Definition

MPLS is a connection-oriented switching technology based on the IP routing and control protocols to the network layer.MPLS encapsulates packets in different types of link layers with short and long labels and implements label switching based on the encapsulated labels.

MPLS adopts a bi-planar structure, which is divided into a Control Plane and a Forwarding Plane. The Control Plane is based on connectionless services and has powerful and flexible routing functions, which can meet the requirements of various new applications on the network. The main function of the control plane is to be responsible for the allocation of labels, the establishment of label forwarding table, the establishment and dismantling of label switching paths, and so on. The forwarding plane, also known as the Data Plane, is connection-oriented and can support Layer 2 networks such as ATM and Ethernet. The main function of the forwarding plane is to add and remove labels to IP packets, and at the same time forward received packets based on the label forwarding table.

Purpose

In the field of packet transport, the main application of MPLS technology is to build an MPLS tunnel to carry various types of services (e.g., TDM, ATM, and Ethernet) transmitted by PWE3 and to realize the end-to-end transmission of services in a packet network.A typical application of MPLS in the field of packet transport is shown in Fig. 1, where services between two NodeBs and the RNC are carried via the PW1 and PW2 carried by MPLS are transmitted.