powerful. The best part is that at each node that follows in the network the decision regarding forwarding the packet is made on the basis of the MPLS label and not on the basis of the IP header. At the very end of the network, the last router which is an edge router will then remove the label. Each of the nodes/routers on the network is known as LSRs or Label Switched Routers.
There will be two types of LSRs which include the ones at the very edge of a given network. Such routers will apply and also remove the labels and are called MPLS edge routers. There are also core LSRs that have the capability of processing the packets (labeled) at very high bandwidths.