1. General

Ten years ago, MPLS (Multi Protocol Label Switching) technology was conceived at the IETF (Internet Engineering Task Force) for transporting unicast flows. MPLS is based on a label inserted after the OSI Layer 2 header, which is used by an MPLS router, known as an LSR (Label Switching Router), to determine the interface and output label. An MPLS path between an input router and an output router is called an "LSP" (Label Switched Path ) or "MPLS tunnel". Operators use MPLS technology to ensure connectivity between their access routers (Provider Edge router, PE ). MPLS technology offers three essential functions: traffic encapsulation (MPLS tunneling), used to support virtual private networks (VPNs); traffic engineering, including admission control and bandwidth optimization, to share the load and avoid congestion; and traffic protection, enabling rerouting in less than 50 ms in the event...