Chapter 1 - Multiprotocol Label Switching

Abstract

This chapter describes the concepts of multiprotocol label switching (MPLS) which is a data forwarding technology for use in packet networks that was developed by the internet engineering task force (IETF) building on several technologies invented by different companies. IETF relies on labeling each packet with a short, unique identifier (or label) that each router can use to determine the next hop for the data packet. It turns out that the same conceptual process used to determine how to forward MPLS packets can also be used in non-packet technologies. At the same time, many of the protocols used to install the forwarding rules at MPLS routers are easily extended to provide data forwarding control in non-packet networks. Label switching relies on associating a small, fixed-format label with each data packet so that it can be forwarded in the network. This means that each packet, frame, or cell must carry some identifier that tells network nodes how to forward it. The path that an MPLS packet follows across the network is called a label switched path (LSP). Sometimes one or more LSPs will be tunneled down another LSP. Signaling protocols allow a flexible approach so that a service request is sent to the network, and the network is responsible for routing the LSP through the label switching router.