MPLS — Multiprotocol Label Switching

This article describes the main features of Multiprotocol Label Switching (MPLS), a standard architecture proposed by the IETF that integrates label swapping forwarding with network layer routing. The role of MPLS in overcoming limitations of overlay models, such as IP over ATM, and of conventional routing in IP networks, is discussed. The main concepts are introduced and the operation of MPLS is explained – classification of packets into Forward Equivalence Classes, label allocation and binding to routes, label distribution, set up of Label Switched Paths and route selection. Finally, support of traffic engineering and Quality of Service mechanisms in MPLS networks is analysed. 1. MPLS- rationale for a new routing and forwarding architecture The success of the Internet is mainly due to its flexible architecture, built upon IP, the ubiquitous internetworking layer protocol. IP networks offer unparalleled scalability and flexibility for the deployment of value-added services and are becoming increasingly attractive for carrying services with hard and soft real-time constraints. This requires extending the traditional best-effort model, designed from