The data plane is responsible for forwarding packets. Packets are forwarded based on destination address or label information. The Cisco Express Forwarding (CEF) Forwarding Information Base (FIB), which is part of the data plane, is built from information in the routing table. When the routing table is updated, the nexthop information in the FIB is also updated. The Label Forwarding Information Base (LFIB), which is also part of the data plane, contains inbound-to-outbound label mappings. These label mappings are used by Multiprotocol Label Switching (MPLS) to forward packets to the correct destination. When a label switch router (LSR) receives an unlabeled packet destined for an MPLSenabled interface, it consults the FIB, adds the appropriate label for the destination address, and forwards the packet.

MPLS includes two primary components: the control plane and the data plane. The control plane is responsible for exchanging routing information by using a routing protocol, such as Border Gateway Protocol (BGP), Enhanced Interior Gateway Routing Protocol (EIGRP),Intermediate SystemtoIntermediate System (ISIS), or Open Shortest Path First (OSPF).Additionally, the control plane is responsible for exchanging label information by using alabel exchange protocol, such as Resource Reservation Protocol (RSVP), Tag Distribution Protocol (TDP), or Label Distribution Protocol (LDP). LDP is a newer standard that includes features of the Ciscoproprietary TDP. RSVP is used by MPLS Traffic Engineering (MPLS TE) to also reserve network bandwidth. Bandwidth is reserved on demand based on destination address or traffic type so that enough bandwidth is available for the traffic.