When an LSR receives a labeled packet, it will use the label as the index to look up the forwarding table. The packet is processed as specified by the forwarding table entry. Before a packet leaves an MPLS domain, its MPLS label is removed and the IP packet extracted. MPLS uses a signaling protocol such as RSVP or LVP to set up these paths. Because CBR considers more than the topology of the network when computing routes, it may find a longer but lightly loaded path, which is better than using a heavily loaded path that may be the shortest.
Network traffic is distributed more evenly.
Enhanced link state IGPs For CBR to compute LSP paths that are subject to constraints, an enhanced link state IGP must be used to propagate the information needed by the constraint-based routing. The enhanced IGP also takes LSPs into consideration while building the routing table. The relationship between CBR, MPLS and enhanced IGP is depicted in Figure 4 . Solving the problems With MPLS, CBR and enhanced IGP, network optimization can be done much more effectively, and the two problems discussed in Traffic Engineering can be solved. First, by configuring the maximum reservable bandwidth for each link as the physical bandwidth of the link, and by specifying the bandwidth requirement for each LSP according to the measured rate of the LSP, CBR can automatically avoid placing too many LSPs on any link.