Junos OS MPLS Applications Library for Routing Devices
These guides provide an overview of Multiprotocol Label Switching (MPLS) concepts, as well as configuration information, examples, and reference information about MPLS. MPLS is a mechanism used to transfer data across large telecommunication networks. In a Layer 3 forwarding model, as a packet travels from one router to the next, an independent forwarding decision is made by each node. The IP network layer header is analyzed, and the next hop is chosen based on this analysis and on the information in the routing table. With MPLS, the analysis of the packet header is performed just once, when a packet enters the MPLS cloud.
The packet is assigned to a path identified by a label (a 20-bit fixed-length value) which is attached to the front of the packet. These paths are called label-switched paths (LSPs) and carry MPLS traffic across the network. At each MPLS node, the label is swapped with another label identifying the next node on the LSP. At the end of the LSP, the MPLS label is removed, and the packet is then forwarded using a standard IP protocol.
